bottle.py

#!/usr/bin/env python
# -*- coding: utf-8 -*-
"""
Bottle is a fast and simple micro-framework for small web applications. It
offers request dispatching (Routes) with URL parameter support, templates,
a built-in HTTP Server and adapters for many third party WSGI/HTTP-server and
template engines - all in a single file and with no dependencies other than the
Python Standard Library.

Homepage and documentation: http://bottlepy.org/

Copyright (c) 2009-2018, Marcel Hellkamp.
License: MIT (see LICENSE for details)
"""

from __future__ import print_function
import sys

__author__ = 'Marcel Hellkamp'
__version__ = '0.13-dev'
__license__ = 'MIT'

###############################################################################
# Command-line interface ######################################################
###############################################################################
# INFO: Some server adapters need to monkey-patch std-lib modules before they
# are imported. This is why some of the command-line handling is done here, but
# the actual call to _main() is at the end of the file.


def _cli_parse(args):  # pragma: no coverage
    from argparse import ArgumentParser

    parser = ArgumentParser(prog=args[0], usage="%(prog)s [options] package.module:app")
    opt = parser.add_argument
    opt("--version", action="store_true", help="show version number.")
    opt("-b", "--bind", metavar="ADDRESS", help="bind socket to ADDRESS.")
    opt("-s", "--server", default='wsgiref', help="use SERVER as backend.")
    opt("-p", "--plugin", action="append", help="install additional plugin/s.")
    opt("-c", "--conf", action="append", metavar="FILE",
        help="load config values from FILE.")
    opt("-C", "--param", action="append", metavar="NAME=VALUE",
        help="override config values.")
    opt("--debug", action="store_true", help="start server in debug mode.")
    opt("--reload", action="store_true", help="auto-reload on file changes.")
    opt('app', help='WSGI app entry point.', nargs='?')

    cli_args = parser.parse_args(args[1:])

    return cli_args, parser


def _cli_patch(cli_args):  # pragma: no coverage
    parsed_args, _ = _cli_parse(cli_args)
    opts = parsed_args
    if opts.server:
        if opts.server.startswith('gevent'):
            import gevent.monkey
            gevent.monkey.patch_all()
        elif opts.server.startswith('eventlet'):
            import eventlet
            eventlet.monkey_patch()


if __name__ == '__main__':
    _cli_patch(sys.argv)

###############################################################################
# Imports and Python 2/3 unification ##########################################
###############################################################################

import base64, calendar, cgi, email.utils, functools, hmac, imp, itertools,\
       mimetypes, os, re, tempfile, threading, time, warnings, weakref, hashlib

from types import FunctionType
from datetime import date as datedate, datetime, timedelta
from tempfile import TemporaryFile
from traceback import format_exc, print_exc
from unicodedata import normalize

try:
    from ujson import dumps as json_dumps, loads as json_lds
except ImportError:
    from json import dumps as json_dumps, loads as json_lds

# inspect.getargspec was removed in Python 3.6, use
# Signature-based version where we can (Python 3.3+)
try:
    from inspect import signature
    def getargspec(func):
        params = signature(func).parameters
        args, varargs, keywords, defaults = [], None, None, []
        for name, param in params.items():
            if param.kind == param.VAR_POSITIONAL:
                varargs = name
            elif param.kind == param.VAR_KEYWORD:
                keywords = name
            else:
                args.append(name)
                if param.default is not param.empty:
                    defaults.append(param.default)
        return (args, varargs, keywords, tuple(defaults) or None)
except ImportError:
    try:
        from inspect import getfullargspec
        def getargspec(func):
            spec = getfullargspec(func)
            kwargs = makelist(spec[0]) + makelist(spec.kwonlyargs)
            return kwargs, spec[1], spec[2], spec[3]
    except ImportError:
        from inspect import getargspec


py = sys.version_info
py3k = py.major > 2

# Lots of stdlib and builtin differences.
if py3k:
    import http.client as httplib
    import _thread as thread
    from urllib.parse import urljoin, SplitResult as UrlSplitResult
    from urllib.parse import urlencode, quote as urlquote, unquote as urlunquote
    urlunquote = functools.partial(urlunquote, encoding='latin1')
    from http.cookies import SimpleCookie, Morsel, CookieError
    from collections.abc import MutableMapping as DictMixin
    import pickle
    from io import BytesIO
    import configparser

    basestring = str
    unicode = str
    json_loads = lambda s: json_lds(touni(s))
    callable = lambda x: hasattr(x, '__call__')
    imap = map

    def _raise(*a):
        raise a[0](a[1]).with_traceback(a[2])
else:  # 2.x
    import httplib
    import thread
    from urlparse import urljoin, SplitResult as UrlSplitResult
    from urllib import urlencode, quote as urlquote, unquote as urlunquote
    from Cookie import SimpleCookie, Morsel, CookieError
    from itertools import imap
    import cPickle as pickle
    from StringIO import StringIO as BytesIO
    import ConfigParser as configparser
    from collections import MutableMapping as DictMixin
    unicode = unicode
    json_loads = json_lds
    exec(compile('def _raise(*a): raise a[0], a[1], a[2]', '<py3fix>', 'exec'))

# Some helpers for string/byte handling
def tob(s, enc='utf8'):
    if isinstance(s, unicode):
        return s.encode(enc)
    return b'' if s is None else bytes(s)


def touni(s, enc='utf8', err='strict'):
    if isinstance(s, bytes):
        return s.decode(enc, err)
    return unicode("" if s is None else s)


tonat = touni if py3k else tob


def _stderr(*args):
    try:
        print(*args, file=sys.stderr)
    except (IOError, AttributeError):
        pass # Some environments do not allow printing (mod_wsgi)


# A bug in functools causes it to break if the wrapper is an instance method
def update_wrapper(wrapper, wrapped, *a, **ka):
    try:
        functools.update_wrapper(wrapper, wrapped, *a, **ka)
    except AttributeError:
        pass

# These helpers are used at module level and need to be defined first.
# And yes, I know PEP-8, but sometimes a lower-case classname makes more sense.


def depr(major, minor, cause, fix):
    text = "Warning: Use of deprecated feature or API. (Deprecated in Bottle-%d.%d)\n"\
           "Cause: %s\n"\
           "Fix: %s\n" % (major, minor, cause, fix)
    if DEBUG == 'strict':
        raise DeprecationWarning(text)
    warnings.warn(text, DeprecationWarning, stacklevel=3)
    return DeprecationWarning(text)


def makelist(data):  # This is just too handy
    if isinstance(data, (tuple, list, set, dict)):
        return list(data)
    elif data:
        return [data]
    else:
        return []


class DictProperty(object):
    """ Property that maps to a key in a local dict-like attribute. """

    def __init__(self, attr, key=None, read_only=False):
        self.attr, self.key, self.read_only = attr, key, read_only

    def __call__(self, func):
        functools.update_wrapper(self, func, updated=[])
        self.getter, self.key = func, self.key or func.__name__
        return self

    def __get__(self, obj, cls):
        if obj is None: return self
        key, storage = self.key, getattr(obj, self.attr)
        if key not in storage: storage[key] = self.getter(obj)
        return storage[key]

    def __set__(self, obj, value):
        if self.read_only: raise AttributeError("Read-Only property.")
        getattr(obj, self.attr)[self.key] = value

    def __delete__(self, obj):
        if self.read_only: raise AttributeError("Read-Only property.")
        del getattr(obj, self.attr)[self.key]


class cached_property(object):
    """ A property that is only computed once per instance and then replaces
        itself with an ordinary attribute. Deleting the attribute resets the
        property. """

    def __init__(self, func):
        update_wrapper(self, func)
        self.func = func

    def __get__(self, obj, cls):
        if obj is None: return self
        value = obj.__dict__[self.func.__name__] = self.func(obj)
        return value


class lazy_attribute(object):
    """ A property that caches itself to the class object. """

    def __init__(self, func):
        functools.update_wrapper(self, func, updated=[])
        self.getter = func

    def __get__(self, obj, cls):
        value = self.getter(cls)
        setattr(cls, self.__name__, value)
        return value

###############################################################################
# Exceptions and Events #######################################################
###############################################################################


class BottleException(Exception):
    """ A base class for exceptions used by bottle. """
    pass

###############################################################################
# Routing ######################################################################
###############################################################################


class RouteError(BottleException):
    """ This is a base class for all routing related exceptions """


class RouteReset(BottleException):
    """ If raised by a plugin or request handler, the route is reset and all
        plugins are re-applied. """


class RouterUnknownModeError(RouteError):

    pass


class RouteSyntaxError(RouteError):
    """ The route parser found something not supported by this router. """


class RouteBuildError(RouteError):
    """ The route could not be built. """


def _re_flatten(p):
    """ Turn all capturing groups in a regular expression pattern into
        non-capturing groups. """
    if '(' not in p:
        return p
    return re.sub(r'(\\*)(\(\?P<[^>]+>|\((?!\?))', lambda m: m.group(0) if
                  len(m.group(1)) % 2 else m.group(1) + '(?:', p)


class Router(object):
    """ A Router is an ordered collection of route->target pairs. It is used to
        efficiently match WSGI requests against a number of routes and return
        the first target that satisfies the request. The target may be anything,
        usually a string, ID or callable object. A route consists of a path-rule
        and a HTTP method.

        The path-rule is either a static path (e.g. `/contact`) or a dynamic
        path that contains wildcards (e.g. `/wiki/<page>`). The wildcard syntax
        and details on the matching order are described in docs:`routing`.
    """

    default_pattern = '[^/]+'
    default_filter = 're'

    #: The current CPython regexp implementation does not allow more
    #: than 99 matching groups per regular expression.
    _MAX_GROUPS_PER_PATTERN = 99

    def __init__(self, strict=False):
        self.rules = []  # All rules in order
        self._groups = {}  # index of regexes to find them in dyna_routes
        self.builder = {}  # Data structure for the url builder
        self.static = {}  # Search structure for static routes
        self.dyna_routes = {}
        self.dyna_regexes = {}  # Search structure for dynamic routes
        #: If true, static routes are no longer checked first.
        self.strict_order = strict
        self.filters = {
            're': lambda conf: (_re_flatten(conf or self.default_pattern),
                                None, None),
            'int': lambda conf: (r'-?\d+', int, lambda x: str(int(x))),
            'float': lambda conf: (r'-?[\d.]+', float, lambda x: str(float(x))),
            'path': lambda conf: (r'.+?', None, None)
        }

    def add_filter(self, name, func):
        """ Add a filter. The provided function is called with the configuration
        string as parameter and must return a (regexp, to_python, to_url) tuple.
        The first element is a string, the last two are callables or None. """
        self.filters[name] = func

    rule_syntax = re.compile('(\\\\*)'
        '(?:(?::([a-zA-Z_][a-zA-Z_0-9]*)?()(?:#(.*?)#)?)'
          '|(?:<([a-zA-Z_][a-zA-Z_0-9]*)?(?::([a-zA-Z_]*)'
            '(?::((?:\\\\.|[^\\\\>])+)?)?)?>))')

    def _itertokens(self, rule):
        offset, prefix = 0, ''
        for match in self.rule_syntax.finditer(rule):
            prefix += rule[offset:match.start()]
            g = match.groups()
            if g[2] is not None:
                depr(0, 13, "Use of old route syntax.",
                            "Use <name> instead of :name in routes.")
            if len(g[0]) % 2:  # Escaped wildcard
                prefix += match.group(0)[len(g[0]):]
                offset = match.end()
                continue
            if prefix:
                yield prefix, None, None
            name, filtr, conf = g[4:7] if g[2] is None else g[1:4]
            yield name, filtr or 'default', conf or None
            offset, prefix = match.end(), ''
        if offset <= len(rule) or prefix:
            yield prefix + rule[offset:], None, None

    def add(self, rule, method, target, name=None):
        """ Add a new rule or replace the target for an existing rule. """
        anons = 0  # Number of anonymous wildcards found
        keys = []  # Names of keys
        pattern = ''  # Regular expression pattern with named groups
        filters = []  # Lists of wildcard input filters
        builder = []  # Data structure for the URL builder
        is_static = True

        for key, mode, conf in self._itertokens(rule):
            if mode:
                is_static = False
                if mode == 'default': mode = self.default_filter
                mask, in_filter, out_filter = self.filters[mode](conf)
                if not key:
                    pattern += '(?:%s)' % mask
                    key = 'anon%d' % anons
                    anons += 1
                else:
                    pattern += '(?P<%s>%s)' % (key, mask)
                    keys.append(key)
                if in_filter: filters.append((key, in_filter))
                builder.append((key, out_filter or str))
            elif key:
                pattern += re.escape(key)
                builder.append((None, key))

        self.builder[rule] = builder
        if name: self.builder[name] = builder

        if is_static and not self.strict_order:
            self.static.setdefault(method, {})
            self.static[method][self.build(rule)] = (target, None)
            return

        try:
            re_pattern = re.compile('^(%s)$' % pattern)
            re_match = re_pattern.match
        except re.error as e:
            raise RouteSyntaxError("Could not add Route: %s (%s)" % (rule, e))

        if filters:

            def getargs(path):
                url_args = re_match(path).groupdict()
                for name, wildcard_filter in filters:
                    try:
                        url_args[name] = wildcard_filter(url_args[name])
                    except ValueError:
                        raise HTTPError(400, 'Path has wrong format.')
                return url_args
        elif re_pattern.groupindex:

            def getargs(path):
                return re_match(path).groupdict()
        else:
            getargs = None

        flatpat = _re_flatten(pattern)
        whole_rule = (rule, flatpat, target, getargs)

        if (flatpat, method) in self._groups:
            if DEBUG:
                msg = 'Route <%s %s> overwrites a previously defined route'
                warnings.warn(msg % (method, rule), RuntimeWarning)
            self.dyna_routes[method][
                self._groups[flatpat, method]] = whole_rule
        else:
            self.dyna_routes.setdefault(method, []).append(whole_rule)
            self._groups[flatpat, method] = len(self.dyna_routes[method]) - 1

        self._compile(method)

    def _compile(self, method):
        all_rules = self.dyna_routes[method]
        comborules = self.dyna_regexes[method] = []
        maxgroups = self._MAX_GROUPS_PER_PATTERN
        for x in range(0, len(all_rules), maxgroups):
            some = all_rules[x:x + maxgroups]
            combined = (flatpat for (_, flatpat, _, _) in some)
            combined = '|'.join('(^%s$)' % flatpat for flatpat in combined)
            combined = re.compile(combined).match
            rules = [(target, getargs) for (_, _, target, getargs) in some]
            comborules.append((combined, rules))

    def build(self, _name, *anons, **query):
        """ Build an URL by filling the wildcards in a rule. """
        builder = self.builder.get(_name)
        if not builder:
            raise RouteBuildError("No route with that name.", _name)
        try:
            for i, value in enumerate(anons):
                query['anon%d' % i] = value
            url = ''.join([f(query.pop(n)) if n else f for (n, f) in builder])
            return url if not query else url + '?' + urlencode(query)
        except KeyError as E:
            raise RouteBuildError('Missing URL argument: %r' % E.args[0])

    def match(self, environ):
        """ Return a (target, url_args) tuple or raise HTTPError(400/404/405). """
        verb = environ['REQUEST_METHOD'].upper()
        path = environ['PATH_INFO'] or '/'

        methods = ('PROXY', 'HEAD', 'GET', 'ANY') if verb == 'HEAD' else ('PROXY', verb, 'ANY')

        for method in methods:
            if method in self.static and path in self.static[method]:
                target, getargs = self.static[method][path]
                return target, getargs(path) if getargs else {}
            elif method in self.dyna_regexes:
                for combined, rules in self.dyna_regexes[method]:
                    match = combined(path)
                    if match:
                        target, getargs = rules[match.lastindex - 1]
                        return target, getargs(path) if getargs else {}

        # No matching route found. Collect alternative methods for 405 response
        allowed = set([])
        nocheck = set(methods)
        for method in set(self.static) - nocheck:
            if path in self.static[method]:
                allowed.add(method)
        for method in set(self.dyna_regexes) - allowed - nocheck:
            for combined, rules in self.dyna_regexes[method]:
                match = combined(path)
                if match:
                    allowed.add(method)
        if allowed:
            allow_header = ",".join(sorted(allowed))
            raise HTTPError(405, "Method not allowed.", Allow=allow_header)

        # No matching route and no alternative method found. We give up
        raise HTTPError(404, "Not found: " + repr(path))


class Route(object):
    """ This class wraps a route callback along with route specific metadata and
        configuration and applies Plugins on demand. It is also responsible for
        turning an URL path rule into a regular expression usable by the Router.
    """

    def __init__(self, app, rule, method, callback,
                 name=None,
                 plugins=None,
                 skiplist=None, **config):
        #: The application this route is installed to.
        self.app = app
        #: The path-rule string (e.g. ``/wiki/<page>``).
        self.rule = rule
        #: The HTTP method as a string (e.g. ``GET``).
        self.method = method
        #: The original callback with no plugins applied. Useful for introspection.
        self.callback = callback
        #: The name of the route (if specified) or ``None``.
        self.name = name or None
        #: A list of route-specific plugins (see :meth:`Bottle.route`).
        self.plugins = plugins or []
        #: A list of plugins to not apply to this route (see :meth:`Bottle.route`).
        self.skiplist = skiplist or []
        #: Additional keyword arguments passed to the :meth:`Bottle.route`
        #: decorator are stored in this dictionary. Used for route-specific
        #: plugin configuration and meta-data.
        self.config = app.config._make_overlay()
        self.config.load_dict(config)

    @cached_property
    def call(self):
        """ The route callback with all plugins applied. This property is
            created on demand and then cached to speed up subsequent requests."""
        return self._make_callback()

    def reset(self):
        """ Forget any cached values. The next time :attr:`call` is accessed,
            all plugins are re-applied. """
        self.__dict__.pop('call', None)

    def prepare(self):
        """ Do all on-demand work immediately (useful for debugging)."""
        self.call

    def all_plugins(self):
        """ Yield all Plugins affecting this route. """
        unique = set()
        for p in reversed(self.app.plugins + self.plugins):
            if True in self.skiplist: break
            name = getattr(p, 'name', False)
            if name and (name in self.skiplist or name in unique): continue
            if p in self.skiplist or type(p) in self.skiplist: continue
            if name: unique.add(name)
            yield p

    def _make_callback(self):
        callback = self.callback
        for plugin in self.all_plugins():
            try:
                if hasattr(plugin, 'apply'):
                    callback = plugin.apply(callback, self)
                else:
                    callback = plugin(callback)
            except RouteReset:  # Try again with changed configuration.
                return self._make_callback()
            if callback is not self.callback:
                update_wrapper(callback, self.callback)
        return callback

    def get_undecorated_callback(self):
        """ Return the callback. If the callback is a decorated function, try to
            recover the original function. """
        func = self.callback
        func = getattr(func, '__func__' if py3k else 'im_func', func)
        closure_attr = '__closure__' if py3k else 'func_closure'
        while hasattr(func, closure_attr) and getattr(func, closure_attr):
            attributes = getattr(func, closure_attr)
            func = attributes[0].cell_contents

            # in case of decorators with multiple arguments
            if not isinstance(func, FunctionType):
                # pick first FunctionType instance from multiple arguments
                func = filter(lambda x: isinstance(x, FunctionType),
                              map(lambda x: x.cell_contents, attributes))
                func = list(func)[0]  # py3 support
        return func

    def get_callback_args(self):
        """ Return a list of argument names the callback (most likely) accepts
            as keyword arguments. If the callback is a decorated function, try
            to recover the original function before inspection. """
        return getargspec(self.get_undecorated_callback())[0]

    def get_config(self, key, default=None):
        """ Lookup a config field and return its value, first checking the
            route.config, then route.app.config."""
        depr(0, 13, "Route.get_config() is deprecated.",
                    "The Route.config property already includes values from the"
                    " application config for missing keys. Access it directly.")
        return self.config.get(key, default)

    def __repr__(self):
        cb = self.get_undecorated_callback()
        return '<%s %s -> %s:%s>' % (self.method, self.rule, cb.__module__, cb.__name__)

###############################################################################
# Application Object ###########################################################
###############################################################################


class Bottle(object):
    """ Each Bottle object represents a single, distinct web application and
        consists of routes, callbacks, plugins, resources and configuration.
        Instances are callable WSGI applications.

        :param catchall: If true (default), handle all exceptions. Turn off to
                         let debugging middleware handle exceptions.
    """

    @lazy_attribute
    def _global_config(cls):
        cfg = ConfigDict()
        cfg.meta_set('catchall', 'validate', bool)
        return cfg

    def __init__(self, **kwargs):
        #: A :class:`ConfigDict` for app specific configuration.
        self.config = self._global_config._make_overlay()
        self.config._add_change_listener(
            functools.partial(self.trigger_hook, 'config'))

        self.config.update({
            "catchall": True
        })

        if kwargs.get('catchall') is False:
            depr(0, 13, "Bottle(catchall) keyword argument.",
                        "The 'catchall' setting is now part of the app "
                        "configuration. Fix: `app.config['catchall'] = False`")
            self.config['catchall'] = False
        if kwargs.get('autojson') is False:
            depr(0, 13, "Bottle(autojson) keyword argument.",
                 "The 'autojson' setting is now part of the app "
                 "configuration. Fix: `app.config['json.enable'] = False`")
            self.config['json.disable'] = True

        self._mounts = []

        #: A :class:`ResourceManager` for application files
        self.resources = ResourceManager()

        self.routes = []  # List of installed :class:`Route` instances.
        self.router = Router()  # Maps requests to :class:`Route` instances.
        self.error_handler = {}

        # Core plugins
        self.plugins = []  # List of installed plugins.
        self.install(JSONPlugin())
        self.install(TemplatePlugin())

    #: If true, most exceptions are caught and returned as :exc:`HTTPError`
    catchall = DictProperty('config', 'catchall')

    __hook_names = 'before_request', 'after_request', 'app_reset', 'config'
    __hook_reversed = {'after_request'}

    @cached_property
    def _hooks(self):
        return dict((name, []) for name in self.__hook_names)

    def add_hook(self, name, func):
        """ Attach a callback to a hook. Three hooks are currently implemented:

            before_request
                Executed once before each request. The request context is
                available, but no routing has happened yet.
            after_request
                Executed once after each request regardless of its outcome.
            app_reset
                Called whenever :meth:`Bottle.reset` is called.
        """
        if name in self.__hook_reversed:
            self._hooks[name].insert(0, func)
        else:
            self._hooks[name].append(func)

    def remove_hook(self, name, func):
        """ Remove a callback from a hook. """
        if name in self._hooks and func in self._hooks[name]:
            self._hooks[name].remove(func)
            return True

    def trigger_hook(self, __name, *args, **kwargs):
        """ Trigger a hook and return a list of results. """
        return [hook(*args, **kwargs) for hook in self._hooks[__name][:]]

    def hook(self, name):
        """ Return a decorator that attaches a callback to a hook. See
            :meth:`add_hook` for details."""

        def decorator(func):
            self.add_hook(name, func)
            return func

        return decorator

    def _mount_wsgi(self, prefix, app, **options):
        segments = [p for p in prefix.split('/') if p]
        if not segments:
            raise ValueError('WSGI applications cannot be mounted to "/".')
        path_depth = len(segments)

        def mountpoint_wrapper():
            try:
                request.path_shift(path_depth)
                rs = HTTPResponse([])

                def start_response(status, headerlist, exc_info=None):
                    if exc_info:
                        _raise(*exc_info)
                    if py3k:
                        # Errors here mean that the mounted WSGI app did not
                        # follow PEP-3333 (which requires latin1) or used a
                        # pre-encoding other than utf8 :/
                        status = status.encode('latin1').decode('utf8')
                        headerlist = [(k, v.encode('latin1').decode('utf8'))
                                      for (k, v) in headerlist]
                    rs.status = status
                    for name, value in headerlist:
                        rs.add_header(name, value)
                    return rs.body.append

                body = app(request.environ, start_response)
                rs.body = itertools.chain(rs.body, body) if rs.body else body
                return rs
            finally:
                request.path_shift(-path_depth)

        options.setdefault('skip', True)
        options.setdefault('method', 'PROXY')
        options.setdefault('mountpoint', {'prefix': prefix, 'target': app})
        options['callback'] = mountpoint_wrapper

        self.route('/%s/<:re:.*>' % '/'.join(segments), **options)
        if not prefix.endswith('/'):
            self.route('/' + '/'.join(segments), **options)

    def _mount_app(self, prefix, app, **options):
        if app in self._mounts or '_mount.app' in app.config:
            depr(0, 13, "Application mounted multiple times. Falling back to WSGI mount.",
                 "Clone application before mounting to a different location.")
            return self._mount_wsgi(prefix, app, **options)

        if options:
            depr(0, 13, "Unsupported mount options. Falling back to WSGI mount.",
                 "Do not specify any route options when mounting bottle application.")
            return self._mount_wsgi(prefix, app, **options)

        if not prefix.endswith("/"):
            depr(0, 13, "Prefix must end in '/'. Falling back to WSGI mount.",
                 "Consider adding an explicit redirect from '/prefix' to '/prefix/' in the parent application.")
            return self._mount_wsgi(prefix, app, **options)

        self._mounts.append(app)
        app.config['_mount.prefix'] = prefix
        app.config['_mount.app'] = self
        for route in app.routes:
            route.rule = prefix + route.rule.lstrip('/')
            self.add_route(route)

    def mount(self, prefix, app, **options):
        """ Mount an application (:class:`Bottle` or plain WSGI) to a specific
            URL prefix. Example::

                parent_app.mount('/prefix/', child_app)

            :param prefix: path prefix or `mount-point`.
            :param app: an instance of :class:`Bottle` or a WSGI application.

            Plugins from the parent application are not applied to the routes
            of the mounted child application. If you need plugins in the child
            application, install them separately.

            While it is possible to use path wildcards within the prefix path
            (:class:`Bottle` childs only), it is highly discouraged.

            The prefix path must end with a slash. If you want to access the
            root of the child application via `/prefix` in addition to
            `/prefix/`, consider adding a route with a 307 redirect to the
            parent application.
        """

        if not prefix.startswith('/'):
            raise ValueError("Prefix must start with '/'")

        if isinstance(app, Bottle):
            return self._mount_app(prefix, app, **options)
        else:
            return self._mount_wsgi(prefix, app, **options)

    def merge(self, routes):
        """ Merge the routes of another :class:`Bottle` application or a list of
            :class:`Route` objects into this application. The routes keep their
            'owner', meaning that the :data:`Route.app` attribute is not
            changed. """
        if isinstance(routes, Bottle):
            routes = routes.routes
        for route in routes:
            self.add_route(route)

    def install(self, plugin):
        """ Add a plugin to the list of plugins and prepare it for being
            applied to all routes of this application. A plugin may be a simple
            decorator or an object that implements the :class:`Plugin` API.
        """
        if hasattr(plugin, 'setup'): plugin.setup(self)
        if not callable(plugin) and not hasattr(plugin, 'apply'):
            raise TypeError("Plugins must be callable or implement .apply()")
        self.plugins.append(plugin)
        self.reset()
        return plugin

    def uninstall(self, plugin):
        """ Uninstall plugins. Pass an instance to remove a specific plugin, a type
            object to remove all plugins that match that type, a string to remove
            all plugins with a matching ``name`` attribute or ``True`` to remove all
            plugins. Return the list of removed plugins. """
        removed, remove = [], plugin
        for i, plugin in list(enumerate(self.plugins))[::-1]:
            if remove is True or remove is plugin or remove is type(plugin) \
            or getattr(plugin, 'name', True) == remove:
                removed.append(plugin)
                del self.plugins[i]
                if hasattr(plugin, 'close'): plugin.close()
        if removed: self.reset()
        return removed

    def reset(self, route=None):
        """ Reset all routes (force plugins to be re-applied) and clear all
            caches. If an ID or route object is given, only that specific route
            is affected. """
        if route is None: routes = self.routes
        elif isinstance(route, Route): routes = [route]
        else: routes = [self.routes[route]]
        for route in routes:
            route.reset()
        if DEBUG:
            for route in routes:
                route.prepare()
        self.trigger_hook('app_reset')

    def close(self):
        """ Close the application and all installed plugins. """
        for plugin in self.plugins:
            if hasattr(plugin, 'close'): plugin.close()

    def run(self, **kwargs):
        """ Calls :func:`run` with the same parameters. """
        run(self, **kwargs)

    def match(self, environ):
        """ Search for a matching route and return a (:class:`Route`, urlargs)
            tuple. The second value is a dictionary with parameters extracted
            from the URL. Raise :exc:`HTTPError` (404/405) on a non-match."""
        return self.router.match(environ)

    def get_url(self, routename, **kargs):
        """ Return a string that matches a named route """
        scriptname = request.environ.get('SCRIPT_NAME', '').strip('/') + '/'
        location = self.router.build(routename, **kargs).lstrip('/')
        return urljoin(urljoin('/', scriptname), location)

    def add_route(self, route):
        """ Add a route object, but do not change the :data:`Route.app`
            attribute."""
        self.routes.append(route)
        self.router.add(route.rule, route.method, route, name=route.name)
        if DEBUG: route.prepare()

    def route(self,
              path=None,
              method='GET',
              callback=None,
              name=None,
              apply=None,
              skip=None, **config):
        """ A decorator to bind a function to a request URL. Example::

                @app.route('/hello/<name>')
                def hello(name):
                    return 'Hello %s' % name

            The ``<name>`` part is a wildcard. See :class:`Router` for syntax
            details.

            :param path: Request path or a list of paths to listen to. If no
              path is specified, it is automatically generated from the
              signature of the function.
            :param method: HTTP method (`GET`, `POST`, `PUT`, ...) or a list of
              methods to listen to. (default: `GET`)
            :param callback: An optional shortcut to avoid the decorator
              syntax. ``route(..., callback=func)`` equals ``route(...)(func)``
            :param name: The name for this route. (default: None)
            :param apply: A decorator or plugin or a list of plugins. These are
              applied to the route callback in addition to installed plugins.
            :param skip: A list of plugins, plugin classes or names. Matching
              plugins are not installed to this route. ``True`` skips all.

            Any additional keyword arguments are stored as route-specific
            configuration and passed to plugins (see :meth:`Plugin.apply`).
        """
        if callable(path): path, callback = None, path
        plugins = makelist(apply)
        skiplist = makelist(skip)

        def decorator(callback):
            if isinstance(callback, basestring): callback = load(callback)
            for rule in makelist(path) or yieldroutes(callback):
                for verb in makelist(method):
                    verb = verb.upper()
                    route = Route(self, rule, verb, callback,
                                  name=name,
                                  plugins=plugins,
                                  skiplist=skiplist, **config)
                    self.add_route(route)
            return callback

        return decorator(callback) if callback else decorator

    def get(self, path=None, method='GET', **options):
        """ Equals :meth:`route`. """
        return self.route(path, method, **options)

    def post(self, path=None, method='POST', **options):
        """ Equals :meth:`route` with a ``POST`` method parameter. """
        return self.route(path, method, **options)

    def put(self, path=None, method='PUT', **options):
        """ Equals :meth:`route` with a ``PUT`` method parameter. """
        return self.route(path, method, **options)

    def delete(self, path=None, method='DELETE', **options):
        """ Equals :meth:`route` with a ``DELETE`` method parameter. """
        return self.route(path, method, **options)

    def patch(self, path=None, method='PATCH', **options):
        """ Equals :meth:`route` with a ``PATCH`` method parameter. """
        return self.route(path, method, **options)

    def error(self, code=500, callback=None):
        """ Register an output handler for a HTTP error code. Can
            be used as a decorator or called directly ::

                def error_handler_500(error):
                    return 'error_handler_500'

                app.error(code=500, callback=error_handler_500)

                @app.error(404)
                def error_handler_404(error):
                    return 'error_handler_404'

        """

        def decorator(callback):
            if isinstance(callback, basestring): callback = load(callback)
            self.error_handler[int(code)] = callback
            return callback

        return decorator(callback) if callback else decorator

    def default_error_handler(self, res):
        return tob(template(ERROR_PAGE_TEMPLATE, e=res, template_settings=dict(name='__ERROR_PAGE_TEMPLATE')))

    def _handle(self, environ):
        path = environ['bottle.raw_path'] = environ['PATH_INFO']
        if py3k:
            environ['PATH_INFO'] = path.encode('latin1').decode('utf8', 'ignore')

        environ['bottle.app'] = self
        request.bind(environ)
        response.bind()

        try:
            while True: # Remove in 0.14 together with RouteReset
                out = None
                try:
                    self.trigger_hook('before_request')
                    route, args = self.router.match(environ)
                    environ['route.handle'] = route
                    environ['bottle.route'] = route
                    environ['route.url_args'] = args
                    out = route.call(**args)
                    break
                except HTTPResponse as E:
                    out = E
                    break
                except RouteReset:
                    depr(0, 13, "RouteReset exception deprecated",
                                "Call route.call() after route.reset() and "
                                "return the result.")
                    route.reset()
                    continue
                finally:
                    if isinstance(out, HTTPResponse):
                        out.apply(response)
                    try:
                        self.trigger_hook('after_request')
                    except HTTPResponse as E:
                        out = E
                        out.apply(response)
        except (KeyboardInterrupt, SystemExit, MemoryError):
            raise
        except Exception as E:
            if not self.catchall: raise
            stacktrace = format_exc()
            environ['wsgi.errors'].write(stacktrace)
            environ['wsgi.errors'].flush()
            environ['bottle.exc_info'] = sys.exc_info()
            out = HTTPError(500, "Internal Server Error", E, stacktrace)
            out.apply(response)

        return out

    def _cast(self, out, peek=None):
        """ Try to convert the parameter into something WSGI compatible and set
        correct HTTP headers when possible.
        Support: False, str, unicode, dict, HTTPResponse, HTTPError, file-like,
        iterable of strings and iterable of unicodes
        """

        # Empty output is done here
        if not out:
            if 'Content-Length' not in response:
                response['Content-Length'] = 0
            return []
        # Join lists of byte or unicode strings. Mixed lists are NOT supported
        if isinstance(out, (tuple, list))\
        and isinstance(out[0], (bytes, unicode)):
            out = out[0][0:0].join(out)  # b'abc'[0:0] -> b''
        # Encode unicode strings
        if isinstance(out, unicode):
            out = out.encode(response.charset)
        # Byte Strings are just returned
        if isinstance(out, bytes):
            if 'Content-Length' not in response:
                response['Content-Length'] = len(out)
            return [out]
        # HTTPError or HTTPException (recursive, because they may wrap anything)
        # TODO: Handle these explicitly in handle() or make them iterable.
        if isinstance(out, HTTPError):
            out.apply(response)
            out = self.error_handler.get(out.status_code,
                                         self.default_error_handler)(out)
            return self._cast(out)
        if isinstance(out, HTTPResponse):
            out.apply(response)
            return self._cast(out.body)

        # File-like objects.
        if hasattr(out, 'read'):
            if 'wsgi.file_wrapper' in request.environ:
                return request.environ['wsgi.file_wrapper'](out)
            elif hasattr(out, 'close') or not hasattr(out, '__iter__'):
                return WSGIFileWrapper(out)

        # Handle Iterables. We peek into them to detect their inner type.
        try:
            iout = iter(out)
            first = next(iout)
            while not first:
                first = next(iout)
        except StopIteration:
            return self._cast('')
        except HTTPResponse as E:
            first = E
        except (KeyboardInterrupt, SystemExit, MemoryError):
            raise
        except Exception as error:
            if not self.catchall: raise
            first = HTTPError(500, 'Unhandled exception', error, format_exc())

        # These are the inner types allowed in iterator or generator objects.
        if isinstance(first, HTTPResponse):
            return self._cast(first)
        elif isinstance(first, bytes):
            new_iter = itertools.chain([first], iout)
        elif isinstance(first, unicode):
            encoder = lambda x: x.encode(response.charset)
            new_iter = imap(encoder, itertools.chain([first], iout))
        else:
            msg = 'Unsupported response type: %s' % type(first)
            return self._cast(HTTPError(500, msg))
        if hasattr(out, 'close'):
            new_iter = _closeiter(new_iter, out.close)
        return new_iter

    def wsgi(self, environ, start_response):
        """ The bottle WSGI-interface. """
        try:
            out = self._cast(self._handle(environ))
            # rfc2616 section 4.3
            if response._status_code in (100, 101, 204, 304)\
            or environ['REQUEST_METHOD'] == 'HEAD':
                if hasattr(out, 'close'): out.close()
                out = []
            exc_info = environ.get('bottle.exc_info')
            if exc_info is not None:
                del environ['bottle.exc_info']
            start_response(response._wsgi_status_line(), response.headerlist, exc_info)
            return out
        except (KeyboardInterrupt, SystemExit, MemoryError):
            raise
        except Exception as E:
            if not self.catchall: raise
            err = '<h1>Critical error while processing request: %s</h1>' \
                  % html_escape(environ.get('PATH_INFO', '/'))
            if DEBUG:
                err += '<h2>Error:</h2>\n<pre>\n%s\n</pre>\n' \
                       '<h2>Traceback:</h2>\n<pre>\n%s\n</pre>\n' \
                       % (html_escape(repr(E)), html_escape(format_exc()))
            environ['wsgi.errors'].write(err)
            environ['wsgi.errors'].flush()
            headers = [('Content-Type', 'text/html; charset=UTF-8')]
            start_response('500 INTERNAL SERVER ERROR', headers, sys.exc_info())
            return [tob(err)]

    def __call__(self, environ, start_response):
        """ Each instance of :class:'Bottle' is a WSGI application. """
        return self.wsgi(environ, start_response)

    def __enter__(self):
        """ Use this application as default for all module-level shortcuts. """
        default_app.push(self)
        return self

    def __exit__(self, exc_type, exc_value, traceback):
        default_app.pop()

    def __setattr__(self, name, value):
        if name in self.__dict__:
            raise AttributeError("Attribute %s already defined. Plugin conflict?" % name)
        self.__dict__[name] = value


###############################################################################
# HTTP and WSGI Tools ##########################################################
###############################################################################


class BaseRequest(object):
    """ A wrapper for WSGI environment dictionaries that adds a lot of
        convenient access methods and properties. Most of them are read-only.

        Adding new attributes to a request actually adds them to the environ
        dictionary (as 'bottle.request.ext.<name>'). This is the recommended
        way to store and access request-specific data.
    """

    __slots__ = ('environ', )

    #: Maximum size of memory buffer for :attr:`body` in bytes.
    MEMFILE_MAX = 102400

    def __init__(self, environ=None):
        """ Wrap a WSGI environ dictionary. """
        #: The wrapped WSGI environ dictionary. This is the only real attribute.
        #: All other attributes actually are read-only properties.
        self.environ = {} if environ is None else environ
        self.environ['bottle.request'] = self

    @DictProperty('environ', 'bottle.app', read_only=True)
    def app(self):
        """ Bottle application handling this request. """
        raise RuntimeError('This request is not connected to an application.')

    @DictProperty('environ', 'bottle.route', read_only=True)
    def route(self):
        """ The bottle :class:`Route` object that matches this request. """
        raise RuntimeError('This request is not connected to a route.')

    @DictProperty('environ', 'route.url_args', read_only=True)
    def url_args(self):
        """ The arguments extracted from the URL. """
        raise RuntimeError('This request is not connected to a route.')

    @property
    def path(self):
        """ The value of ``PATH_INFO`` with exactly one prefixed slash (to fix
            broken clients and avoid the "empty path" edge case). """
        return '/' + self.environ.get('PATH_INFO', '').lstrip('/')

    @property
    def method(self):
        """ The ``REQUEST_METHOD`` value as an uppercase string. """
        return self.environ.get('REQUEST_METHOD', 'GET').upper()

    @DictProperty('environ', 'bottle.request.headers', read_only=True)
    def headers(self):
        """ A :class:`WSGIHeaderDict` that provides case-insensitive access to
            HTTP request headers. """
        return WSGIHeaderDict(self.environ)

    def get_header(self, name, default=None):
        """ Return the value of a request header, or a given default value. """
        return self.headers.get(name, default)

    @DictProperty('environ', 'bottle.request.cookies', read_only=True)
    def cookies(self):
        """ Cookies parsed into a :class:`FormsDict`. Signed cookies are NOT
            decoded. Use :meth:`get_cookie` if you expect signed cookies. """
        cookies = SimpleCookie(self.environ.get('HTTP_COOKIE', '')).values()
        return FormsDict((c.key, c.value) for c in cookies)

    def get_cookie(self, key, default=None, secret=None, digestmod=hashlib.sha256):
        """ Return the content of a cookie. To read a `Signed Cookie`, the
            `secret` must match the one used to create the cookie (see
            :meth:`BaseResponse.set_cookie`). If anything goes wrong (missing
            cookie or wrong signature), return a default value. """
        value = self.cookies.get(key)
        if secret:
            # See BaseResponse.set_cookie for details on signed cookies.
            if value and value.startswith('!') and '?' in value:
                sig, msg = map(tob, value[1:].split('?', 1))
                hash = hmac.new(tob(secret), msg, digestmod=digestmod).digest()
                if _lscmp(sig, base64.b64encode(hash)):
                    dst = pickle.loads(base64.b64decode(msg))
                    if dst and dst[0] == key:
                        return dst[1]
            return default
        return value or default

    @DictProperty('environ', 'bottle.request.query', read_only=True)
    def query(self):
        """ The :attr:`query_string` parsed into a :class:`FormsDict`. These
            values are sometimes called "URL arguments" or "GET parameters", but
            not to be confused with "URL wildcards" as they are provided by the
            :class:`Router`. """
        get = self.environ['bottle.get'] = FormsDict()
        pairs = _parse_qsl(self.environ.get('QUERY_STRING', ''))
        for key, value in pairs:
            get[key] = value
        return get

    @DictProperty('environ', 'bottle.request.forms', read_only=True)
    def forms(self):
        """ Form values parsed from an `url-encoded` or `multipart/form-data`
            encoded POST or PUT request body. The result is returned as a
            :class:`FormsDict`. All keys and values are strings. File uploads
            are stored separately in :attr:`files`. """
        forms = FormsDict()
        forms.recode_unicode = self.POST.recode_unicode
        for name, item in self.POST.allitems():
            if not isinstance(item, FileUpload):
                forms[name] = item
        return forms

    @DictProperty('environ', 'bottle.request.params', read_only=True)
    def params(self):
        """ A :class:`FormsDict` with the combined values of :attr:`query` and
            :attr:`forms`. File uploads are stored in :attr:`files`. """
        params = FormsDict()
        for key, value in self.query.allitems():
            params[key] = value
        for key, value in self.forms.allitems():
            params[key] = value
        return params

    @DictProperty('environ', 'bottle.request.files', read_only=True)
    def files(self):
        """ File uploads parsed from `multipart/form-data` encoded POST or PUT
            request body. The values are instances of :class:`FileUpload`.

        """
        files = FormsDict()
        files.recode_unicode = self.POST.recode_unicode
        for name, item in self.POST.allitems():
            if isinstance(item, FileUpload):
                files[name] = item
        return files

    @DictProperty('environ', 'bottle.request.json', read_only=True)
    def json(self):
        """ If the ``Content-Type`` header is ``application/json`` or
            ``application/json-rpc``, this property holds the parsed content
            of the request body. Only requests smaller than :attr:`MEMFILE_MAX`
            are processed to avoid memory exhaustion.
            Invalid JSON raises a 400 error response.
        """
        ctype = self.environ.get('CONTENT_TYPE', '').lower().split(';')[0]
        if ctype in ('application/json', 'application/json-rpc'):
            b = self._get_body_string(self.MEMFILE_MAX)
            if not b:
                return None
            try:
                return json_loads(b)
            except (ValueError, TypeError):
                raise HTTPError(400, 'Invalid JSON')
        return None

    def _iter_body(self, read, bufsize):
        maxread = max(0, self.content_length)
        while maxread:
            part = read(min(maxread, bufsize))
            if not part: break
            yield part
            maxread -= len(part)

    @staticmethod
    def _iter_chunked(read, bufsize):
        err = HTTPError(400, 'Error while parsing chunked transfer body.')
        rn, sem, bs = tob('\r\n'), tob(';'), tob('')
        while True:
            header = read(1)
            while header[-2:] != rn:
                c = read(1)
                header += c
                if not c: raise err
                if len(header) > bufsize: raise err
            size, _, _ = header.partition(sem)
            try:
                maxread = int(tonat(size.strip()), 16)
            except ValueError:
                raise err
            if maxread == 0: break
            buff = bs
            while maxread > 0:
                if not buff:
                    buff = read(min(maxread, bufsize))
                part, buff = buff[:maxread], buff[maxread:]
                if not part: raise err
                yield part
                maxread -= len(part)
            if read(2) != rn:
                raise err

    @DictProperty('environ', 'bottle.request.body', read_only=True)
    def _body(self):
        try:
            read_func = self.environ['wsgi.input'].read
        except KeyError:
            self.environ['wsgi.input'] = BytesIO()
            return self.environ['wsgi.input']
        body_iter = self._iter_chunked if self.chunked else self._iter_body
        body, body_size, is_temp_file = BytesIO(), 0, False
        for part in body_iter(read_func, self.MEMFILE_MAX):
            body.write(part)
            body_size += len(part)
            if not is_temp_file and body_size > self.MEMFILE_MAX:
                body, tmp = TemporaryFile(mode='w+b'), body
                body.write(tmp.getvalue())
                del tmp
                is_temp_file = True
        self.environ['wsgi.input'] = body
        body.seek(0)
        return body

    def _get_body_string(self, maxread):
        """ Read body into a string. Raise HTTPError(413) on requests that are
            to large. """
        if self.content_length > maxread:
            raise HTTPError(413, 'Request entity too large')
        data = self.body.read(maxread + 1)
        if len(data) > maxread:
            raise HTTPError(413, 'Request entity too large')
        return data

    @property
    def body(self):
        """ The HTTP request body as a seek-able file-like object. Depending on
            :attr:`MEMFILE_MAX`, this is either a temporary file or a
            :class:`io.BytesIO` instance. Accessing this property for the first
            time reads and replaces the ``wsgi.input`` environ variable.
            Subsequent accesses just do a `seek(0)` on the file object. """
        self._body.seek(0)
        return self._body

    @property
    def chunked(self):
        """ True if Chunked transfer encoding was. """
        return 'chunked' in self.environ.get(
            'HTTP_TRANSFER_ENCODING', '').lower()

    #: An alias for :attr:`query`.
    GET = query

    @DictProperty('environ', 'bottle.request.post', read_only=True)
    def POST(self):
        """ The values of :attr:`forms` and :attr:`files` combined into a single
            :class:`FormsDict`. Values are either strings (form values) or
            instances of :class:`cgi.FieldStorage` (file uploads).
        """
        post = FormsDict()
        # We default to application/x-www-form-urlencoded for everything that
        # is not multipart and take the fast path (also: 3.1 workaround)
        if not self.content_type.startswith('multipart/'):
            body = tonat(self._get_body_string(self.MEMFILE_MAX), 'latin1')
            for key, value in _parse_qsl(body):
                post[key] = value
            return post

        safe_env = {'QUERY_STRING': ''}  # Build a safe environment for cgi
        for key in ('REQUEST_METHOD', 'CONTENT_TYPE', 'CONTENT_LENGTH'):
            if key in self.environ: safe_env[key] = self.environ[key]
        args = dict(fp=self.body, environ=safe_env, keep_blank_values=True)

        if py3k:
            args['encoding'] = 'utf8'
            post.recode_unicode = False
        data = cgi.FieldStorage(**args)
        self['_cgi.FieldStorage'] = data  #http://bugs.python.org/issue18394
        data = data.list or []
        for item in data:
            if item.filename:
                post[item.name] = FileUpload(item.file, item.name,
                                             item.filename, item.headers)
            else:
                post[item.name] = item.value
        return post

    @property
    def url(self):
        """ The full request URI including hostname and scheme. If your app
            lives behind a reverse proxy or load balancer and you get confusing
            results, make sure that the ``X-Forwarded-Host`` header is set
            correctly. """
        return self.urlparts.geturl()

    @DictProperty('environ', 'bottle.request.urlparts', read_only=True)
    def urlparts(self):
        """ The :attr:`url` string as an :class:`urlparse.SplitResult` tuple.
            The tuple contains (scheme, host, path, query_string and fragment),
            but the fragment is always empty because it is not visible to the
            server. """
        env = self.environ
        http = env.get('HTTP_X_FORWARDED_PROTO') \
             or env.get('wsgi.url_scheme', 'http')
        host = env.get('HTTP_X_FORWARDED_HOST') or env.get('HTTP_HOST')
        if not host:
            # HTTP 1.1 requires a Host-header. This is for HTTP/1.0 clients.
            host = env.get('SERVER_NAME', '127.0.0.1')
            port = env.get('SERVER_PORT')
            if port and port != ('80' if http == 'http' else '443'):
                host += ':' + port
        path = urlquote(self.fullpath)
        return UrlSplitResult(http, host, path, env.get('QUERY_STRING'), '')

    @property
    def fullpath(self):
        """ Request path including :attr:`script_name` (if present). """
        return urljoin(self.script_name, self.path.lstrip('/'))

    @property
    def query_string(self):
        """ The raw :attr:`query` part of the URL (everything in between ``?``
            and ``#``) as a string. """
        return self.environ.get('QUERY_STRING', '')

    @property
    def script_name(self):
        """ The initial portion of the URL's `path` that was removed by a higher
            level (server or routing middleware) before the application was
            called. This script path is returned with leading and tailing
            slashes. """
        script_name = self.environ.get('SCRIPT_NAME', '').strip('/')
        return '/' + script_name + '/' if script_name else '/'

    def path_shift(self, shift=1):
        """ Shift path segments from :attr:`path` to :attr:`script_name` and
            vice versa.

           :param shift: The number of path segments to shift. May be negative
                         to change the shift direction. (default: 1)
        """
        script, path = path_shift(self.environ.get('SCRIPT_NAME', '/'), self.path, shift)
        self['SCRIPT_NAME'], self['PATH_INFO'] = script, path

    @property
    def content_length(self):
        """ The request body length as an integer. The client is responsible to
            set this header. Otherwise, the real length of the body is unknown
            and -1 is returned. In this case, :attr:`body` will be empty. """
        return int(self.environ.get('CONTENT_LENGTH') or -1)

    @property
    def content_type(self):
        """ The Content-Type header as a lowercase-string (default: empty). """
        return self.environ.get('CONTENT_TYPE', '').lower()

    @property
    def is_xhr(self):
        """ True if the request was triggered by a XMLHttpRequest. This only
            works with JavaScript libraries that support the `X-Requested-With`
            header (most of the popular libraries do). """
        requested_with = self.environ.get('HTTP_X_REQUESTED_WITH', '')
        return requested_with.lower() == 'xmlhttprequest'

    @property
    def is_ajax(self):
        """ Alias for :attr:`is_xhr`. "Ajax" is not the right term. """
        return self.is_xhr

    @property
    def auth(self):
        """ HTTP authentication data as a (user, password) tuple. This
            implementation currently supports basic (not digest) authentication
            only. If the authentication happened at a higher level (e.g. in the
            front web-server or a middleware), the password field is None, but
            the user field is looked up from the ``REMOTE_USER`` environ
            variable. On any errors, None is returned. """
        basic = parse_auth(self.environ.get('HTTP_AUTHORIZATION', ''))
        if basic: return basic
        ruser = self.environ.get('REMOTE_USER')
        if ruser: return (ruser, None)
        return None

    @property
    def remote_route(self):
        """ A list of all IPs that were involved in this request, starting with
            the client IP and followed by zero or more proxies. This does only
            work if all proxies support the ```X-Forwarded-For`` header. Note
            that this information can be forged by malicious clients. """
        proxy = self.environ.get('HTTP_X_FORWARDED_FOR')
        if proxy: return [ip.strip() for ip in proxy.split(',')]
        remote = self.environ.get('REMOTE_ADDR')
        return [remote] if remote else []

    @property
    def remote_addr(self):
        """ The client IP as a string. Note that this information can be forged
            by malicious clients. """
        route = self.remote_route
        return route[0] if route else None

    def copy(self):
        """ Return a new :class:`Request` with a shallow :attr:`environ` copy. """
        return Request(self.environ.copy())

    def get(self, value, default=None):
        return self.environ.get(value, default)

    def __getitem__(self, key):
        return self.environ[key]

    def __delitem__(self, key):
        self[key] = ""
        del (self.environ[key])

    def __iter__(self):
        return iter(self.environ)

    def __len__(self):
        return len(self.environ)

    def keys(self):
        return self.environ.keys()

    def __setitem__(self, key, value):
        """ Change an environ value and clear all caches that depend on it. """

        if self.environ.get('bottle.request.readonly'):
            raise KeyError('The environ dictionary is read-only.')

        self.environ[key] = value
        todelete = ()

        if key == 'wsgi.input':
            todelete = ('body', 'forms', 'files', 'params', 'post', 'json')
        elif key == 'QUERY_STRING':
            todelete = ('query', 'params')
        elif key.startswith('HTTP_'):
            todelete = ('headers', 'cookies')

        for key in todelete:
            self.environ.pop('bottle.request.' + key, None)

    def __repr__(self):
        return '<%s: %s %s>' % (self.__class__.__name__, self.method, self.url)

    def __getattr__(self, name):
        """ Search in self.environ for additional user defined attributes. """
        try:
            var = self.environ['bottle.request.ext.%s' % name]
            return var.__get__(self) if hasattr(var, '__get__') else var
        except KeyError:
            raise AttributeError('Attribute %r not defined.' % name)

    def __setattr__(self, name, value):
        if name == 'environ': return object.__setattr__(self, name, value)
        key = 'bottle.request.ext.%s' % name
        if key in self.environ:
            raise AttributeError("Attribute already defined: %s" % name)
        self.environ[key] = value

    def __delattr__(self, name):
        try:
            del self.environ['bottle.request.ext.%s' % name]
        except KeyError:
            raise AttributeError("Attribute not defined: %s" % name)


def _hkey(key):
    if '\n' in key or '\r' in key or '\0' in key:
        raise ValueError("Header names must not contain control characters: %r" % key)
    return key.title().replace('_', '-')


def _hval(value):
    value = tonat(value)
    if '\n' in value or '\r' in value or '\0' in value:
        raise ValueError("Header value must not contain control characters: %r" % value)
    return value


class HeaderProperty(object):
    def __init__(self, name, reader=None, writer=None, default=''):
        self.name, self.default = name, default
        self.reader, self.writer = reader, writer
        self.__doc__ = 'Current value of the %r header.' % name.title()

    def __get__(self, obj, _):
        if obj is None: return self
        value = obj.get_header(self.name, self.default)
        return self.reader(value) if self.reader else value

    def __set__(self, obj, value):
        obj[self.name] = self.writer(value) if self.writer else value

    def __delete__(self, obj):
        del obj[self.name]


class BaseResponse(object):
    """ Storage class for a response body as well as headers and cookies.

        This class does support dict-like case-insensitive item-access to
        headers, but is NOT a dict. Most notably, iterating over a response
        yields parts of the body and not the headers.

        :param body: The response body as one of the supported types.
        :param status: Either an HTTP status code (e.g. 200) or a status line
                       including the reason phrase (e.g. '200 OK').
        :param headers: A dictionary or a list of name-value pairs.

        Additional keyword arguments are added to the list of headers.
        Underscores in the header name are replaced with dashes.
    """

    default_status = 200
    default_content_type = 'text/html; charset=UTF-8'

    # Header blacklist for specific response codes
    # (rfc2616 section 10.2.3 and 10.3.5)
    bad_headers = {
        204: frozenset(('Content-Type', 'Content-Length')),
        304: frozenset(('Allow', 'Content-Encoding', 'Content-Language',
                  'Content-Length', 'Content-Range', 'Content-Type',
                  'Content-Md5', 'Last-Modified'))
    }

    def __init__(self, body='', status=None, headers=None, **more_headers):
        self._cookies = None
        self._headers = {}
        self.body = body
        self.status = status or self.default_status
        if headers:
            if isinstance(headers, dict):
                headers = headers.items()
            for name, value in headers:
                self.add_header(name, value)
        if more_headers:
            for name, value in more_headers.items():
                self.add_header(name, value)

    def copy(self, cls=None):
        """ Returns a copy of self. """
        cls = cls or BaseResponse
        assert issubclass(cls, BaseResponse)
        copy = cls()
        copy.status = self.status
        copy._headers = dict((k, v[:]) for (k, v) in self._headers.items())
        if self._cookies:
            cookies = copy._cookies = SimpleCookie()
            for k,v in self._cookies.items():
                cookies[k] = v.value
                cookies[k].update(v) # also copy cookie attributes
        return copy

    def __iter__(self):
        return iter(self.body)

    def close(self):
        if hasattr(self.body, 'close'):
            self.body.close()

    @property
    def status_line(self):
        """ The HTTP status line as a string (e.g. ``404 Not Found``)."""
        return self._status_line

    @property
    def status_code(self):
        """ The HTTP status code as an integer (e.g. 404)."""
        return self._status_code

    def _set_status(self, status):
        if isinstance(status, int):
            code, status = status, _HTTP_STATUS_LINES.get(status)
        elif ' ' in status:
            if '\n' in status or '\r' in status or '\0' in status:
                raise ValueError('Status line must not include control chars.')
            status = status.strip()
            code = int(status.split()[0])
        else:
            raise ValueError('String status line without a reason phrase.')
        if not 100 <= code <= 999:
            raise ValueError('Status code out of range.')
        self._status_code = code
        self._status_line = str(status or ('%d Unknown' % code))

    def _get_status(self):
        return self._status_line

    status = property(
        _get_status, _set_status, None,
        ''' A writeable property to change the HTTP response status. It accepts
            either a numeric code (100-999) or a string with a custom reason
            phrase (e.g. "404 Brain not found"). Both :data:`status_line` and
            :data:`status_code` are updated accordingly. The return value is
            always a status string. ''')
    del _get_status, _set_status

    @property
    def headers(self):
        """ An instance of :class:`HeaderDict`, a case-insensitive dict-like
            view on the response headers. """
        hdict = HeaderDict()
        hdict.dict = self._headers
        return hdict

    def __contains__(self, name):
        return _hkey(name) in self._headers

    def __delitem__(self, name):
        del self._headers[_hkey(name)]

    def __getitem__(self, name):
        return self._headers[_hkey(name)][-1]

    def __setitem__(self, name, value):
        self._headers[_hkey(name)] = [_hval(value)]

    def get_header(self, name, default=None):
        """ Return the value of a previously defined header. If there is no
            header with that name, return a default value. """
        return self._headers.get(_hkey(name), [default])[-1]

    def set_header(self, name, value):
        """ Create a new response header, replacing any previously defined
            headers with the same name. """
        self._headers[_hkey(name)] = [_hval(value)]

    def add_header(self, name, value):
        """ Add an additional response header, not removing duplicates. """
        self._headers.setdefault(_hkey(name), []).append(_hval(value))

    def iter_headers(self):
        """ Yield (header, value) tuples, skipping headers that are not
            allowed with the current response status code. """
        return self.headerlist

    def _wsgi_status_line(self):
        """ WSGI conform status line (latin1-encodeable) """
        if py3k:
            return self._status_line.encode('utf8').decode('latin1')
        return self._status_line

    @property
    def headerlist(self):
        """ WSGI conform list of (header, value) tuples. """
        out = []
        headers = list(self._headers.items())
        if 'Content-Type' not in self._headers:
            headers.append(('Content-Type', [self.default_content_type]))
        if self._status_code in self.bad_headers:
            bad_headers = self.bad_headers[self._status_code]
            headers = [h for h in headers if h[0] not in bad_headers]
        out += [(name, val) for (name, vals) in headers for val in vals]
        if self._cookies:
            for c in self._cookies.values():
                out.append(('Set-Cookie', _hval(c.OutputString())))
        if py3k:
            out = [(k, v.encode('utf8').decode('latin1')) for (k, v) in out]
        return out

    content_type = HeaderProperty('Content-Type')
    content_length = HeaderProperty('Content-Length', reader=int, default=-1)
    expires = HeaderProperty(
        'Expires',
        reader=lambda x: datetime.utcfromtimestamp(parse_date(x)),
        writer=lambda x: http_date(x))

    @property
    def charset(self, default='UTF-8'):
        """ Return the charset specified in the content-type header (default: utf8). """
        if 'charset=' in self.content_type:
            return self.content_type.split('charset=')[-1].split(';')[0].strip()
        return default

    def set_cookie(self, name, value, secret=None, digestmod=hashlib.sha256, **options):
        """ Create a new cookie or replace an old one. If the `secret` parameter is
            set, create a `Signed Cookie` (described below).

            :param name: the name of the cookie.
            :param value: the value of the cookie.
            :param secret: a signature key required for signed cookies.

            Additionally, this method accepts all RFC 2109 attributes that are
            supported by :class:`cookie.Morsel`, including:

            :param maxage: maximum age in seconds. (default: None)
            :param expires: a datetime object or UNIX timestamp. (default: None)
            :param domain: the domain that is allowed to read the cookie.
              (default: current domain)
            :param path: limits the cookie to a given path (default: current path)
            :param secure: limit the cookie to HTTPS connections (default: off).
            :param httponly: prevents client-side javascript to read this cookie
              (default: off, requires Python 2.6 or newer).
            :param samesite: Control or disable third-party use for this cookie.
              Possible values: `lax`, `strict` or `none` (default).

            If neither `expires` nor `maxage` is set (default), the cookie will
            expire at the end of the browser session (as soon as the browser
            window is closed).

            Signed cookies may store any pickle-able object and are
            cryptographically signed to prevent manipulation. Keep in mind that
            cookies are limited to 4kb in most browsers.

            Warning: Pickle is a potentially dangerous format. If an attacker
            gains access to the secret key, he could forge cookies that execute
            code on server side if unpickled. Using pickle is discouraged and
            support for it will be removed in later versions of bottle.

            Warning: Signed cookies are not encrypted (the client can still see
            the content) and not copy-protected (the client can restore an old
            cookie). The main intention is to make pickling and unpickling
            save, not to store secret information at client side.
        """
        if not self._cookies:
            self._cookies = SimpleCookie()

        # Monkey-patch Cookie lib to support 'SameSite' parameter
        # https://tools.ietf.org/html/draft-west-first-party-cookies-07#section-4.1
        if py < (3, 8, 0):
            Morsel._reserved.setdefault('samesite', 'SameSite')

        if secret:
            if not isinstance(value, basestring):
                depr(0, 13, "Pickling of arbitrary objects into cookies is "
                            "deprecated.", "Only store strings in cookies. "
                            "JSON strings are fine, too.")
            encoded = base64.b64encode(pickle.dumps([name, value], -1))
            sig = base64.b64encode(hmac.new(tob(secret), encoded,
                                            digestmod=digestmod).digest())
            value = touni(tob('!') + sig + tob('?') + encoded)
        elif not isinstance(value, basestring):
            raise TypeError('Secret key required for non-string cookies.')

        # Cookie size plus options must not exceed 4kb.
        if len(name) + len(value) > 3800:
            raise ValueError('Content does not fit into a cookie.')

        self._cookies[name] = value

        for key, value in options.items():
            if key in ('max_age', 'maxage'): # 'maxage' variant added in 0.13
                key = 'max-age'
                if isinstance(value, timedelta):
                    value = value.seconds + value.days * 24 * 3600
            if key == 'expires':
                value = http_date(value)
            if key in ('same_site', 'samesite'): # 'samesite' variant added in 0.13
                key, value = 'samesite', (value or "none").lower()
                if value not in ('lax', 'strict', 'none'):
                    raise CookieError("Invalid value for SameSite")
            if key in ('secure', 'httponly') and not value:
                continue
            self._cookies[name][key] = value

    def delete_cookie(self, key, **kwargs):
        """ Delete a cookie. Be sure to use the same `domain` and `path`
            settings as used to create the cookie. """
        kwargs['max_age'] = -1
        kwargs['expires'] = 0
        self.set_cookie(key, '', **kwargs)

    def __repr__(self):
        out = ''
        for name, value in self.headerlist:
            out += '%s: %s\n' % (name.title(), value.strip())
        return out


def _local_property():
    ls = threading.local()

    def fget(_):
        try:
            return ls.var
        except AttributeError:
            raise RuntimeError("Request context not initialized.")

    def fset(_, value):
        ls.var = value

    def fdel(_):
        del ls.var

    return property(fget, fset, fdel, 'Thread-local property')


class LocalRequest(BaseRequest):
    """ A thread-local subclass of :class:`BaseRequest` with a different
        set of attributes for each thread. There is usually only one global
        instance of this class (:data:`request`). If accessed during a
        request/response cycle, this instance always refers to the *current*
        request (even on a multithreaded server). """
    bind = BaseRequest.__init__
    environ = _local_property()


class LocalResponse(BaseResponse):
    """ A thread-local subclass of :class:`BaseResponse` with a different
        set of attributes for each thread. There is usually only one global
        instance of this class (:data:`response`). Its attributes are used
        to build the HTTP response at the end of the request/response cycle.
    """
    bind = BaseResponse.__init__
    _status_line = _local_property()
    _status_code = _local_property()
    _cookies = _local_property()
    _headers = _local_property()
    body = _local_property()


Request = BaseRequest
Response = BaseResponse


class HTTPResponse(Response, BottleException):
    def __init__(self, body='', status=None, headers=None, **more_headers):
        super(HTTPResponse, self).__init__(body, status, headers, **more_headers)

    def apply(self, other):
        other._status_code = self._status_code
        other._status_line = self._status_line
        other._headers = self._headers
        other._cookies = self._cookies
        other.body = self.body


class HTTPError(HTTPResponse):
    default_status = 500

    def __init__(self,
                 status=None,
                 body=None,
                 exception=None,
                 traceback=None, **more_headers):
        self.exception = exception
        self.traceback = traceback
        super(HTTPError, self).__init__(body, status, **more_headers)

###############################################################################
# Plugins ######################################################################
###############################################################################


class PluginError(BottleException):
    pass


class JSONPlugin(object):
    name = 'json'
    api = 2

    def __init__(self, json_dumps=json_dumps):
        self.json_dumps = json_dumps

    def setup(self, app):
        app.config._define('json.enable', default=True, validate=bool,
                          help="Enable or disable automatic dict->json filter.")
        app.config._define('json.ascii', default=False, validate=bool,
                          help="Use only 7-bit ASCII characters in output.")
        app.config._define('json.indent', default=True, validate=bool,
                          help="Add whitespace to make json more readable.")
        app.config._define('json.dump_func', default=None,
                          help="If defined, use this function to transform"
                               " dict into json. The other options no longer"
                               " apply.")

    def apply(self, callback, route):
        dumps = self.json_dumps
        if not self.json_dumps: return callback

        def wrapper(*a, **ka):
            try:
                rv = callback(*a, **ka)
            except HTTPResponse as resp:
                rv = resp

            if isinstance(rv, dict):
                #Attempt to serialize, raises exception on failure
                json_response = dumps(rv)
                #Set content type only if serialization successful
                response.content_type = 'application/json'
                return json_response
            elif isinstance(rv, HTTPResponse) and isinstance(rv.body, dict):
                rv.body = dumps(rv.body)
                rv.content_type = 'application/json'
            return rv

        return wrapper


class TemplatePlugin(object):
    """ This plugin applies the :func:`view` decorator to all routes with a
        `template` config parameter. If the parameter is a tuple, the second
        element must be a dict with additional options (e.g. `template_engine`)
        or default variables for the template. """
    name = 'template'
    api = 2

    def setup(self, app):
        app.tpl = self

    def apply(self, callback, route):
        conf = route.config.get('template')
        if isinstance(conf, (tuple, list)) and len(conf) == 2:
            return view(conf[0], **conf[1])(callback)
        elif isinstance(conf, str):
            return view(conf)(callback)
        else:
            return callback


#: Not a plugin, but part of the plugin API. TODO: Find a better place.
class _ImportRedirect(object):
    def __init__(self, name, impmask):
        """ Create a virtual package that redirects imports (see PEP 302). """
        self.name = name
        self.impmask = impmask
        self.module = sys.modules.setdefault(name, imp.new_module(name))
        self.module.__dict__.update({
            '__file__': __file__,
            '__path__': [],
            '__all__': [],
            '__loader__': self
        })
        sys.meta_path.append(self)

    def find_module(self, fullname, path=None):
        if '.' not in fullname: return
        packname = fullname.rsplit('.', 1)[0]
        if packname != self.name: return
        return self

    def load_module(self, fullname):
        if fullname in sys.modules: return sys.modules[fullname]
        modname = fullname.rsplit('.', 1)[1]
        realname = self.impmask % modname
        __import__(realname)
        module = sys.modules[fullname] = sys.modules[realname]
        setattr(self.module, modname, module)
        module.__loader__ = self
        return module

###############################################################################
# Common Utilities #############################################################
###############################################################################


class MultiDict(DictMixin):
    """ This dict stores multiple values per key, but behaves exactly like a
        normal dict in that it returns only the newest value for any given key.
        There are special methods available to access the full list of values.
    """

    def __init__(self, *a, **k):
        self.dict = dict((k, [v]) for (k, v) in dict(*a, **k).items())

    def __len__(self):
        return len(self.dict)

    def __iter__(self):
        return iter(self.dict)

    def __contains__(self, key):
        return key in self.dict

    def __delitem__(self, key):
        del self.dict[key]

    def __getitem__(self, key):
        return self.dict[key][-1]

    def __setitem__(self, key, value):
        self.append(key, value)

    def keys(self):
        return self.dict.keys()

    if py3k:

        def values(self):
            return (v[-1] for v in self.dict.values())

        def items(self):
            return ((k, v[-1]) for k, v in self.dict.items())

        def allitems(self):
            return ((k, v) for k, vl in self.dict.items() for v in vl)

        iterkeys = keys
        itervalues = values
        iteritems = items
        iterallitems = allitems

    else:

        def values(self):
            return [v[-1] for v in self.dict.values()]

        def items(self):
            return [(k, v[-1]) for k, v in self.dict.items()]

        def iterkeys(self):
            return self.dict.iterkeys()

        def itervalues(self):
            return (v[-1] for v in self.dict.itervalues())

        def iteritems(self):
            return ((k, v[-1]) for k, v in self.dict.iteritems())

        def iterallitems(self):
            return ((k, v) for k, vl in self.dict.iteritems() for v in vl)

        def allitems(self):
            return [(k, v) for k, vl in self.dict.iteritems() for v in vl]

    def get(self, key, default=None, index=-1, type=None):
        """ Return the most recent value for a key.

            :param default: The default value to be returned if the key is not
                   present or the type conversion fails.
            :param index: An index for the list of available values.
            :param type: If defined, this callable is used to cast the value
                    into a specific type. Exception are suppressed and result in
                    the default value to be returned.
        """
        try:
            val = self.dict[key][index]
            return type(val) if type else val
        except Exception:
            pass
        return default

    def append(self, key, value):
        """ Add a new value to the list of values for this key. """
        self.dict.setdefault(key, []).append(value)

    def replace(self, key, value):
        """ Replace the list of values with a single value. """
        self.dict[key] = [value]

    def getall(self, key):
        """ Return a (possibly empty) list of values for a key. """
        return self.dict.get(key) or []

    #: Aliases for WTForms to mimic other multi-dict APIs (Django)
    getone = get
    getlist = getall


class FormsDict(MultiDict):
    """ This :class:`MultiDict` subclass is used to store request form data.
        Additionally to the normal dict-like item access methods (which return
        unmodified data as native strings), this container also supports
        attribute-like access to its values. Attributes are automatically de-
        or recoded to match :attr:`input_encoding` (default: 'utf8'). Missing
        attributes default to an empty string. """

    #: Encoding used for attribute values.
    input_encoding = 'utf8'
    #: If true (default), unicode strings are first encoded with `latin1`
    #: and then decoded to match :attr:`input_encoding`.
    recode_unicode = True

    def _fix(self, s, encoding=None):
        if isinstance(s, unicode) and self.recode_unicode:  # Python 3 WSGI
            return s.encode('latin1').decode(encoding or self.input_encoding)
        elif isinstance(s, bytes):  # Python 2 WSGI
            return s.decode(encoding or self.input_encoding)
        else:
            return s

    def decode(self, encoding=None):
        """ Returns a copy with all keys and values de- or recoded to match
            :attr:`input_encoding`. Some libraries (e.g. WTForms) want a
            unicode dictionary. """
        copy = FormsDict()
        enc = copy.input_encoding = encoding or self.input_encoding
        copy.recode_unicode = False
        for key, value in self.allitems():
            copy.append(self._fix(key, enc), self._fix(value, enc))
        return copy

    def getunicode(self, name, default=None, encoding=None):
        """ Return the value as a unicode string, or the default. """
        try:
            return self._fix(self[name], encoding)
        except (UnicodeError, KeyError):
            return default

    def __getattr__(self, name, default=unicode()):
        # Without this guard, pickle generates a cryptic TypeError:
        if name.startswith('__') and name.endswith('__'):
            return super(FormsDict, self).__getattr__(name)
        return self.getunicode(name, default=default)

class HeaderDict(MultiDict):
    """ A case-insensitive version of :class:`MultiDict` that defaults to
        replace the old value instead of appending it. """

    def __init__(self, *a, **ka):
        self.dict = {}
        if a or ka: self.update(*a, **ka)

    def __contains__(self, key):
        return _hkey(key) in self.dict

    def __delitem__(self, key):
        del self.dict[_hkey(key)]

    def __getitem__(self, key):
        return self.dict[_hkey(key)][-1]

    def __setitem__(self, key, value):
        self.dict[_hkey(key)] = [_hval(value)]

    def append(self, key, value):
        self.dict.setdefault(_hkey(key), []).append(_hval(value))

    def replace(self, key, value):
        self.dict[_hkey(key)] = [_hval(value)]

    def getall(self, key):
        return self.dict.get(_hkey(key)) or []

    def get(self, key, default=None, index=-1):
        return MultiDict.get(self, _hkey(key), default, index)

    def filter(self, names):
        for name in (_hkey(n) for n in names):
            if name in self.dict:
                del self.dict[name]


class WSGIHeaderDict(DictMixin):
    """ This dict-like class wraps a WSGI environ dict and provides convenient
        access to HTTP_* fields. Keys and values are native strings
        (2.x bytes or 3.x unicode) and keys are case-insensitive. If the WSGI
        environment contains non-native string values, these are de- or encoded
        using a lossless 'latin1' character set.

        The API will remain stable even on changes to the relevant PEPs.
        Currently PEP 333, 444 and 3333 are supported. (PEP 444 is the only one
        that uses non-native strings.)
    """
    #: List of keys that do not have a ``HTTP_`` prefix.
    cgikeys = ('CONTENT_TYPE', 'CONTENT_LENGTH')

    def __init__(self, environ):
        self.environ = environ

    def _ekey(self, key):
        """ Translate header field name to CGI/WSGI environ key. """
        key = key.replace('-', '_').upper()
        if key in self.cgikeys:
            return key
        return 'HTTP_' + key

    def raw(self, key, default=None):
        """ Return the header value as is (may be bytes or unicode). """
        return self.environ.get(self._ekey(key), default)

    def __getitem__(self, key):
        val = self.environ[self._ekey(key)]
        if py3k:
            if isinstance(val, unicode):
                val = val.encode('latin1').decode('utf8')
            else:
                val = val.decode('utf8')
        return val

    def __setitem__(self, key, value):
        raise TypeError("%s is read-only." % self.__class__)

    def __delitem__(self, key):
        raise TypeError("%s is read-only." % self.__class__)

    def __iter__(self):
        for key in self.environ:
            if key[:5] == 'HTTP_':
                yield _hkey(key[5:])
            elif key in self.cgikeys:
                yield _hkey(key)

    def keys(self):
        return [x for x in self]

    def __len__(self):
        return len(self.keys())

    def __contains__(self, key):
        return self._ekey(key) in self.environ

_UNSET = object()

class ConfigDict(dict):
    """ A dict-like configuration storage with additional support for
        namespaces, validators, meta-data, overlays and more.

        This dict-like class is heavily optimized for read access. All read-only
        methods as well as item access should be as fast as the built-in dict.
    """

    __slots__ = ('_meta', '_change_listener', '_overlays', '_virtual_keys', '_source', '__weakref__')

    def __init__(self):
        self._meta = {}
        self._change_listener = []
        #: Weak references of overlays that need to be kept in sync.
        self._overlays = []
        #: Config that is the source for this overlay.
        self._source = None
        #: Keys of values copied from the source (values we do not own)
        self._virtual_keys = set()

    def load_module(self, path, squash=True):
        """Load values from a Python module.

           Example modue ``config.py``::

                DEBUG = True
                SQLITE = {
                    "db": ":memory:"
                }


           >>> c = ConfigDict()
           >>> c.load_module('config')
           {DEBUG: True, 'SQLITE.DB': 'memory'}
           >>> c.load_module("config", False)
           {'DEBUG': True, 'SQLITE': {'DB': 'memory'}}

           :param squash: If true (default), dictionary values are assumed to
                          represent namespaces (see :meth:`load_dict`).
        """
        config_obj = load(path)
        obj = {key: getattr(config_obj, key) for key in dir(config_obj)
               if key.isupper()}

        if squash:
            self.load_dict(obj)
        else:
            self.update(obj)
        return self

    def load_config(self, filename, **options):
        """ Load values from an ``*.ini`` style config file.

            A configuration file consists of sections, each led by a
            ``[section]`` header, followed by key/value entries separated by
            either ``=`` or ``:``. Section names and keys are case-insensitive.
            Leading and trailing whitespace is removed from keys and values.
            Values can be omitted, in which case the key/value delimiter may
            also be left out. Values can also span multiple lines, as long as
            they are indented deeper than the first line of the value. Commands
            are prefixed by ``#`` or ``;`` and may only appear on their own on
            an otherwise empty line.

            Both section and key names may contain dots (``.``) as namespace
            separators. The actual configuration parameter name is constructed
            by joining section name and key name together and converting to
            lower case.

            The special sections ``bottle`` and ``ROOT`` refer to the root
            namespace and the ``DEFAULT`` section defines default values for all
            other sections.

            With Python 3, extended string interpolation is enabled.

            :param filename: The path of a config file, or a list of paths.
            :param options: All keyword parameters are passed to the underlying
                :class:`python:configparser.ConfigParser` constructor call.

        """
        options.setdefault('allow_no_value', True)
        if py3k:
            options.setdefault('interpolation',
                               configparser.ExtendedInterpolation())
        conf = configparser.ConfigParser(**options)
        conf.read(filename)
        for section in conf.sections():
            for key in conf.options(section):
                value = conf.get(section, key)
                if section not in ('bottle', 'ROOT'):
                    key = section + '.' + key
                self[key.lower()] = value
        return self

    def load_dict(self, source, namespace=''):
        """ Load values from a dictionary structure. Nesting can be used to
            represent namespaces.

            >>> c = ConfigDict()
            >>> c.load_dict({'some': {'namespace': {'key': 'value'} } })
            {'some.namespace.key': 'value'}
        """
        for key, value in source.items():
            if isinstance(key, basestring):
                nskey = (namespace + '.' + key).strip('.')
                if isinstance(value, dict):
                    self.load_dict(value, namespace=nskey)
                else:
                    self[nskey] = value
            else:
                raise TypeError('Key has type %r (not a string)' % type(key))
        return self

    def update(self, *a, **ka):
        """ If the first parameter is a string, all keys are prefixed with this
            namespace. Apart from that it works just as the usual dict.update().

            >>> c = ConfigDict()
            >>> c.update('some.namespace', key='value')
        """
        prefix = ''
        if a and isinstance(a[0], basestring):
            prefix = a[0].strip('.') + '.'
            a = a[1:]
        for key, value in dict(*a, **ka).items():
            self[prefix + key] = value

    def setdefault(self, key, value):
        if key not in self:
            self[key] = value
        return self[key]

    def __setitem__(self, key, value):
        if not isinstance(key, basestring):
            raise TypeError('Key has type %r (not a string)' % type(key))

        self._virtual_keys.discard(key)

        value = self.meta_get(key, 'filter', lambda x: x)(value)
        if key in self and self[key] is value:
            return

        self._on_change(key, value)
        dict.__setitem__(self, key, value)

        for overlay in self._iter_overlays():
            overlay._set_virtual(key, value)

    def __delitem__(self, key):
        if key not in self:
            raise KeyError(key)
        if key in self._virtual_keys:
            raise KeyError("Virtual keys cannot be deleted: %s" % key)

        if self._source and key in self._source:
            # Not virtual, but present in source -> Restore virtual value
            dict.__delitem__(self, key)
            self._set_virtual(key, self._source[key])
        else:  # not virtual, not present in source. This is OUR value
            self._on_change(key, None)
            dict.__delitem__(self, key)
            for overlay in self._iter_overlays():
                overlay._delete_virtual(key)

    def _set_virtual(self, key, value):
        """ Recursively set or update virtual keys. Do nothing if non-virtual
            value is present. """
        if key in self and key not in self._virtual_keys:
            return  # Do nothing for non-virtual keys.

        self._virtual_keys.add(key)
        if key in self and self[key] is not value:
            self._on_change(key, value)
        dict.__setitem__(self, key, value)
        for overlay in self._iter_overlays():
            overlay._set_virtual(key, value)

    def _delete_virtual(self, key):
        """ Recursively delete virtual entry. Do nothing if key is not virtual.
        """
        if key not in self._virtual_keys:
            return  # Do nothing for non-virtual keys.

        if key in self:
            self._on_change(key, None)
        dict.__delitem__(self, key)
        self._virtual_keys.discard(key)
        for overlay in self._iter_overlays():
            overlay._delete_virtual(key)

    def _on_change(self, key, value):
        for cb in self._change_listener:
            if cb(self, key, value):
                return True

    def _add_change_listener(self, func):
        self._change_listener.append(func)
        return func

    def meta_get(self, key, metafield, default=None):
        """ Return the value of a meta field for a key. """
        return self._meta.get(key, {}).get(metafield, default)

    def meta_set(self, key, metafield, value):
        """ Set the meta field for a key to a new value. """
        self._meta.setdefault(key, {})[metafield] = value

    def meta_list(self, key):
        """ Return an iterable of meta field names defined for a key. """
        return self._meta.get(key, {}).keys()

    def _define(self, key, default=_UNSET, help=_UNSET, validate=_UNSET):
        """ (Unstable) Shortcut for plugins to define own config parameters. """
        if default is not _UNSET:
            self.setdefault(key, default)
        if help is not _UNSET:
            self.meta_set(key, 'help', help)
        if validate is not _UNSET:
            self.meta_set(key, 'validate', validate)

    def _iter_overlays(self):
        for ref in self._overlays:
            overlay = ref()
            if overlay is not None:
                yield overlay

    def _make_overlay(self):
        """ (Unstable) Create a new overlay that acts like a chained map: Values
            missing in the overlay are copied from the source map. Both maps
            share the same meta entries.

            Entries that were copied from the source are called 'virtual'. You
            can not delete virtual keys, but overwrite them, which turns them
            into non-virtual entries. Setting keys on an overlay never affects
            its source, but may affect any number of child overlays.

            Other than collections.ChainMap or most other implementations, this
            approach does not resolve missing keys on demand, but instead
            actively copies all values from the source to the overlay and keeps
            track of virtual and non-virtual keys internally. This removes any
            lookup-overhead. Read-access is as fast as a build-in dict for both
            virtual and non-virtual keys.

            Changes are propagated recursively and depth-first. A failing
            on-change handler in an overlay stops the propagation of virtual
            values and may result in an partly updated tree. Take extra care
            here and make sure that on-change handlers never fail.

            Used by Route.config
        """
        # Cleanup dead references
        self._overlays[:] = [ref for ref in self._overlays if ref() is not None]

        overlay = ConfigDict()
        overlay._meta = self._meta
        overlay._source = self
        self._overlays.append(weakref.ref(overlay))
        for key in self:
            overlay._set_virtual(key, self[key])
        return overlay




class AppStack(list):
    """ A stack-like list. Calling it returns the head of the stack. """

    def __call__(self):
        """ Return the current default application. """
        return self.default

    def push(self, value=None):
        """ Add a new :class:`Bottle` instance to the stack """
        if not isinstance(value, Bottle):
            value = Bottle()
        self.append(value)
        return value
    new_app = push

    @property
    def default(self):
        try:
            return self[-1]
        except IndexError:
            return self.push()


class WSGIFileWrapper(object):
    def __init__(self, fp, buffer_size=1024 * 64):
        self.fp, self.buffer_size = fp, buffer_size
        for attr in 'fileno', 'close', 'read', 'readlines', 'tell', 'seek':
            if hasattr(fp, attr): setattr(self, attr, getattr(fp, attr))

    def __iter__(self):
        buff, read = self.buffer_size, self.read
        part = read(buff)
        while part:
            yield part
            part = read(buff)


class _closeiter(object):
    """ This only exists to be able to attach a .close method to iterators that
        do not support attribute assignment (most of itertools). """

    def __init__(self, iterator, close=None):
        self.iterator = iterator
        self.close_callbacks = makelist(close)

    def __iter__(self):
        return iter(self.iterator)

    def close(self):
        for func in self.close_callbacks:
            func()


class ResourceManager(object):
    """ This class manages a list of search paths and helps to find and open
        application-bound resources (files).

        :param base: default value for :meth:`add_path` calls.
        :param opener: callable used to open resources.
        :param cachemode: controls which lookups are cached. One of 'all',
                         'found' or 'none'.
    """

    def __init__(self, base='./', opener=open, cachemode='all'):
        self.opener = opener
        self.base = base
        self.cachemode = cachemode

        #: A list of search paths. See :meth:`add_path` for details.
        self.path = []
        #: A cache for resolved paths. ``res.cache.clear()`` clears the cache.
        self.cache = {}

    def add_path(self, path, base=None, index=None, create=False):
        """ Add a new path to the list of search paths. Return False if the
            path does not exist.

            :param path: The new search path. Relative paths are turned into
                an absolute and normalized form. If the path looks like a file
                (not ending in `/`), the filename is stripped off.
            :param base: Path used to absolutize relative search paths.
                Defaults to :attr:`base` which defaults to ``os.getcwd()``.
            :param index: Position within the list of search paths. Defaults
                to last index (appends to the list).

            The `base` parameter makes it easy to reference files installed
            along with a python module or package::

                res.add_path('./resources/', __file__)
        """
        base = os.path.abspath(os.path.dirname(base or self.base))
        path = os.path.abspath(os.path.join(base, os.path.dirname(path)))
        path += os.sep
        if path in self.path:
            self.path.remove(path)
        if create and not os.path.isdir(path):
            os.makedirs(path)
        if index is None:
            self.path.append(path)
        else:
            self.path.insert(index, path)
        self.cache.clear()
        return os.path.exists(path)

    def __iter__(self):
        """ Iterate over all existing files in all registered paths. """
        search = self.path[:]
        while search:
            path = search.pop()
            if not os.path.isdir(path): continue
            for name in os.listdir(path):
                full = os.path.join(path, name)
                if os.path.isdir(full): search.append(full)
                else: yield full

    def lookup(self, name):
        """ Search for a resource and return an absolute file path, or `None`.

            The :attr:`path` list is searched in order. The first match is
            returned. Symlinks are followed. The result is cached to speed up
            future lookups. """
        if name not in self.cache or DEBUG:
            for path in self.path:
                fpath = os.path.join(path, name)
                if os.path.isfile(fpath):
                    if self.cachemode in ('all', 'found'):
                        self.cache[name] = fpath
                    return fpath
            if self.cachemode == 'all':
                self.cache[name] = None
        return self.cache[name]

    def open(self, name, mode='r', *args, **kwargs):
        """ Find a resource and return a file object, or raise IOError. """
        fname = self.lookup(name)
        if not fname: raise IOError("Resource %r not found." % name)
        return self.opener(fname, mode=mode, *args, **kwargs)


class FileUpload(object):
    def __init__(self, fileobj, name, filename, headers=None):
        """ Wrapper for file uploads. """
        #: Open file(-like) object (BytesIO buffer or temporary file)
        self.file = fileobj
        #: Name of the upload form field
        self.name = name
        #: Raw filename as sent by the client (may contain unsafe characters)
        self.raw_filename = filename
        #: A :class:`HeaderDict` with additional headers (e.g. content-type)
        self.headers = HeaderDict(headers) if headers else HeaderDict()

    content_type = HeaderProperty('Content-Type')
    content_length = HeaderProperty('Content-Length', reader=int, default=-1)

    def get_header(self, name, default=None):
        """ Return the value of a header within the multipart part. """
        return self.headers.get(name, default)

    @cached_property
    def filename(self):
        """ Name of the file on the client file system, but normalized to ensure
            file system compatibility. An empty filename is returned as 'empty'.

            Only ASCII letters, digits, dashes, underscores and dots are
            allowed in the final filename. Accents are removed, if possible.
            Whitespace is replaced by a single dash. Leading or tailing dots
            or dashes are removed. The filename is limited to 255 characters.
        """
        fname = self.raw_filename
        if not isinstance(fname, unicode):
            fname = fname.decode('utf8', 'ignore')
        fname = normalize('NFKD', fname)
        fname = fname.encode('ASCII', 'ignore').decode('ASCII')
        fname = os.path.basename(fname.replace('\\', os.path.sep))
        fname = re.sub(r'[^a-zA-Z0-9-_.\s]', '', fname).strip()
        fname = re.sub(r'[-\s]+', '-', fname).strip('.-')
        return fname[:255] or 'empty'

    def _copy_file(self, fp, chunk_size=2 ** 16):
        read, write, offset = self.file.read, fp.write, self.file.tell()
        while 1:
            buf = read(chunk_size)
            if not buf: break
            write(buf)
        self.file.seek(offset)

    def save(self, destination, overwrite=False, chunk_size=2 ** 16):
        """ Save file to disk or copy its content to an open file(-like) object.
            If *destination* is a directory, :attr:`filename` is added to the
            path. Existing files are not overwritten by default (IOError).

            :param destination: File path, directory or file(-like) object.
            :param overwrite: If True, replace existing files. (default: False)
            :param chunk_size: Bytes to read at a time. (default: 64kb)
        """
        if isinstance(destination, basestring):  # Except file-likes here
            if os.path.isdir(destination):
                destination = os.path.join(destination, self.filename)
            if not overwrite and os.path.exists(destination):
                raise IOError('File exists.')
            with open(destination, 'wb') as fp:
                self._copy_file(fp, chunk_size)
        else:
            self._copy_file(destination, chunk_size)

###############################################################################
# Application Helper ###########################################################
###############################################################################


def abort(code=500, text='Unknown Error.'):
    """ Aborts execution and causes a HTTP error. """
    raise HTTPError(code, text)


def redirect(url, code=None):
    """ Aborts execution and causes a 303 or 302 redirect, depending on
        the HTTP protocol version. """
    if not code:
        code = 303 if request.get('SERVER_PROTOCOL') == "HTTP/1.1" else 302
    res = response.copy(cls=HTTPResponse)
    res.status = code
    res.body = ""
    res.set_header('Location', urljoin(request.url, url))
    raise res


def _file_iter_range(fp, offset, bytes, maxread=1024 * 1024, close=False):
    """ Yield chunks from a range in a file, optionally closing it at the end.
        No chunk is bigger than maxread. """
    fp.seek(offset)
    while bytes > 0:
        part = fp.read(min(bytes, maxread))
        if not part:
            break
        bytes -= len(part)
        yield part
    if close:
        fp.close()


def static_file(filename, root,
                mimetype=True,
                download=False,
                charset='UTF-8',
                etag=None,
                headers=None):
    """ Open a file in a safe way and return an instance of :exc:`HTTPResponse`
        that can be sent back to the client.

        :param filename: Name or path of the file to send, relative to ``root``.
        :param root: Root path for file lookups. Should be an absolute directory
            path.
        :param mimetype: Provide the content-type header (default: guess from
            file extension)
        :param download: If True, ask the browser to open a `Save as...` dialog
            instead of opening the file with the associated program. You can
            specify a custom filename as a string. If not specified, the
            original filename is used (default: False).
        :param charset: The charset for files with a ``text/*`` mime-type.
            (default: UTF-8)
        :param etag: Provide a pre-computed ETag header. If set to ``False``,
            ETag handling is disabled. (default: auto-generate ETag header)
        :param headers: Additional headers dict to add to the response.

        While checking user input is always a good idea, this function provides
        additional protection against malicious ``filename`` parameters from
        breaking out of the ``root`` directory and leaking sensitive information
        to an attacker.

        Read-protected files or files outside of the ``root`` directory are
        answered with ``403 Access Denied``. Missing files result in a
        ``404 Not Found`` response. Conditional requests (``If-Modified-Since``,
        ``If-None-Match``) are answered with ``304 Not Modified`` whenever
        possible. ``HEAD`` and ``Range`` requests (used by download managers to
        check or continue partial downloads) are also handled automatically.

    """

    root = os.path.join(os.path.abspath(root), '')
    filename = os.path.abspath(os.path.join(root, filename.strip('/\\')))
    headers = headers.copy() if headers else {}

    if not filename.startswith(root):
        return HTTPError(403, "Access denied.")
    if not os.path.exists(filename) or not os.path.isfile(filename):
        return HTTPError(404, "File does not exist.")
    if not os.access(filename, os.R_OK):
        return HTTPError(403, "You do not have permission to access this file.")

    if mimetype is True:
        if download and download is not True:
            mimetype, encoding = mimetypes.guess_type(download)
        else:
            mimetype, encoding = mimetypes.guess_type(filename)
        if encoding:
            headers['Content-Encoding'] = encoding

    if mimetype:
        if (mimetype[:5] == 'text/' or mimetype == 'application/javascript')\
          and charset and 'charset' not in mimetype:
            mimetype += '; charset=%s' % charset
        headers['Content-Type'] = mimetype

    if download:
        download = os.path.basename(filename if download is True else download)
        headers['Content-Disposition'] = 'attachment; filename="%s"' % download

    stats = os.stat(filename)
    headers['Content-Length'] = clen = stats.st_size
    headers['Last-Modified'] = email.utils.formatdate(stats.st_mtime,
                                                      usegmt=True)
    headers['Date'] = email.utils.formatdate(time.time(), usegmt=True)

    getenv = request.environ.get

    if etag is None:
        etag = '%d:%d:%d:%d:%s' % (stats.st_dev, stats.st_ino, stats.st_mtime,
                                   clen, filename)
        etag = hashlib.sha1(tob(etag)).hexdigest()

    if etag:
        headers['ETag'] = etag
        check = getenv('HTTP_IF_NONE_MATCH')
        if check and check == etag:
            return HTTPResponse(status=304, **headers)

    ims = getenv('HTTP_IF_MODIFIED_SINCE')
    if ims:
        ims = parse_date(ims.split(";")[0].strip())
    if ims is not None and ims >= int(stats.st_mtime):
        return HTTPResponse(status=304, **headers)

    body = '' if request.method == 'HEAD' else open(filename, 'rb')

    headers["Accept-Ranges"] = "bytes"
    range_header = getenv('HTTP_RANGE')
    if range_header:
        ranges = list(parse_range_header(range_header, clen))
        if not ranges:
            return HTTPError(416, "Requested Range Not Satisfiable")
        offset, end = ranges[0]
        headers["Content-Range"] = "bytes %d-%d/%d" % (offset, end - 1, clen)
        headers["Content-Length"] = str(end - offset)
        if body: body = _file_iter_range(body, offset, end - offset, close=True)
        return HTTPResponse(body, status=206, **headers)
    return HTTPResponse(body, **headers)

###############################################################################
# HTTP Utilities and MISC (TODO) ###############################################
###############################################################################


def debug(mode=True):
    """ Change the debug level.
    There is only one debug level supported at the moment."""
    global DEBUG
    if mode: warnings.simplefilter('default')
    DEBUG = bool(mode)


def http_date(value):
    if isinstance(value, basestring):
        return value
    if isinstance(value, datetime):
        # aware datetime.datetime is converted to UTC time
        # naive datetime.datetime is treated as UTC time
        value = value.utctimetuple()
    elif isinstance(value, datedate):
        # datetime.date is naive, and is treated as UTC time
        value = value.timetuple()
    if not isinstance(value, (int, float)):
        # convert struct_time in UTC to UNIX timestamp
        value = calendar.timegm(value)
    return email.utils.formatdate(value, usegmt=True)


def parse_date(ims):
    """ Parse rfc1123, rfc850 and asctime timestamps and return UTC epoch. """
    try:
        ts = email.utils.parsedate_tz(ims)
        return calendar.timegm(ts[:8] + (0, )) - (ts[9] or 0)
    except (TypeError, ValueError, IndexError, OverflowError):
        return None


def parse_auth(header):
    """ Parse rfc2617 HTTP authentication header string (basic) and return (user,pass) tuple or None"""
    try:
        method, data = header.split(None, 1)
        if method.lower() == 'basic':
            user, pwd = touni(base64.b64decode(tob(data))).split(':', 1)
            return user, pwd
    except (KeyError, ValueError):
        return None


def parse_range_header(header, maxlen=0):
    """ Yield (start, end) ranges parsed from a HTTP Range header. Skip
        unsatisfiable ranges. The end index is non-inclusive."""
    if not header or header[:6] != 'bytes=': return
    ranges = [r.split('-', 1) for r in header[6:].split(',') if '-' in r]
    for start, end in ranges:
        try:
            if not start:  # bytes=-100    -> last 100 bytes
                start, end = max(0, maxlen - int(end)), maxlen
            elif not end:  # bytes=100-    -> all but the first 99 bytes
                start, end = int(start), maxlen
            else:  # bytes=100-200 -> bytes 100-200 (inclusive)
                start, end = int(start), min(int(end) + 1, maxlen)
            if 0 <= start < end <= maxlen:
                yield start, end
        except ValueError:
            pass


#: Header tokenizer used by _parse_http_header()
_hsplit = re.compile('(?:(?:"((?:[^"\\\\]|\\\\.)*)")|([^;,=]+))([;,=]?)').findall

def _parse_http_header(h):
    """ Parses a typical multi-valued and parametrised HTTP header (e.g. Accept headers) and returns a list of values
        and parameters. For non-standard or broken input, this implementation may return partial results.
    :param h: A header string (e.g. ``text/html,text/plain;q=0.9,*/*;q=0.8``)
    :return: List of (value, params) tuples. The second element is a (possibly empty) dict.
    """
    values = []
    if '"' not in h:  # INFO: Fast path without regexp (~2x faster)
        for value in h.split(','):
            parts = value.split(';')
            values.append((parts[0].strip(), {}))
            for attr in parts[1:]:
                name, value = attr.split('=', 1)
                values[-1][1][name.strip()] = value.strip()
    else:
        lop, key, attrs = ',', None, {}
        for quoted, plain, tok in _hsplit(h):
            value = plain.strip() if plain else quoted.replace('\\"', '"')
            if lop == ',':
                attrs = {}
                values.append((value, attrs))
            elif lop == ';':
                if tok == '=':
                    key = value
                else:
                    attrs[value] = ''
            elif lop == '=' and key:
                attrs[key] = value
                key = None
            lop = tok
    return values


def _parse_qsl(qs):
    r = []
    for pair in qs.split('&'):
        if not pair: continue
        nv = pair.split('=', 1)
        if len(nv) != 2: nv.append('')
        key = urlunquote(nv[0].replace('+', ' '))
        value = urlunquote(nv[1].replace('+', ' '))
        r.append((key, value))
    return r


def _lscmp(a, b):
    """ Compares two strings in a cryptographically safe way:
        Runtime is not affected by length of common prefix. """
    return not sum(0 if x == y else 1
                   for x, y in zip(a, b)) and len(a) == len(b)


def cookie_encode(data, key, digestmod=None):
    """ Encode and sign a pickle-able object. Return a (byte) string """
    depr(0, 13, "cookie_encode() will be removed soon.",
                "Do not use this API directly.")
    digestmod = digestmod or hashlib.sha256
    msg = base64.b64encode(pickle.dumps(data, -1))
    sig = base64.b64encode(hmac.new(tob(key), msg, digestmod=digestmod).digest())
    return tob('!') + sig + tob('?') + msg


def cookie_decode(data, key, digestmod=None):
    """ Verify and decode an encoded string. Return an object or None."""
    depr(0, 13, "cookie_decode() will be removed soon.",
                "Do not use this API directly.")
    data = tob(data)
    if cookie_is_encoded(data):
        sig, msg = data.split(tob('?'), 1)
        digestmod = digestmod or hashlib.sha256
        hashed = hmac.new(tob(key), msg, digestmod=digestmod).digest()
        if _lscmp(sig[1:], base64.b64encode(hashed)):
            return pickle.loads(base64.b64decode(msg))
    return None


def cookie_is_encoded(data):
    """ Return True if the argument looks like a encoded cookie."""
    depr(0, 13, "cookie_is_encoded() will be removed soon.",
                "Do not use this API directly.")
    return bool(data.startswith(tob('!')) and tob('?') in data)


def html_escape(string):
    """ Escape HTML special characters ``&<>`` and quotes ``'"``. """
    return string.replace('&', '&amp;').replace('<', '&lt;').replace('>', '&gt;')\
                 .replace('"', '&quot;').replace("'", '&#039;')


def html_quote(string):
    """ Escape and quote a string to be used as an HTTP attribute."""
    return '"%s"' % html_escape(string).replace('\n', '&#10;')\
                    .replace('\r', '&#13;').replace('\t', '&#9;')


def yieldroutes(func):
    """ Return a generator for routes that match the signature (name, args)
    of the func parameter. This may yield more than one route if the function
    takes optional keyword arguments. The output is best described by example::

        a()         -> '/a'
        b(x, y)     -> '/b/<x>/<y>'
        c(x, y=5)   -> '/c/<x>' and '/c/<x>/<y>'
        d(x=5, y=6) -> '/d' and '/d/<x>' and '/d/<x>/<y>'
    """
    path = '/' + func.__name__.replace('__', '/').lstrip('/')
    spec = getargspec(func)
    argc = len(spec[0]) - len(spec[3] or [])
    path += ('/<%s>' * argc) % tuple(spec[0][:argc])
    yield path
    for arg in spec[0][argc:]:
        path += '/<%s>' % arg
        yield path


def path_shift(script_name, path_info, shift=1):
    """ Shift path fragments from PATH_INFO to SCRIPT_NAME and vice versa.

        :return: The modified paths.
        :param script_name: The SCRIPT_NAME path.
        :param script_name: The PATH_INFO path.
        :param shift: The number of path fragments to shift. May be negative to
          change the shift direction. (default: 1)
    """
    if shift == 0: return script_name, path_info
    pathlist = path_info.strip('/').split('/')
    scriptlist = script_name.strip('/').split('/')
    if pathlist and pathlist[0] == '': pathlist = []
    if scriptlist and scriptlist[0] == '': scriptlist = []
    if 0 < shift <= len(pathlist):
        moved = pathlist[:shift]
        scriptlist = scriptlist + moved
        pathlist = pathlist[shift:]
    elif 0 > shift >= -len(scriptlist):
        moved = scriptlist[shift:]
        pathlist = moved + pathlist
        scriptlist = scriptlist[:shift]
    else:
        empty = 'SCRIPT_NAME' if shift < 0 else 'PATH_INFO'
        raise AssertionError("Cannot shift. Nothing left from %s" % empty)
    new_script_name = '/' + '/'.join(scriptlist)
    new_path_info = '/' + '/'.join(pathlist)
    if path_info.endswith('/') and pathlist: new_path_info += '/'
    return new_script_name, new_path_info


def auth_basic(check, realm="private", text="Access denied"):
    """ Callback decorator to require HTTP auth (basic).
        TODO: Add route(check_auth=...) parameter. """

    def decorator(func):

        @functools.wraps(func)
        def wrapper(*a, **ka):
            user, password = request.auth or (None, None)
            if user is None or not check(user, password):
                err = HTTPError(401, text)
                err.add_header('WWW-Authenticate', 'Basic realm="%s"' % realm)
                return err
            return func(*a, **ka)

        return wrapper

    return decorator

# Shortcuts for common Bottle methods.
# They all refer to the current default application.


def make_default_app_wrapper(name):
    """ Return a callable that relays calls to the current default app. """

    @functools.wraps(getattr(Bottle, name))
    def wrapper(*a, **ka):
        return getattr(app(), name)(*a, **ka)

    return wrapper


route     = make_default_app_wrapper('route')
get       = make_default_app_wrapper('get')
post      = make_default_app_wrapper('post')
put       = make_default_app_wrapper('put')
delete    = make_default_app_wrapper('delete')
patch     = make_default_app_wrapper('patch')
error     = make_default_app_wrapper('error')
mount     = make_default_app_wrapper('mount')
hook      = make_default_app_wrapper('hook')
install   = make_default_app_wrapper('install')
uninstall = make_default_app_wrapper('uninstall')
url       = make_default_app_wrapper('get_url')

###############################################################################
# Server Adapter ###############################################################
###############################################################################

# Before you edit or add a server adapter, please read:
# - https://github.com/bottlepy/bottle/pull/647#issuecomment-60152870
# - https://github.com/bottlepy/bottle/pull/865#issuecomment-242795341

class ServerAdapter(object):
    quiet = False

    def __init__(self, host='127.0.0.1', port=8080, **options):
        self.options = options
        self.host = host
        self.port = int(port)

    def run(self, handler):  # pragma: no cover
        pass

    def __repr__(self):
        args = ', '.join('%s=%s' % (k, repr(v))
                          for k, v in self.options.items())
        return "%s(%s)" % (self.__class__.__name__, args)


class CGIServer(ServerAdapter):
    quiet = True

    def run(self, handler):  # pragma: no cover
        from wsgiref.handlers import CGIHandler

        def fixed_environ(environ, start_response):
            environ.setdefault('PATH_INFO', '')
            return handler(environ, start_response)

        CGIHandler().run(fixed_environ)


class FlupFCGIServer(ServerAdapter):
    def run(self, handler):  # pragma: no cover
        import flup.server.fcgi
        self.options.setdefault('bindAddress', (self.host, self.port))
        flup.server.fcgi.WSGIServer(handler, **self.options).run()


class WSGIRefServer(ServerAdapter):
    def run(self, app):  # pragma: no cover
        from wsgiref.simple_server import make_server
        from wsgiref.simple_server import WSGIRequestHandler, WSGIServer
        import socket

        class FixedHandler(WSGIRequestHandler):
            def address_string(self):  # Prevent reverse DNS lookups please.
                return self.client_address[0]

            def log_request(*args, **kw):
                if not self.quiet:
                    return WSGIRequestHandler.log_request(*args, **kw)

        handler_cls = self.options.get('handler_class', FixedHandler)
        server_cls = self.options.get('server_class', WSGIServer)

        if ':' in self.host:  # Fix wsgiref for IPv6 addresses.
            if getattr(server_cls, 'address_family') == socket.AF_INET:

                class server_cls(server_cls):
                    address_family = socket.AF_INET6

        self.srv = make_server(self.host, self.port, app, server_cls,
                               handler_cls)
        self.port = self.srv.server_port  # update port actual port (0 means random)
        try:
            self.srv.serve_forever()
        except KeyboardInterrupt:
            self.srv.server_close()  # Prevent ResourceWarning: unclosed socket
            raise


class CherryPyServer(ServerAdapter):
    def run(self, handler):  # pragma: no cover
        depr(0, 13, "The wsgi server part of cherrypy was split into a new "
                    "project called 'cheroot'.", "Use the 'cheroot' server "
                    "adapter instead of cherrypy.")
        from cherrypy import wsgiserver # This will fail for CherryPy >= 9

        self.options['bind_addr'] = (self.host, self.port)
        self.options['wsgi_app'] = handler

        certfile = self.options.get('certfile')
        if certfile:
            del self.options['certfile']
        keyfile = self.options.get('keyfile')
        if keyfile:
            del self.options['keyfile']

        server = wsgiserver.CherryPyWSGIServer(**self.options)
        if certfile:
            server.ssl_certificate = certfile
        if keyfile:
            server.ssl_private_key = keyfile

        try:
            server.start()
        finally:
            server.stop()


class CherootServer(ServerAdapter):
    def run(self, handler): # pragma: no cover
        from cheroot import wsgi
        from cheroot.ssl import builtin
        self.options['bind_addr'] = (self.host, self.port)
        self.options['wsgi_app'] = handler
        certfile = self.options.pop('certfile', None)
        keyfile = self.options.pop('keyfile', None)
        chainfile = self.options.pop('chainfile', None)
        server = wsgi.Server(**self.options)
        if certfile and keyfile:
            server.ssl_adapter = builtin.BuiltinSSLAdapter(
                    certfile, keyfile, chainfile)
        try:
            server.start()
        finally:
            server.stop()


class WaitressServer(ServerAdapter):
    def run(self, handler):
        from waitress import serve
        serve(handler, host=self.host, port=self.port, _quiet=self.quiet, **self.options)


class PasteServer(ServerAdapter):
    def run(self, handler):  # pragma: no cover
        from paste import httpserver
        from paste.translogger import TransLogger
        handler = TransLogger(handler, setup_console_handler=(not self.quiet))
        httpserver.serve(handler,
                         host=self.host,
                         port=str(self.port), **self.options)


class MeinheldServer(ServerAdapter):
    def run(self, handler):
        from meinheld import server
        server.listen((self.host, self.port))
        server.run(handler)


class FapwsServer(ServerAdapter):
    """ Extremely fast webserver using libev. See http://www.fapws.org/ """

    def run(self, handler):  # pragma: no cover
        depr(0, 13, "fapws3 is not maintained and support will be dropped.")
        import fapws._evwsgi as evwsgi
        from fapws import base, config
        port = self.port
        if float(config.SERVER_IDENT[-2:]) > 0.4:
            # fapws3 silently changed its API in 0.5
            port = str(port)
        evwsgi.start(self.host, port)
        # fapws3 never releases the GIL. Complain upstream. I tried. No luck.
        if 'BOTTLE_CHILD' in os.environ and not self.quiet:
            _stderr("WARNING: Auto-reloading does not work with Fapws3.")
            _stderr("         (Fapws3 breaks python thread support)")
        evwsgi.set_base_module(base)

        def app(environ, start_response):
            environ['wsgi.multiprocess'] = False
            return handler(environ, start_response)

        evwsgi.wsgi_cb(('', app))
        evwsgi.run()


class TornadoServer(ServerAdapter):
    """ The super hyped asynchronous server by facebook. Untested. """

    def run(self, handler):  # pragma: no cover
        import tornado.wsgi, tornado.httpserver, tornado.ioloop
        container = tornado.wsgi.WSGIContainer(handler)
        server = tornado.httpserver.HTTPServer(container)
        server.listen(port=self.port, address=self.host)
        tornado.ioloop.IOLoop.instance().start()


class AppEngineServer(ServerAdapter):
    """ Adapter for Google App Engine. """
    quiet = True

    def run(self, handler):
        depr(0, 13, "AppEngineServer no longer required",
             "Configure your application directly in your app.yaml")
        from google.appengine.ext.webapp import util
        # A main() function in the handler script enables 'App Caching'.
        # Lets makes sure it is there. This _really_ improves performance.
        module = sys.modules.get('__main__')
        if module and not hasattr(module, 'main'):
            module.main = lambda: util.run_wsgi_app(handler)
        util.run_wsgi_app(handler)


class TwistedServer(ServerAdapter):
    """ Untested. """

    def run(self, handler):
        from twisted.web import server, wsgi
        from twisted.python.threadpool import ThreadPool
        from twisted.internet import reactor
        thread_pool = ThreadPool()
        thread_pool.start()
        reactor.addSystemEventTrigger('after', 'shutdown', thread_pool.stop)
        factory = server.Site(wsgi.WSGIResource(reactor, thread_pool, handler))
        reactor.listenTCP(self.port, factory, interface=self.host)
        if not reactor.running:
            reactor.run()


class DieselServer(ServerAdapter):
    """ Untested. """

    def run(self, handler):
        depr(0, 13, "Diesel is not tested or supported and will be removed.")
        from diesel.protocols.wsgi import WSGIApplication
        app = WSGIApplication(handler, port=self.port)
        app.run()


class GeventServer(ServerAdapter):
    """ Untested. Options:

        * See gevent.wsgi.WSGIServer() documentation for more options.
    """

    def run(self, handler):
        from gevent import pywsgi, local
        if not isinstance(threading.local(), local.local):
            msg = "Bottle requires gevent.monkey.patch_all() (before import)"
            raise RuntimeError(msg)
        if self.quiet:
            self.options['log'] = None
        address = (self.host, self.port)
        server = pywsgi.WSGIServer(address, handler, **self.options)
        if 'BOTTLE_CHILD' in os.environ:
            import signal
            signal.signal(signal.SIGINT, lambda s, f: server.stop())
        server.serve_forever()


class GunicornServer(ServerAdapter):
    """ Untested. See http://gunicorn.org/configure.html for options. """

    def run(self, handler):
        from gunicorn.app.base import BaseApplication

        if self.host.startswith("unix:"):
            config = {'bind': self.host}
        else:
            config = {'bind': "%s:%d" % (self.host, self.port)}

        config.update(self.options)

        class GunicornApplication(BaseApplication):
            def load_config(self):
                for key, value in config.items():
                    self.cfg.set(key, value)

            def load(self):
                return handler

        GunicornApplication().run()


class EventletServer(ServerAdapter):
    """ Untested. Options:

        * `backlog` adjust the eventlet backlog parameter which is the maximum
          number of queued connections. Should be at least 1; the maximum
          value is system-dependent.
        * `family`: (default is 2) socket family, optional. See socket
          documentation for available families.
    """

    def run(self, handler):
        from eventlet import wsgi, listen, patcher
        if not patcher.is_monkey_patched(os):
            msg = "Bottle requires eventlet.monkey_patch() (before import)"
            raise RuntimeError(msg)
        socket_args = {}
        for arg in ('backlog', 'family'):
            try:
                socket_args[arg] = self.options.pop(arg)
            except KeyError:
                pass
        address = (self.host, self.port)
        try:
            wsgi.server(listen(address, **socket_args), handler,
                        log_output=(not self.quiet))
        except TypeError:
            # Fallback, if we have old version of eventlet
            wsgi.server(listen(address), handler)


class BjoernServer(ServerAdapter):
    """ Fast server written in C: https://github.com/jonashaag/bjoern """

    def run(self, handler):
        from bjoern import run
        run(handler, self.host, self.port, reuse_port=True)

class AsyncioServerAdapter(ServerAdapter):
    """ Extend ServerAdapter for adding custom event loop """
    def get_event_loop(self):
        pass

class AiohttpServer(AsyncioServerAdapter):
    """ Asynchronous HTTP client/server framework for asyncio
        https://pypi.python.org/pypi/aiohttp/
        https://pypi.org/project/aiohttp-wsgi/
    """

    def get_event_loop(self):
        import asyncio
        return asyncio.new_event_loop()

    def run(self, handler):
        import asyncio
        from aiohttp_wsgi.wsgi import serve
        self.loop = self.get_event_loop()
        asyncio.set_event_loop(self.loop)

        if 'BOTTLE_CHILD' in os.environ:
            import signal
            signal.signal(signal.SIGINT, lambda s, f: self.loop.stop())

        serve(handler, host=self.host, port=self.port)


class AiohttpUVLoopServer(AiohttpServer):
    """uvloop
       https://github.com/MagicStack/uvloop
    """
    def get_event_loop(self):
        import uvloop
        return uvloop.new_event_loop()

class AutoServer(ServerAdapter):
    """ Untested. """
    adapters = [WaitressServer, PasteServer, TwistedServer, CherryPyServer,
                CherootServer, WSGIRefServer]

    def run(self, handler):
        for sa in self.adapters:
            try:
                return sa(self.host, self.port, **self.options).run(handler)
            except ImportError:
                pass


server_names = {
    'cgi': CGIServer,
    'flup': FlupFCGIServer,
    'wsgiref': WSGIRefServer,
    'waitress': WaitressServer,
    'cherrypy': CherryPyServer,
    'cheroot': CherootServer,
    'paste': PasteServer,
    'fapws3': FapwsServer,
    'tornado': TornadoServer,
    'gae': AppEngineServer,
    'twisted': TwistedServer,
    'diesel': DieselServer,
    'meinheld': MeinheldServer,
    'gunicorn': GunicornServer,
    'eventlet': EventletServer,
    'gevent': GeventServer,
    'bjoern': BjoernServer,
    'aiohttp': AiohttpServer,
    'uvloop': AiohttpUVLoopServer,
    'auto': AutoServer,
}

###############################################################################
# Application Control ##########################################################
###############################################################################


def load(target, **namespace):
    """ Import a module or fetch an object from a module.

        * ``package.module`` returns `module` as a module object.
        * ``pack.mod:name`` returns the module variable `name` from `pack.mod`.
        * ``pack.mod:func()`` calls `pack.mod.func()` and returns the result.

        The last form accepts not only function calls, but any type of
        expression. Keyword arguments passed to this function are available as
        local variables. Example: ``import_string('re:compile(x)', x='[a-z]')``
    """
    module, target = target.split(":", 1) if ':' in target else (target, None)
    if module not in sys.modules: __import__(module)
    if not target: return sys.modules[module]
    if target.isalnum(): return getattr(sys.modules[module], target)
    package_name = module.split('.')[0]
    namespace[package_name] = sys.modules[package_name]
    return eval('%s.%s' % (module, target), namespace)


def load_app(target):
    """ Load a bottle application from a module and make sure that the import
        does not affect the current default application, but returns a separate
        application object. See :func:`load` for the target parameter. """
    global NORUN
    NORUN, nr_old = True, NORUN
    tmp = default_app.push()  # Create a new "default application"
    try:
        rv = load(target)  # Import the target module
        return rv if callable(rv) else tmp
    finally:
        default_app.remove(tmp)  # Remove the temporary added default application
        NORUN = nr_old


_debug = debug


def run(app=None,
        server='wsgiref',
        host='127.0.0.1',
        port=8080,
        interval=1,
        reloader=False,
        quiet=False,
        plugins=None,
        debug=None,
        config=None, **kargs):
    """ Start a server instance. This method blocks until the server terminates.

        :param app: WSGI application or target string supported by
               :func:`load_app`. (default: :func:`default_app`)
        :param server: Server adapter to use. See :data:`server_names` keys
               for valid names or pass a :class:`ServerAdapter` subclass.
               (default: `wsgiref`)
        :param host: Server address to bind to. Pass ``0.0.0.0`` to listens on
               all interfaces including the external one. (default: 127.0.0.1)
        :param port: Server port to bind to. Values below 1024 require root
               privileges. (default: 8080)
        :param reloader: Start auto-reloading server? (default: False)
        :param interval: Auto-reloader interval in seconds (default: 1)
        :param quiet: Suppress output to stdout and stderr? (default: False)
        :param options: Options passed to the server adapter.
     """
    if NORUN: return
    if reloader and not os.environ.get('BOTTLE_CHILD'):
        import subprocess
        lockfile = None
        try:
            fd, lockfile = tempfile.mkstemp(prefix='bottle.', suffix='.lock')
            os.close(fd)  # We only need this file to exist. We never write to it
            while os.path.exists(lockfile):
                args = [sys.executable] + sys.argv
                environ = os.environ.copy()
                environ['BOTTLE_CHILD'] = 'true'
                environ['BOTTLE_LOCKFILE'] = lockfile
                p = subprocess.Popen(args, env=environ)
                while p.poll() is None:  # Busy wait...
                    os.utime(lockfile, None)  # I am alive!
                    time.sleep(interval)
                if p.poll() != 3:
                    if os.path.exists(lockfile): os.unlink(lockfile)
                    sys.exit(p.poll())
        except KeyboardInterrupt:
            pass
        finally:
            if os.path.exists(lockfile):
                os.unlink(lockfile)
        return

    try:
        if debug is not None: _debug(debug)
        app = app or default_app()
        if isinstance(app, basestring):
            app = load_app(app)
        if not callable(app):
            raise ValueError("Application is not callable: %r" % app)

        for plugin in plugins or []:
            if isinstance(plugin, basestring):
                plugin = load(plugin)
            app.install(plugin)

        if config:
            app.config.update(config)

        if server in server_names:
            server = server_names.get(server)
        if isinstance(server, basestring):
            server = load(server)
        if isinstance(server, type):
            server = server(host=host, port=port, **kargs)
        if not isinstance(server, ServerAdapter):
            raise ValueError("Unknown or unsupported server: %r" % server)

        server.quiet = server.quiet or quiet
        if not server.quiet:
            _stderr("Bottle v%s server starting up (using %s)..." %
                    (__version__, repr(server)))
            if server.host.startswith("unix:"):
                _stderr("Listening on %s" % server.host)
            else:
                _stderr("Listening on http://%s:%d/" %
                        (server.host, server.port))
            _stderr("Hit Ctrl-C to quit.\n")

        if reloader:
            lockfile = os.environ.get('BOTTLE_LOCKFILE')
            bgcheck = FileCheckerThread(lockfile, interval)
            with bgcheck:
                server.run(app)
            if bgcheck.status == 'reload':
                sys.exit(3)
        else:
            server.run(app)
    except KeyboardInterrupt:
        pass
    except (SystemExit, MemoryError):
        raise
    except:
        if not reloader: raise
        if not getattr(server, 'quiet', quiet):
            print_exc()
        time.sleep(interval)
        sys.exit(3)


class FileCheckerThread(threading.Thread):
    """ Interrupt main-thread as soon as a changed module file is detected,
        the lockfile gets deleted or gets too old. """

    def __init__(self, lockfile, interval):
        threading.Thread.__init__(self)
        self.daemon = True
        self.lockfile, self.interval = lockfile, interval
        #: Is one of 'reload', 'error' or 'exit'
        self.status = None

    def run(self):
        exists = os.path.exists
        mtime = lambda p: os.stat(p).st_mtime
        files = dict()

        for module in list(sys.modules.values()):
            path = getattr(module, '__file__', '') or ''
            if path[-4:] in ('.pyo', '.pyc'): path = path[:-1]
            if path and exists(path): files[path] = mtime(path)

        while not self.status:
            if not exists(self.lockfile)\
            or mtime(self.lockfile) < time.time() - self.interval - 5:
                self.status = 'error'
                thread.interrupt_main()
            for path, lmtime in list(files.items()):
                if not exists(path) or mtime(path) > lmtime:
                    self.status = 'reload'
                    thread.interrupt_main()
                    break
            time.sleep(self.interval)

    def __enter__(self):
        self.start()

    def __exit__(self, exc_type, *_):
        if not self.status: self.status = 'exit'  # silent exit
        self.join()
        return exc_type is not None and issubclass(exc_type, KeyboardInterrupt)

###############################################################################
# Template Adapters ############################################################
###############################################################################


class TemplateError(BottleException):
    pass


class BaseTemplate(object):
    """ Base class and minimal API for template adapters """
    extensions = ['tpl', 'html', 'thtml', 'stpl']
    settings = {}  #used in prepare()
    defaults = {}  #used in render()

    def __init__(self,
                 source=None,
                 name=None,
                 lookup=None,
                 encoding='utf8', **settings):
        """ Create a new template.
        If the source parameter (str or buffer) is missing, the name argument
        is used to guess a template filename. Subclasses can assume that
        self.source and/or self.filename are set. Both are strings.
        The lookup, encoding and settings parameters are stored as instance
        variables.
        The lookup parameter stores a list containing directory paths.
        The encoding parameter should be used to decode byte strings or files.
        The settings parameter contains a dict for engine-specific settings.
        """
        self.name = name
        self.source = source.read() if hasattr(source, 'read') else source
        self.filename = source.filename if hasattr(source, 'filename') else None
        self.lookup = [os.path.abspath(x) for x in lookup] if lookup else []
        self.encoding = encoding
        self.settings = self.settings.copy()  # Copy from class variable
        self.settings.update(settings)  # Apply
        if not self.source and self.name:
            self.filename = self.search(self.name, self.lookup)
            if not self.filename:
                raise TemplateError('Template %s not found.' % repr(name))
        if not self.source and not self.filename:
            raise TemplateError('No template specified.')
        self.prepare(**self.settings)

    @classmethod
    def search(cls, name, lookup=None):
        """ Search name in all directories specified in lookup.
        First without, then with common extensions. Return first hit. """
        if not lookup:
            raise depr(0, 12, "Empty template lookup path.", "Configure a template lookup path.")

        if os.path.isabs(name):
            raise depr(0, 12, "Use of absolute path for template name.",
                       "Refer to templates with names or paths relative to the lookup path.")

        for spath in lookup:
            spath = os.path.abspath(spath) + os.sep
            fname = os.path.abspath(os.path.join(spath, name))
            if not fname.startswith(spath): continue
            if os.path.isfile(fname): return fname
            for ext in cls.extensions:
                if os.path.isfile('%s.%s' % (fname, ext)):
                    return '%s.%s' % (fname, ext)

    @classmethod
    def global_config(cls, key, *args):
        """ This reads or sets the global settings stored in class.settings. """
        if args:
            cls.settings = cls.settings.copy()  # Make settings local to class
            cls.settings[key] = args[0]
        else:
            return cls.settings[key]

    def prepare(self, **options):
        """ Run preparations (parsing, caching, ...).
        It should be possible to call this again to refresh a template or to
        update settings.
        """
        raise NotImplementedError

    def render(self, *args, **kwargs):
        """ Render the template with the specified local variables and return
        a single byte or unicode string. If it is a byte string, the encoding
        must match self.encoding. This method must be thread-safe!
        Local variables may be provided in dictionaries (args)
        or directly, as keywords (kwargs).
        """
        raise NotImplementedError


class MakoTemplate(BaseTemplate):
    def prepare(self, **options):
        from mako.template import Template
        from mako.lookup import TemplateLookup
        options.update({'input_encoding': self.encoding})
        options.setdefault('format_exceptions', bool(DEBUG))
        lookup = TemplateLookup(directories=self.lookup, **options)
        if self.source:
            self.tpl = Template(self.source, lookup=lookup, **options)
        else:
            self.tpl = Template(uri=self.name,
                                filename=self.filename,
                                lookup=lookup, **options)

    def render(self, *args, **kwargs):
        for dictarg in args:
            kwargs.update(dictarg)
        _defaults = self.defaults.copy()
        _defaults.update(kwargs)
        return self.tpl.render(**_defaults)


class CheetahTemplate(BaseTemplate):
    def prepare(self, **options):
        from Cheetah.Template import Template
        self.context = threading.local()
        self.context.vars = {}
        options['searchList'] = [self.context.vars]
        if self.source:
            self.tpl = Template(source=self.source, **options)
        else:
            self.tpl = Template(file=self.filename, **options)

    def render(self, *args, **kwargs):
        for dictarg in args:
            kwargs.update(dictarg)
        self.context.vars.update(self.defaults)
        self.context.vars.update(kwargs)
        out = str(self.tpl)
        self.context.vars.clear()
        return out


class Jinja2Template(BaseTemplate):
    def prepare(self, filters=None, tests=None, globals={}, **kwargs):
        from jinja2 import Environment, FunctionLoader
        self.env = Environment(loader=FunctionLoader(self.loader), **kwargs)
        if filters: self.env.filters.update(filters)
        if tests: self.env.tests.update(tests)
        if globals: self.env.globals.update(globals)
        if self.source:
            self.tpl = self.env.from_string(self.source)
        else:
            self.tpl = self.env.get_template(self.name)

    def render(self, *args, **kwargs):
        for dictarg in args:
            kwargs.update(dictarg)
        _defaults = self.defaults.copy()
        _defaults.update(kwargs)
        return self.tpl.render(**_defaults)

    def loader(self, name):
        if name == self.filename:
            fname = name
        else:
            fname = self.search(name, self.lookup)
        if not fname: return
        with open(fname, "rb") as f:
            return (f.read().decode(self.encoding), fname, lambda: False)


class SimpleTemplate(BaseTemplate):
    def prepare(self,
                escape_func=html_escape,
                noescape=False,
                syntax=None, **ka):
        self.cache = {}
        enc = self.encoding
        self._str = lambda x: touni(x, enc)
        self._escape = lambda x: escape_func(touni(x, enc))
        self.syntax = syntax
        if noescape:
            self._str, self._escape = self._escape, self._str

    @cached_property
    def co(self):
        return compile(self.code, self.filename or '<string>', 'exec')

    @cached_property
    def code(self):
        source = self.source
        if not source:
            with open(self.filename, 'rb') as f:
                source = f.read()
        try:
            source, encoding = touni(source), 'utf8'
        except UnicodeError:
            raise depr(0, 11, 'Unsupported template encodings.', 'Use utf-8 for templates.')
        parser = StplParser(source, encoding=encoding, syntax=self.syntax)
        code = parser.translate()
        self.encoding = parser.encoding
        return code

    def _rebase(self, _env, _name=None, **kwargs):
        _env['_rebase'] = (_name, kwargs)

    def _include(self, _env, _name=None, **kwargs):
        env = _env.copy()
        env.update(kwargs)
        if _name not in self.cache:
            self.cache[_name] = self.__class__(name=_name, lookup=self.lookup, syntax=self.syntax)
        return self.cache[_name].execute(env['_stdout'], env)

    def execute(self, _stdout, kwargs):
        env = self.defaults.copy()
        env.update(kwargs)
        env.update({
            '_stdout': _stdout,
            '_printlist': _stdout.extend,
            'include': functools.partial(self._include, env),
            'rebase': functools.partial(self._rebase, env),
            '_rebase': None,
            '_str': self._str,
            '_escape': self._escape,
            'get': env.get,
            'setdefault': env.setdefault,
            'defined': env.__contains__
        })
        exec(self.co, env)
        if env.get('_rebase'):
            subtpl, rargs = env.pop('_rebase')
            rargs['base'] = ''.join(_stdout)  #copy stdout
            del _stdout[:]  # clear stdout
            return self._include(env, subtpl, **rargs)
        return env

    def render(self, *args, **kwargs):
        """ Render the template using keyword arguments as local variables. """
        env = {}
        stdout = []
        for dictarg in args:
            env.update(dictarg)
        env.update(kwargs)
        self.execute(stdout, env)
        return ''.join(stdout)


class StplSyntaxError(TemplateError):
    pass


class StplParser(object):
    """ Parser for stpl templates. """
    _re_cache = {}  #: Cache for compiled re patterns

    # This huge pile of voodoo magic splits python code into 8 different tokens.
    # We use the verbose (?x) regex mode to make this more manageable

    _re_tok = r'''(
        [urbURB]*
        (?:  ''(?!')
            |""(?!")
            |'{6}
            |"{6}
            |'(?:[^\\']|\\.)+?'
            |"(?:[^\\"]|\\.)+?"
            |'{3}(?:[^\\]|\\.|\n)+?'{3}
            |"{3}(?:[^\\]|\\.|\n)+?"{3}
        )
    )'''

    _re_inl = _re_tok.replace(r'|\n', '')  # We re-use this string pattern later

    _re_tok += r'''
        # 2: Comments (until end of line, but not the newline itself)
        |(\#.*)

        # 3: Open and close (4) grouping tokens
        |([\[\{\(])
        |([\]\}\)])

        # 5,6: Keywords that start or continue a python block (only start of line)
        |^([\ \t]*(?:if|for|while|with|try|def|class)\b)
        |^([\ \t]*(?:elif|else|except|finally)\b)

        # 7: Our special 'end' keyword (but only if it stands alone)
        |((?:^|;)[\ \t]*end[\ \t]*(?=(?:%(block_close)s[\ \t]*)?\r?$|;|\#))

        # 8: A customizable end-of-code-block template token (only end of line)
        |(%(block_close)s[\ \t]*(?=\r?$))

        # 9: And finally, a single newline. The 10th token is 'everything else'
        |(\r?\n)
    '''

    # Match the start tokens of code areas in a template
    _re_split = r'''(?m)^[ \t]*(\\?)((%(line_start)s)|(%(block_start)s))'''
    # Match inline statements (may contain python strings)
    _re_inl = r'''%%(inline_start)s((?:%s|[^'"\n])*?)%%(inline_end)s''' % _re_inl

    # add the flag in front of the regexp to avoid Deprecation warning (see Issue #949)
    # verbose and dot-matches-newline mode
    _re_tok = '(?mx)' + _re_tok
    _re_inl = '(?mx)' + _re_inl


    default_syntax = '<% %> % {{ }}'

    def __init__(self, source, syntax=None, encoding='utf8'):
        self.source, self.encoding = touni(source, encoding), encoding
        self.set_syntax(syntax or self.default_syntax)
        self.code_buffer, self.text_buffer = [], []
        self.lineno, self.offset = 1, 0
        self.indent, self.indent_mod = 0, 0
        self.paren_depth = 0

    def get_syntax(self):
        """ Tokens as a space separated string (default: <% %> % {{ }}) """
        return self._syntax

    def set_syntax(self, syntax):
        self._syntax = syntax
        self._tokens = syntax.split()
        if syntax not in self._re_cache:
            names = 'block_start block_close line_start inline_start inline_end'
            etokens = map(re.escape, self._tokens)
            pattern_vars = dict(zip(names.split(), etokens))
            patterns = (self._re_split, self._re_tok, self._re_inl)
            patterns = [re.compile(p % pattern_vars) for p in patterns]
            self._re_cache[syntax] = patterns
        self.re_split, self.re_tok, self.re_inl = self._re_cache[syntax]

    syntax = property(get_syntax, set_syntax)

    def translate(self):
        if self.offset: raise RuntimeError('Parser is a one time instance.')
        while True:
            m = self.re_split.search(self.source, pos=self.offset)
            if m:
                text = self.source[self.offset:m.start()]
                self.text_buffer.append(text)
                self.offset = m.end()
                if m.group(1):  # Escape syntax
                    line, sep, _ = self.source[self.offset:].partition('\n')
                    self.text_buffer.append(self.source[m.start():m.start(1)] +
                                            m.group(2) + line + sep)
                    self.offset += len(line + sep)
                    continue
                self.flush_text()
                self.offset += self.read_code(self.source[self.offset:],
                                              multiline=bool(m.group(4)))
            else:
                break
        self.text_buffer.append(self.source[self.offset:])
        self.flush_text()
        return ''.join(self.code_buffer)

    def read_code(self, pysource, multiline):
        code_line, comment = '', ''
        offset = 0
        while True:
            m = self.re_tok.search(pysource, pos=offset)
            if not m:
                code_line += pysource[offset:]
                offset = len(pysource)
                self.write_code(code_line.strip(), comment)
                break
            code_line += pysource[offset:m.start()]
            offset = m.end()
            _str, _com, _po, _pc, _blk1, _blk2, _end, _cend, _nl = m.groups()
            if self.paren_depth > 0 and (_blk1 or _blk2):  # a if b else c
                code_line += _blk1 or _blk2
                continue
            if _str:  # Python string
                code_line += _str
            elif _com:  # Python comment (up to EOL)
                comment = _com
                if multiline and _com.strip().endswith(self._tokens[1]):
                    multiline = False  # Allow end-of-block in comments
            elif _po:  # open parenthesis
                self.paren_depth += 1
                code_line += _po
            elif _pc:  # close parenthesis
                if self.paren_depth > 0:
                    # we could check for matching parentheses here, but it's
                    # easier to leave that to python - just check counts
                    self.paren_depth -= 1
                code_line += _pc
            elif _blk1:  # Start-block keyword (if/for/while/def/try/...)
                code_line = _blk1
                self.indent += 1
                self.indent_mod -= 1
            elif _blk2:  # Continue-block keyword (else/elif/except/...)
                code_line = _blk2
                self.indent_mod -= 1
            elif _cend:  # The end-code-block template token (usually '%>')
                if multiline: multiline = False
                else: code_line += _cend
            elif _end:
                self.indent -= 1
                self.indent_mod += 1
            else:  # \n
                self.write_code(code_line.strip(), comment)
                self.lineno += 1
                code_line, comment, self.indent_mod = '', '', 0
                if not multiline:
                    break

        return offset

    def flush_text(self):
        text = ''.join(self.text_buffer)
        del self.text_buffer[:]
        if not text: return
        parts, pos, nl = [], 0, '\\\n' + '  ' * self.indent
        for m in self.re_inl.finditer(text):
            prefix, pos = text[pos:m.start()], m.end()
            if prefix:
                parts.append(nl.join(map(repr, prefix.splitlines(True))))
            if prefix.endswith('\n'): parts[-1] += nl
            parts.append(self.process_inline(m.group(1).strip()))
        if pos < len(text):
            prefix = text[pos:]
            lines = prefix.splitlines(True)
            if lines[-1].endswith('\\\\\n'): lines[-1] = lines[-1][:-3]
            elif lines[-1].endswith('\\\\\r\n'): lines[-1] = lines[-1][:-4]
            parts.append(nl.join(map(repr, lines)))
        code = '_printlist((%s,))' % ', '.join(parts)
        self.lineno += code.count('\n') + 1
        self.write_code(code)

    @staticmethod
    def process_inline(chunk):
        if chunk[0] == '!': return '_str(%s)' % chunk[1:]
        return '_escape(%s)' % chunk

    def write_code(self, line, comment=''):
        code = '  ' * (self.indent + self.indent_mod)
        code += line.lstrip() + comment + '\n'
        self.code_buffer.append(code)


def template(*args, **kwargs):
    """
    Get a rendered template as a string iterator.
    You can use a name, a filename or a template string as first parameter.
    Template rendering arguments can be passed as dictionaries
    or directly (as keyword arguments).
    """
    tpl = args[0] if args else None
    for dictarg in args[1:]:
        kwargs.update(dictarg)
    adapter = kwargs.pop('template_adapter', SimpleTemplate)
    lookup = kwargs.pop('template_lookup', TEMPLATE_PATH)
    tplid = (id(lookup), tpl)
    if tplid not in TEMPLATES or DEBUG:
        settings = kwargs.pop('template_settings', {})
        if isinstance(tpl, adapter):
            TEMPLATES[tplid] = tpl
            if settings: TEMPLATES[tplid].prepare(**settings)
        elif "\n" in tpl or "{" in tpl or "%" in tpl or '$' in tpl:
            TEMPLATES[tplid] = adapter(source=tpl, lookup=lookup, **settings)
        else:
            TEMPLATES[tplid] = adapter(name=tpl, lookup=lookup, **settings)
    if not TEMPLATES[tplid]:
        abort(500, 'Template (%s) not found' % tpl)
    return TEMPLATES[tplid].render(kwargs)


mako_template = functools.partial(template, template_adapter=MakoTemplate)
cheetah_template = functools.partial(template,
                                     template_adapter=CheetahTemplate)
jinja2_template = functools.partial(template, template_adapter=Jinja2Template)


def view(tpl_name, **defaults):
    """ Decorator: renders a template for a handler.
        The handler can control its behavior like that:

          - return a dict of template vars to fill out the template
          - return something other than a dict and the view decorator will not
            process the template, but return the handler result as is.
            This includes returning a HTTPResponse(dict) to get,
            for instance, JSON with autojson or other castfilters.
    """

    def decorator(func):

        @functools.wraps(func)
        def wrapper(*args, **kwargs):
            result = func(*args, **kwargs)
            if isinstance(result, (dict, DictMixin)):
                tplvars = defaults.copy()
                tplvars.update(result)
                return template(tpl_name, **tplvars)
            elif result is None:
                return template(tpl_name, defaults)
            return result

        return wrapper

    return decorator


mako_view = functools.partial(view, template_adapter=MakoTemplate)
cheetah_view = functools.partial(view, template_adapter=CheetahTemplate)
jinja2_view = functools.partial(view, template_adapter=Jinja2Template)

###############################################################################
# Constants and Globals ########################################################
###############################################################################

TEMPLATE_PATH = ['./', './views/']
TEMPLATES = {}
DEBUG = False
NORUN = False  # If set, run() does nothing. Used by load_app()

#: A dict to map HTTP status codes (e.g. 404) to phrases (e.g. 'Not Found')
HTTP_CODES = httplib.responses.copy()
HTTP_CODES[418] = "I'm a teapot"  # RFC 2324
HTTP_CODES[428] = "Precondition Required"
HTTP_CODES[429] = "Too Many Requests"
HTTP_CODES[431] = "Request Header Fields Too Large"
HTTP_CODES[451] = "Unavailable For Legal Reasons" # RFC 7725
HTTP_CODES[511] = "Network Authentication Required"
_HTTP_STATUS_LINES = dict((k, '%d %s' % (k, v))
                          for (k, v) in HTTP_CODES.items())

#: The default template used for error pages. Override with @error()
ERROR_PAGE_TEMPLATE = """
%%try:
    %%from %s import DEBUG, request
    <!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML 2.0//EN">
    <html>
        <head>
            <title>Error: {{e.status}}</title>
            <style type="text/css">
              html {background-color: #eee; font-family: sans-serif;}
              body {background-color: #fff; border: 1px solid #ddd;
                    padding: 15px; margin: 15px;}
              pre {background-color: #eee; border: 1px solid #ddd; padding: 5px;}
            </style>
        </head>
        <body>
            <h1>Error: {{e.status}}</h1>
            <p>Sorry, the requested URL <tt>{{repr(request.url)}}</tt>
               caused an error:</p>
            <pre>{{e.body}}</pre>
            %%if DEBUG and e.exception:
              <h2>Exception:</h2>
              %%try:
                %%exc = repr(e.exception)
              %%except:
                %%exc = '<unprintable %%s object>' %% type(e.exception).__name__
              %%end
              <pre>{{exc}}</pre>
            %%end
            %%if DEBUG and e.traceback:
              <h2>Traceback:</h2>
              <pre>{{e.traceback}}</pre>
            %%end
        </body>
    </html>
%%except ImportError:
    <b>ImportError:</b> Could not generate the error page. Please add bottle to
    the import path.
%%end
""" % __name__

#: A thread-safe instance of :class:`LocalRequest`. If accessed from within a
#: request callback, this instance always refers to the *current* request
#: (even on a multi-threaded server).
request = LocalRequest()

#: A thread-safe instance of :class:`LocalResponse`. It is used to change the
#: HTTP response for the *current* request.
response = LocalResponse()

#: A thread-safe namespace. Not used by Bottle.
local = threading.local()

# Initialize app stack (create first empty Bottle app now deferred until needed)
# BC: 0.6.4 and needed for run()
apps = app = default_app = AppStack()

#: A virtual package that redirects import statements.
#: Example: ``import bottle.ext.sqlite`` actually imports `bottle_sqlite`.
ext = _ImportRedirect('bottle.ext' if __name__ == '__main__' else
                      __name__ + ".ext", 'bottle_%s').module


def _main(argv):  # pragma: no coverage
    args, parser = _cli_parse(argv)

    def _cli_error(cli_msg):
        parser.print_help()
        _stderr('\nError: %s\n' % cli_msg)
        sys.exit(1)

    if args.version:
        print('Bottle %s' % __version__)
        sys.exit(0)
    if not args.app:
        _cli_error("No application entry point specified.")

    sys.path.insert(0, '.')
    sys.modules.setdefault('bottle', sys.modules['__main__'])

    host, port = (args.bind or 'localhost'), 8080
    if ':' in host and host.rfind(']') < host.rfind(':'):
        host, port = host.rsplit(':', 1)
    host = host.strip('[]')

    config = ConfigDict()

    for cfile in args.conf or []:
        try:
            if cfile.endswith('.json'):
                with open(cfile, 'rb') as fp:
                    config.load_dict(json_loads(fp.read()))
            else:
                config.load_config(cfile)
        except configparser.Error as parse_error:
            _cli_error(parse_error)
        except IOError:
            _cli_error("Unable to read config file %r" % cfile)
        except (UnicodeError, TypeError, ValueError) as error:
            _cli_error("Unable to parse config file %r: %s" % (cfile, error))

    for cval in args.param or []:
        if '=' in cval:
            config.update((cval.split('=', 1),))
        else:
            config[cval] = True

    run(args.app,
        host=host,
        port=int(port),
        server=args.server,
        reloader=args.reload,
        plugins=args.plugin,
        debug=args.debug,
        config=config)


if __name__ == '__main__':  # pragma: no coverage
    _main(sys.argv)