Dynamic response headers

README.md

@@ -63,10 +63,42 @@ This will install `http-server` globally so that it may be run from the command
 
 `-h` or `--help` Print this list and exit.
 
+## Headers
+
+An optional file called `headers.json` may be placed in the root path (as specified by the [path] argument) being
+served.  If this file is present, the contents are used to add headers to the server response.  Request paths can be
+added to the json file with an array of objects that contain information about the headers to add.
+
+The `headers.json` file follows this format:
+```
+{
+  "Path to Match": [
+    {"header": "Name of the header to add", "value": "value of header", "append": true/false},
+    {"header": "Second header on same path", "value": "value of header", "append": true/false}
+  ],
+  "Second Path to match": [
+    {"header": "Name of the header to add", "value": "value of header", "append": true/false}
+  ]
+}
+```
+
+Notes about the `headers.json` file:
+- "Path to match" uses [minimatch](https://www.npmjs.com/package/minimatch) to match to the request.  For example,
+  an entry for `/**` would match all requests.
+- The headers are added in the order they appear in the file.  Unless `append` is set to true, previous values will
+  be overwritten
+- `append` is optional.  If not present, or set to false, a matched header will be overwritten.  If set to true,
+  the value specified will be appended to the existing header value separated by a comma (,) and a space as
+  specified [here](https://tools.ietf.org/html/rfc7230#section-3.2).
+- Headers added with this file will be added/set AFTER headers set by command line arguments.  This will allow you
+  to selectively override/change headers set at http-server startup.
+
+
 ## Magic Files
 
 - `index.html` will be served as the default file to any directory requests.
 - `404.html` will be served if a file is not found. This can be used for Single-Page App (SPA) hosting to serve the entry page.
+- `headers.json` will be read (if present) and used to add headers to the response.
 
 # Development
 

lib/http-server.js

@@ -4,8 +4,10 @@ var fs = require('fs'),
     union = require('union'),
     ecstatic = require('ecstatic'),
     httpProxy = require('http-proxy'),
-    corser = require('corser');
+    corser = require('corser'),
+    minimatch = require('minimatch');
 
+var HEADERS_FILE_NAME = 'headers.json';
 //
 // Remark: backwards compatibility for previous
 // case convention of HTTP
@@ -93,6 +95,26 @@ function HttpServer(options) {
     });
   }
 
+  if (fs.existsSync(this.root + '/' + HEADERS_FILE_NAME)) {
+    console.log('Loading Headers file:', this.root + '/' + HEADERS_FILE_NAME);
+    var headers = JSON.parse(fs.readFileSync(this.root + '/' + HEADERS_FILE_NAME)) || {};
+    var paths = Object.keys(headers);
+    before.push(function (req, res) {
+      paths.forEach(function (p) {
+        if (minimatch(req.url, p, {})) {
+          headers[p].forEach(function (h) {
+            var value = h.value.trim();
+            if (h.hasOwnProperty('append') && h.append) {
+              value = res.getHeader(h.header).trim() + ', ' + value; // Trim .getHeader() as we may not have set it
+            }
+            res.setHeader(h.header, value);
+          });
+        }
+      });
+      res.emit('next');
+    });
+  }
+
   before.push(ecstatic({
     root: this.root,
     cache: this.cache,