i3-save-tree

#!/usr/bin/env perl
# vim:ts=4:sw=4:expandtab
#
# © 2013-2014 Michael Stapelberg
#
# Requires perl ≥ v5.10, AnyEvent::I3 and JSON::XS

use strict;
use warnings qw(FATAL utf8);
use Data::Dumper;
use IPC::Open2;
use POSIX qw(locale_h);
use File::Find;
use File::Basename qw(basename);
use File::Temp qw(tempfile);
use Getopt::Long;
use Pod::Usage;
use AnyEvent::I3;
use JSON::XS;
use List::Util qw(first);
use Encode qw(decode);
use v5.10;
use utf8;
use open ':encoding(UTF-8)';

binmode STDOUT, ':utf8';
binmode STDERR, ':utf8';

my $workspace;
my $output;
my $result = GetOptions(
    'workspace=s' => \$workspace,
    'output=s' => \$output,
    'version' => sub {
        say "i3-save-tree 0.1 © 2013 Michael Stapelberg";
        exit 0;
    },
    'help' => sub {
        pod2usage(-exitval => 0);
    });

die "Could not parse command line options" unless $result;

if (!defined($workspace) && !defined($output)) {
    die "One of --workspace or --output need to be specified";
}

unless (defined($workspace) ^ defined($output)) {
    die "Only one of --workspace or --output can be specified";
}

$workspace = decode('utf-8', $workspace);
$output = decode('utf-8', $output);

my $i3 = i3();
if (!$i3->connect->recv) {
    die "Could not connect to i3";
}

sub filter_containers {
    my ($tree, $pred) = @_;

    $_ = $tree;
    return $tree if $pred->();

    for my $child (@{$tree->{nodes}}, @{$tree->{floating_nodes}}) {
        my $result = filter_containers($child, $pred);
        return $result if defined($result);
    }

    return undef;
}

sub leaf_node {
    my ($tree) = @_;

    return $tree->{type} eq 'con' &&
           @{$tree->{nodes}} == 0 &&
           @{$tree->{floating_nodes}} == 0;
}

my %allowed_keys = map { ($_, 1) } qw(
    type
    fullscreen_mode
    layout
    border
    current_border_width
    floating
    percent
    nodes
    floating_nodes
    name
    geometry
    window_properties
);

sub strip_containers {
    my ($tree) = @_;

    # layout is not relevant for a leaf container
    delete $tree->{layout} if leaf_node($tree);

    # fullscreen_mode conveys no state at all, it can either be 0 or 1 and the
    # default is _always_ 0, so skip noop entries.
    delete $tree->{fullscreen_mode} if $tree->{fullscreen_mode} == 0;

    # names for non-leafs are auto-generated and useful only for i3 debugging
    delete $tree->{name} unless leaf_node($tree);

    delete $tree->{geometry} if zero_rect($tree->{geometry});

    delete $tree->{current_border_width} if $tree->{current_border_width} == -1;

    for my $key (keys %$tree) {
        next if exists($allowed_keys{$key});

        delete $tree->{$key};
    }

    for my $key (qw(nodes floating_nodes)) {
        $tree->{$key} = [ map { strip_containers($_) } @{$tree->{$key}} ];
    }

    return $tree;
}

my $json_xs = JSON::XS->new->pretty(1)->allow_nonref->space_before(0)->canonical(1);

sub zero_rect {
    my ($rect) = @_;
    return $rect->{x} == 0 &&
           $rect->{y} == 0 &&
           $rect->{width} == 0 &&
           $rect->{height} == 0;
}

# Dumps the containers in JSON, but with comments to explain the user what she
# needs to fix.
sub dump_containers {
    my ($tree, $ws, $last) = @_;

    $ws //= "";

    say $ws . '{';

    $ws .= (' ' x 4);

    if (!leaf_node($tree)) {
        my $desc = $tree->{layout} . ' split container';
        if ($tree->{type} ne 'con') {
            $desc = $tree->{type};
        }
        say "$ws// $desc with " . @{$tree->{nodes}} . " children";
    }

    # Turn “window_properties” into “swallows” expressions, but only for leaf
    # nodes. It only makes sense for leaf nodes to swallow anything.
    if (leaf_node($tree)) {
        my $swallows = {};
        for my $property (keys %{$tree->{window_properties}}) {
            $swallows->{$property} = '^' . quotemeta($tree->{window_properties}->{$property}) . '$';
        }
        $tree->{swallows} = [ $swallows ];
    }
    delete $tree->{window_properties};

    my @keys = sort keys %$tree;
    for (0 .. (@keys-1)) {
        my $key = $keys[$_];
        # Those are handled recursively, not printed.
        next if $key eq 'nodes' || $key eq 'floating_nodes';

        # JSON::XS’s encode appends a newline
        chomp(my $val = $json_xs->encode($tree->{$key}));

        # Fix indentation. Keep in mind we are producing output to be
        # read/modified by a human.
        $val =~ s/^/$ws/mg;
        $val =~ s/^\s+//;

        # Comment out all swallows criteria, they are just suggestions.
        if ($key eq 'swallows') {
            $val =~ s,^(\s*)\s{3}",\1// ",gm;
        }

        # Append a comma unless this is the last value.
        # Ugly, but necessary so that we can print all values before recursing.
        my $comma = ($_ == (@keys-1) &&
                     @{$tree->{nodes}} == 0 &&
                     @{$tree->{floating_nodes}} == 0 ? '' : ',');
        say qq#$ws"$key": $val$comma#;
    }

    for my $key (qw(nodes floating_nodes)) {
        my $num = scalar @{$tree->{$key}};
        next if !$num;

        say qq#$ws"$key": [#;
        for (0 .. ($num-1)) {
            dump_containers(
                $tree->{$key}->[$_],
                $ws . (' ' x 4),
                ($_ == ($num-1)));
        }
        say qq#$ws]#;
    }

    $ws =~ s/\s{4}$//;

    say $ws . ($last ? '}' : '},');
}

my $tree = $i3->get_tree->recv;

my $dump;
if (defined($workspace)) {
    $dump = filter_containers($tree, sub {
        $_->{type} eq 'workspace' && $_->{name} eq $workspace
    });
} else {
    $dump = filter_containers($tree, sub {
        $_->{type} eq 'output' && $_->{name} eq $output
    });
    # Get the output’s content container (living beneath dockarea containers).
    $dump = first { $_->{type} eq 'con' } @{$dump->{nodes}};
}

$dump = strip_containers($dump);

say "// vim:ts=4:sw=4:et";
for my $key (qw(nodes floating_nodes)) {
    for (0 .. (@{$dump->{$key}} - 1)) {
        dump_containers($dump->{$key}->[$_], undef, 1);
        # Newlines separate containers so that one can use { and } in vim to
        # jump out of the current container.
        say '';
    }
}

=encoding utf-8

=head1 NAME

    i3-save-tree - save (parts of) the layout tree for restoring

=head1 SYNOPSIS

    i3-save-tree [--workspace=name] [--output=name]

=head1 DESCRIPTION

Dumps a workspace (or an entire output) to stdout. The data is supposed to be
edited a bit by a human, then later fed to i3 via the append_layout command.

The append_layout command will create placeholder windows, arranged in the
layout the input file specifies. Each container should have a swallows
specification. When a window is mapped (made visible on the screen) that
matches the specification, i3 will put it into that place and kill the
placeholder.

=head1 OPTIONS

=over

=item B<--workspace=name>

Specifies the workspace that should be dumped, e.g. 1. Either this or --output
need to be specified.

=item B<--output=name>

Specifies the output that should be dumped, e.g. LVDS-1. Either this or
--workspace need to be specified.

=back

=head1 VERSION

Version 0.1

=head1 AUTHOR

Michael Stapelberg, C<< <michael at i3wm.org> >>

=head1 LICENSE AND COPYRIGHT

Copyright 2013 Michael Stapelberg.

This program is free software; you can redistribute it and/or modify it
under the terms of the BSD license.

=cut