#!/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 List::Util qw(first);
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 "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 get_current_workspace {
    my $current = first { $_->{focused} } @{$i3->get_workspaces->recv};
    return $current->{name};
}

if (!defined($workspace) && !defined($output)) {
    $workspace = get_current_workspace();
}

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
    mark
);

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 $workspace || ($workspace =~ /^\d+$/ && $_->{num} 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|number] [--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.

If neither argument is specified, the currently focused workspace will be used.

=head1 OPTIONS

=over

=item B<--workspace=name|number>

Specifies the workspace that should be dumped, e.g. 1. This can either be a
name or the number of a workspace.

=item B<--output=name>

Specifies the output that should be dumped, e.g. LVDS-1.

=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
