package Local::Desktop;

# graphical desktop management functions
#
# Copyright (C) 2020-2022 Sean Whitton
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or (at
# your option) any later version.
#
# This program is distributed in the hope that it will be useful, but
# WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
# General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.

use 5.028;
use strict;
use warnings;

use Carp;
use JSON;
use File::Find;
use File::LibMagic;
use File::Spec::Functions "rel2abs";
use Exporter "import";
use File::Copy;
use List::Util "first";

our @EXPORT = qw(
  $wmipc wmipc
  fresh_workspace
  compact_workspaces
  select_wallpaper_files
  ensure_resize_for_current_outputs
  resize_for_current_outputs
  pick_random_wallpapers );

`sh -c "command -v i3-msg"`;
our $wmipc = $? == 0 ? "i3-msg" : "swaymsg";
sub wmipc { system "$wmipc -q " . join ", ", @_ }

my $output_re = qr/ ([0-9]+)x([0-9]+)\+([0-9]+)\+([0-9]+) /;

my @all_workspaces = (
    "1",     "2",      "3",      "4",     "5",     "6",
    "7",     "8",      "9",      "10",    "11:F1", "12:F2",
    "13:F3", "14:F4",  "15:F5",  "16:F6", "17:F7", "18:F8",
    "19:F9", "20:F10", "21:F11", "22:F12"
);

=head fresh_workspace($send)

Switch to the next free workspace, if any.  Return the name of that workspace,
or undef if no workspace was available.  If $send, send the current window to
the fresh workspace instead of switching focus there.

=cut

sub fresh_workspace {
    my $next_free_workspace = compact_workspaces(leave_gap => 1);

    if ($next_free_workspace) {
	my @cmds;
	my %opts = @_;

	push @cmds, "move container to workspace $next_free_workspace"
	  if $opts{send};

	# When !$opts{go} we should execute neither of these commands, but we
	# must work around <https://github.com/swaywm/sway/issues/6081>.
	#
	# In the case that !$opts{go}, can use 'C-i S-;' to move any other
	# wanted containers over, before finally going there with 'C-i ;'.
	push @cmds, "workspace $next_free_workspace";
	push @cmds, "workspace back_and_forth" unless $opts{go};

	wmipc @cmds;
    }
    $next_free_workspace
}

=head compact_workspaces(%opts)

Rename workspaces so as to remove gaps in the sequence of workspaces.

If C<$opts{leave_gap}>, ensure there is a gap of one workspace after the
currently focused workspace and return the name of the gap workspace, or just
return undef if there is no space for a gap.

=cut

sub compact_workspaces {
    my %opts       = @_;
    my @workspaces = @{ decode_json `$wmipc -t get_workspaces` };
    @workspaces < @all_workspaces or return;
    my ($current_workspace, $gap_workspace);
    if ($opts{leave_gap}) {
        $_->{focused} and $current_workspace = $_->{name}, last
          for @workspaces
    }

    my ($i, @cmds);
    while (my $next = shift @workspaces) {
        my $workspace = $all_workspaces[$i++];
        $opts{leave_gap}
          and $next->{name} eq $current_workspace
          and $gap_workspace = $all_workspaces[$i++];
        next if $next->{name} eq $workspace;
        my $pair = [$next->{name}, $workspace];
        _wsnum($next->{name}) > _wsnum($workspace)
          ? push @cmds, $pair
          : unshift @cmds, $pair
    }

    wmipc map "rename workspace $_->[0] to $_->[1]", @cmds;

    $opts{leave_gap} and $gap_workspace
}

=head select_wallpaper_files(@files)

Select the first entry of @files as the wallpaper for the first output, the
second entry of @files as the wallpaper for the second output, etc.

This function works by creating copies of those wallpapers in ~/local.

=cut

sub select_wallpaper_files {
    my $i;
    unlink <"$ENV{HOME}/local/wallpaper??.*">;
    for (@_) {
        -r or croak "$_ could not be read!";
        copy $_,
          sprintf "$ENV{HOME}/local/wallpaper%02d." . (/\.([^.]+)\z/)[0], $i++;
    }
}

=head resize_for_current_outputs()

Based on the output of xrandr(1), create ~/local/wallpaper.png from
~/local/wallpaperNN.*, such that executing `feh --bg-scale --no-xinerama
~/local/wallpaper.png` will put wallpaper00.* on the first output,
wallpaper01.* on the second, etc.  There should not be more than one file
matching ~/local/wallpaperNN.* for each NN.

Returns the value of $? right after executing convert(1).

=cut

sub resize_for_current_outputs {
    # note that swaybg and swaylock have per-output wallpapers built in, so
    # this function is only for X11

    chomp(my @xrandr = `xrandr`);
    my ($canvas_w, $canvas_h) = _get_screen_size(@xrandr);
    # sort the displays from left to right and then from top to bottom
    my @displays = sort {
        my (undef, undef, $a_x, $a_y) = $a =~ $output_re;
        my (undef, undef, $b_x, $b_y) = $b =~ $output_re;
        $a_y <=> $b_y or $a_x <=> $b_x
    } grep / connected /, @xrandr;

    my @wallpapers = sort {
        ($a =~ /wallpaper([0-9]+)\./)[0] <=> ($b =~ /wallpaper([0-9]+)\./)[0]
    } <"$ENV{HOME}/local/wallpaper??.*">;

    my @args = ("-page", "${canvas_w}x${canvas_h}", qw(-background none));
    for (@displays) {
        /$output_re/;
        push @args, '(', (shift @wallpapers || "canvas:#FFFFF6"),
          "-resize", "${1}x${2}^",
          qw(-gravity center -extent), "${1}x${2}",
          "-repage", "${1}x${2}+${3}+${4}", ')';
    }
    push @args, qw(-layers merge), "$ENV{HOME}/local/wallpaper.png";

    system "convert", @args;
    return $?;
}

=head ensure_resize_for_current_outputs()

Call C<resize_for_current_outputs()> if it looks to be needed.

=cut

sub ensure_resize_for_current_outputs {
    return unless <"$ENV{HOME}/local/wallpaper??.*">;
    resize_for_current_outputs(), return
      unless -e "$ENV{HOME}/local/wallpaper.png";
    my ($screen_w, $screen_h) = _get_screen_size(`xrandr`);
    my $magic = File::LibMagic->new;
    my ($img_w, $img_h)
      = $magic->info_from_filename("$ENV{HOME}/local/wallpaper.png")
      ->{description} =~ / ([0-9]+) x ([0-9]+),/;
    resize_for_current_outputs()
      if $img_w
      and $img_h
      and ($screen_w != $img_w or $screen_h != $img_h);
}

=head pick_random_wallpapers($n, @dirs)

Pick C<$n> random wallpapers from files in any of the directories listed in
C<@dirs>.

=cut

sub pick_random_wallpapers {
    my $n = shift;
    my $magic = File::LibMagic->new(follow_symlinks => 1);
    my (@images, @picks);
    find sub {
        push @images, $File::Find::name
          if $magic->info_from_filename($_)->{description} =~ /^\w+ image/
    }, @_;
    push @picks, splice @images, int(rand @images), 1 for 1 .. $n;
    return @picks;
}

sub _get_screen_size {
    chomp(@_);
    my ($canvas) = grep /^Screen 0:/, @_;
    $canvas =~ /current ([0-9]+) x ([0-9]+)/;
}

sub _wsnum { (split /:/, $_[0])[0] }

1;