#!/usr/bin/env perl

# i3status-wrapper -- wrapper for i3status(1), plus other monitoring
#
# Copyright (C) 2019, 2021-2024 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 5.032;
use strict;
use warnings;
use lib "$ENV{HOME}/src/dotfiles/perl5";

use JSON;
use IO::Pipe;
use IPC::Shareable ":lock";
use Local::Desktop::WMIPC;
use Sys::Hostname;
use POSIX "floor", "mkfifo";
use File::Basename "basename", "dirname";
use File::Spec::Functions "catfile";
use List::Util qw(first min max zip);

$| = 1;

my $pipe = IO::Pipe->new;

my $i3status = fork // die "couldn't fork()!";
unless ($i3status) {
    $pipe->writer;
    open STDOUT, ">&=", $pipe->fileno
      or die "couldn't open child's STDOUT";
    exec "i3status";
}

tie my %info, "IPC::Shareable", undef, { destroy => 1 };

my $wmipc = Local::Desktop::WMIPC->new;
sub with_ignored_events (&) {
    $wmipc->send_tick("i3status-wrapper-ign");
    $_[0]->();
    $wmipc->send_tick("i3status-wrapper-unign");
}

sub for_each_node (&) {
    my @trees = $wmipc->get_tree;
    while (@trees) {
	foreach my $node ((shift @trees)->{nodes}->@*) {
	    $_[0]->($node);
	    unshift @trees, $node;
	}
    }
}

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"
);

unless (fork // warn "couldn't fork monitoring loop") {
    my $events = Local::Desktop::WMIPC->new;
    $events->subscribe(qw(tick window workspace));

    # Determine the initial state -- the WM might just have been reloaded.
    # Move any previously-hidden containers to a fresh workspace for perusal.

    tied(%info)->lock;
    my @old_ids;
    for ($wmipc->get_workspaces->@*) {
	$info{focused_ws} = $_->{id} if $_->{focused};
	push @old_ids, $1 if $_->{name} =~ /\A\*(\d+)\*\z/;
    }
    if (@old_ids) {
	fresh_workspace(go => 1);
	$wmipc->cmd(
	    map("[con_id=$_] move container workspace current, floating disable",
		@old_ids),
	    "focus child");
    }
    for_each_node {
	my $node = shift;
	if ($node->{type} eq "workspace"
	    && grep $_ eq $node->{name}, @all_workspaces) {
	    my $entry = $info{paper_ws}{$node->{id}}
	      //= { name => $node->{name}, off_left => [], off_right => [],
		    last_dir => 1 };
	    sync_cols($node => $entry);
	    $entry->{ncols} = max 2, scalar $entry->{cols}->@*;
	} elsif (grep $_ eq "caffeinated", $node->{marks}->@*) {
	    register_caffeinated($node);
	}
    };
    tied(%info)->unlock;

    # Now loop forever reading events, assuming no exceptions.

    eval {
	while (my $e = <$events>) {
	    state $last_e;
	    tied(%info)->lock;

	    # New containers
	    if ($last_e && $last_e->{change} && $last_e->{change} eq "new") {
		normalise_ws_cols()
		  unless $e->{change} && $e->{change} eq "floating";
		undef $last_e;
	    } elsif ($e->{change} && $e->{change} eq "new"
		     && exists $info{paper_ws}{$info{focused_ws}}) {
		# We have to go round the loop once more to find out if it's
		# just a floating dialog that we'll ignore.
		$last_e = $e;
	    } elsif ($e->{change} && exists $info{paper_ws}{$info{focused_ws}}
		     && $e->{change} eq "floating"
		     && $e->{container}{type} ne "floating_con") {
		# A container stopped floating -- it's as though it's new.
		normalise_ws_cols();
		kill USR1 => $i3status;
	    }

	    # Other container changes
	    elsif ($e->{change} && exists $info{paper_ws}{$info{focused_ws}}
		   && ($e->{change} eq "close"
		       || $e->{change} eq "focus" && !$e->{current}
		       || $e->{change} eq "move"
		       && $e->{container} && $e->{container}{type} eq "con"
		       || $e->{change} eq "floating"
		       && $e->{container}{type} eq "floating_con")) {
		# Generally we seek to update $info{paper_ws} with the
		# information we receive by subscription, but in some cases we
		# can't be sure of what has happened.
		# For example, as we don't maintain a representation of the
		# whole tree, on a change=move event, we don't know where the
		# container has gone.  Or a focus change might be due to a new
		# container, in which case we might need to push one off.
		normalise_ws_cols();
		kill USR1 => $i3status;
	    }

	    # Ticks
	    elsif ($e->{payload} && $e->{payload} eq "i3status-wrapper-ign") {
		# Ignore everything until tick telling us to unignore.
		# Forked child that sent the ignore is responsible for
		# updating data structures in the meantime.
		while (my $next = <$events>) {
		    last if $next->{payload}
		      && $next->{payload} eq "i3status-wrapper-unign";
		}
	    }

	    # Workspace changes
	    elsif ($e->{change} && $e->{change} eq "focus" && $e->{current}) {
		$info{focused_ws} = $e->{current}{id};
		# Must normalise in case containers have moved to or from here
		# in our absence.
		normalise_ws_cols()
		  if exists $info{paper_ws}{$info{focused_ws}};
		kill USR1 => $i3status;
	    } elsif ($e->{change} && $e->{change} eq "init" && $e->{current}
		     && grep $_ eq $e->{current}{name}, @all_workspaces) {
		$info{paper_ws}{$e->{current}{id}}
		  = { name => $e->{current}{name}, ncols => 2, cols => [],
		      off_left => [], off_right => [], last_dir => 1 };
	    } elsif ($e->{change} && $e->{change} eq "rename"
		     && exists $info{paper_ws}{$e->{current}{id}}) {
		$info{paper_ws}{$e->{current}{id}}{name}
		  = $e->{current}{name};
		kill USR1 => $i3status;
	    } elsif ($e->{change} && $e->{change} eq "empty"
		     && $e->{current}) {
		delete $info{paper_ws}{$e->{current}{id}};
		kill USR1 => $i3status;
	    }

	    # Mark changes
	    elsif ($e->{change} && $e->{change} eq "mark") {
		if (grep $_ eq "caffeinated", $e->{container}{marks}->@*) {
		    register_caffeinated($e->{container});
		} elsif ($info{caffeinated_id}
			 and $info{caffeinated_id} == $e->{container}{id}) {
		    clear_caffeinated();
		}
	    }

	    tied(%info)->unlock;
	}
    };

    # Give up if there's a decoding error.  We can't ignore the problem
    # because we don't want our ideas regarding what workspaces there are, and
    # whether anything is caffeinated, to get out of sync.
    #
    # The user can use the WM's "reload" command to restart this loop.
    $@ and wsbuttons("yes"), clear_caffeinated();
}

my $wm_ipc_socket = $ENV{SWAYSOCK} || $ENV{I3SOCK};
(basename $wm_ipc_socket) =~ /\d[\d.]*\d/;
my $cmdpipe = catfile dirname($wm_ipc_socket), "i3status-wrapper.$&.pipe";
-e and unlink for $cmdpipe;

unless (fork // warn "couldn't fork command pipe reader") {
    mkfifo $cmdpipe, 0700 or die "mkfifo $cmdpipe failed: $!";
    open my $cmdpipe_r, "<", $cmdpipe;

    # Hold the pipe open with a writer that won't write anything.
    open my $cmdpipe_w, ">", $cmdpipe;

    while (my $cmd = <$cmdpipe_r>) {
	tied(%info)->lock;

	my $ws = $info{paper_ws}{$info{focused_ws}};
	my $cols = $ws->{cols};
	my $col_rows = $info{col_rows}{$ws->{focused_col}};
	my $i = first { $cols->[$_] == $ws->{focused_col} } 0..$#$cols;

	my $mv = sub {
	    my ($j, $move) = @_;
	    if (@$cols > $j >= 0) {
		if ($move) {
		    # This does not trigger any events.
		    $wmipc->cmd(
"[con_id=@$cols[$i]] swap container with con_id @$cols[$j]"
		    );
		    @$cols[$i, $j] = @$cols[$j, $i];
		} else {
		    $wmipc->cmd($j > $i ? "focus right" : "focus left");
		}
	    } elsif ($move && $ws->{monocle}) {
		if ($j > $i && $ws->{off_right}->@*) {
		    push $ws->{off_left}->@*, pop $ws->{off_right}->@*;
		} elsif ($j < $i && $ws->{off_left}->@*) {
		    push $ws->{off_right}->@*, pop $ws->{off_left}->@*;
		}
	    } elsif ($j == @$cols && $ws->{off_right}->@*) {
		my $pushed = shift @$cols;
		my $pulled = pop $ws->{off_right}->@*;
		my @cmds = show_con($pulled);
		push $ws->{off_left}->@*, $pushed;

		if ($move) {
		    if ($col_rows || @$cols) {
			push @cmds, $col_rows
			  ? "move left"
			  : "swap container with con_id @$cols[-1]";
			push @cmds, "focus right";
		    }
		    if (@$cols) {
			my $tem = pop @$cols;
			push @$cols, $pulled, $tem;
		    } else {
			push @$cols, $pulled;
		    }
		} else {
		    $ws->{focused_col} = $pulled;
		    push @cmds, "move right" if $col_rows;
		    push @$cols, $pulled;
		    push @cmds, "focus child" if $info{col_rows}{$pulled};
		}

		with_ignored_events { $wmipc->cmd(@cmds, hide_con($pushed)) };
		kill USR1 => $i3status;
	    } elsif ($j == -1 && $ws->{off_left}->@*) {
		my $pushed = pop @$cols;
		my $pulled = pop $ws->{off_left}->@*;
		my @cmds = show_con($pulled);

		push $ws->{off_right}->@*, $pushed;

		if ($move) {
		    if (@$cols) {
			push @cmds, "move right" if $col_rows;
			push @cmds, "focus left";
			my $tem = shift @$cols;
			unshift @$cols, $tem, $pulled;
		    } else {
			unshift @$cols, $pulled;
		    }
		} else {
		    if ($col_rows) {
			push @cmds, "move left";
		    } elsif (@$cols) {
			push @cmds, "swap container with con_id @$cols[0]";
		    }
		    $ws->{focused_col} = $pulled;
		    unshift @$cols, $pulled;
		    push @cmds, "focus child" if $info{col_rows}{$pulled};
		}

		with_ignored_events { $wmipc->cmd(@cmds, hide_con($pushed)) };
		kill USR1 => $i3status;
	    }
	    $ws->{last_dir} = $j > $i ? 1 : -1;
	};

	# Command dispatch

	if ($cmd =~ /^(focus|move) (left|right)$/) {
	    $mv->($2 eq "right" ? $i+1 : $i-1, $1 eq "move");
	} elsif ($cmd =~ /^cols (incr|decr)$/) {
	    $ws->{ncols} += $1 eq "incr" ? 1 : -1;
	    normalise_ws_cols();
	    kill USR1 => $i3status;
	}

	elsif ($cmd =~ /^other column$/) {
	    # This is meant to be similar to my custom Emacs C-x o.
	    if ($i == 0 || $ws->{last_dir} == -1 && $i < $#$cols) {
		$mv->($i+1);
	    } elsif ($i == $#$cols || $ws->{last_dir} == 1) {
		$mv->($i-1);
	    }
	} elsif ($cmd eq "monocle toggle\n") {
	    unless (ensure_disable_monocle($ws)) {
		$ws->{monocle} = -$i-1;
		normalise_ws_cols();
	    }
	    kill USR1 => $i3status;
	}

	elsif ($cmd =~ /^fresh-workspace ?(take|send)?$/) {
	    fresh_workspace(do {
		if ($1 && $1 eq "take") {
		    go => 1, send => 1;
		} elsif ($1 && $1 eq "send") {
		    send => 1;
		} else {
		    go => 1;
		}
	    });
	}

	elsif ($cmd =~ /^absorb_expel ?(left|right)?$/) {
	    my $dir = $1 eq "right" ? 1 : -1;
	    if ($col_rows > 1) { # expel
		# If the column to the right or left also has rows, we'll just
		# move the container into that column instead of expelling it.
		# Possibly we could float the container, select the
		# appropriate full column and unfloat it into place?
		$wmipc->cmd(sprintf "move %s", $dir > 0 ? "right" : "left");
		$ws->{last_dir} = $dir;
	    } else { 		# absorb
		my @cmds;
		if ($i == 0 && $dir < 0 && $ws->{off_left}->@*) {
		    my $pulled = pop $ws->{off_left}->@*;
		    push @cmds, show_con($pulled), "move left";
		    push @cmds, "splitv" unless $info{col_rows}{$pulled};
		    push @cmds, "focus right", "move left";

		    with_ignored_events { $wmipc->cmd(@cmds) };
		    normalise_ws_cols();
		} elsif ($i == $#$cols && $dir > 0 && $ws->{off_right}->@*) {
		    my $pulled = pop $ws->{off_right}->@*;
		    push @cmds, show_con($pulled);
		    push @cmds, "move right" if $col_rows;
		    push @cmds, "splitv" unless $info{col_rows}{$pulled};
		    push @cmds, "focus left", "move right";

		    with_ignored_events { $wmipc->cmd(@cmds) };
		    normalise_ws_cols();
		} elsif ($i == $#$cols && $dir < 0
			 || $#$cols > $i > 0
			 || $i == 0 && $dir > 0) {
		    push @cmds, $dir > 0
		      ? ("focus right", "splitv", "focus left")
		      : ("focus left",  "splitv", "focus right")
		      unless $info{col_rows}{ @$cols[$i+$dir] };
		    push @cmds, $dir > 0 ? "move right" : "move left";

		    with_ignored_events { $wmipc->cmd(@cmds) };
		    normalise_ws_cols($ws->{off_left}->@* && $dir > 0
				      || $ws->{off_right}->@* && $dir < 0
				      ? min($#$cols, max 0, $i+$dir) : $i);
		}
		if (@cmds) {
		    $ws->{last_dir} = $dir;
		    kill USR1 => $i3status;
		}
	    }
	}

	# Basic purpose of this wrapper command is to prevent accidentally
	# moving to one of the holding workspaces using Sway's own commands.
	elsif ($cmd =~ /^(move_)?workspace (prev|next)$/) {
	    my ($move, $dir) = (!!$1, $2);
	    $move && ensure_disable_monocle($ws);
	    my @keys = sorted_paper_ws();
	    my $k = first { $keys[$_] == $info{focused_ws} } 0..$#keys;
	    if ($dir eq "next" && $k < $#keys || $dir eq "prev" && $k > 0) {
		my @cmds = "workspace $dir";
		$info{focused_ws} = $keys[$dir eq "next" ? $k+1 : $k-1];
		if ($move) {
		    push @cmds, show_con($ws->{focused_col});
		    push @cmds, "move right"
		      if $info{col_rows}
		      { $info{paper_ws}{$info{focused_ws}}{focused_col} };
		    push @cmds, "focus child" if $col_rows;
		}
		$wmipc->cmd(@cmds);
	    }
	}

	tied(%info)->unlock;
    }
}

$pipe->reader;
open STDIN, "<&=", $pipe->fileno or die "couldn't reopen STDIN!";

# Following based on Michael Stapelberg's sample i3status-wrapper script.

my $hostname = hostname;
my $username = $ENV{LOGNAME} || $ENV{USER} || getpwuid($<);
my $hostinfo
  = { name => "hostinfo", full_text => $username . "@" . $hostname };

# Skip the first line which contains the version header.
print scalar <>;

# The second line contains the start of the infinite array.
print scalar <>;

wsbuttons("no");

# Read lines forever, ignore a comma at the beginning if it exists.
while (my ($statusline) = (<> =~ /^,?(.*)/)) {
    # If there is a decoding error, just skip this line, to minimise status
    # bar freezes.  This should be fine here because this filtering loop is in
    # itself stateless.  It's only if the decoding error involves newlines in
    # the wrong places, or similar, that this skip could cause us to produce
    # invalid output.
    my $blocks = eval { decode_json $statusline } // next;

    tied(%info)->lock(LOCK_SH);

    if ($info{focused_ws}
	&& $info{paper_ws} && keys $info{paper_ws}->%* > 1) {
	my @disp;
	my @keys = sorted_paper_ws();
	foreach my $key (@keys) {
	    push @disp,
	      sprintf +($info{focused_ws} == $key ? "<b>%s</b>" : "%s"),
	      ws_name($info{paper_ws}{$key}{name})

	}
	unshift @$blocks,
	  { name => "ws", markup => "pango", full_text => join " ", @disp };
    }

    if ($info{focused_ws} && exists $info{paper_ws}{ $info{focused_ws} }) {
	sub nwin { join " ", ("\x{2021}")x$_[0] }

	my $ws    = $info{paper_ws}{ $info{focused_ws} };
	my $left  = $ws->{off_left}->@*;
	my $right = $ws->{off_right}->@*;

	my $disp = sprintf "<b>%s</b>",
	  $ws->{monocle} ? "\x{2020}" : nwin($ws->{ncols});
	$disp = sprintf "%s %s", nwin($left), $disp if $left;
	$disp = sprintf "%s %s", $disp, nwin($right) if $right;

	unshift @$blocks,
	  { name => "cols", markup => "pango", full_text => $disp };
    }

    unshift @$blocks,
      {
	  name      => "caffeinated",
	  full_text => "Caffeinated: " . $info{caffeinated_name} }
      if $info{caffeinated_name};

    tied(%info)->unlock;

    unshift @$blocks, $hostinfo;

    print encode_json($blocks) . ",\n";
}

sub wsbuttons {
    return unless $ENV{XDG_CURRENT_DESKTOP} eq "sway";
    $wmipc->cmd("bar bar-0 workspace_buttons $_[0]");
}

sub register_caffeinated {
    $info{caffeinated_id} = $_[0]->{id};
    $info{caffeinated_name} = $_[0]->{name};
    kill USR1 => $i3status;
}

sub clear_caffeinated {
    undef $info{caffeinated_id};
    undef $info{caffeinated_name};
    kill USR1 => $i3status;
}

sub sync_cols {
    my ($node, $entry) = @_;

    # Here we assume that the containers for the columns are directly below
    # the type=workspace node.  That won't be true if workspace_layout is not
    # configured to 'default'.
    foreach my $child_id ($node->{focus}->@*) {
	my $child_node = first { $_->{id} == $child_id } $node->{nodes}->@*;
	$entry->{focused_col} = $child_id, last
	  if $child_node->{type} eq "con";
    }
    $entry->{cols} = [];
    foreach my $child_node ($node->{nodes}->@*) {
	next unless $child_node->{type} eq "con";
	push $entry->{cols}->@*, $child_node->{id};
	$info{col_rows}{$child_node->{id}} = $child_node->{nodes}->@*;
    }
}

sub normalise_ws_cols {
    my $ws = $info{paper_ws}{$info{focused_ws}};
    my $floating_focus;
    my $old_cols = $ws->{cols};
    my $old_i = shift // first { $old_cols->[$_] == $ws->{focused_col} }
      0..$#$old_cols;
    for_each_node {
	my $node = shift;
	if ($node->{id} == $info{focused_ws}) {
	    sync_cols($node => $ws);
	    my $first_focus = $node->{focus}->[0];
	    $floating_focus = ! grep $_ == $first_focus, $ws->{cols}->@*;
	    goto DONE;
	}
    };
  DONE:
    my $cols = $ws->{cols};
    my $i = first { $cols->[$_] eq $ws->{focused_col} } 0..$#$cols;

    my @cmds;
    my $avail_l = scalar $ws->{off_left}->@*;
    my $avail_r = scalar $ws->{off_right}->@*;

    if ($ws->{monocle} && !@$cols) {
	undef $ws->{monocle};
	$i = $old_i = !!$avail_l;
    }

    if ($ws->{focused_col} && $info{col_rows}{$ws->{focused_col}}
	&& $info{col_rows}{$ws->{focused_col}} == 1) {
	# Attempt to delete the vertically split container by moving the
	# single window it contains over one of its edges.
	# We can't always do this.  We assume the default focus_wrapping.
	if ($i < $#$cols && !$info{col_rows}{ @$cols[$i+1] }) {
	    push @cmds, "move right";
	    delete $info{col_rows}{$ws->{focused_col}};
	    $ws->{focused_col} = $cols->[$i] = node_first_child($cols->[$i]);
	} elsif ($i > 0 && !$info{col_rows}{ @$cols[$i-1] }) {
	    push @cmds, "move left";
	    delete $info{col_rows}{$ws->{focused_col}};
	    $ws->{focused_col} = $cols->[$i] = node_first_child($cols->[$i]);
	}
    }

    if (!$ws->{monocle} && $ws->{ncols} > @$cols && ($avail_l || $avail_r)) {
	# Pull columns in if there are too few columns but some available.
	# Want the focused column, after pulls, to be the $old_i'th.
	my ($from_l, $from_r);
	my $want = $ws->{ncols} - @$cols;
	# When we lose columns, the focused column either moves left or
	# stays the same.  So always $old_i >= $i.
	if ($old_i > $i) {
	    if ($old_i == $#$old_cols) {
		# We were in the final column.  Either we closed the
		# rightmost column, or we lost arbitrary columns from the
		# left (e.g. monocle from the last column).
		# In either case it is fine to pull more from the left.
		$from_l = min $avail_l, $want;
	    } else {
		# We have $i < $old_i < $#$old_cols.
		# We must have lost at least $old_i-$i from the left.
		$from_l = min $avail_l, $old_i-$i;
	    }
	} else {		# $old_i == $i.
	    if ($old_i == 0) {
		# We were in the first column.  Either we closed the leftmost
		# column, or we lost arbitrary columns from the left
		# (e.g. monocle from the first column).  We prefer to pull
		# from the left in the former case.  If we are indeed exiting
		# monocle mode, we must pull from the right.
		if (@$cols == 1) {
		    $from_r = min $avail_r, $want;
		} else {
		    $from_l = !!$avail_l;
		}
	    } else {
		# It must be that we lost columns from the right.
		$from_r = min $avail_r, $want;
	    }
	}

	if ($from_l //= min $avail_l, $want-$from_r) {
	    my @pulled = splice $ws->{off_left}->@*, -$from_l, $from_l;
	    my @to_pull = reverse @pulled;
	    @to_pull = zip \@to_pull, [@$cols[0], @to_pull[0..$#to_pull-1]];

	    push @cmds, ("focus left")x$i;
	    for (@to_pull) {
		push @cmds, show_con(@$_[0]);
		next unless @$_[1];
		push @cmds, $info{col_rows}{@$_[1]}
		  ? "move left"
		  : "swap container with con_id @$_[1]";
	    }

	    unshift @$cols, @pulled;
	    $i = 0;
	}
	if ($from_r //= min $avail_r, $want-$from_l) {
	    my @pulled
	      = reverse splice $ws->{off_right}->@*, -$from_r, $from_r;
	    my @to_pull = zip \@pulled, [@$cols[-1], @pulled[1..$#pulled]];
	    push @cmds, ("focus right")x($#$cols-$i);
	    for (@to_pull) {
		push @cmds, show_con(@$_[0]);
		push @cmds, "move right" if @$_[1] && $info{col_rows}{@$_[1]};
	    }

	    push @$cols, @pulled;
	    $i = $#$cols;
	}

	if ($i > $old_i) {
	    push @cmds, ("focus left")x($i-$old_i);
	} elsif ($old_i > $i) {
	    push @cmds, ("focus right")x($old_i-$i);
	}

	$ws->{focused_col} = $cols->[$old_i];
	push @cmds, "focus child" if $info{col_rows}{$ws->{focused_col}};
    }
    # Push columns off if there are too many columns.
    # This should never change which container is focused.
    elsif (my $n = $ws->{monocle} ? @$cols-1 : @$cols-$ws->{ncols} > 0) {
	my $left = $i;
	my $right = $#$cols-$i;
	if ($left >= $right) {
	    $left = min $left, $n;
	    $right = $n-$left;
	} else {
	    $right = min $right, $n;
	    $left = $n-$right;
	}
	my @to_left = splice @$cols, 0, $left;
	my @to_right = reverse splice @$cols, -$right, $right;

	push @cmds, map hide_con($_), @to_left, @to_right;
	push $ws->{off_left}->@*, @to_left;
	push $ws->{off_right}->@*, @to_right;
    }
    if (@cmds) {
	push @cmds, "focus floating" if $floating_focus;
	with_ignored_events { $wmipc->cmd("focus tiling", @cmds) }
    }
}

=head fresh_workspace(%opts)

Switch to the next free workspace, if any.  Return the name of that workspace,
or undef if no workspace was available.

=cut

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

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

	# Special case: if we're about to leave a workspace empty by removing
	# its monocle mode container, then that workspace will get an empty
	# event, and we'll lose track of any windows pushed off to the sides.
	# So turn off monocle mode first.
	ensure_disable_monocle(my $ws = $info{paper_ws}{$info{focused_ws}});

	# We need to ensure that the monitoring loop doesn't process the move
	# event before it knows about the workspace change.  Otherwise, that
	# loop might try to unhide containers from the old workspace onto the
	# new one.  We do need it to process the workspace init event, else we
	# don't know the ID of the new workspace without making our own query.
	#
	# We also want to ensure that the fresh workspace is the one that
	# C-i ; will take us to.  In the case that !$opts{go}, can use C-i M-j
	# to move any other wanted containers over, before a final C-i ;.
	#
	# There is a relevant i3/Sway difference here:
	#     <https://github.com/swaywm/sway/issues/6081>.
	# (Our use of hide_con elsewhere assumes Sway's behaviour.  Possibly
	# we should write wrapper code that can handle either case.)

	push @cmds, "workspace $next_free_workspace";
	push @cmds, show_con($info{paper_ws}{$info{focused_ws}}{focused_col})
	  if $opts{send};
	push @cmds, "workspace back_and_forth" unless $opts{go};

	$wmipc->cmd(@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 = sorted_paper_ws();
    @workspaces < @all_workspaces or return;
    my ($i, $gap_workspace, @pairs);

    while (my $next = shift @workspaces) {
        my $workspace = $all_workspaces[$i++];

        $opts{leave_gap}
          and $next == $info{focused_ws}
          and $gap_workspace = $all_workspaces[$i++];
	my $next_name = $info{paper_ws}{$next}{name};
        next if $next_name eq $workspace;
        my $pair = [$next, $workspace];
        ws_num($next_name) > ws_num($workspace)
          ? push @pairs, $pair
          : unshift @pairs, $pair
    }

    with_ignored_events {
	$wmipc->cmd(
	    map sprintf("rename workspace %s to %s",
			$info{paper_ws}{$_->[0]}{name}, $_->[1]),
	    @pairs)
    };
    $info{paper_ws}{$_->[0]}{name} = $_->[1] for @pairs;

    $opts{leave_gap} and $gap_workspace
}

sub node_first_child {
    my $node_id = shift;
    my $child_id;
    for_each_node {
	my $node = shift;
	if ($node->{id} == $node_id) {
	    $child_id = $node->{nodes}[0]{id};
	    goto DONE;
	}
    };
  DONE:
    return $child_id;
}

sub ensure_disable_monocle {
    my $ws = shift;
    my $m = $ws->{monocle} or return 0;
    undef $ws->{monocle};
    normalise_ws_cols(abs ++$m);
    return 1;
}

sub sorted_paper_ws {
    sort { ws_num($info{paper_ws}{$a}{name})
	     <=> ws_num($info{paper_ws}{$b}{name}) }
      keys $info{paper_ws}->%*
}

sub hide_con {
    # Enable floating in order to preserve any rows the container might have.
    # Otherwise, Sway subsumes the rows to the hidden workspace and the
    # container with our known ID ceases to exist, s.t. we can't unhide it.
    sprintf "[con_id=%s] floating enable, move container to workspace %s",
      $_[0], "*$_[0]*"
}

sub show_con {
    sprintf "[con_id=%s] %s",
      $_[0], join ", ", "move container to workspace current",
      "floating disable", "focus";
}

sub ws_name {
    my ($before, $after) = split /:/, $_[0];
    $after // $before
}
sub ws_num { (split /:/, $_[0])[0] }