#!/usr/bin/php
<?php

function getWorkspaces(): array
{
    $output = shell_exec('i3-msg -t get_workspaces');

    return json_decode($output, true);
}

function getVisibleWorkspaces(): array
{
    $workspaces = [];

    foreach (getWorkspaces() as $wp) {
        if (true === $wp['visible']) {
            $workspaces[] = $wp;
        }
    }

    return $workspaces;
}

function getTree(): array
{
    $output = shell_exec('i3-msg -t get_tree');

    return json_decode($output, true);
}

function getVisibleWorkspacesNodes(array $tree, array $workspaces): array
{
    $nodes = [];
    $num = $tree['num'] ?? null;
    $output = $tree['output'] ?? null;

    foreach ($workspaces as $workspace) {
        if ($num === $workspace['num']) {
            $nodes = array_merge(
                $nodes,
                $tree['nodes']
            );

            $nodes = array_merge(
                $nodes,
                $tree['floating_nodes']
            );
        } elseif ('__i3' === $output && isset($tree['window'])) {
            $nodes[] = $tree;
        }
    }

    foreach ($tree as $node) {
        if (is_array($node)) {
            $nodes = array_merge(
                $nodes,
                getVisibleWorkspacesNodes($node, $workspaces)
            );
        }
    }

    foreach ($nodes as $k => $n) {
        if (!isset($n['window'])) {
            unset($nodes[$k]);

            foreach ($n['nodes'] as $node) {
                $nodes[] = $node;
            }

            foreach ($n['floating_nodes'] as $node) {
                $nodes[] = $node;
            }
        }
    }

    return $nodes;
}

$nodes = getVisibleWorkspacesNodes(getTree(), getVisibleWorkspaces());

foreach ($nodes as $key => $node) {
    if ($node['focused']) {
        shell_exec(sprintf('i3-msg "[id=%s] focus"', $nodes[(++$key) % count($nodes)]['window']));
    }
}