<?php
namespace Zadex\Theme;

defined('ABSPATH') || exit;

use Zadex\Editor\EditorLoader;
use Zadex\Frontend\Kses;
use Zadex\Theme\Compat\ThemeCompat;

/**
 * Puts the header / footer templates in place of the theme's own.
 *
 *  - Block themes: `render_block` for `core/template-part` blocks of the header / footer area returns the
 *    rendered Zadex template instead of the part.
 *  - Classic themes with a compat class (Compat\*): the theme's header/footer hook callbacks are replaced.
 *  - Other classic themes: on `get_header` we print views/header.php (doctype, wp_head, body_class,
 *    wp_body_open, our header) and load the theme's header.php inside an output buffer with
 *    locate_template(..., true), so get_header()'s own require_once becomes a no-op. Same for `get_footer`.
 *
 * Mode: 'block' | 'classic' | a compat slug | 'none', filterable through `zadex/theme/support`
 * (string $mode, string $template); return 'none' to disable the injection.
 */
final class ThemeSupport
{
    private TemplateRenderer $renderer;
    /** @var callable(string): ?int */
    private $resolve;
    /** @var array<string, bool> parts already printed on this request */
    private array $done = [];

    public function __construct(TemplateRenderer $renderer, ?callable $resolve = null)
    {
        $this->renderer = $renderer;
        $this->resolve = $resolve ?? [Resolver::class, 'for_location'];
    }

    public function register(): void
    {
        // After the main query and the themes' own hook setup, before the template is loaded.
        add_action('template_redirect', [$this, 'setup'], 99);
    }

    public function mode(): string
    {
        $template = function_exists('get_template') ? (string) get_template() : '';
        if (function_exists('wp_is_block_theme') && wp_is_block_theme()) {
            $mode = 'block';
        } else {
            $compat = ThemeCompat::detect($template);
            $mode = $compat !== '' ? $compat : 'classic';
        }
        $filtered = apply_filters('zadex/theme/support', $mode, $template);
        return is_string($filtered) && $filtered !== '' ? $filtered : $mode;
    }

    public function setup(): void
    {
        if (EditorLoader::mode() === 'edit') {
            return;
        }
        $mode = $this->mode();
        if ($mode === 'none') {
            return;
        }
        add_filter('body_class', [$this, 'body_class']);
        if ($mode === 'block') {
            add_filter('render_block', [$this, 'render_block'], 10, 2);
            return;
        }
        $compat = $mode !== 'classic' ? ThemeCompat::make($mode) : null;
        foreach (['header', 'footer'] as $part) {
            if (!$this->resolve($part)) {
                continue;
            }
            if ($compat && $compat->replace($part, fn() => $this->print_part($part))) {
                continue;
            }
            if ($part === 'header') {
                add_action('get_header', [$this, 'classic_header'], 10, 2);
            } else {
                add_action('get_footer', [$this, 'classic_footer'], 10, 2);
            }
        }
    }

    public function resolve(string $part): ?int
    {
        $id = ($this->resolve)($part);
        return is_int($id) && $id > 0 ? $id : null;
    }

    /** Prints a part once (compat hooks may fire more than once). */
    public function print_part(string $part): void
    {
        if (!empty($this->done[$part]) || !($id = $this->resolve($part))) {
            return;
        }
        $this->done[$part] = true;
        Kses::begin();
        echo wp_kses($this->renderer->render($id), Kses::allowed_html());
        Kses::end();
    }

    /** Block themes: swaps the header / footer template parts. */
    public function render_block(string $content, array $block): string
    {
        if (($block['blockName'] ?? '') !== 'core/template-part') {
            return $content;
        }
        $area = self::part_area(is_array($block['attrs'] ?? null) ? $block['attrs'] : []);
        if ($area === '' || !($id = $this->resolve($area))) {
            return $content;
        }
        return Kses::restore(wp_kses($this->renderer->render($id), Kses::allowed_html()));
    }

    /** 'header' / 'footer' / '' for a template-part block's attributes. */
    public static function part_area(array $attrs): string
    {
        $area = isset($attrs['area']) && is_string($attrs['area']) ? $attrs['area'] : '';
        $slug = isset($attrs['slug']) && is_string($attrs['slug']) ? $attrs['slug'] : '';
        if ($area === '' && $slug !== '' && class_exists('\WP_Theme_JSON_Resolver')) {
            $parts = \WP_Theme_JSON_Resolver::get_theme_data([], ['with_supports' => false])->get_template_parts();
            if (isset($parts[$slug]['area']) && is_string($parts[$slug]['area'])) {
                $area = $parts[$slug]['area'];
            }
        }
        if ($area === '' && $slug !== '') {
            if ($slug === 'header' || str_contains($slug, 'header')) {
                $area = 'header';
            } elseif ($slug === 'footer' || str_contains($slug, 'footer') || $slug === 'colophon') {
                $area = 'footer';
            }
        }
        if ($area === '' && isset($attrs['tagName']) && is_string($attrs['tagName'])) {
            if ($attrs['tagName'] === 'header' || $attrs['tagName'] === 'footer') {
                $area = $attrs['tagName'];
            }
        }
        return in_array($area, ['header', 'footer'], true) ? $area : '';
    }

    /** Classic fallback for get_header(). */
    public function classic_header($name = null, $args = []): void
    {
        if (!empty($this->done['header']) || !($id = $this->resolve('header'))) {
            return;
        }
        $this->done['header'] = true;
        $zadex_template_html = $this->renderer->render($id);
        include __DIR__ . '/views/header.php';
        self::swallow_theme_file('header', $name, is_array($args) ? $args : []);
    }

    /** Classic fallback for get_footer(). */
    public function classic_footer($name = null, $args = []): void
    {
        if (!empty($this->done['footer']) || !($id = $this->resolve('footer'))) {
            return;
        }
        $this->done['footer'] = true;
        $zadex_template_html = $this->renderer->render($id);
        include __DIR__ . '/views/footer.php';
        self::swallow_theme_file('footer', $name, is_array($args) ? $args : []);
    }

    /**
     * Loads the theme's header.php / footer.php once, discarding its output, so the require_once in
     * get_header() / get_footer() that runs right after this action loads nothing.
     */
    public static function swallow_theme_file(string $part, $name, array $args = []): void
    {
        $templates = [];
        $name = (string) $name;
        if ($name !== '') {
            $templates[] = "{$part}-{$name}.php";
        }
        $templates[] = "{$part}.php";
        ob_start();
        locate_template($templates, true, true, $args);
        ob_end_clean();
    }

    public function body_class(array $classes): array
    {
        foreach (['header', 'footer'] as $part) {
            if ($this->resolve($part)) {
                $classes[] = 'zadex-has-' . $part;
            }
        }
        return $classes;
    }
}