<?php
namespace Zadex\Loop;

defined('ABSPATH') || exit;

use WP_Error;
use WP_REST_Request;
use WP_REST_Response;
use Zadex\Documents\Document;
use Zadex\Frontend\Renderer;

/**
 * Public REST route for loop pagination and the Taxonomy filter (T118 / T119):
 *
 *   GET zadex/v1/loop/{postId}/{elementId}?page=2&tax[category]=news,tech&ctx=<current post>&qv[cat]=3
 *   → { html, pagination, page, maxPages, found, hasMore, empty }
 *
 * Also serves the registered paginated widget types (LoopRenderer::register_type, e.g. the Posts widget, T180): their
 * items are rendered by the type's own item renderer instead of a loop-item template.
 *
 * The loop is read from the SAVED document of a published, non password-protected Zadex page (or published theme
 * template: loops in archive/single templates, nested loops in loop items); the request only chooses the page, the
 * filter terms, the current post (related / exclude current) and — for the "current query" source — whitelisted main
 * query vars. Results are always published posts of viewable post types (Query::guard()). No nonce: visitors and
 * cached pages call it, and it exposes nothing a visitor cannot already see.
 */
final class LoopController
{
    private Renderer $renderer;
    /** @var callable(int): array|null document loader (tests) */
    private $loader;

    public function __construct(Renderer $renderer, ?callable $loader = null)
    {
        $this->renderer = $renderer;
        $this->loader = $loader;
    }

    public function register(): void
    {
        add_action('rest_api_init', [$this, 'routes']);
    }

    public function routes(): void
    {
        register_rest_route('zadex/v1', '/loop/(?P<post>\d+)/(?P<element>[A-Za-z0-9_-]{1,64})', [
            'methods'             => 'GET',
            'callback'            => [$this, 'handle'],
            // Public on purpose: loop pagination / "load more" / taxonomy filters run for visitors. Read-only: the
            // loop element is looked up in the saved document of a published, non-password-protected Zadex page or
            // theme template (is_public_document()); its saved query settings (not the request) decide what is
            // queried, and the request only supplies the page number, filter slugs and the public context post.
            'permission_callback' => '__return_true',
        ]);
    }

    /** @return WP_REST_Response|WP_Error */
    public function handle(WP_REST_Request $request)
    {
        $post_id = (int) $request['post'];
        $element_id = (string) $request['element'];
        if (!$this->is_public_document($post_id)) {
            return new WP_Error('zadex_not_found', __('Not found.', 'zadex'), ['status' => 404]);
        }
        $elements = $this->elements($post_id);
        $element = LoopRenderer::find($elements, $element_id);
        if ($element === null || !LoopRenderer::is_loop((string) ($element['type'] ?? ''))) {
            return new WP_Error('zadex_not_found', __('Loop not found.', 'zadex'), ['status' => 404]);
        }
        $settings = $this->renderer->settings($element);
        $page = max(1, min(1000, (int) ($request['page'] ?? 1)));
        $ctx_post = $this->context_post((int) ($request['ctx'] ?? 0), $post_id);
        $main = ($settings['query_source'] ?? '') === 'current' && is_array($request['qv'] ?? null) ? Query::main_vars($request['qv']) : [];
        $filters = $this->filters($request['tax'] ?? null);

        $previous = $this->renderer->explicit_context();
        $this->renderer->set_context(\Zadex\Dynamic\Context::for_post($ctx_post));
        try {
            $exclude = !empty($settings['query_avoid_duplicates']) ? $this->preceding_ids($elements, $element_id, $ctx_post, $main) : [];
            // The CSS of the documents rendered in the items (loop-item templates, components ...) is returned as
            // `css` (handle => css) and inserted by the frontend runtime; the HTML itself carries no style tags.
            [$result, $css] = \Zadex\Frontend\Styles::capture(fn(): array => LoopRenderer::render($this->renderer, $settings, [
                'page'       => $page,
                'filters'    => $filters,
                'main'       => $main,
                'post_id'    => $ctx_post,
                // phpcs:ignore WordPressVIPMinimum.Performance.WPQueryParams.PostNotIn_exclude -- Zadex query-context key, not a WP_Query argument.
                'exclude'    => $exclude,
                'item_class' => ($element['type'] ?? '') === 'loop-carousel' ? 'zx-loop-carousel__slide zx-slider__slide' : '',
                'track'      => false,
                'item'       => LoopRenderer::item_renderer((string) ($element['type'] ?? '')),
            ]));
            if (LoopRenderer::item_renderer((string) ($element['type'] ?? '')) === null) {
                [, $tpl_css] = \Zadex\Frontend\Styles::capture(static fn() => LoopRenderer::template_styles(LoopRenderer::template_ids($settings)));
                $css = $tpl_css + $css;
            }
        } finally {
            $this->renderer->set_context($previous);
        }
        $pagination = (string) ($settings['pagination'] ?? 'none');
        $pagination = in_array($pagination, LoopRenderer::PAGINATION, true) ? $pagination : 'none';
        $labels = ['load_more' => (string) ($settings['load_more_text'] ?? ''), 'prev' => (string) ($settings['prev_text'] ?? ''), 'next' => (string) ($settings['next_text'] ?? '')];
        $base = function_exists('get_permalink') ? (string) get_permalink($post_id) : '';
        return new WP_REST_Response([
            'html'       => \Zadex\Frontend\Kses::restore(wp_kses($result['html'], \Zadex\Frontend\Kses::allowed_html())),
            'css'        => (object) $css,
            'pagination' => wp_kses(LoopRenderer::pagination($pagination, $result['page'], $result['max_pages'], $element_id, $labels, $base), \Zadex\Frontend\Kses::allowed_html()),
            'page'       => $result['page'],
            'maxPages'   => $result['max_pages'],
            'found'      => $result['found'],
            'hasMore'    => $result['page'] < $result['max_pages'],
            'empty'      => count($result['ids']) === 0,
        ]);
    }

    /** Published, not password protected, and either a Zadex page or a theme template. */
    public function is_public_document(int $post_id): bool
    {
        $post = $post_id > 0 ? get_post($post_id) : null;
        if (!$post || ($post->post_status ?? '') !== 'publish' || (string) ($post->post_password ?? '') !== '') {
            return false;
        }
        if (($post->post_type ?? '') === \Zadex\Theme\TemplatePost::POST_TYPE) {
            return true;
        }
        return Document::is_builder($post_id);
    }

    private function elements(int $post_id): array
    {
        $data = $this->loader ? ($this->loader)($post_id) : Document::get_data($post_id);
        return is_array($data['elements'] ?? null) ? $data['elements'] : [];
    }

    /** The current post passed by the page (related / exclude current) must be public too; else the document. */
    private function context_post(int $ctx, int $doc): int
    {
        if ($ctx > 0 && $ctx !== $doc) {
            $post = get_post($ctx);
            if ($post && ($post->post_status ?? '') === 'publish' && (string) ($post->post_password ?? '') === '') {
                return $ctx;
            }
        }
        $doc_post = get_post($doc);
        return $doc_post && ($doc_post->post_type ?? '') === \Zadex\Theme\TemplatePost::POST_TYPE ? 0 : $doc;
    }

    /** `tax[category]=a,b` → ['category' => ['a','b']] (at most 5 taxonomies, 20 terms each). */
    private function filters($raw): array
    {
        if (!is_array($raw)) {
            return [];
        }
        $out = [];
        foreach (array_slice($raw, 0, 5, true) as $tax => $terms) {
            $tax = Query::taxonomy((string) $tax);
            if ($tax === '' || (function_exists('taxonomy_exists') && !taxonomy_exists($tax))) {
                continue;
            }
            if (function_exists('is_taxonomy_viewable') && !is_taxonomy_viewable($tax)) {
                continue;
            }
            $list = LoopRenderer::terms_param(is_array($terms) ? implode(',', array_map('strval', $terms)) : (string) $terms);
            if ($list) {
                $out[$tax] = $list;
            }
        }
        return $out;
    }

    /** "Avoid duplicates": ids the loops above this one show on their first page. @return int[] */
    private function preceding_ids(array $elements, string $element_id, int $ctx_post, array $main): array
    {
        $shown = [];
        foreach (LoopRenderer::loops_in($elements) as $loop) {
            if (($loop['id'] ?? '') === $element_id) {
                break;
            }
            $s = $this->renderer->settings($loop);
            $exclude = !empty($s['query_avoid_duplicates']) ? $shown : [];
            // phpcs:ignore WordPressVIPMinimum.Performance.WPQueryParams.PostNotIn_exclude -- Zadex query-context key, not a WP_Query argument.
            $res = Query::run(Query::build_args($s, ['post_id' => $ctx_post, 'page' => 1, 'exclude' => $exclude, 'main' => ($s['query_source'] ?? '') === 'current' ? $main : []]), $s);
            $shown = array_values(array_unique(array_merge($shown, $res['ids'])));
        }
        return $shown;
    }
}