<?php
/**
 * Post lists (blog, archives, search, Query Loop, custom WP_Query) show only
 * posts in the current language. A query can ask for another language with
 * 'lang' => 'uk', or for every language with 'lang' => 'all'. Single posts are
 * not filtered: a post in another language is redirected to its own URL.
 * The site-wide comments feed (/uk/comments/feed/) follows the same rule:
 * only comments on posts in its language.
 */

declare( strict_types = 1 );

namespace AddBlack\Lang\Frontend;

defined( 'ABSPATH' ) || exit;

use AddBlack\Lang\Hookable;
use AddBlack\Lang\Hooks;
use AddBlack\Lang\Install\Schema;
use AddBlack\Lang\Routing\CurrentLanguage;
use AddBlack\Lang\Settings\SettingsRepository;
use WP_Query;

final class QueryFilter implements Hookable {

	public function __construct(
		private readonly CurrentLanguage $current,
		private readonly SettingsRepository $settings,
		private readonly Schema $schema,
		private readonly \wpdb $db
	) {}

	public function register(): void {
		Hooks::action( 'pre_get_posts', array( $this, 'pre_get_posts' ) );
		Hooks::filter( 'posts_clauses', array( $this, 'posts_clauses' ), 10, 2 );
		Hooks::filter( 'comment_feed_join', array( $this, 'comment_feed_join' ), 10, 2 );
		Hooks::filter( 'comment_feed_where', array( $this, 'comment_feed_where' ), 10, 2 );
	}

	/** Decide the language of a query: its 'lang' var, else the page language for lists. */
	public function pre_get_posts( WP_Query $q ): void {
		$lang = $q->get( 'lang' );
		if ( '' === $lang || null === $lang ) {
			if ( is_admin() || '' === $this->current->get() ) {
				return;
			}
			// The posts page (Settings > Reading) keeps its pagename/page_id vars, but it is a list.
			$one_post = $q->is_singular() || $q->get( 'post__in' ) || $q->get( 'p' ) || $q->get( 'page_id' ) || $q->get( 'name' ) || $q->get( 'pagename' );
			if ( $one_post && ! $q->is_posts_page ) {
				return;
			}
			$lang = $this->current->get();
		}
		$q->set( 'blocklingo_lang', 'all' === $lang ? '' : $lang );
	}

	/**
	 * Join the translations table. Tagged posts: their language must match.
	 * Untagged: the default language, or a post type that is not translated.
	 *
	 * @param array<string, string> $clauses
	 * @return array<string, string>
	 */
	public function posts_clauses( array $clauses, WP_Query $q ): array {
		$lang = $this->query_language( $q );
		if ( '' === $lang ) {
			return $clauses;
		}
		$clauses['join']  .= $this->join_sql();
		$clauses['where'] .= $this->where_sql( $lang );
		return $clauses;
	}

	/** Comment feeds of lists (not of one post): join the language of the commented post. */
	public function comment_feed_join( mixed $join, mixed $q ): mixed {
		if ( ! is_string( $join ) || ! $q instanceof WP_Query || $q->is_singular() || '' === $this->query_language( $q ) ) {
			return $join;
		}
		return $join . $this->join_sql();
	}

	public function comment_feed_where( mixed $where, mixed $q ): mixed {
		if ( ! is_string( $where ) || ! $q instanceof WP_Query || $q->is_singular() ) {
			return $where;
		}
		$lang = $this->query_language( $q );
		return '' === $lang ? $where : $where . $this->where_sql( $lang );
	}

	/** Language a query is limited to ('' = not limited). */
	private function query_language( WP_Query $q ): string {
		$lang     = (string) $q->get( 'blocklingo_lang' );
		$settings = $this->settings->get();
		return '' !== $lang && $settings->is_language( $lang ) && $settings->post_types() ? $lang : '';
	}

	private function join_sql(): string {
		$posts = $this->db->posts;
		return (string) $this->db->prepare( " LEFT JOIN %i AS blocklingo_l ON blocklingo_l.object_type = 'post' AND blocklingo_l.object_id = {$posts}.ID", $this->schema->translations() ); // phpcs:ignore WordPress.DB.PreparedSQL.InterpolatedNotPrepared -- core table name.
	}

	/** Tagged posts: their language must match. Untagged: the default language, or a post type that is not translated. */
	private function where_sql( string $lang ): string {
		$settings = $this->settings->get();
		$posts    = $this->db->posts;
		$in       = implode( ',', array_fill( 0, count( $settings->post_types() ), '%s' ) );
		$is_def   = $settings->default_code() === $lang ? 1 : 0;
		// phpcs:ignore WordPress.DB.PreparedSQL.InterpolatedNotPrepared, WordPress.DB.PreparedSQLPlaceholders.UnfinishedPrepare -- core table name; $in holds %s placeholders.
		return (string) $this->db->prepare( " AND ( blocklingo_l.lang = %s OR ( blocklingo_l.lang IS NULL AND ( {$is_def} = 1 OR {$posts}.post_type NOT IN ({$in}) ) ) )", array_merge( array( $lang ), $settings->post_types() ) );
	}
}