<?php
/**
 * Content selection for feeds.
 *
 * @package FeedWeaver
 */

namespace FeedWeaver\Query;

use FeedWeaver\Config\Feed_Config;

defined( 'ABSPATH' ) || exit;

/**
 * Selects only public, published, non-password-protected content and bounds
 * every query. Visibility is enforced twice: in the query and again per post.
 */
class Content_Query {

	/**
	 * Post types a feed may use (see Eligibility for the policy).
	 *
	 * @return array<string,string> Post type => label.
	 */
	public function eligible_post_types(): array {
		return Eligibility::post_types();
	}

	/**
	 * Fetches the posts for a feed.
	 *
	 * All selected post types are queried together, so the newest-first order and
	 * the item limit apply to the combined results. Taxonomy filters combine with
	 * AND between taxonomies and OR between the terms of one taxonomy. A post type
	 * that does not use a filtered taxonomy cannot match and is left out of the query.
	 *
	 * @param Feed_Config $config Feed configuration.
	 * @return \WP_Post[]|\WP_Error
	 */
	public function fetch( Feed_Config $config ) {
		foreach ( $config->post_types as $post_type ) {
			if ( ! Eligibility::is_post_type_eligible( $post_type ) ) {
				return new \WP_Error( 'feedweaver_post_type', __( 'A selected content type is not publicly available.', 'feedweaver' ) );
			}
		}

		$types     = $config->post_types;
		$tax_query = array( 'relation' => 'AND' );
		foreach ( $config->tax_filters as $taxonomy => $term_ids ) {
			if ( ! Eligibility::is_taxonomy_eligible( $taxonomy ) ) {
				return new \WP_Error( 'feedweaver_taxonomy', __( 'A selected taxonomy filter is not available.', 'feedweaver' ) );
			}
			$types       = array_values(
				array_filter(
					$types,
					static function ( $type ) use ( $taxonomy ) {
						return is_object_in_taxonomy( $type, $taxonomy );
					}
				)
			);
			$tax_query[] = array(
				'taxonomy'         => $taxonomy,
				'field'            => 'term_id',
				'terms'            => array_map( 'intval', $term_ids ),
				'operator'         => 'IN',
				'include_children' => is_taxonomy_hierarchical( $taxonomy ),
			);
		}
		if ( ! $types ) {
			return array();
		}

		$args = array(
			'post_type'           => $types,
			'post_status'         => 'publish',
			'has_password'        => false,
			'posts_per_page'      => max( 1, min( Feed_Config::MAX_ITEMS, $config->limit ) ),
			// Newest first; the ID makes the order deterministic when dates are equal.
			'orderby'             => array(
				'date' => 'DESC',
				'ID'   => 'DESC',
			),
			'no_found_rows'       => true,
			'ignore_sticky_posts' => true,
		);
		if ( count( $tax_query ) > 1 ) {
			$args['tax_query'] = $tax_query; // phpcs:ignore WordPress.DB.SlowDBQuery.slow_db_query_tax_query -- bounded, indexed query.
		}

		$query = new \WP_Query( $args );
		// Prime caches in bulk so large feeds do not run a query per post. Term caches are
		// primed by WP_Query itself (update_post_term_cache defaults to true).
		update_post_thumbnail_cache( $query );
		cache_users( array_unique( wp_list_pluck( $query->posts, 'post_author' ) ) );

		$posts = array();
		foreach ( $query->posts as $post ) {
			if ( $this->is_eligible( $post ) ) {
				$posts[] = $post;
			}
		}
		return $posts;
	}

	/**
	 * Defence in depth: never trust the query alone.
	 *
	 * @param \WP_Post $post Post.
	 * @return bool
	 */
	public function is_eligible( \WP_Post $post ): bool {
		return 'publish' === $post->post_status
			&& '' === $post->post_password
			&& is_post_publicly_viewable( $post );
	}
}