<?php
/**
 * Maps FAQs to API items and content hashes.
 *
 * @package Spindle_FAQ
 */

if ( ! defined( 'ABSPATH' ) ) {
	exit;
}

final class SPFAQ_API_Mapper {

	const API_VERSION = 1;

	/**
	 * Whether a post may be exposed to companion plugins.
	 *
	 * @param WP_Post|int $post Post.
	 * @return bool
	 */
	public static function eligible( $post ) {
		$post = get_post( $post );
		if ( ! $post || 'spfaq_faq' !== $post->post_type || 'publish' !== $post->post_status || '' !== $post->post_password ) {
			return false;
		}
		if ( 'excluded' === get_post_meta( $post->ID, '_spfaq_sync', true ) ) {
			return false;
		}
		return (bool) apply_filters( 'spfaq_knowledge_eligible', true, $post );
	}

	/**
	 * Stable ID for a FAQ, created on first use. Survives edits, slug changes and exports.
	 *
	 * @param int $post_id Post ID.
	 * @return string
	 */
	public static function uid( $post_id ) {
		$uid = (string) get_post_meta( $post_id, '_spfaq_uid', true );
		if ( '' === $uid ) {
			$uid = wp_generate_uuid4();
			update_post_meta( $post_id, '_spfaq_uid', $uid );
		}
		return $uid;
	}

	/**
	 * Resolve a stable ID (or numeric ID) to a post.
	 *
	 * @param string $id UID or numeric ID.
	 * @return WP_Post|null
	 */
	public static function resolve( $id ) {
		$id = sanitize_text_field( (string) $id );
		if ( ctype_digit( $id ) ) {
			$post = get_post( (int) $id );
			return ( $post && 'spfaq_faq' === $post->post_type ) ? $post : null;
		}
		if ( ! preg_match( '/^[0-9a-f-]{36}$/i', $id ) ) {
			return null;
		}
		$found = get_posts(
			array(
				'post_type'      => 'spfaq_faq',
				'post_status'    => 'any',
				'posts_per_page' => 1,
				'fields'         => 'ids',
				'no_found_rows'  => true,
				'meta_key'       => '_spfaq_uid', // phpcs:ignore WordPress.DB.SlowDBQuery.slow_db_query_meta_key -- single indexed lookup
				'meta_value'     => strtolower( $id ), // phpcs:ignore WordPress.DB.SlowDBQuery.slow_db_query_meta_value
			)
		);
		return $found ? get_post( $found[0] ) : null;
	}

	/**
	 * Plain-text answer.
	 *
	 * @param WP_Post $post Post.
	 * @return string
	 */
	private static function answer_text( $post ) {
		$text = wp_strip_all_tags( strip_shortcodes( $post->post_content ), true );
		return trim( preg_replace( '/\s+/u', ' ', html_entity_decode( $text, ENT_QUOTES, 'UTF-8' ) ) );
	}

	/**
	 * Terms of a taxonomy as small arrays.
	 *
	 * @param int    $post_id  Post ID.
	 * @param string $taxonomy Taxonomy.
	 * @return array
	 */
	private static function terms( $post_id, $taxonomy ) {
		$terms = get_the_terms( $post_id, $taxonomy );
		$out   = array();
		if ( is_array( $terms ) ) {
			foreach ( $terms as $t ) {
				$out[] = array(
					'id'   => (int) $t->term_id,
					'slug' => $t->slug,
					'name' => wp_strip_all_tags( $t->name ),
				);
			}
		}
		return $out;
	}

	/**
	 * Content hash. Changes whenever the question, answer, URL or topics change.
	 *
	 * @param WP_Post $post Post.
	 * @return string
	 */
	public static function content_hash( $post ) {
		$cats = wp_list_pluck( self::terms( $post->ID, 'spfaq_category' ), 'slug' );
		$tags = wp_list_pluck( self::terms( $post->ID, 'spfaq_tag' ), 'slug' );
		sort( $cats );
		sort( $tags );
		return hash(
			'sha256',
			wp_json_encode(
				array(
					wp_strip_all_tags( $post->post_title ),
					self::answer_text( $post ),
					get_permalink( $post ),
					$cats,
					$tags,
				)
			)
		);
	}

	/**
	 * Sync status for a FAQ: excluded, pending, indexed or stale.
	 *
	 * @param WP_Post $post Post.
	 * @param string  $hash Current content hash.
	 * @return string
	 */
	public static function sync_status( $post, $hash ) {
		if ( 'excluded' === get_post_meta( $post->ID, '_spfaq_sync', true ) ) {
			return 'excluded';
		}
		$ack = (string) get_post_meta( $post->ID, '_spfaq_sync_ack', true );
		if ( '' === $ack ) {
			return 'pending';
		}
		return hash_equals( $ack, $hash ) ? 'indexed' : 'stale';
	}

	/**
	 * Public representation of a FAQ.
	 *
	 * @param WP_Post $post Post.
	 * @return array
	 */
	public static function item( $post ) {
		$hash = self::content_hash( $post );
		$item = array(
			'id'            => self::uid( $post->ID ),
			'wp_id'         => (int) $post->ID,
			'title'         => wp_strip_all_tags( $post->post_title ),
			'answer_text'   => self::answer_text( $post ),
			'answer_html'   => wp_kses_post( wpautop( strip_shortcodes( $post->post_content ) ) ),
			'url'           => get_permalink( $post ),
			'anchor'        => 'faq-' . $post->post_name,
			'updated_gmt'   => self::iso( $post->post_modified_gmt ),
			'published_gmt' => self::iso( $post->post_date_gmt ),
			'content_hash'  => $hash,
			'language'      => get_locale(),
			'categories'    => self::terms( $post->ID, 'spfaq_category' ),
			'groups'        => self::terms( $post->ID, 'spfaq_group' ),
			'tags'          => self::terms( $post->ID, 'spfaq_tag' ),
			'votes'         => array(
				'yes' => (int) get_post_meta( $post->ID, 'spfaq_yes', true ),
				'no'  => (int) get_post_meta( $post->ID, 'spfaq_no', true ),
			),
			'sync'          => array(
				'status'     => self::sync_status( $post, $hash ),
				'indexed_at' => (string) get_post_meta( $post->ID, '_spfaq_sync_ack_at', true ),
			),
		);
		/**
		 * Filter the knowledge item before it is returned.
		 *
		 * @param array   $item Item.
		 * @param WP_Post $post Post.
		 */
		return apply_filters( 'spfaq_knowledge_item', $item, $post );
	}

	/**
	 * GMT MySQL date to ISO 8601 with an explicit Z, so clients never guess the zone.
	 *
	 * @param string $mysql_gmt Date as Y-m-d H:i:s in GMT.
	 * @return string
	 */
	public static function iso( $mysql_gmt ) {
		$ts = strtotime( $mysql_gmt . ' UTC' );
		return $ts ? gmdate( 'Y-m-d\TH:i:s\Z', $ts ) : '';
	}

	/**
	 * Parse an ISO 8601 date to a GMT MySQL string, or false.
	 *
	 * @param string $value Date.
	 * @return string|false
	 */
	public static function parse_date( $value ) {
		$ts = strtotime( (string) $value );
		return $ts ? gmdate( 'Y-m-d H:i:s', $ts ) : false;
	}

	/**
	 * Base query arguments for eligible FAQs.
	 *
	 * @return array
	 */
	public static function base_args() {
		return array(
			'post_type'    => 'spfaq_faq',
			'post_status'  => 'publish',
			'has_password' => false,
			'meta_query'   => array( // phpcs:ignore WordPress.DB.SlowDBQuery.slow_db_query_meta_query -- needed to honour the per-FAQ exclusion flag
				'relation' => 'OR',
				array(
					'key'     => '_spfaq_sync',
					'compare' => 'NOT EXISTS',
				),
				array(
					'key'     => '_spfaq_sync',
					'value'   => 'excluded',
					'compare' => '!=',
				),
			),
		);
	}
}