<?php
if ( ! defined( 'ABSPATH' ) ) {
    exit;
}

/**
 * Select and rank related gallery content.
 *
 * Candidates must share at least one category or tag. Category matches remain
 * strongest, shared tags add relevance, and view counts are used only as a
 * secondary ordering signal.
 */
final class SG7G_Related {
    private const MAX_CANDIDATES = 200;

    /**
     * Return ranked related post IDs.
     *
     * @param int   $post_id      Current gallery post.
     * @param int   $limit        Number of requested results.
     * @param int[] $excluded_ids Additional post IDs to exclude.
     *
     * @return int[]
     */
    public static function get_ids( int $post_id, int $limit, array $excluded_ids = array() ): array {
        $post_id = absint( $post_id );
        $limit   = min( 12, max( 0, absint( $limit ) ) );

        if ( $post_id <= 0 || $limit <= 0 ) {
            return array();
        }

        $post = get_post( $post_id );
        if ( ! $post instanceof WP_Post || 'sg7g_media' !== $post->post_type || 'publish' !== $post->post_status ) {
            return array();
        }

        $category_ids = self::term_ids( $post_id, 'sg7g_category' );
        $tag_ids      = self::term_ids( $post_id, 'sg7g_tag' );

        if ( empty( $category_ids ) && empty( $tag_ids ) ) {
            return array();
        }

        $excluded_ids   = array_values( array_unique( array_filter( array_map( 'absint', array_merge( array( $post_id ), $excluded_ids ) ) ) ) );
        $candidate_ids  = self::candidate_ids( $category_ids, $tag_ids, $excluded_ids );
        $current_source = self::source_key( $post_id );

        if ( empty( $candidate_ids ) ) {
            return array();
        }

        update_meta_cache( 'post', $candidate_ids );
        update_object_term_cache( $candidate_ids, 'sg7g_media' );

        $scored = array();

        foreach ( $candidate_ids as $candidate_id ) {
            $candidate_id = absint( $candidate_id );
            if ( $candidate_id <= 0 || in_array( $candidate_id, $excluded_ids, true ) ) {
                continue;
            }

            $candidate = get_post( $candidate_id );
            if (
                ! $candidate instanceof WP_Post
                || 'publish' !== $candidate->post_status
                || '' !== (string) $candidate->post_password
            ) {
                continue;
            }

            $candidate_source = self::source_key( $candidate_id );
            if ( '' !== $current_source && '' !== $candidate_source && hash_equals( $current_source, $candidate_source ) ) {
                continue;
            }

            $candidate_categories = self::term_ids( $candidate_id, 'sg7g_category' );
            $candidate_tags       = self::term_ids( $candidate_id, 'sg7g_tag' );
            $category_matches     = count( array_intersect( $category_ids, $candidate_categories ) );
            $tag_matches          = count( array_intersect( $tag_ids, $candidate_tags ) );

            if ( 0 === $category_matches && 0 === $tag_matches ) {
                continue;
            }

            $views = SG7G_Views::get( $candidate_id );
            $score = ( $category_matches * 100 ) + ( $tag_matches * 30 );

            $scored[] = array(
                'id'         => $candidate_id,
                'score'      => $score,
                'categories' => $category_matches,
                'tags'       => $tag_matches,
                'views'      => $views,
                'date'       => (int) get_post_timestamp( $candidate ),
                'source'     => $candidate_source,
            );
        }

        if ( empty( $scored ) ) {
            return array();
        }

        usort(
            $scored,
            static function ( array $left, array $right ): int {
                foreach ( array( 'score', 'categories', 'tags', 'views', 'date' ) as $key ) {
                    $comparison = $right[ $key ] <=> $left[ $key ];
                    if ( 0 !== $comparison ) {
                        return $comparison;
                    }
                }

                return $right['id'] <=> $left['id'];
            }
        );

        $result       = array();
        $seen_sources = '' !== $current_source ? array( $current_source => true ) : array();

        foreach ( $scored as $item ) {
            $source_key = (string) $item['source'];
            if ( '' !== $source_key && isset( $seen_sources[ $source_key ] ) ) {
                continue;
            }

            $result[] = (int) $item['id'];
            if ( '' !== $source_key ) {
                $seen_sources[ $source_key ] = true;
            }

            if ( count( $result ) >= $limit ) {
                break;
            }
        }

        return $result;
    }

    /**
     * Collect candidates from category and tag matches.
     *
     * @param int[] $category_ids Category IDs.
     * @param int[] $tag_ids      Tag IDs.
     * @param int[] $excluded_ids Excluded post IDs.
     *
     * @return int[]
     */
    private static function candidate_ids( array $category_ids, array $tag_ids, array $excluded_ids ): array {
        $tax_query = array( 'relation' => 'OR' );

        if ( ! empty( $category_ids ) ) {
            $tax_query[] = array(
                'taxonomy' => 'sg7g_category',
                'field'    => 'term_id',
                'terms'    => $category_ids,
            );
        }

        if ( ! empty( $tag_ids ) ) {
            $tax_query[] = array(
                'taxonomy' => 'sg7g_tag',
                'field'    => 'term_id',
                'terms'    => $tag_ids,
            );
        }

        if ( count( $tax_query ) <= 1 ) {
            return array();
        }

        $ids = get_posts(
            array(
                'post_type'              => 'sg7g_media',
                'post_status'            => 'publish',
                'has_password'           => false,
                'posts_per_page'         => self::MAX_CANDIDATES,
                'fields'                 => 'ids',
                // phpcs:ignore WordPressVIPMinimum.Performance.WPQueryParams.PostNotIn_post__not_in -- Bounded exclusion list for related content.
                'post__not_in'           => $excluded_ids,
                'ignore_sticky_posts'    => true,
                'no_found_rows'          => true,
                'orderby'                => 'date',
                'order'                  => 'DESC',
                // phpcs:ignore WordPress.DB.SlowDBQuery.slow_db_query_tax_query -- Bounded related-content taxonomy match.
                'tax_query'              => $tax_query,
                'update_post_meta_cache' => false,
                'update_post_term_cache' => false,
            )
        );

        return array_values( array_unique( array_filter( array_map( 'absint', $ids ) ) ) );
    }

    /**
     * Return term IDs safely.
     *
     * @return int[]
     */
    private static function term_ids( int $post_id, string $taxonomy ): array {
        $terms = wp_get_post_terms( $post_id, $taxonomy, array( 'fields' => 'ids' ) );
        return is_wp_error( $terms ) ? array() : array_values( array_unique( array_map( 'absint', $terms ) ) );
    }

    /**
     * Build a canonical source key to suppress duplicate media records.
     */
    private static function source_key( int $post_id ): string {
        $source  = (string) get_post_meta( $post_id, '_sg7g_source', true );
        $file_id = absint( get_post_meta( $post_id, '_sg7g_file_id', true ) );
        $url     = html_entity_decode( (string) get_post_meta( $post_id, '_sg7g_source_url', true ), ENT_QUOTES, 'UTF-8' );

        if ( $file_id > 0 ) {
            return 'file:' . $file_id;
        }

        if ( '' === $url ) {
            return '';
        }

        if ( in_array( $source, array( 'youtube', 'youtube_music' ), true ) ) {
            $video_id    = SG7G_Meta_Boxes::youtube_id( $url );
            $playlist_id = SG7G_Meta_Boxes::youtube_playlist_id( $url );
            if ( $video_id || $playlist_id ) {
                return 'youtube:' . $video_id . ':' . $playlist_id;
            }
        }

        if ( 'vimeo' === $source ) {
            $video_id = SG7G_Meta_Boxes::vimeo_id( $url );
            if ( $video_id ) {
                return 'vimeo:' . $video_id . ':' . SG7G_Meta_Boxes::vimeo_hash( $url );
            }
        }

        $parts = wp_parse_url( $url );
        $path  = trim( (string) ( is_array( $parts ) ? ( $parts['path'] ?? '' ) : '' ), '/' );

        if ( 'spotify' === $source ) {
            $segments = self::normalized_segments( $path );
            if ( isset( $segments[0] ) && 'embed' === strtolower( $segments[0] ) ) {
                array_shift( $segments );
            }
            if ( isset( $segments[0], $segments[1] ) ) {
                return 'spotify:' . strtolower( $segments[0] ) . ':' . $segments[1];
            }
        }

        if ( 'deezer' === $source ) {
            $segments = self::normalized_segments( $path );
            if ( isset( $segments[0], $segments[1] ) ) {
                return 'deezer:' . strtolower( $segments[0] ) . ':' . $segments[1];
            }
        }

        if ( 'apple_music' === $source ) {
            $query = array();
            if ( is_array( $parts ) && ! empty( $parts['query'] ) ) {
                parse_str( (string) $parts['query'], $query );
            }
            if ( ! empty( $query['i'] ) ) {
                return 'apple_music:track:' . sanitize_key( (string) $query['i'] );
            }
            if ( preg_match( '/(?:^|\/)(\d+)(?:\/)?$/', $path, $matches ) ) {
                return 'apple_music:collection:' . $matches[1];
            }
        }

        if ( ! is_array( $parts ) || empty( $parts['host'] ) ) {
            return strtolower( trim( $url ) );
        }

        $host  = strtolower( preg_replace( '/^www\./', '', (string) $parts['host'] ) );
        $path  = untrailingslashit( '/' . ltrim( (string) ( $parts['path'] ?? '' ), '/' ) );
        $query = array();

        if ( ! empty( $parts['query'] ) ) {
            parse_str( (string) $parts['query'], $query );
            foreach ( array_keys( $query ) as $key ) {
                if ( str_starts_with( strtolower( (string) $key ), 'utm_' ) || in_array( strtolower( (string) $key ), array( 'fbclid', 'gclid', 'si', 'feature' ), true ) ) {
                    unset( $query[ $key ] );
                }
            }
            ksort( $query );
        }

        return $source . ':' . $host . rawurldecode( $path ) . ( $query ? '?' . http_build_query( $query ) : '' );
    }

    /**
     * Remove locale prefixes from platform paths.
     *
     * @return string[]
     */
    private static function normalized_segments( string $path ): array {
        $segments = array_values( array_filter( explode( '/', trim( $path, '/' ) ) ) );
        if (
            isset( $segments[0] )
            && (
                preg_match( '/^intl-[a-z]{2}$/i', $segments[0] )
                || preg_match( '/^[a-z]{2}(?:-[a-z]{2})?$/i', $segments[0] )
            )
        ) {
            array_shift( $segments );
        }

        return $segments;
    }

}