<?php
/**
 * Detects posts that have no internal links pointing to them.
 *
 * @package Postlinkly
 * @since   1.0.0
 */

declare(strict_types=1);

namespace Postlinkly\InternalRot;

use Postlinkly\Database\TableNames;

/**
 * Detects orphaned posts — published posts with zero inbound internal links.
 *
 * An orphaned post is one that no other post on the site links to. From
 * an SEO perspective these are "dead ends" — search engines can find them
 * via the sitemap but they receive no PageRank from internal linking.
 *
 * The query strategy:
 *   - Selects all published posts of the configured types.
 *   - LEFT JOINs against `report_links` on target_id where is_internal = 1.
 *   - Returns posts where the join produced no match (zero inbound links).
 *
 * This is a pure DB query — no HTTP, no cron, no scanner state.
 * The report page calls it on demand.
 *
 * @since 1.0.0
 */
final class OrphanedPostsDetector {

	/**
	 * Returns all published posts that have no inbound internal links.
	 *
	 * @since 1.0.0
	 *
	 * @param int                $limit      Optional. Maximum rows to return. Default 500.
	 * @param array<int, string> $post_types Optional. Post types to check. Default ['post', 'page'].
	 *
	 * @return array<int, object> Each object has ID, post_title, post_name, post_type, post_date.
	 */
	public function detect( int $limit = 500, array $post_types = array( 'post', 'page' ) ): array {
		global $wpdb;

		if ( ! isset( $wpdb ) || array() === $post_types ) {
			return array();
		}

		$limit      = max( 1, min( $limit, 5000 ) );
		$table      = TableNames::report_links();
		$type_count = count( $post_types );

		if ( $type_count <= 0 ) {
			return array();
		}

		$placeholders = implode( ', ', array_fill( 0, $type_count, '%s' ) );

		// phpcs:disable WordPress.DB.DirectDatabaseQuery.DirectQuery,WordPress.DB.DirectDatabaseQuery.NoCaching,WordPress.DB.PreparedSQL.InterpolatedNotPrepared,WordPress.DB.PreparedSQLPlaceholders.ReplacementsWrongNumber -- $placeholders is built from %s literals; dynamic IN() list is the standard WP pattern.
		$rows = $wpdb->get_results(
			$wpdb->prepare(
				"SELECT p.ID, p.post_title, p.post_name, p.post_type, p.post_date
				FROM {$wpdb->posts} AS p
				LEFT JOIN %i AS rl
					ON rl.target_id = p.ID
					AND rl.is_internal = 1
				WHERE p.post_status = 'publish'
				AND p.post_type IN ({$placeholders})
				AND rl.id IS NULL
				ORDER BY p.post_date DESC
				LIMIT %d",
				array_merge( array( $table ), $post_types, array( $limit ) )
			)
		);
		// phpcs:enable

		return is_array( $rows ) ? $rows : array();
	}

	/**
	 * Returns the count of orphaned posts without fetching them.
	 *
	 * @since 1.0.0
	 *
	 * @param array<int, string> $post_types Optional. Post types to check. Default ['post', 'page'].
	 *
	 * @return int
	 */
	public function count( array $post_types = array( 'post', 'page' ) ): int {
		global $wpdb;

		if ( ! isset( $wpdb ) || array() === $post_types ) {
			return 0;
		}

		$table        = TableNames::report_links();
		$type_count   = count( $post_types );
		$placeholders = implode( ', ', array_fill( 0, $type_count, '%s' ) );

		// phpcs:disable WordPress.DB.DirectDatabaseQuery.DirectQuery,WordPress.DB.DirectDatabaseQuery.NoCaching,WordPress.DB.PreparedSQL.InterpolatedNotPrepared,WordPress.DB.PreparedSQLPlaceholders.ReplacementsWrongNumber -- $placeholders is built from %s literals.
		$count = $wpdb->get_var(
			$wpdb->prepare(
				"SELECT COUNT(p.ID)
				FROM {$wpdb->posts} AS p
				LEFT JOIN %i AS rl
					ON rl.target_id = p.ID
					AND rl.is_internal = 1
				WHERE p.post_status = 'publish'
				AND p.post_type IN ({$placeholders})
				AND rl.id IS NULL",
				array_merge( array( $table ), $post_types )
			)
		);
		// phpcs:enable

		return is_numeric( $count ) ? (int) $count : 0;
	}
}