<?php
/**
 * Redirect rules storage and validation.
 *
 * @package Unbreak
 */

namespace Unbreak\Redirects;

use Unbreak\Install\Schema;
use Unbreak\Support\Clock;
use Unbreak\Support\Url;

defined( 'ABSPATH' ) || exit;

/**
 * CRUD for {prefix}unbreak_redirects with loop and chain detection on save.
 */
final class RedirectRepository {

	public const CODES     = array( 301, 302, 307, 308 );
	public const MODES     = array( '404', 'always' );
	public const MAX_CHAIN = 3;

	/**
	 * Paginated list.
	 *
	 * @param string $search   Search in source/target.
	 * @param int    $page     Page (1-based).
	 * @param int    $per_page Rows per page.
	 * @return array{items:array<int,array<string,mixed>>,total:int}
	 */
	public function paginate( string $search = '', int $page = 1, int $per_page = 50 ): array {
		global $wpdb;
		$table  = Schema::table( 'redirects' );
		$like   = '%' . $wpdb->esc_like( $search ) . '%';
		$offset = max( 0, ( $page - 1 ) * $per_page );
		// An empty search makes the first condition true, so one literal query covers both cases.
		// phpcs:disable WordPress.DB.DirectDatabaseQuery.DirectQuery,WordPress.DB.DirectDatabaseQuery.NoCaching -- Plugin table.
		$total = (int) $wpdb->get_var( $wpdb->prepare( "SELECT COUNT(*) FROM %i WHERE ( %s = '' OR source_path LIKE %s OR target_url LIKE %s )", $table, $search, $like, $like ) );
		$rows  = $wpdb->get_results( $wpdb->prepare( "SELECT * FROM %i WHERE ( %s = '' OR source_path LIKE %s OR target_url LIKE %s ) ORDER BY id DESC LIMIT %d OFFSET %d", $table, $search, $like, $like, $per_page, $offset ), ARRAY_A );
		// phpcs:enable
		return array(
			'items' => array_map( array( self::class, 'shape' ), (array) $rows ),
			'total' => $total,
		);
	}

	/**
	 * All enabled rules (used to build the front-end map).
	 *
	 * @return array<int,array<string,mixed>>
	 */
	public function enabled(): array {
		global $wpdb;
		$table = Schema::table( 'redirects' );
		// phpcs:ignore WordPress.DB.PreparedSQL.InterpolatedNotPrepared,WordPress.DB.DirectDatabaseQuery.DirectQuery,WordPress.DB.DirectDatabaseQuery.NoCaching -- Cached by Redirector.
		return (array) $wpdb->get_results( $wpdb->prepare( 'SELECT id, source_path, target_url, code, match_mode FROM %i WHERE enabled = 1', $table ), ARRAY_A );
	}

	/**
	 * One rule.
	 *
	 * @param int $id ID.
	 * @return array<string,mixed>|null
	 */
	public function find( int $id ): ?array {
		global $wpdb;
		$table = Schema::table( 'redirects' );
		// phpcs:ignore WordPress.DB.PreparedSQL.InterpolatedNotPrepared,WordPress.DB.DirectDatabaseQuery.DirectQuery,WordPress.DB.DirectDatabaseQuery.NoCaching -- Plugin table.
		$row = $wpdb->get_row( $wpdb->prepare( 'SELECT * FROM %i WHERE id = %d', $table, $id ), ARRAY_A );
		return is_array( $row ) ? self::shape( $row ) : null;
	}

	/**
	 * Find by normalized source.
	 *
	 * @param string $source Normalized source path.
	 * @return array<string,mixed>|null
	 */
	public function find_by_source( string $source ): ?array {
		global $wpdb;
		$table = Schema::table( 'redirects' );
		// phpcs:ignore WordPress.DB.PreparedSQL.InterpolatedNotPrepared,WordPress.DB.DirectDatabaseQuery.DirectQuery,WordPress.DB.DirectDatabaseQuery.NoCaching -- Plugin table.
		$row = $wpdb->get_row( $wpdb->prepare( 'SELECT * FROM %i WHERE source_hash = %s', $table, sha1( $source ) ), ARRAY_A );
		return is_array( $row ) ? self::shape( $row ) : null;
	}

	/**
	 * Create or update a rule after validation.
	 *
	 * @param array<string,mixed> $input  source_path, target_url, code, match_mode, enabled.
	 * @param int                 $id     Existing ID (0 = create).
	 * @return array<string,mixed>|\WP_Error Saved rule or error.
	 */
	public function save( array $input, int $id = 0 ) {
		global $wpdb;
		$clean = $this->validate( $input, $id );
		if ( is_wp_error( $clean ) ) {
			return $clean;
		}
		$table = Schema::table( 'redirects' );
		$data  = array(
			'source_path' => $clean['source_path'],
			'source_hash' => sha1( $clean['source_path'] ),
			'target_url'  => $clean['target_url'],
			'code'        => $clean['code'],
			'match_mode'  => $clean['match_mode'],
			'enabled'     => $clean['enabled'],
		);
		if ( $id > 0 ) {
			$wpdb->update( $table, $data, array( 'id' => $id ) ); // phpcs:ignore WordPress.DB.DirectDatabaseQuery.DirectQuery,WordPress.DB.DirectDatabaseQuery.NoCaching -- Plugin table.
		} else {
			$data['created_at'] = Clock::mysql();
			$wpdb->insert( $table, $data ); // phpcs:ignore WordPress.DB.DirectDatabaseQuery.DirectQuery -- Plugin table.
			$id = (int) $wpdb->insert_id;
		}
		Redirector::flush_cache();
		$saved = $this->find( $id );
		return null !== $saved ? $saved : new \WP_Error( 'unbreak_redirect_save', __( 'The redirect could not be saved.', 'unbreak' ) );
	}

	/**
	 * Delete a rule.
	 *
	 * @param int $id ID.
	 */
	public function delete( int $id ): bool {
		global $wpdb;
		$deleted = (bool) $wpdb->delete( Schema::table( 'redirects' ), array( 'id' => $id ), array( '%d' ) ); // phpcs:ignore WordPress.DB.DirectDatabaseQuery.DirectQuery,WordPress.DB.DirectDatabaseQuery.NoCaching -- Plugin table.
		Redirector::flush_cache();
		return $deleted;
	}

	/**
	 * Count a hit.
	 *
	 * @param int $id ID.
	 */
	public function hit( int $id ): void {
		global $wpdb;
		$table = Schema::table( 'redirects' );
		// phpcs:ignore WordPress.DB.PreparedSQL.InterpolatedNotPrepared,WordPress.DB.DirectDatabaseQuery.DirectQuery,WordPress.DB.DirectDatabaseQuery.NoCaching -- One write per redirected request.
		$wpdb->query( $wpdb->prepare( 'UPDATE %i SET hits = hits + 1, last_hit_at = %s WHERE id = %d', $table, Clock::mysql(), $id ) );
	}

	/**
	 * Validate and normalize input.
	 *
	 * @param array<string,mixed> $input Input.
	 * @param int                 $id    Rule being edited (0 = new).
	 * @return array{source_path:string,target_url:string,code:int,match_mode:string,enabled:int}|\WP_Error
	 */
	public function validate( array $input, int $id = 0 ) {
		$source = Path::normalize( (string) ( $input['source_path'] ?? '' ), true );
		if ( null === $source || '/' === $source ) {
			return new \WP_Error( 'unbreak_redirect_source', __( 'Enter a valid source path on this site, for example /old-page/.', 'unbreak' ), array( 'status' => 400 ) );
		}

		$target_raw = trim( (string) ( $input['target_url'] ?? '' ) );
		if ( '' === $target_raw ) {
			return new \WP_Error( 'unbreak_redirect_target', __( 'Enter a target URL or path.', 'unbreak' ), array( 'status' => 400 ) );
		}
		if ( '/' === $target_raw[0] && ( ! isset( $target_raw[1] ) || '/' !== $target_raw[1] ) ) {
			$target = esc_url_raw( home_url( $target_raw ) );
		} else {
			$target = esc_url_raw( $target_raw, array( 'http', 'https' ) );
		}
		if ( '' === $target || null === Url::canonicalize( $target ) ) {
			return new \WP_Error( 'unbreak_redirect_target', __( 'The target must be an http(s) URL or a path starting with /.', 'unbreak' ), array( 'status' => 400 ) );
		}

		$code = (int) ( $input['code'] ?? 301 );
		if ( ! in_array( $code, self::CODES, true ) ) {
			$code = 301;
		}
		$mode = (string) ( $input['match_mode'] ?? '404' );
		if ( ! in_array( $mode, self::MODES, true ) ) {
			$mode = '404';
		}
		$enabled = ! isset( $input['enabled'] ) || ! empty( $input['enabled'] ) ? 1 : 0;

		$existing = $this->find_by_source( $source );
		if ( null !== $existing && (int) $existing['id'] !== $id ) {
			return new \WP_Error( 'unbreak_redirect_duplicate', __( 'A redirect for this source path already exists.', 'unbreak' ), array( 'status' => 409 ) );
		}

		$target_key = Url::is_internal( $target ) ? Path::normalize( $target, true ) : null;
		if ( null !== $target_key && ( $target_key === $source || Path::strip_query( $target_key ) === $source ) ) {
			return new \WP_Error( 'unbreak_redirect_loop', __( 'This redirect points to itself.', 'unbreak' ), array( 'status' => 400 ) );
		}

		$chain = $this->chain_error( $source, $target_key, $id );
		if ( null !== $chain ) {
			return $chain;
		}

		return array(
			'source_path' => $source,
			'target_url'  => $target,
			'code'        => $code,
			'match_mode'  => $mode,
			'enabled'     => $enabled,
		);
	}

	/**
	 * Detect loops and chains longer than MAX_CHAIN hops that the new rule would create.
	 *
	 * @param string      $source     New rule source.
	 * @param string|null $target_key New rule internal target (null = external target).
	 * @param int         $id         Rule being edited.
	 */
	private function chain_error( string $source, ?string $target_key, int $id ): ?\WP_Error {
		$edges = array();
		foreach ( $this->enabled() as $rule ) {
			if ( (int) $rule['id'] === $id ) {
				continue;
			}
			$to = Url::is_internal( (string) $rule['target_url'] ) ? Path::normalize( (string) $rule['target_url'], true ) : null;
			if ( null !== $to ) {
				$edges[ (string) $rule['source_path'] ] = $to;
			}
		}
		if ( null !== $target_key ) {
			$edges[ $source ] = $target_key;
		}

		// Forward: follow the chain starting at the new rule.
		$forward = 0;
		$seen    = array( $source => true );
		$current = $source;
		while ( isset( $edges[ $current ] ) ) {
			$current = $edges[ $current ];
			++$forward;
			if ( isset( $seen[ $current ] ) ) {
				return new \WP_Error( 'unbreak_redirect_loop', __( 'This redirect would create a redirect loop.', 'unbreak' ), array( 'status' => 400 ) );
			}
			$seen[ $current ] = true;
		}

		// Backward: rules that already lead to the new source.
		$backward = 0;
		$frontier = array( $source );
		$visited  = array( $source => true );
		while ( $backward <= self::MAX_CHAIN ) {
			$next = array();
			foreach ( $edges as $from => $to ) {
				if ( in_array( $to, $frontier, true ) && ! isset( $visited[ $from ] ) ) {
					$next[]           = $from;
					$visited[ $from ] = true;
				}
			}
			if ( empty( $next ) ) {
				break;
			}
			++$backward;
			$frontier = $next;
		}

		if ( $forward + $backward > self::MAX_CHAIN ) {
			return new \WP_Error(
				'unbreak_redirect_chain',
				/* translators: %d: maximum number of hops. */
				sprintf( __( 'This redirect would create a chain of more than %d hops. Point it at the final destination instead.', 'unbreak' ), self::MAX_CHAIN ),
				array( 'status' => 400 )
			);
		}
		return null;
	}

	/**
	 * Cast a DB row for the API.
	 *
	 * @param array<string,mixed> $row Row.
	 * @return array<string,mixed>
	 */
	public static function shape( array $row ): array {
		return array(
			'id'          => (int) $row['id'],
			'source_path' => (string) $row['source_path'],
			'target_url'  => (string) $row['target_url'],
			'code'        => (int) $row['code'],
			'match_mode'  => (string) $row['match_mode'],
			'hits'        => isset( $row['hits'] ) ? (int) $row['hits'] : 0,
			'last_hit_at' => isset( $row['last_hit_at'] ) ? $row['last_hit_at'] : null,
			'created_at'  => isset( $row['created_at'] ) ? $row['created_at'] : null,
			'enabled'     => isset( $row['enabled'] ) ? (bool) (int) $row['enabled'] : true,
		);
	}
}