<?php
/**
 * Front-end redirect execution.
 *
 * @package Unbreak
 */

namespace Unbreak\Redirects;

use Unbreak\Support\Settings;

defined( 'ABSPATH' ) || exit;

/**
 * Runs on template_redirect. Normal page views cost no queries: "always" rules live in an
 * autoloaded transient, "404" rules are only loaded on 404 responses.
 */
final class Redirector {

	public const MAP_ALWAYS = 'unbreak_redirect_map_always';
	public const MAP_404    = 'unbreak_redirect_map_404';

	/**
	 * Repository.
	 *
	 * @var RedirectRepository
	 */
	private $repo;

	/**
	 * Constructor.
	 *
	 * @param RedirectRepository|null $repo Repository.
	 */
	public function __construct( ?RedirectRepository $repo = null ) {
		$this->repo = $repo ?? new RedirectRepository();
	}

	/**
	 * Register hooks.
	 */
	public function register(): void {
		add_action( 'template_redirect', array( $this, 'maybe_redirect' ), 1 );
	}

	/**
	 * Invalidate cached maps.
	 */
	public static function flush_cache(): void {
		delete_transient( self::MAP_ALWAYS );
		delete_transient( self::MAP_404 );
	}

	/**
	 * Redirect the current request if a rule matches.
	 */
	public function maybe_redirect(): void {
		$uri   = isset( $_SERVER['REQUEST_URI'] ) ? wp_unslash( $_SERVER['REQUEST_URI'] ) : ''; // phpcs:ignore WordPress.Security.ValidatedSanitizedInput.InputNotSanitized -- Normalized by Path::normalize().
		$match = $this->match( (string) $uri, is_404() );
		if ( null === $match ) {
			return;
		}
		$this->repo->hit( (int) $match['id'] );
		// phpcs:ignore WordPress.Security.SafeRedirect.wp_redirect_wp_redirect -- Targets are admin-defined and may be external.
		if ( wp_redirect( $match['target'], (int) $match['code'], 'Unbreak' ) ) {
			$this->stop();
		}
	}

	/**
	 * Exit after redirecting (separate so the behaviour can be overridden via the filter).
	 */
	private function stop(): void {
		/**
		 * Whether to exit after sending a redirect.
		 *
		 * @param bool $exit Exit.
		 */
		if ( apply_filters( 'unbreak_redirect_exit', true ) ) {
			exit;
		}
	}

	/**
	 * Find the rule for a request.
	 *
	 * @param string $request_uri Request URI.
	 * @param bool   $is_404      Whether WordPress resolved the request to a 404.
	 * @return array{id:int,target:string,code:int}|null
	 */
	public function match( string $request_uri, bool $is_404 ): ?array {
		$always = $this->map( 'always' );
		if ( ! $is_404 && empty( $always ) ) {
			return null;
		}
		$mode = (string) Settings::get( 'redirect_query' );
		$full = Path::normalize( $request_uri, true );
		$path = Path::normalize( $request_uri, false );
		if ( null === $path ) {
			return null;
		}
		$keys = array();
		if ( null !== $full && $full !== $path ) {
			$keys[] = $full;
		}
		if ( 'exact' !== $mode || $full === $path ) {
			$keys[] = $path;
		}

		$maps = $is_404 ? array( $always, $this->map( '404' ) ) : array( $always );
		foreach ( $maps as $map ) {
			foreach ( $keys as $key ) {
				if ( isset( $map[ $key ] ) ) {
					$rule   = $map[ $key ];
					$target = (string) $rule[1];
					if ( 'pass' === $mode && null !== $full && $full !== $path && false === strpos( $target, '?' ) ) {
						$target .= '?' . substr( $full, strlen( $path ) + 1 );
					}
					return array(
						'id'     => (int) $rule[0],
						'target' => $target,
						'code'   => (int) $rule[2],
					);
				}
			}
		}
		return null;
	}

	/**
	 * Cached map for one match mode: normalized source => [id, target, code].
	 *
	 * @param string $mode "always" or "404".
	 * @return array<string,array{0:int,1:string,2:int}>
	 */
	public function map( string $mode ): array {
		$name   = 'always' === $mode ? self::MAP_ALWAYS : self::MAP_404;
		$cached = get_transient( $name );
		if ( is_array( $cached ) ) {
			return $cached;
		}
		$always = array();
		$on404  = array();
		foreach ( $this->repo->enabled() as $rule ) {
			$entry = array( (int) $rule['id'], (string) $rule['target_url'], (int) $rule['code'] );
			if ( 'always' === $rule['match_mode'] ) {
				$always[ (string) $rule['source_path'] ] = $entry;
			} else {
				$on404[ (string) $rule['source_path'] ] = $entry;
			}
		}
		// No expiration => autoloaded => zero queries on normal page views.
		set_transient( self::MAP_ALWAYS, $always );
		set_transient( self::MAP_404, $on404, WEEK_IN_SECONDS );
		return 'always' === $mode ? $always : $on404;
	}
}