<?php

/**
 * Provides permalink migration facilities
 */
class Red_Permalinks {
	/**
	 * List of migrated permalink structures
	 *
	 * @var string[]
	 */
	private $permalinks = [];

	/**
	 * Current permalink structure
	 *
	 * @var string|null
	 */
	private $current_permalink = null;

	/**
	 * Constructor
	 *
	 * @param string[] $permalinks List of migrated permalinks.
	 */
	public function __construct( $permalinks ) {
		$this->permalinks = $permalinks;
	}

	/**
	 * Match and migrate any permalinks
	 *
	 * @param WP_Query $query Query.
	 * @return void
	 */
	public function migrate( WP_Query $query ) {
		global $wp;

		if ( count( $this->permalinks ) === 0 ) {
			return;
		}

		if ( ! $this->needs_migrating() ) {
			return;
		}

		$this->intercept_permalinks();

		foreach ( $this->permalinks as $old ) {
			// Set the current permalink
			$this->current_permalink = $old;

			// Run the WP query again
			$wp->init();
			$wp->parse_request();

			// Anything matched?
			if ( $wp->matched_rule ) {
				// Perform the post query
				$wp->query_posts();

				// A single post?
				if ( is_single() && count( $query->posts ) > 0 ) {
					// Restore permalinks
					$this->release_permalinks();

					// Get real URL from the post ID
					$url = get_permalink( $query->posts[0]->ID );
					if ( $url ) {
						wp_safe_redirect( $url, 301, 'redirection' );
						die();
					}
				}

				break;
			}
		}

		$this->release_permalinks();
	}

	/**
	 * Determine if the current request needs migrating. This is based on `WP::handle_404` in class-wp.php
	 *
	 * @return boolean
	 */
	private function needs_migrating() {
		global $wp_query;

		// It's a 404 - shortcut to yes
		if ( is_404() ) {
			return true;
		}

		// Not admin pages
		if ( is_admin() || is_robots() || is_favicon() ) {
			return false;
		}

		if ( $wp_query->posts && ! $wp_query->is_posts_page && empty( $this->query_vars['page'] ) ) {
			return false;
		}

		if ( ! is_paged() ) {
			$author = get_query_var( 'author' );

			// Don't 404 for authors without posts as long as they matched an author on this site.
			if ( is_author() && is_numeric( $author ) && $author > 0 && is_user_member_of_blog( $author )
				// Don't 404 for these queries if they matched an object.
				|| ( is_tag() || is_category() || is_tax() || is_post_type_archive() ) && get_queried_object()
				// Don't 404 for these queries either.
				|| is_home() || is_search() || is_feed()
			) {
				return false;
			}
		}

		// If we've got this far then it's a 404
		return true;
	}

	/**
	 * Hook the permalink options and return the migrated one
	 *
	 * @return void
	 */
	private function intercept_permalinks() {
		add_filter( 'pre_option_rewrite_rules', [ $this, 'get_old_rewrite_rules' ] );
		add_filter( 'pre_option_permalink_structure', [ $this, 'get_old_permalink' ] );
	}

	/**
	 * Restore the hooked option
	 *
	 * @return void
	 */
	private function release_permalinks() {
		remove_filter( 'pre_option_rewrite_rules', [ $this, 'get_old_rewrite_rules' ] );
		remove_filter( 'pre_option_permalink_structure', [ $this, 'get_old_permalink' ] );
	}

	/**
	 * Returns rewrite rules for the current migrated permalink
	 *
	 * @param array $rules Current rules.
	 * @return array
	 */
	public function get_old_rewrite_rules( $rules ) {
		global $wp_rewrite;

		if ( $this->current_permalink ) {
			$wp_rewrite->init();
			$wp_rewrite->matches = 'matches';
			return $wp_rewrite->rewrite_rules();
		}

		return $rules;
	}

	/**
	 * Get the current migrated permalink structure
	 *
	 * @param string $result Current value.
	 * @return string
	 */
	public function get_old_permalink( $result ) {
		if ( $this->current_permalink ) {
			return $this->current_permalink;
		}

		return $result;
	}
}