<?php
/**
 * Intelligent page cache engine.
 *
 * @package AceloraSiteAccelerator
 */

namespace Acelora\SiteAccelerator\Modules;

use Acelora\SiteAccelerator\Includes\Filesystem;
use Acelora\SiteAccelerator\Includes\Logger;
use Acelora\SiteAccelerator\Includes\Settings;

if ( ! defined( 'ABSPATH' ) ) {
	exit;
}

/**
 * Serves, expires, and purges static HTML cache files.
 */
class Page_Cache {

	/**
	 * Settings.
	 *
	 * @var Settings
	 */
	private $settings;

	/**
	 * Logger.
	 *
	 * @var Logger
	 */
	private $logger;

	/**
	 * Filesystem.
	 *
	 * @var Filesystem
	 */
	private $filesystem;

	/**
	 * Constructor.
	 *
	 * @param Settings   $settings   Settings.
	 * @param Logger     $logger     Logger.
	 * @param Filesystem $filesystem Filesystem.
	 */
	public function __construct( Settings $settings, Logger $logger, Filesystem $filesystem ) {
		$this->settings   = $settings;
		$this->logger     = $logger;
		$this->filesystem = $filesystem;
	}

	/**
	 * Register hooks.
	 *
	 * @return void
	 */
	public function register() {
		add_action( 'init', array( $this, 'serve_cached_page' ), 0 );
		add_action( 'save_post', array( $this, 'purge_on_content_change' ), 10, 2 );
		add_action( 'deleted_post', array( $this, 'purge_all' ) );
		add_action( 'transition_post_status', array( $this, 'purge_all' ) );
		add_action( 'comment_post', array( $this, 'purge_all' ) );
		add_action( 'edit_terms', array( $this, 'purge_all' ) );
		add_action( 'switch_theme', array( $this, 'purge_all' ) );
	}

	/**
	 * Serve a cached page early.
	 *
	 * @return void
	 */
	public function serve_cached_page() {
		if ( ! $this->is_cacheable_request( true ) ) {
			return;
		}

		$file = $this->cache_file_for_current_request();

		if ( ! file_exists( $file ) || ! $this->is_fresh( $file ) ) {
			return;
		}

		if ( ! headers_sent() ) {
			header( 'X-Acelora-Cache: HIT' );
			header( 'Content-Type: text/html; charset=' . get_bloginfo( 'charset' ) );
		}

		$this->logger->log( 'info', 'Cache hit.', array( 'url' => $this->current_url() ) );
		echo $this->filesystem->get_contents( $file ); // phpcs:ignore WordPress.Security.EscapeOutput.OutputNotEscaped -- Cached HTML is generated from WordPress output and sent as the response body.
		exit;
	}

	/**
	 * Purge all cached pages.
	 *
	 * @return int
	 */
	public function purge_all() {
		$deleted = $this->filesystem->clear_directory( $this->filesystem->page_cache_dir() );
		$this->logger->log( 'info', 'Cache purged.', array( 'deleted' => $deleted ) );

		return $deleted;
	}

	/**
	 * Purge cache when content changes.
	 *
	 * @param int      $post_id Post ID.
	 * @param \WP_Post $post    Post object.
	 * @return void
	 */
	public function purge_on_content_change( $post_id, $post ) {
		if ( wp_is_post_revision( $post_id ) || 'auto-draft' === $post->post_status ) {
			return;
		}

		$this->purge_all();
	}

	/**
	 * Purge a single URL.
	 *
	 * @param string $url URL.
	 * @return bool
	 */
	public function purge_url( $url ) {
		$file = $this->cache_file_for_url( $url, $this->device_bucket() );

		if ( file_exists( $file ) ) {
			return $this->filesystem->delete_file( $file );
		}

		return false;
	}

	/**
	 * Remove expired pages.
	 *
	 * @return int
	 */
	public function cleanup_expired() {
		$directory = $this->filesystem->page_cache_dir();
		$removed   = 0;

		if ( ! is_dir( $directory ) ) {
			return 0;
		}

		$iterator = new \RecursiveIteratorIterator(
			new \RecursiveDirectoryIterator( $directory, \FilesystemIterator::SKIP_DOTS )
		);

		foreach ( $iterator as $file ) {
			if ( $file->isFile() && 'html' === strtolower( $file->getExtension() ) && ! $this->is_fresh( $file->getPathname() ) ) {
				if ( $this->filesystem->delete_file( $file->getPathname() ) ) {
					++$removed;
				}
			}
		}

		$this->logger->log( 'info', 'Expired cache cleanup completed.', array( 'removed' => $removed ) );

		return $removed;
	}

	/**
	 * Get current cache file.
	 *
	 * @return string
	 */
	private function cache_file_for_current_request() {
		return $this->cache_file_for_url( $this->current_url(), $this->device_bucket() );
	}

	/**
	 * Cache file for a URL.
	 *
	 * @param string $url    URL.
	 * @param string $device Device bucket.
	 * @return string
	 */
	private function cache_file_for_url( $url, $device ) {
		$hash = hash( 'sha256', strtolower( $url ) . '|' . $device );

		return $this->filesystem->page_cache_dir() . $device . '/' . substr( $hash, 0, 2 ) . '/' . $hash . '.html';
	}

	/**
	 * Determine whether cache file is fresh.
	 *
	 * @param string $file File path.
	 * @return bool
	 */
	private function is_fresh( $file ) {
		$lifetime = max( 60, absint( $this->settings->get( 'cache.lifetime', 86400 ) ) );

		return filemtime( $file ) >= ( time() - $lifetime );
	}

	/**
	 * Is the current request eligible for caching?
	 *
	 * @param bool $early Whether this check runs before main query conditionals.
	 * @return bool
	 */
	private function is_cacheable_request( $early ) {
		if ( ! $this->settings->get( 'cache.enabled', 1 ) || is_admin() || wp_doing_ajax() || wp_doing_cron() ) {
			return false;
		}

		if ( defined( 'REST_REQUEST' ) && REST_REQUEST ) {
			return false;
		}

		$method = isset( $_SERVER['REQUEST_METHOD'] ) ? sanitize_key( wp_unslash( $_SERVER['REQUEST_METHOD'] ) ) : 'GET';

		if ( 'GET' !== strtoupper( $method ) ) {
			return false;
		}

		if ( is_user_logged_in() && ! $this->settings->get( 'cache.logged_in_cache', 0 ) ) {
			return false;
		}

		if ( is_user_logged_in() && $this->has_excluded_role() ) {
			return false;
		}

		if ( $this->has_excluded_cookie() || $this->has_excluded_query_string() || $this->has_excluded_url() ) {
			return false;
		}

		return $early || ! is_preview();
	}

	/**
	 * Is the resolved WordPress view cacheable?
	 *
	 * @return bool
	 */
	private function is_cacheable_wp_view() {
		if ( is_404() || is_search() || is_feed() || is_trackback() || is_robots() || is_preview() || is_customize_preview() ) {
			return false;
		}

		if ( is_singular() && post_password_required() ) {
			return false;
		}

		return true;
	}

	/**
	 * Check excluded URL patterns.
	 *
	 * @return bool
	 */
	private function has_excluded_url() {
		$url  = $this->current_url();
		$path = (string) wp_parse_url( $url, PHP_URL_PATH );

		foreach ( $this->settings->list_value( $this->settings->get( 'cache.excluded_urls', '' ) ) as $pattern ) {
			if ( '' !== $pattern && ( false !== stripos( $path, $pattern ) || false !== stripos( $url, $pattern ) ) ) {
				return true;
			}
		}

		return false;
	}

	/**
	 * Check excluded cookie patterns.
	 *
	 * @return bool
	 */
	private function has_excluded_cookie() {
		$excluded = $this->settings->list_value( $this->settings->get( 'cache.excluded_cookies', '' ) );

		foreach ( array_keys( $_COOKIE ) as $cookie ) {
			foreach ( $excluded as $pattern ) {
				if ( '' !== $pattern && false !== stripos( $cookie, $pattern ) ) {
					return true;
				}
			}
		}

		return false;
	}

	/**
	 * Check query strings.
	 *
	 * @return bool
	 */
	private function has_excluded_query_string() {
		$query_string = isset( $_SERVER['QUERY_STRING'] ) ? sanitize_text_field( wp_unslash( $_SERVER['QUERY_STRING'] ) ) : '';

		if ( '' === $query_string ) {
			return false;
		}

		parse_str( $query_string, $query );
		$excluded = $this->settings->list_value( $this->settings->get( 'cache.excluded_queries', '' ) );

		foreach ( array_keys( $query ) as $key ) {
			if ( in_array( (string) $key, $excluded, true ) ) {
				return true;
			}
		}

		return true;
	}

	/**
	 * Check excluded roles.
	 *
	 * @return bool
	 */
	private function has_excluded_role() {
		$user     = wp_get_current_user();
		$excluded = $this->settings->list_value( $this->settings->get( 'cache.excluded_roles', '' ) );

		return (bool) array_intersect( (array) $user->roles, $excluded );
	}

	/**
	 * Device bucket for mobile cache handling.
	 *
	 * @return string
	 */
	private function device_bucket() {
		if ( ! $this->settings->get( 'cache.mobile_cache', 1 ) ) {
			return 'all';
		}

		return wp_is_mobile() ? 'mobile' : 'desktop';
	}

	/**
	 * Current URL.
	 *
	 * @return string
	 */
	private function current_url() {
		$scheme = is_ssl() ? 'https://' : 'http://';
		$host   = isset( $_SERVER['HTTP_HOST'] ) ? sanitize_text_field( wp_unslash( $_SERVER['HTTP_HOST'] ) ) : wp_parse_url( home_url(), PHP_URL_HOST );
		$uri    = isset( $_SERVER['REQUEST_URI'] ) ? esc_url_raw( wp_unslash( $_SERVER['REQUEST_URI'] ) ) : '/';

		return $scheme . $host . $uri;
	}
}