<?php

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

class Argus_Static_Cache {

	const STATUS_HIT         = 'HIT';
	const STATUS_MISS        = 'MISS';
	const STATUS_BYPASS      = 'BYPASS';
	const STATUS_EXPIRED     = 'EXPIRED';
	const STATUS_STALE       = 'STALE';
	const STATUS_REVALIDATED = 'REVALIDATED';
	const STATUS_WARMED      = 'WARMED';
	const STATUS_PURGED      = 'PURGED';
	const STATUS_EXCLUDED    = 'EXCLUDED';

	public static function init() {
		if ( class_exists( 'Argus_Settings' ) ) {
			$custom_excludes = (array) Argus_Settings::get( 'cache_custom_exclude_paths', array() );
			if ( ! empty( $custom_excludes ) ) {
				add_filter(
					'argus_wpd_cache_protected_paths',
					function ( $paths ) use ( $custom_excludes ) {
						return array_merge( $paths, $custom_excludes );
					}
				);
			}
		}

		if ( ! Argus_Settings::get( 'static_cache_enabled', false ) ) {
			return;
		}

		add_action( 'send_headers', array( __CLASS__, 'maybe_serve_cached' ), 0 );

		foreach ( array( 'switch_theme', 'customize_save_after', 'activated_plugin', 'deactivated_plugin' ) as $hook ) {
			add_action( $hook, array( __CLASS__, 'purge_all' ) );
		}
		add_action( 'save_post', array( __CLASS__, 'purge_related_to_post' ) );
		add_action( 'deleted_post', array( __CLASS__, 'purge_related_to_post' ) );
		add_action( 'comment_post', array( __CLASS__, 'purge_related_to_comment' ) );
		add_action( 'wp_set_comment_status', array( __CLASS__, 'purge_related_to_comment' ) );
	}

	public static function maybe_serve_cached() {
		$start = microtime( true );
		$url   = self::current_url();

		$classification = Argus_Cache_Eligibility::classify_request( self::request_context() );

		if ( self::SAFE_TO_CACHE_STATUS() !== $classification['status'] ) {
			$log_status = Argus_Cache_Eligibility::FORCE_EXCLUDED === $classification['status'] ? self::STATUS_EXCLUDED : self::STATUS_BYPASS;
			Argus_Cache_Log::record( $log_status, $url, $classification['reason'] );
			return;
		}

		$key   = self::cache_key( $url );
		$paths = self::cache_paths( $key );
		$ttl   = (int) Argus_Settings::get( 'static_cache_ttl_secs', 3600 );
		$grace = (int) Argus_Settings::get( 'cache_stale_grace_secs', 600 );

		if ( file_exists( $paths['html'] ) ) {
			$age = time() - filemtime( $paths['html'] );

			if ( $age < $ttl ) {
				self::serve_hit( $paths, $url, self::STATUS_HIT, $start );
				return; 
			}

			if ( $age < ( $ttl + $grace ) ) {
				$lock = self::acquire_lock( $key );
				if ( ! $lock ) {
					self::serve_hit( $paths, $url, self::STATUS_STALE, $start );
					return; 
				}

				self::start_capture( $url, $key, $paths, self::STATUS_REVALIDATED, $start, $lock );
				return;
			}
		}

		$lock = self::acquire_lock( $key );
		if ( ! $lock ) {

			Argus_Cache_Log::record( self::STATUS_MISS, $url, 'Cache miss (another request is already regenerating this URL).', null );
			return;
		}

		self::start_capture( $url, $key, $paths, self::STATUS_MISS, $start, $lock );
	}

	protected static function SAFE_TO_CACHE_STATUS() {
		return Argus_Cache_Eligibility::SAFE_TO_CACHE;
	}

	protected static function start_capture( $url, $key, array $paths, $status, $start, $lock ) {
		header( 'X-Argus-Cache: ' . $status );
		ob_start(
			function ( $html ) use ( $url, $key, $paths, $status, $start, $lock ) {
				return self::capture_and_store( $html, $url, $key, $paths, $status, $start, $lock );
			}
		);
	}

	public static function capture_and_store( $html, $url, $key, array $paths, $status, $start, $lock ) {
		$response_ms = (int) round( ( microtime( true ) - $start ) * 1000 );

		$response_context = array(
			'status_code'     => http_response_code(),
			'headers'         => self::response_headers(),
			'new_cookies_set' => self::response_cookie_names(),
			'content_type'    => self::response_content_type(),
		);

		$classification = Argus_Cache_Eligibility::classify_response( $response_context );

		if ( Argus_Cache_Eligibility::SAFE_TO_CACHE !== $classification['status'] || '' === $html ) {
			$log_status = '' === $html ? self::STATUS_BYPASS : ( Argus_Cache_Eligibility::FORCE_EXCLUDED === $classification['status'] ? self::STATUS_EXCLUDED : self::STATUS_BYPASS );
			Argus_Cache_Log::record( $log_status, $url, '' === $html ? 'Empty response body.' : $classification['reason'], $response_ms );
			self::release_lock( $lock );
			return $html;
		}

		self::write_cache_entry( $paths, $html, $url );
		Argus_Cache_Log::record( $status, $url, 'Stored.', $response_ms );
		self::release_lock( $lock );

		return $html;
	}

	protected static function write_cache_entry( array $paths, $html, $url ) {
		wp_mkdir_p( dirname( $paths['html'] ) );
		file_put_contents( $paths['html'], $html ); // phpcs:ignore WordPress.WP.AlternativeFunctions

		$min_bytes = (int) Argus_Settings::get( 'cache_min_compress_bytes', 1024 );
		if ( strlen( $html ) >= $min_bytes ) {
			if ( Argus_Settings::get( 'cache_gzip_enabled', true ) && function_exists( 'gzencode' ) ) {
				$level = (int) Argus_Settings::get( 'cache_gzip_level', 6 );
				file_put_contents( $paths['gz'], gzencode( $html, max( 1, min( 9, $level ) ) ) ); // phpcs:ignore
			} else {
				@unlink( $paths['gz'] ); // phpcs:ignore
			}
			if ( Argus_Settings::get( 'cache_brotli_enabled', true ) && function_exists( 'brotli_compress' ) ) {
				$level = (int) Argus_Settings::get( 'cache_brotli_level', 5 );
				file_put_contents( $paths['br'], brotli_compress( $html, max( 0, min( 11, $level ) ) ) ); // phpcs:ignore
			} else {
				@unlink( $paths['br'] ); // phpcs:ignore
			}
		} else {
			@unlink( $paths['gz'] ); // phpcs:ignore
			@unlink( $paths['br'] ); // phpcs:ignore
		}

		file_put_contents( // phpcs:ignore
			$paths['meta'],
			wp_json_encode(
				array(
					'url'        => $url,
					'bytes'      => strlen( $html ),
					'created_at' => current_time( 'mysql', true ),
				)
			)
		);
	}

	protected static function serve_hit( array $paths, $url, $status, $start ) {
		$encoding = self::negotiate_encoding();
		$source   = $paths['html'];
		$header_encoding = '';

		if ( 'br' === $encoding && file_exists( $paths['br'] ) ) {
			$source = $paths['br'];
			$header_encoding = 'br';
		} elseif ( 'gzip' === $encoding && file_exists( $paths['gz'] ) ) {
			$source = $paths['gz'];
			$header_encoding = 'gzip';
		}

		header( 'X-Argus-Cache: ' . $status );
		header( 'X-Argus-Cache-Age: ' . ( time() - filemtime( $paths['html'] ) ) );
		header( 'Vary: Accept-Encoding' );
		if ( $header_encoding ) {
			header( 'Content-Encoding: ' . $header_encoding );
		}
		header( 'Content-Type: text/html; charset=UTF-8' );
		readfile( $source ); // phpcs:ignore WordPress.WP.AlternativeFunctions

		Argus_Cache_Log::record( $status, $url, 'Served from cache.', (int) round( ( microtime( true ) - $start ) * 1000 ) );
		exit;
	}

	protected static function negotiate_encoding() {
		$accept = strtolower( (string) ( $_SERVER['HTTP_ACCEPT_ENCODING'] ?? '' ) ); // phpcs:ignore WordPress.Security.ValidatedSanitizedInput
		if ( false !== strpos( $accept, 'br' ) ) {
			return 'br';
		}
		if ( false !== strpos( $accept, 'gzip' ) ) {
			return 'gzip';
		}
		return '';
	}

	protected static function request_context() {
		$cookies = array();
		foreach ( (array) $_COOKIE as $name => $value ) { // phpcs:ignore WordPress.Security.NonceVerification
			$cookies[ (string) $name ] = ''; 
		}

		return array(
			'method'                   => $_SERVER['REQUEST_METHOD'] ?? 'GET', // phpcs:ignore WordPress.Security.ValidatedSanitizedInput
			'path'                     => (string) wp_parse_url( self::current_url(), PHP_URL_PATH ),
			'query'                    => $_GET, // phpcs:ignore WordPress.Security.NonceVerification
			'is_admin'                 => is_admin(),
			'is_logged_in'             => is_user_logged_in(),
			'cookies'                  => $cookies,
			'has_authorization_header' => ! empty( $_SERVER['HTTP_AUTHORIZATION'] ) || ! empty( $_SERVER['REDIRECT_HTTP_AUTHORIZATION'] ), // phpcs:ignore
			'is_ajax'                  => wp_doing_ajax(),
			'is_rest'                  => defined( 'REST_REQUEST' ) && REST_REQUEST,
			'is_cron'                  => defined( 'DOING_CRON' ) && DOING_CRON,
		) + self::conditional_tag_excludes();
	}

	protected static function conditional_tag_excludes() {
		if ( is_feed() || is_trackback() || is_preview() || is_search() || is_404() ) {
			return array( 'is_admin' => true ); 
		}
		return array();
	}

	protected static function response_headers() {
		$out = array();
		foreach ( headers_list() as $header ) {
			$parts = explode( ':', $header, 2 );
			if ( 2 !== count( $parts ) ) {
				continue;
			}
			$name = strtolower( trim( $parts[0] ) );
			if ( isset( $out[ $name ] ) ) {
				$out[ $name ] .= ', ' . trim( $parts[1] );
			} else {
				$out[ $name ] = trim( $parts[1] );
			}
		}
		return $out;
	}

	protected static function response_cookie_names() {
		$names = array();
		foreach ( headers_list() as $header ) {
			if ( 0 === stripos( $header, 'Set-Cookie:' ) && preg_match( '/^Set-Cookie:\s*([^=]+)=/i', $header, $m ) ) {
				$names[] = trim( $m[1] );
			}
		}
		return $names;
	}

	protected static function response_content_type() {
		foreach ( headers_list() as $header ) {
			if ( 0 === stripos( $header, 'Content-Type:' ) ) {
				return trim( substr( $header, strlen( 'Content-Type:' ) ) );
			}
		}
		return '';
	}

	protected static function current_url() {
		$scheme = is_ssl() ? 'https' : 'http';
		$host   = (string) ( $_SERVER['HTTP_HOST'] ?? 'default' ); // phpcs:ignore WordPress.Security.ValidatedSanitizedInput
		$uri    = (string) ( $_SERVER['REQUEST_URI'] ?? '/' ); // phpcs:ignore WordPress.Security.ValidatedSanitizedInput
		return $scheme . '://' . $host . $uri;
	}

	public static function cache_key( $url ) {
		$parts = wp_parse_url( $url );
		$path  = $parts['path'] ?? '/';
		$query = array();
		if ( ! empty( $parts['query'] ) ) {
			parse_str( $parts['query'], $query );
			$query = array_diff_key( $query, array_flip( Argus_Cache_Eligibility::IGNORABLE_QUERY_PARAMS ) );
			ksort( $query );
		}
		$host = (string) ( $parts['host'] ?? 'default' );
		return md5( $host . '|' . $path . '|' . http_build_query( $query ) );
	}

	protected static function cache_dir() {
		$uploads = wp_get_upload_dir();
		return trailingslashit( $uploads['basedir'] ) . 'argus-wpd-data/html-cache';
	}

	public static function cache_paths( $key ) {
		$base = trailingslashit( self::cache_dir() ) . $key;
		return array(
			'html' => $base . '.html',
			'gz'   => $base . '.html.gz',
			'br'   => $base . '.html.br',
			'meta' => $base . '.meta.json',
		);
	}

	protected static function lock_dir() {
		return trailingslashit( self::cache_dir() ) . 'locks';
	}

	protected static function acquire_lock( $key ) {
		$dir = self::lock_dir();
		if ( ! is_dir( $dir ) ) {
			wp_mkdir_p( $dir );
		}
		$path = trailingslashit( $dir ) . $key . '.lock';
		$fh   = @fopen( $path, 'c' ); // phpcs:ignore WordPress.WP.AlternativeFunctions,WordPress.PHP.NoSilencedErrors
		if ( ! $fh ) {
			return false;
		}
		if ( ! flock( $fh, LOCK_EX | LOCK_NB ) ) {
			fclose( $fh ); // phpcs:ignore WordPress.WP.AlternativeFunctions
			return false;
		}
		return $fh;
	}

	protected static function release_lock( $fh ) {
		if ( $fh ) {
			flock( $fh, LOCK_UN );
			fclose( $fh ); // phpcs:ignore WordPress.WP.AlternativeFunctions
		}
	}

	public static function purge_all() {
		$dir = self::cache_dir();
		if ( ! is_dir( $dir ) ) {
			return 0;
		}
		$count = 0;
		foreach ( array( '*.html', '*.html.gz', '*.html.br', '*.meta.json' ) as $glob ) {
			foreach ( glob( trailingslashit( $dir ) . $glob ) ?: array() as $file ) {
				@unlink( $file ); // phpcs:ignore WordPress.PHP.NoSilencedErrors
				++$count;
			}
		}
		Argus_Cache_Log::record( self::STATUS_PURGED, '*', 'Purge everything.' );
		return $count;
	}

	public static function purge_url( $url ) {
		$key = self::cache_key( $url );
		foreach ( self::cache_paths( $key ) as $path ) {
			@unlink( $path ); // phpcs:ignore WordPress.PHP.NoSilencedErrors
		}
		Argus_Cache_Log::record( self::STATUS_PURGED, $url, 'Purge single URL.' );
	}

	public static function purge_pattern( $pattern ) {
		$dir = self::cache_dir();
		if ( ! is_dir( $dir ) ) {
			return 0;
		}
		$regex = '/^' . str_replace( '\*', '.*', preg_quote( $pattern, '/' ) ) . '$/i';
		$count = 0;
		foreach ( glob( trailingslashit( $dir ) . '*.meta.json' ) ?: array() as $meta_file ) {
			$meta = json_decode( (string) file_get_contents( $meta_file ), true ); // phpcs:ignore
			if ( ! is_array( $meta ) || empty( $meta['url'] ) || ! preg_match( $regex, $meta['url'] ) ) {
				continue;
			}
			$key = basename( $meta_file, '.meta.json' );
			foreach ( self::cache_paths( $key ) as $path ) {
				@unlink( $path ); // phpcs:ignore WordPress.PHP.NoSilencedErrors
			}
			++$count;
		}
		Argus_Cache_Log::record( self::STATUS_PURGED, $pattern, 'Purge by pattern (' . $count . ' entries).' );
		return $count;
	}

	public static function purge_related_to_post( $post_id ) {
		if ( wp_is_post_revision( $post_id ) || wp_is_post_autosave( $post_id ) ) {
			return;
		}
		$permalink = get_permalink( $post_id );
		if ( $permalink ) {
			self::purge_url( $permalink );
		}
		self::purge_url( home_url( '/' ) );
		$page_for_posts = (int) get_option( 'page_for_posts' );
		if ( $page_for_posts ) {
			self::purge_url( get_permalink( $page_for_posts ) );
		}
	}

	public static function purge_related_to_comment( $comment_id ) {
		$comment = get_comment( $comment_id );
		if ( $comment && $comment->comment_post_ID ) {
			self::purge_related_to_post( (int) $comment->comment_post_ID );
		}
	}

	public static function stats() {
		$dir = self::cache_dir();
		if ( ! is_dir( $dir ) ) {
			return array( 'file_count' => 0, 'total_bytes' => 0 );
		}
		$files = glob( trailingslashit( $dir ) . '*.html' ) ?: array();
		$bytes = 0;
		foreach ( $files as $file ) {
			$bytes += filesize( $file );
			foreach ( array( '.gz', '.br' ) as $ext ) {
				$variant = $file . $ext;
				if ( file_exists( $variant ) ) {
					$bytes += filesize( $variant );
				}
			}
		}
		return array( 'file_count' => count( $files ), 'total_bytes' => $bytes );
	}

	public static function compression_stats() {
		$dir = self::cache_dir();
		$out = array(
			'gzip'   => array( 'files' => 0, 'avg_savings_pct' => 0.0, 'bytes_saved' => 0 ),
			'brotli' => array( 'files' => 0, 'avg_savings_pct' => 0.0, 'bytes_saved' => 0 ),
			'total_bytes_saved' => 0,
		);
		if ( ! is_dir( $dir ) ) {
			return $out;
		}

		$files = glob( trailingslashit( $dir ) . '*.html' ) ?: array();
		$pct_sums = array( 'gzip' => 0.0, 'brotli' => 0.0 );

		foreach ( $files as $file ) {
			$plain_size = filesize( $file );
			if ( ! $plain_size ) {
				continue;
			}
			foreach ( array( 'gzip' => '.gz', 'brotli' => '.br' ) as $format => $ext ) {
				$variant = $file . $ext;
				if ( ! file_exists( $variant ) ) {
					continue;
				}
				$variant_size = filesize( $variant );
				if ( ! $variant_size || $variant_size >= $plain_size ) {
					continue; 
				}
				$saved = $plain_size - $variant_size;
				++$out[ $format ]['files'];
				$out[ $format ]['bytes_saved'] += $saved;
				$out['total_bytes_saved'] += $saved;
				$pct_sums[ $format ] += ( $saved / $plain_size ) * 100;
			}
		}

		foreach ( array( 'gzip', 'brotli' ) as $format ) {
			if ( $out[ $format ]['files'] > 0 ) {
				$out[ $format ]['avg_savings_pct'] = round( $pct_sums[ $format ] / $out[ $format ]['files'], 1 );
			}
		}

		return $out;
	}

	public static function list_cached( $limit = 100 ) {
		$dir = self::cache_dir();
		if ( ! is_dir( $dir ) ) {
			return array();
		}
		$meta_files = glob( trailingslashit( $dir ) . '*.meta.json' ) ?: array();
		usort(
			$meta_files,
			function ( $a, $b ) {
				return filemtime( $b ) <=> filemtime( $a );
			}
		);

		$out = array();
		foreach ( array_slice( $meta_files, 0, $limit ) as $meta_file ) {
			$meta = json_decode( (string) file_get_contents( $meta_file ), true ); // phpcs:ignore
			if ( ! is_array( $meta ) ) {
				continue;
			}
			$key = basename( $meta_file, '.meta.json' );
			$paths = self::cache_paths( $key );
			$out[] = array(
				'url'         => $meta['url'] ?? '',
				'bytes'       => (int) ( $meta['bytes'] ?? 0 ),
				'created_at'  => $meta['created_at'] ?? '',
				'age_secs'    => file_exists( $paths['html'] ) ? ( time() - filemtime( $paths['html'] ) ) : null,
				'has_gzip'    => file_exists( $paths['gz'] ),
				'has_brotli'  => file_exists( $paths['br'] ),
			);
		}
		return $out;
	}
}