<?php
if ( ! defined( 'ABSPATH' ) ) {
	exit;
}
// phpcs:disable WordPress.WP.AlternativeFunctions -- Cache plugin: direct file operations are limited to wp-content/cache/velox, its own config/drop-in and the site .htaccess; WP_Filesystem is unsuitable for per-request cache writes.

/**
 * Page cache: storage, purge, lifecycle (drop-in + wp-config handling).
 */
class Velox_Cache {

	const MARK = 'Added by AngelForce Cache';

	/* ---------- paths ---------- */

	public static function dir() {
		return trailingslashit( WP_CONTENT_DIR ) . 'cache/velox/';
	}

	public static function url() {
		return trailingslashit( content_url( 'cache/velox' ) );
	}

	public static function pages_dir() {
		return self::dir() . 'pages/';
	}

	/**
	 * Build cache file path. Keep logic identical to dropin/advanced-cache.php.
	 */
	public static function file_for( $host, $uri, $mobile, $https, $webp = false ) {
		$host = preg_replace( '/[^a-z0-9.\-_]/i', '', strtolower( preg_replace( '/:\d+$/', '', (string) $host ) ) );
		$path = (string) wp_parse_url( $uri, PHP_URL_PATH );
		$path = preg_replace( '#[^a-zA-Z0-9/\-_.%~]#', '', $path );
		$path = str_replace( '..', '', $path );
		$path = '/' . trim( $path, '/' );
		if ( '/' !== $path ) {
			$path .= '/';
		}
		return self::pages_dir() . $host . $path . 'index' . ( $mobile ? '-mobile' : '' ) . ( $https ? '-https' : '' ) . ( true === $webp ? '-webp' : ( 'avif' === $webp ? '-avif' : '' ) ) . '.html';
	}

	/** Same detection as dropin/advanced-cache.php (reverse proxies included). */
	public static function request_is_https() {
		return ( ! empty( $_SERVER['HTTPS'] ) && 'off' !== $_SERVER['HTTPS'] )
			|| ( isset( $_SERVER['SERVER_PORT'] ) && '443' === sanitize_text_field( wp_unslash( $_SERVER['SERVER_PORT'] ) ) )
			|| ( isset( $_SERVER['HTTP_X_FORWARDED_PROTO'] ) && 'https' === $_SERVER['HTTP_X_FORWARDED_PROTO'] );
	}

	public static function is_mobile_ua() {
		$ua = isset( $_SERVER['HTTP_USER_AGENT'] ) ? sanitize_text_field( wp_unslash( $_SERVER['HTTP_USER_AGENT'] ) ) : '';
		return (bool) preg_match( '/Mobile|Android|iPhone|iPod|Opera Mini|IEMobile|BlackBerry/i', $ua );
	}

	/* ---------- bootstrap ---------- */

	public static function init() {
		add_action( 'template_redirect', array( __CLASS__, 'start_buffer' ), 0 );
		add_action( 'velox_clean_expired', array( __CLASS__, 'clean_expired' ) );
		if ( ! wp_next_scheduled( 'velox_clean_expired' ) ) {
			wp_schedule_event( time() + 300, 'hourly', 'velox_clean_expired' );
		}

		// Purge hooks.
		add_action( 'save_post', array( __CLASS__, 'on_save_post' ), 20, 2 );
		add_action( 'deleted_post', array( __CLASS__, 'purge_post_id' ) );
		add_action( 'trashed_post', array( __CLASS__, 'purge_post_id' ) );
		add_action( 'comment_post', array( __CLASS__, 'on_comment' ), 20, 2 );
		add_action( 'transition_comment_status', array( __CLASS__, 'on_comment_status' ), 20, 3 );
		foreach ( array( 'upgrader_process_complete', 'switch_theme', 'customize_save_after', 'wp_update_nav_menu', 'update_option_sidebars_widgets', 'update_option_permalink_structure', 'update_option_blogname', 'update_option_page_on_front', 'update_option_show_on_front' ) as $hook ) {
			add_action( $hook, array( __CLASS__, 'purge_all' ) );
		}

		add_action( 'activated_plugin', array( __CLASS__, 'on_plugin_toggle' ) );
		add_action( 'deactivated_plugin', array( __CLASS__, 'on_plugin_toggle' ) );
		add_action( 'update_option_' . Velox_Settings::OPTION, array( __CLASS__, 'on_settings_saved' ), 10, 0 );
		add_action( 'add_option_' . Velox_Settings::OPTION, array( __CLASS__, 'on_settings_saved' ), 10, 0 );
	}

	/** Another plugin was (de)activated: its output may change, purge. Ignore our own (de)activation. */
	public static function on_plugin_toggle( $plugin ) {
		if ( plugin_basename( VELOX_FILE ) === $plugin ) {
			return;
		}
		self::purge_all();
	}

	public static function on_settings_saved() {
		Velox_Settings::flush();
		self::write_config();
		Velox_Htaccess::sync();
		self::purge_all();
		Velox_Database::reschedule();
		do_action( 'velox_settings_saved', Velox_Settings::all() );
	}

	/* ---------- output buffering ---------- */

	public static function start_buffer() {
		if ( ! Velox_Optimizer::should_run() ) {
			return;
		}
		if ( isset( $_SERVER['REQUEST_METHOD'] ) && 'GET' !== $_SERVER['REQUEST_METHOD'] ) {
			return;
		}
		if ( is_robots() || is_trackback() || is_embed() ) {
			return;
		}
		if ( Velox_Settings::get( 'webp' ) ) {
			header( 'Vary: Accept', false );
		}
		ob_start( array( __CLASS__, 'handle_buffer' ) );
	}

	public static function handle_buffer( $html ) {
		if ( ! headers_sent() ) {
			header( 'X-Velox-Cache: MISS' );
		}
		if ( strlen( $html ) < 255 || false === stripos( $html, '</html>' ) ) {
			return $html;
		}
		$t0        = microtime( true );
		$processed = Velox_Optimizer::process( $html );
		if ( ! is_string( $processed ) || '' === $processed ) {
			$processed = $html;
		}
		$t1 = microtime( true );
		if ( Velox_Optimizer::$css_pending && ! headers_sent() ) {
			header( 'X-Velox-CSS: pending' ); // Tells the preloader to fetch the page once more.
		}
		// A page built before its critical CSS existed is not stored; the next build includes it.
		if ( self::is_cacheable() && ! Velox_Optimizer::$css_pending ) {
			self::store( $processed );
			Velox_Server::count_build();
		}
		if ( ! headers_sent() ) {
			// Standard Server-Timing header (browser DevTools > Network > Timing): where the time of an
			// uncached request went. Cached pages are static files and never carry it.
			$start = isset( $_SERVER['REQUEST_TIME_FLOAT'] ) ? (float) $_SERVER['REQUEST_TIME_FLOAT'] : $t0;
			header(
				sprintf(
					'Server-Timing: wp;desc="WordPress";dur=%.1f, vxopt;desc="Optimize";dur=%.1f, vxcss;desc="CSS";dur=%.1f, vxstore;desc="Cache store";dur=%.1f',
					( $t0 - $start ) * 1000,
					( $t1 - $t0 ) * 1000,
					Velox_Optimizer::$css_ms,
					( microtime( true ) - $t1 ) * 1000
				)
			);
		}
		return $processed;
	}

	public static function is_cacheable() {
		if ( ! Velox_Settings::get( 'cache_enabled' ) ) {
			return false;
		}
		if ( defined( 'DONOTCACHEPAGE' ) && DONOTCACHEPAGE ) {
			return false;
		}
		if ( is_user_logged_in() || is_search() || is_404() || is_feed() || is_preview() || is_customize_preview() ) {
			return false;
		}
		if ( is_singular() && post_password_required() ) {
			return false;
		}
		if ( function_exists( 'is_cart' ) && ( is_cart() || is_checkout() || is_account_page() ) ) {
			return false;
		}
		$code = (int) http_response_code();
		if ( $code && 200 !== $code ) {
			return false;
		}
		foreach ( headers_list() as $h ) {
			if ( 0 === stripos( $h, 'Set-Cookie:' ) ) {
				return false;
			}
		}
		$uri = isset( $_SERVER['REQUEST_URI'] ) ? sanitize_text_field( wp_unslash( $_SERVER['REQUEST_URI'] ) ) : '/';
		// A page rendered with any query string is never stored, not even with tracking parameters:
		// themes and plugins may print those values (utm_* into forms or links), and the stored copy
		// is shown to everyone. Visitors with tracking parameters still get the cached clean page from
		// the drop-in once it exists.
		if ( '' !== (string) wp_parse_url( $uri, PHP_URL_QUERY ) ) {
			return false;
		}
		foreach ( $_COOKIE as $name => $v ) {
			if ( preg_match( '/^(wordpress_logged_in_|wp-postpass_|comment_author_|woocommerce_items_in_cart|wp_woocommerce_session_)/', (string) $name ) ) {
				return false;
			}
		}
		// Only cache for the site's own host (prevents Host header abuse).
		$host      = isset( $_SERVER['HTTP_HOST'] ) ? strtolower( preg_replace( '/:\d+$/', '', sanitize_text_field( wp_unslash( $_SERVER['HTTP_HOST'] ) ) ) ) : '';
		$home_host = strtolower( (string) wp_parse_url( home_url(), PHP_URL_HOST ) );
		if ( '' === $host || $host !== $home_host ) {
			return false;
		}
		$path = (string) wp_parse_url( $uri, PHP_URL_PATH );
		foreach ( self::exclude_regexes() as $re ) {
			if ( preg_match( $re, $path ) ) {
				return false;
			}
		}
		// Other plugins can keep a page out of the cache (they can never force one in).
		return (bool) apply_filters( 'velox_is_cacheable', true );
	}

	/**
	 * Explains, for the current front-end request, whether an anonymous visitor would get this page
	 * from the cache and if not, why. Used by the admin bar. Returns [ cacheable(bool), reasons[] , has_file(bool) ].
	 */
	public static function explain() {
		$why = array();
		if ( ! Velox_Settings::get( 'cache_enabled' ) ) {
			$why[] = __( 'page cache is disabled', 'angelforce-cache' );
		}
		if ( defined( 'DONOTCACHEPAGE' ) && DONOTCACHEPAGE ) {
			$why[] = __( 'a plugin set DONOTCACHEPAGE', 'angelforce-cache' );
		}
		if ( is_search() ) {
			$why[] = __( 'search results', 'angelforce-cache' );
		}
		if ( is_404() ) {
			$why[] = __( '404 page', 'angelforce-cache' );
		}
		if ( is_feed() ) {
			$why[] = __( 'feed', 'angelforce-cache' );
		}
		if ( is_preview() || is_customize_preview() ) {
			$why[] = __( 'preview', 'angelforce-cache' );
		}
		if ( is_singular() && post_password_required() ) {
			$why[] = __( 'password protected', 'angelforce-cache' );
		}
		if ( function_exists( 'is_cart' ) && ( is_cart() || is_checkout() || is_account_page() ) ) {
			$why[] = __( 'WooCommerce cart / checkout / account page', 'angelforce-cache' );
		}
		$uri = isset( $_SERVER['REQUEST_URI'] ) ? sanitize_text_field( wp_unslash( $_SERVER['REQUEST_URI'] ) ) : '/';
		$q   = (string) wp_parse_url( $uri, PHP_URL_QUERY );
		if ( '' !== $q ) {
			parse_str( $q, $params );
			foreach ( array_keys( $params ) as $k ) {
				if ( ! preg_match( '/^(utm_|fbclid|gclid|msclkid|mc_|_ga|yclid|ttclid|twclid|dclid|srsltid)/', (string) $k ) ) {
					$why[] = sprintf( /* translators: %s: query parameter name */ __( 'query parameter "%s"', 'angelforce-cache' ), $k );
					break;
				}
			}
		}
		$path = (string) wp_parse_url( $uri, PHP_URL_PATH );
		foreach ( self::exclude_regexes() as $re ) {
			if ( preg_match( $re, $path ) ) {
				$why[] = __( 'URL is in the exclusion list', 'angelforce-cache' );
				break;
			}
		}
		$host    = isset( $_SERVER['HTTP_HOST'] ) ? sanitize_text_field( wp_unslash( $_SERVER['HTTP_HOST'] ) ) : '';
		$variant = false;
		if ( Velox_Settings::get( 'webp' ) ) {
			$variant = ( Velox_Settings::get( 'avif' ) && Velox_Optimizer::accepts_avif() ) ? 'avif' : ( Velox_Optimizer::accepts_webp() ? true : false );
		}
		$file = self::file_for( $host, $uri, false, self::request_is_https(), $variant );
		return array( empty( $why ), $why, is_file( $file ) );
	}

	public static function exclude_regexes() {
		$lines = preg_split( '/\r\n|\r|\n/', (string) Velox_Settings::get( 'cache_exclude' ) );
		$lines = array_merge( array( '/wp-admin/*', '/wp-login.php', '/wp-json/*', '/xmlrpc.php' ), $lines );
		$out   = array();
		foreach ( $lines as $line ) {
			$line = trim( $line );
			if ( '' === $line ) {
				continue;
			}
			$out[] = '#^' . str_replace( '\*', '.*', preg_quote( $line, '#' ) ) . '$#i';
		}
		return $out;
	}

	public static function store( $html ) {
		$https  = self::request_is_https();
		$mobile = Velox_Settings::get( 'cache_mobile' ) && self::is_mobile_ua();
		$webp   = false;
		if ( Velox_Settings::get( 'webp' ) ) {
			if ( Velox_Settings::get( 'avif' ) && Velox_Optimizer::accepts_avif() ) {
				$webp = 'avif';
			} elseif ( Velox_Optimizer::accepts_webp() ) {
				$webp = true;
			}
		}
		$host = isset( $_SERVER['HTTP_HOST'] ) ? sanitize_text_field( wp_unslash( $_SERVER['HTTP_HOST'] ) ) : '';
		$uri  = isset( $_SERVER['REQUEST_URI'] ) ? sanitize_text_field( wp_unslash( $_SERVER['REQUEST_URI'] ) ) : '/';
		$file = self::file_for( $host, $uri, $mobile, $https, $webp );
		$dir  = dirname( $file );
		if ( ! wp_mkdir_p( $dir ) ) {
			return false;
		}
		self::protect_dir();
		$html .= "\n<!-- Cached by AngelForce Cache on " . gmdate( 'Y-m-d H:i:s' ) . ' UTC -->';
		$tmp   = $file . '.' . wp_generate_password( 6, false ) . '.tmp';
		if ( false === file_put_contents( $tmp, $html, LOCK_EX ) ) {
			return false;
		}
		if ( ! @rename( $tmp, $file ) ) {
			wp_delete_file( $tmp );
			return false;
		}
		// Pre-compressed copies: the web server sends them as-is, no CPU spent on compression per request.
		// Brotli (smaller) when the PHP extension exists, gzip always.
		if ( function_exists( 'brotli_compress' ) ) {
			$br = brotli_compress( $html, 9 );
			if ( false !== $br ) {
				@file_put_contents( $file . '.br', $br, LOCK_EX );
			}
		} else {
			wp_delete_file( $file . '.br' );
		}
		if ( function_exists( 'gzencode' ) ) {
			$gz = gzencode( $html, 6 );
			if ( false !== $gz ) {
				@file_put_contents( $file . '.gz', $gz, LOCK_EX );
			}
		} else {
			wp_delete_file( $file . '.gz' );
		}
		return true;
	}

	private static function protect_dir() {
		$base = self::dir();
		if ( ! file_exists( $base . 'index.html' ) ) {
			@file_put_contents( $base . 'index.html', '' );
		}
		if ( is_file( $base . 'index.php' ) ) {
			wp_delete_file( $base . 'index.php' ); // Written by versions before 2.2.0.
		}
		// Data files (settings for the drop-in, logs, CSS records) are never served to visitors.
		$rules = "Options -Indexes\n<FilesMatch \"\\.(php|tmp|log|json|phtml|php[0-9]|phar|inc)$\">\n<IfModule mod_authz_core.c>\nRequire all denied\n</IfModule>\n<IfModule !mod_authz_core.c>\nOrder allow,deny\nDeny from all\n</IfModule>\n</FilesMatch>\n";
		if ( ! file_exists( $base . '.htaccess' ) || (string) file_get_contents( $base . '.htaccess' ) !== $rules ) {
			@file_put_contents( $base . '.htaccess', $rules );
		}
	}

	/* ---------- purge ---------- */

	public static function on_save_post( $post_id, $post ) {
		if ( wp_is_post_revision( $post_id ) || wp_is_post_autosave( $post_id ) ) {
			return;
		}
		if ( ! $post || ! in_array( $post->post_status, array( 'publish', 'trash', 'private' ), true ) ) {
			return;
		}
		self::purge_post_id( $post_id );
	}

	public static function purge_post_id( $post_id ) {
		$post = get_post( $post_id );
		if ( ! $post || ! is_post_type_viewable( $post->post_type ) ) {
			return;
		}
		self::purge_url( get_permalink( $post ) );
		self::purge_url( home_url( '/' ) );
		$archive = get_post_type_archive_link( $post->post_type );
		if ( $archive ) {
			self::purge_url( $archive );
		}
		$taxes = get_object_taxonomies( $post->post_type );
		foreach ( $taxes as $tax ) {
			$terms = get_the_terms( $post, $tax );
			if ( is_array( $terms ) ) {
				foreach ( $terms as $term ) {
					$link = get_term_link( $term );
					if ( ! is_wp_error( $link ) ) {
						self::purge_url( $link );
					}
				}
			}
		}
		self::purge_url( get_author_posts_url( $post->post_author ) );
		$blog = (int) get_option( 'page_for_posts' );
		if ( $blog ) {
			self::purge_url( get_permalink( $blog ) );
		}
	}

	public static function on_comment( $comment_id, $approved ) {
		$c = get_comment( $comment_id );
		if ( $c && 1 === (int) $approved ) {
			self::purge_url( get_permalink( $c->comment_post_ID ) );
		}
	}

	public static function on_comment_status( $new, $old, $comment ) {
		if ( $comment && isset( $comment->comment_post_ID ) ) {
			self::purge_url( get_permalink( $comment->comment_post_ID ) );
		}
	}

	public static function purge_url( $url ) {
		if ( ! $url ) {
			return;
		}
		Velox_Cloudflare::queue_url( $url );
		$host = (string) wp_parse_url( $url, PHP_URL_HOST );
		$path = (string) wp_parse_url( $url, PHP_URL_PATH );
		$dir  = dirname( self::file_for( $host, $path, false, false ) );
		foreach ( glob( $dir . '/index*.html*' ) ?: array() as $file ) {
			wp_delete_file( $file );
		}
		do_action( 'velox_purged_url', $url );
	}

	public static function purge_all() {
		self::rrmdir( self::pages_dir(), false );
		Velox_Cloudflare::queue_all();
		Velox_CSS::purge();
		update_option( 'velox_last_purge', time(), false );
		delete_transient( 'velox_stats' );
		Velox_Preload::schedule();
		do_action( 'velox_purged_all' );
	}

	public static function rrmdir( $dir, $remove_self = true ) {
		if ( ! is_dir( $dir ) ) {
			return;
		}
		$items = @scandir( $dir );
		if ( ! $items ) {
			return;
		}
		foreach ( $items as $item ) {
			if ( '.' === $item || '..' === $item ) {
				continue;
			}
			$path = $dir . '/' . $item;
			if ( is_dir( $path ) && ! is_link( $path ) ) {
				self::rrmdir( $path, true );
			} else {
				wp_delete_file( $path );
			}
		}
		if ( $remove_self ) {
			@rmdir( $dir );
		}
	}

	public static function clean_expired() {
		$life = max( 1, (int) Velox_Settings::get( 'cache_lifespan' ) ) * HOUR_IN_SECONDS;
		self::walk(
			self::pages_dir(),
			function ( $file ) use ( $life ) {
				if ( time() - filemtime( $file ) > $life ) {
					wp_delete_file( $file );
				}
			}
		);
		// Parsed stylesheet caches are rebuilt on demand; drop month-old ones (stale theme versions).
		foreach ( array_merge( glob( self::dir() . 'css/p-*.php' ) ?: array(), glob( self::dir() . 'css/p-*.json' ) ?: array() ) as $file ) {
			if ( time() - filemtime( $file ) > 30 * DAY_IN_SECONDS ) {
				wp_delete_file( $file );
			}
		}
		self::walk(
			self::dir() . 'min/',
			function ( $file ) {
				if ( time() - filemtime( $file ) > 30 * DAY_IN_SECONDS ) {
					wp_delete_file( $file );
				}
			}
		);
	}

	private static function walk( $dir, $cb ) {
		if ( ! is_dir( $dir ) ) {
			return;
		}
		$it = new RecursiveIteratorIterator( new RecursiveDirectoryIterator( $dir, FilesystemIterator::SKIP_DOTS ) );
		foreach ( $it as $file ) {
			if ( $file->isFile() ) {
				call_user_func( $cb, $file->getPathname() );
			}
		}
	}

	public static function stats() {
		$cached = get_transient( 'velox_stats' );
		if ( is_array( $cached ) ) {
			return $cached;
		}
		$count = 0;
		$size  = 0;
		self::walk(
			self::pages_dir(),
			function ( $file ) use ( &$count, &$size ) {
				if ( preg_match( '/index(-mobile)?(-https)?\.html$/', $file ) ) {
					$count++;
					$size += filesize( $file );
				}
			}
		);
		$out = array(
			'pages' => $count,
			'size'  => $size,
		);
		set_transient( 'velox_stats', $out, 5 * MINUTE_IN_SECONDS );
		return $out;
	}

	/* ---------- drop-in config ---------- */

	public static function write_config() {
		wp_mkdir_p( self::dir() );
		wp_mkdir_p( self::pages_dir() );
		self::protect_dir();
		$cfg = array(
			'enabled'        => (bool) Velox_Settings::get( 'cache_enabled' ),
			'mobile'         => (bool) Velox_Settings::get( 'cache_mobile' ),
			'lifespan'       => max( 1, (int) Velox_Settings::get( 'cache_lifespan' ) ) * HOUR_IN_SECONDS,
			'exclude'        => self::exclude_regexes(),
			'webp'           => (bool) Velox_Settings::get( 'webp' ),
			'avif'           => (bool) ( Velox_Settings::get( 'webp' ) && Velox_Settings::get( 'avif' ) ),
			'host'           => strtolower( (string) wp_parse_url( home_url(), PHP_URL_HOST ) ),
			'brotli'         => function_exists( 'brotli_compress' ),
			'brotli_dynamic' => (bool) Velox_Settings::get( 'brotli_dynamic' ),
		);
		// Plain JSON data read by the advanced-cache.php drop-in (blocked from web access by the cache folder's .htaccess).
		@file_put_contents( self::dir() . 'config.json', wp_json_encode( $cfg ), LOCK_EX );
		if ( is_file( self::dir() . 'config.php' ) ) {
			wp_delete_file( self::dir() . 'config.php' ); // Written by versions before 2.2.0.
		}
	}

	public static function dropin_path() {
		return trailingslashit( WP_CONTENT_DIR ) . 'advanced-cache.php';
	}

	public static function dropin_is_ours() {
		$f = self::dropin_path();
		return is_file( $f ) && 1 === preg_match( '/(AngelForce|Velox) Cache drop-in/', (string) file_get_contents( $f, false, null, 0, 600 ) );
	}

	public static function install_dropin() {
		$f = self::dropin_path();
		if ( file_exists( $f ) && ! self::dropin_is_ours() ) {
			return false; // Another plugin owns it.
		}
		return @copy( VELOX_DIR . 'dropin/advanced-cache.php', $f );
	}

	public static function remove_dropin() {
		if ( self::dropin_is_ours() ) {
			wp_delete_file( self::dropin_path() );
		}
	}

	public static function wp_config_path() {
		$f = ABSPATH . 'wp-config.php';
		if ( ! file_exists( $f ) ) {
			$f = dirname( ABSPATH ) . '/wp-config.php';
		}
		return is_file( $f ) ? $f : false;
	}

	public static function set_wp_cache( $on ) {
		$f = self::wp_config_path();
		if ( ! $f || ! is_writable( $f ) ) {
			return false;
		}
		$c   = file_get_contents( $f );
		$old = $c;
		if ( $on ) {
			if ( preg_match( "/define\(\s*['\"]WP_CACHE['\"]\s*,\s*true\s*\)/i", $c ) ) {
				return true;
			}
			if ( preg_match( "/define\(\s*['\"]WP_CACHE['\"]\s*,\s*false\s*\)/i", $c ) ) {
				$c = preg_replace( "/define\(\s*['\"]WP_CACHE['\"]\s*,\s*false\s*\)/i", "define( 'WP_CACHE', true ) /* " . self::MARK . ' */', $c, 1 );
			} else {
				$c = preg_replace( '/<\?php/', "<?php\ndefine( 'WP_CACHE', true ); // " . self::MARK, $c, 1 );
			}
		} else {
			// Also removes the line written by the plugin's earlier name (Velox Cache).
			$c = preg_replace( "/^define\( 'WP_CACHE', true \); \/\/ Added by (AngelForce|Velox) Cache\R/m", '', $c );
			// A line this plugin switched from false to true goes back to false.
			$c = preg_replace( "/define\( 'WP_CACHE', true \) \/\* Added by (AngelForce|Velox) Cache \*\//", "define( 'WP_CACHE', false )", (string) $c );
		}
		if ( $c !== $old && null !== $c ) {
			return false !== file_put_contents( $f, $c, LOCK_EX );
		}
		return true;
	}

	public static function wp_cache_active() {
		return defined( 'WP_CACHE' ) && WP_CACHE;
	}

	/* ---------- lifecycle ---------- */

	public static function activate() {
		Velox_Settings::flush();
		if ( false === get_option( Velox_Settings::OPTION ) ) {
			add_option( Velox_Settings::OPTION, Velox_Settings::defaults() );
		}
		self::write_config();
		self::install_dropin();
		self::set_wp_cache( true );
		Velox_Htaccess::sync();
		Velox_Database::reschedule();
		if ( ! wp_next_scheduled( 'velox_clean_expired' ) ) {
			wp_schedule_event( time() + 300, 'hourly', 'velox_clean_expired' );
		}
		update_option( 'angelforce_cache_ready', VELOX_VERSION, false );
	}

	/* ---------- setup after updates ---------- */

	/**
	 * Runs the setup once after an update (new drop-in, its settings file, .htaccess rules) and when
	 * the plugin was activated while the earlier copy was still active, so the activation hook stayed idle.
	 */
	public static function maybe_finish_setup() {
		$prev = get_option( 'angelforce_cache_ready' );
		if ( VELOX_VERSION === $prev || ! current_user_can( 'activate_plugins' ) ) {
			return;
		}
		self::activate();
		if ( $prev ) {
			self::purge_all(); // Pages built by the previous version carry its markup.
		}
	}

	public static function deactivate() {
		remove_action( 'deactivated_plugin', array( __CLASS__, 'on_plugin_toggle' ) );
		self::rrmdir( self::pages_dir(), false );
		self::remove_dropin();
		self::set_wp_cache( false );
		Velox_Htaccess::remove();
		wp_clear_scheduled_hook( 'velox_clean_expired' );
		wp_clear_scheduled_hook( 'velox_db_cleanup' );
		wp_clear_scheduled_hook( 'velox_preload_run' );
		delete_option( 'angelforce_cache_ready' );
	}
}