<?php

/**
 * Stores generated blocker-resistant assets in WordPress' shared cache area.
 *
 * @package    AdUnblocker
 * @subpackage AdUnblocker/includes
 */

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

class AdUnblocker_Asset_Cache
{
	const CACHE_DIRECTORY = 'cache';
	const MARKER_FILE = '.daau-cache-bundle';
	const MARKER_PREFIX = 'adunblocker:';

	private static $filesystem;

	/**
	 * Returns the absolute path for an opaque cache bundle or asset.
	 *
	 * @param string $bundle_key Opaque bundle directory name.
	 * @param string $file_name Optional asset file name.
	 * @return string
	 */
	public static function get_path($bundle_key, $file_name = '')
	{
		if (! self::is_safe_bundle_key($bundle_key)) {
			return '';
		}

		$path = trailingslashit(WP_CONTENT_DIR) . self::CACHE_DIRECTORY . '/' . $bundle_key;
		if ('' !== $file_name) {
			if (! self::is_safe_asset_file_name($file_name)) {
				return '';
			}
			$path .= '/' . $file_name;
		}

		return $path;
	}

	/**
	 * Returns the public URL for an opaque cache asset.
	 *
	 * @param string $bundle_key Opaque bundle directory name.
	 * @param string $file_name Asset file name.
	 * @return string
	 */
	public static function get_url($bundle_key, $file_name)
	{
		if (! self::is_safe_bundle_key($bundle_key) || ! self::is_safe_asset_file_name($file_name)) {
			return '';
		}

		return content_url(
			self::CACHE_DIRECTORY . '/' . rawurlencode($bundle_key) . '/' . rawurlencode($file_name)
		);
	}

	/**
	 * Ensures an owned cache bundle exists and has the expected marker.
	 *
	 * @param string $bundle_key Opaque bundle directory name.
	 * @param string $owner Bundle owner identifier.
	 * @return bool
	 */
	public static function ensure_bundle($bundle_key, $owner)
	{
		if (! self::is_safe_bundle_key($bundle_key) || ! self::is_safe_owner($owner)) {
			return false;
		}

		$filesystem = self::get_filesystem();
		if (! $filesystem) {
			return false;
		}

		$cache_root = trailingslashit(WP_CONTENT_DIR) . self::CACHE_DIRECTORY;
		$bundle_path = self::get_path($bundle_key);
		if ('' === $bundle_path) {
			return false;
		}

		if (! $filesystem->is_dir($cache_root) && ! wp_mkdir_p($cache_root)) {
			return false;
		}

		$bundle_existed = $filesystem->is_dir($bundle_path);
		if (! $bundle_existed) {
			if ($filesystem->exists($bundle_path) || ! wp_mkdir_p($bundle_path)) {
				return false;
			}
		}

		$marker_path = $bundle_path . '/' . self::MARKER_FILE;
		$expected_marker = self::MARKER_PREFIX . $owner;
		if (! $filesystem->exists($marker_path)) {
			// Never claim a pre-existing cache directory that we did not create.
			if ($bundle_existed) {
				return false;
			}
			if (! $filesystem->put_contents($marker_path, $expected_marker, self::file_permissions())) {
				return false;
			}
		}

		$marker = $filesystem->get_contents($marker_path);

		return is_string($marker) && hash_equals($expected_marker, $marker);
	}

	/**
	 * Writes an asset atomically inside an owned cache bundle.
	 *
	 * @param string $bundle_key Opaque bundle directory name.
	 * @param string $owner Bundle owner identifier.
	 * @param string $file_name Asset file name.
	 * @param string $contents Asset contents.
	 * @return bool
	 */
	public static function write($bundle_key, $owner, $file_name, $contents)
	{
		if (
			! is_string($contents) ||
			! self::is_safe_asset_file_name($file_name) ||
			! self::ensure_bundle($bundle_key, $owner)
		) {
			return false;
		}

		$filesystem = self::get_filesystem();
		$target_path = self::get_path($bundle_key, $file_name);
		$temp_name = $file_name . '.tmp-' . self::generate_opaque_name(6);
		$temp_path = self::get_path($bundle_key) . '/' . $temp_name;

		if (! $filesystem || '' === $target_path) {
			return false;
		}

		if (! $filesystem->put_contents($temp_path, $contents, self::file_permissions())) {
			return false;
		}

		if (! $filesystem->move($temp_path, $target_path, true)) {
			$filesystem->delete($temp_path, false, 'f');
			return false;
		}

		return $filesystem->is_file($target_path);
	}

	/**
	 * Copies a bundled plugin asset into an owned cache bundle.
	 *
	 * @param string $bundle_key Opaque bundle directory name.
	 * @param string $owner Bundle owner identifier.
	 * @param string $file_name Asset file name.
	 * @param string $source_path Absolute source path.
	 * @return bool
	 */
	public static function copy($bundle_key, $owner, $file_name, $source_path)
	{
		$contents = self::read($source_path);
		if (! is_string($contents)) {
			return false;
		}

		return self::write($bundle_key, $owner, $file_name, $contents);
	}

	/**
	 * Reads a local source file through the WordPress filesystem abstraction.
	 *
	 * @param string $source_path Absolute source path.
	 * @return string|false
	 */
	public static function read($source_path)
	{
		$filesystem = self::get_filesystem();
		if (! $filesystem || ! is_string($source_path) || ! $filesystem->is_file($source_path)) {
			return false;
		}

		$contents = $filesystem->get_contents($source_path);

		return is_string($contents) ? $contents : false;
	}

	/**
	 * Checks that an owned cache bundle contains all requested assets.
	 *
	 * @param string   $bundle_key Opaque bundle directory name.
	 * @param string   $owner Bundle owner identifier.
	 * @param string[] $file_names Asset file names.
	 * @return bool
	 */
	public static function is_ready($bundle_key, $owner, $file_names)
	{
		if (! self::has_valid_marker($bundle_key, $owner) || ! is_array($file_names)) {
			return false;
		}

		foreach ($file_names as $file_name) {
			$path = self::get_path($bundle_key, $file_name);
			if ('' === $path || ! is_file($path)) {
				return false;
			}
		}

		return true;
	}

	/**
	 * Deletes one asset from an owned cache bundle.
	 *
	 * @param string $bundle_key Opaque bundle directory name.
	 * @param string $owner Bundle owner identifier.
	 * @param string $file_name Asset file name.
	 * @return bool
	 */
	public static function delete_file($bundle_key, $owner, $file_name)
	{
		if (! self::has_valid_marker($bundle_key, $owner)) {
			return false;
		}

		$filesystem = self::get_filesystem();
		$file_path = self::get_path($bundle_key, $file_name);
		if (! $filesystem || '' === $file_path || ! $filesystem->exists($file_path)) {
			return false;
		}

		return (bool) $filesystem->delete($file_path, false, 'f');
	}

	/**
	 * Deletes an owned cache bundle without touching the shared cache root.
	 *
	 * @param string $bundle_key Opaque bundle directory name.
	 * @param string $owner Bundle owner identifier.
	 * @return bool
	 */
	public static function delete_bundle($bundle_key, $owner)
	{
		if (! self::has_valid_marker($bundle_key, $owner)) {
			return false;
		}

		$filesystem = self::get_filesystem();
		$bundle_path = self::get_path($bundle_key);
		if (! $filesystem || '' === $bundle_path) {
			return false;
		}

		return (bool) $filesystem->delete($bundle_path, true, 'd');
	}

	/**
	 * Removes a legacy frontend bundle from WP_PLUGIN_DIR after migration.
	 *
	 * Only a directory containing the two exact generated assets is removed.
	 *
	 * @param string $bundle_key Legacy bundle directory and file prefix.
	 * @return bool
	 */
	public static function delete_legacy_frontend_bundle($bundle_key)
	{
		if (! self::is_safe_bundle_key($bundle_key)) {
			return false;
		}

		$filesystem = self::get_filesystem();
		$directory = trailingslashit(WP_PLUGIN_DIR) . $bundle_key;
		if (! $filesystem || ! $filesystem->is_dir($directory)) {
			return false;
		}

		$allowed_files = array($bundle_key . '.css', $bundle_key . '.js');
		$entries = $filesystem->dirlist($directory, false, false);
		if (! is_array($entries) || empty($entries)) {
			return false;
		}

		foreach ($entries as $file_name => $entry) {
			if (! in_array($file_name, $allowed_files, true) || ! isset($entry['type']) || 'f' !== $entry['type']) {
				return false;
			}
		}

		return (bool) $filesystem->delete($directory, true, 'd');
	}

	/**
	 * Removes a legacy marked admin bundle from WP_PLUGIN_DIR after migration.
	 *
	 * @param string $bundle_key Legacy bundle directory name.
	 * @param string $marker_file Legacy marker file name.
	 * @param string $marker_content Expected legacy marker contents.
	 * @return bool
	 */
	public static function delete_legacy_marked_bundle($bundle_key, $marker_file, $marker_content)
	{
		if (
			! self::is_safe_bundle_key($bundle_key) ||
			! is_string($marker_file) ||
			wp_basename($marker_file) !== $marker_file ||
			! is_string($marker_content)
		) {
			return false;
		}

		$filesystem = self::get_filesystem();
		$directory = trailingslashit(WP_PLUGIN_DIR) . $bundle_key;
		$marker_path = $directory . '/' . $marker_file;
		if (! $filesystem || ! $filesystem->is_dir($directory) || ! $filesystem->is_file($marker_path)) {
			return false;
		}

		$marker = $filesystem->get_contents($marker_path);
		if (! is_string($marker) || ! hash_equals($marker_content, $marker)) {
			return false;
		}

		return (bool) $filesystem->delete($directory, true, 'd');
	}

	/**
	 * Returns whether a bundle key is safe to append to the cache root.
	 *
	 * @param mixed $bundle_key Candidate key.
	 * @return bool
	 */
	public static function is_safe_bundle_key($bundle_key)
	{
		return is_string($bundle_key) && 1 === preg_match('/^[a-z]{6,32}$/', $bundle_key);
	}

	private static function is_safe_asset_file_name($file_name)
	{
		return is_string($file_name) && 1 === preg_match('/^[a-z]{6,32}\.(css|js)$/', $file_name);
	}

	private static function is_safe_owner($owner)
	{
		return is_string($owner) && 1 === preg_match('/^[a-z]{2,16}$/', $owner);
	}

	private static function has_valid_marker($bundle_key, $owner)
	{
		if (! self::is_safe_bundle_key($bundle_key) || ! self::is_safe_owner($owner)) {
			return false;
		}

		$bundle_path = self::get_path($bundle_key);
		$marker_path = $bundle_path . '/' . self::MARKER_FILE;
		if ('' === $bundle_path || ! is_file($marker_path)) {
			return false;
		}

		$marker = file_get_contents($marker_path);

		return is_string($marker) && hash_equals(self::MARKER_PREFIX . $owner, $marker);
	}

	private static function get_filesystem()
	{
		if (is_object(self::$filesystem)) {
			return self::$filesystem;
		}

		if (! function_exists('WP_Filesystem')) {
			require_once ABSPATH . 'wp-admin/includes/file.php';
		}

		global $wp_filesystem;
		if (! WP_Filesystem() || ! is_object($wp_filesystem)) {
			return false;
		}

		self::$filesystem = $wp_filesystem;

		return self::$filesystem;
	}

	private static function file_permissions()
	{
		return defined('FS_CHMOD_FILE') ? FS_CHMOD_FILE : 0644;
	}

	private static function generate_opaque_name($length)
	{
		$characters = 'abcdefghijklmnopqrstuvwxyz';
		$name = '';
		$max_index = strlen($characters) - 1;

		for ($index = 0; $index < $length; $index++) {
			$name .= $characters[random_int(0, $max_index)];
		}

		return $name;
	}
}