<?php
/**
 * Request caching tool.
 *
 * @package GoogleAnalytics
 */

/**
 * Cache class.
 */
class Ga_Cache {

	/**
	 * Time until expiration in seconds
	 */
	const GA_DATA_EXPIRATION_TIME = 86400;// 60 * 60 * 24 = 86400; // 24h

	const GA_TRANSIENT_PREFIX = 'googleanalytics_cache_';

	const GA_LAST_CACHE_OPTION_NAME = 'googleanalytics_cache_last_cache_time';

	const GA_LAST_TIME_ATTEMPT_OPTION_NAME = 'googleanalytics_cache_last_time_attempt';

	const GA_BUFFER_CACHE_OPTION_NAME = 'googleanalytics_cache_buffer';

	const GA_WAIT_AFTER_ERROR_TIME = 300; // 60 * 5 = 5 min

	/**
	 * Add cache options.
	 *
	 * @return void
	 */
	public static function add_cache_options() {
		add_option( self::GA_LAST_CACHE_OPTION_NAME );
		add_option( self::GA_BUFFER_CACHE_OPTION_NAME );
		add_option( self::GA_LAST_TIME_ATTEMPT_OPTION_NAME );
	}

	/**
	 * Delete cache options.
	 *
	 * @return void
	 */
	public static function delete_cache_options() {
		delete_option( self::GA_LAST_CACHE_OPTION_NAME );
		delete_option( self::GA_BUFFER_CACHE_OPTION_NAME );
		delete_option( self::GA_LAST_TIME_ATTEMPT_OPTION_NAME );
	}

	/**
	 * Generates transient name.
	 *
	 * @param string $rest_url    Rest URL string.
	 * @param array  $query_params Query params.
	 * @param string $appendix    String to append.
	 *
	 * @return string
	 */
	public static function get_transient_name( $rest_url, $query_params, $appendix = '' ) {

		if ( is_array( $query_params ) ) {
			$query_params = wp_json_encode( $query_params );
		}

		$name = md5( $rest_url . $query_params );

		return self::GA_TRANSIENT_PREFIX . $name . '_' . $appendix;
	}

	/**
	 * Gets cached data.
	 *
	 * @param string $name Cache key string.
	 *
	 * @return bool|mixed
	 */
	public static function get_cached_result( $name ) {
		$data = get_option( self::GA_BUFFER_CACHE_OPTION_NAME );

		// Check if cache exists.
		if ( false === empty( $data[ $name ] ) ) {
			return $data[ $name ];
		} else {
			return false;
		}
	}

	/**
	 * Sets cache value.
	 *
	 * @param string $name   Cache key name.
	 * @param mixed  $result Cache key value.
	 */
	public static function set_cache( $name, $result ) {
		if ( false === empty( $result ) ) {
			self::set_last_cache_time( $name );
			self::set_cache_buffer( $name, $result );
			self::delete_last_time_attempt();
		}
	}

	/**
	 * Updates the time the response was cached.
	 *
	 * @param string $name Cache key name.
	 */
	public static function set_last_cache_time( $name ) {
		$data = get_option( self::GA_LAST_CACHE_OPTION_NAME );

		if ( empty( $data ) ) {
			$data          = array();
			$data[ $name ] = time();
		} else {
			$data = array_merge( $data, array( $name => time() ) );
		}

		update_option( self::GA_LAST_CACHE_OPTION_NAME, $data );
	}

	/**
	 * Sets or update data cache.
	 *
	 * @param string $name   Cache key name.
	 * @param string $result Cache key value.
	 */
	public static function set_cache_buffer( $name, $result ) {
		$data = get_option( self::GA_BUFFER_CACHE_OPTION_NAME );

		if ( empty( $data ) ) {
			$data          = array();
			$data[ $name ] = $result;
		} else {
			$data = array_merge( $data, array( $name => $result ) );
		}

		update_option( self::GA_BUFFER_CACHE_OPTION_NAME, $data );
	}

	/**
	 * Sets last time attempt option
	 */
	public static function set_last_time_attempt() {
		update_option( self::GA_LAST_TIME_ATTEMPT_OPTION_NAME, time() );
	}

	/**
	 * Deletes last time attepmt option
	 */
	public static function delete_last_time_attempt() {
		delete_option( self::GA_LAST_TIME_ATTEMPT_OPTION_NAME );
	}

	/**
	 * Checks if the next rest API request is allowed.
	 *
	 * Next api request is allowed when there was an unsuccessful attempt and data_cache is empty.
	 *
	 * @param string $name Name string.
	 *
	 * @return bool
	 */
	public static function is_next_request_allowed( $name ) {
		$last_time_attempt = get_option( self::GA_LAST_TIME_ATTEMPT_OPTION_NAME );

		if ( true === empty( $last_time_attempt ) ) {
			// If there is no last_time_attempt then return true.
			return true;
		} else {
			$outdated_last_attempt_time = ( $last_time_attempt + self::GA_WAIT_AFTER_ERROR_TIME ) < time();
		}

		return ( false === empty( self::get_cached_result( $name ) ) && true === $outdated_last_attempt_time );
	}

	/**
	 * Checks whether data cache is outdated.
	 *
	 * @param string $name     Cache key name string.
	 * @param string $appendix Cache key string to append.
	 *
	 * @return bool
	 */
	public static function is_data_cache_outdated( $name = '', $appendix = '' ) {
		$last_time = get_option( self::GA_LAST_CACHE_OPTION_NAME );
		$outdated  = 0;
		if ( false === empty( $last_time ) ) {

			// Validate cache for given rest name.
			if ( false === empty( $name ) ) {

				// If appendix is set then check only that cache which concerns given appendix.
				if ( false === empty( $appendix ) ) {
					return (
						preg_match( '/' . $appendix . '/', $name )
						&& ( $last_time[ $name ] + self::GA_DATA_EXPIRATION_TIME ) < time()
					);
				} else {
					return ! empty( $last_time[ $name ] ) && ( $last_time[ $name ] + self::GA_DATA_EXPIRATION_TIME ) < time();
				}
			} else { // Validate cache for all requests.

				// If any of existing caches is outdated.
				foreach ( $last_time as $item => $time ) {
					// If appendix is set then check only entries concerns given appendix.
					if ( false === empty( $appendix ) ) {
						if (
							preg_match( '/' . $appendix . '/', $item )
							&& ( $time + self::GA_DATA_EXPIRATION_TIME ) < time() ) {
							$outdated ++;
						}
					} else {
						if ( ( $time + self::GA_DATA_EXPIRATION_TIME ) < time() ) {
							$outdated ++;
						}
					}
				}

				return $outdated > 0;
			}
		}

		return false;
	}
}