<?php

abstract class ITSEC_Scheduler {

	const S_TWICE_HOURLY = 'twice-hourly';
	const S_HOURLY = 'hourly';
	const S_FOUR_DAILY = 'four-daily';
	const S_TWICE_DAILY = 'twice-daily';
	const S_DAILY = 'daily';
	const S_WEEKLY = 'weekly';
	const S_MONTHLY = 'monthly';

	const LOCK_SCHEDULING = 'scheduling';

	/** @var array */
	protected $custom_schedules = array();

	/** @var array */
	protected $loops = array();

	/** @var bool */
	private $is_running = false;

	/**
	 * Schedule a recurring event.
	 *
	 * Only one event with the given id can be scheduled at a time.
	 *
	 * @param string $schedule
	 * @param string $id
	 * @param array  $data
	 * @param array  $opts
	 *  - fire_at: Manually specify the first time the event should be fired.
	 *
	 * @return bool
	 */
	abstract public function schedule( $schedule, $id, $data = array(), $opts = array() );

	/**
	 * Schedule a single event.
	 *
	 * Only one event with the given id and same set of data can be scheduled at the same time.
	 *
	 * Unlike Core's CRON implementation, event if a single event is more than 10 minutes in the future, it cannot be scheduled.
	 *
	 * @param int    $at
	 * @param string $id
	 * @param array  $data
	 *
	 * @return bool
	 */
	abstract public function schedule_once( $at, $id, $data = array() );

	/**
	 * Schedule a single event to run soon.
	 *
	 * @param string $id
	 * @param array  $data
	 *
	 * @return bool
	 */
	public function schedule_soon( $id, $data = array() ) {
		return $this->schedule_once( ITSEC_Core::get_current_time_gmt() + 60 * mt_rand( 1, 10 ), $id, $data );
	}

	/**
	 * Schedule an event loop.
	 *
	 * @param string $id   The event ID.
	 * @param array  $data Event data.
	 * @param array  $opts
	 *  - fire_at: Manually specify the first time the event should be fired.
	 */
	public function schedule_loop( $id, $data = array(), $opts = array() ) {
		$start = isset( $opts['fire_at'] ) ? $opts['fire_at'] : ITSEC_Core::get_current_time_gmt() + 60 * mt_rand( 1, 30 );

		$this->schedule_once( $start, $id, array_merge( $data, array(
			'loop_start' => $start,
			'loop_item'  => 1,
		) ) );
	}

	/**
	 * Is a recurring event scheduled.
	 *
	 * @param string $id
	 *
	 * @return bool
	 */
	abstract public function is_recurring_scheduled( $id );

	/**
	 * Is a single event scheduled with the given data.
	 *
	 * @param string     $id   The event ID to check.
	 * @param array|null $data The event data. Pass null to check if any event is scheduled with that ID,
	 *                         regardless of the data.
	 *
	 * @return bool
	 */
	abstract public function is_single_scheduled( $id, $data = array() );

	/**
	 * Unschedule a recurring event.
	 *
	 * @param string $id
	 *
	 * @return bool
	 */
	abstract public function unschedule( $id );

	/**
	 * Unschedule a single event.
	 *
	 * The data specified needs to be identical to the data the single event was scheduled with.
	 *
	 * @param string     $id The event ID to unschedule.
	 * @param array|null $data Unschedules the event with the given data. Pass null to delete any and all events matching the ID.
	 *
	 * @return bool
	 */
	abstract public function unschedule_single( $id, $data = array() );

	/**
	 * Get all of the scheduled recurring events.
	 *
	 * Each event is an array with the following properties.
	 *  - id: The ID the event was scheduled with.
	 *  - data: The data the event was scheduled with.
	 *  - fire_at: The next time the event should be fired.
	 *  - schedule: The selected schedule. See S_HOURLY, etc...
	 *
	 * @return array
	 */
	abstract public function get_recurring_events();

	/**
	 * Get all of the single events.
	 *
	 * Each event is an array with the following properties.
	 *  - id: The ID the event was scheduled with.
	 *  - data: The data the event was scheduled with.
	 *  - fire_at: The time the event should be fired.
	 *  - hash: The event's data hash.
	 *
	 * @return array
	 */
	abstract public function get_single_events();

	/**
	 * Run a recurring event, even if it is not time to.
	 *
	 * This will _not_ update the last fired time.
	 *
	 * @param string $id
	 *
	 * @return void
	 */
	abstract public function run_recurring_event( $id );

	/**
	 * Run a single event, even if it is not time to.
	 *
	 * This will clear the event from the schedule.
	 *
	 * @param string $id
	 * @param array  $data
	 *
	 * @return void
	 */
	abstract public function run_single_event( $id, $data = array() );

	/**
	 * Run a single event by it's hash.
	 *
	 * @param string $id
	 * @param string $hash
	 *
	 * @return void
	 */
	abstract public function run_single_event_by_hash( $id, $hash );

	/**
	 * Run any events that are due now.
	 *
	 * @param int $now
	 *
	 * @return void
	 */
	abstract public function run_due_now( $now = 0 );

	/**
	 * Code executed on every page load to setup the scheduler.
	 *
	 * @return void
	 */
	abstract public function run();

	/**
	 * Check whether the scheduler is currently executing an event.
	 *
	 * @return bool
	 */
	final public function is_running() {
		return $this->is_running;
	}

	/**
	 * Manually trigger modules to register their scheduled events.
	 *
	 * @return void
	 */
	public function register_events() {
		/**
		 * Register scheduled events.
		 *
		 * Events should be registered in response to a user action, for example activating a module or changing a setting.
		 * Occasionally, iThemes Security will manually ask for all events to be scheduled.
		 *
		 * @param ITSEC_Scheduler $this
		 */
		do_action( 'itsec_scheduler_register_events', $this );
		$this->register_events_for_module( ':active' );
	}

	/**
	 * Registers events for a given module using the "scheduling.php" module file.
	 *
	 * @param string $module
	 */
	public function register_events_for_module( $module ) {
		ITSEC_Modules::load_module_file( 'scheduling.php', $module, function ( $fn ) {
			if ( ! is_callable( $fn ) ) {
				_doing_it_wrong( 'scheduling.php', __( 'An iThemes Security module\'s scheduling.php file must return a callable.', 'better-wp-security' ), '5.8.0' );

				return;
			}

			$fn( $this );
		} );
	}

	/**
	 * Register a custom schedule.
	 *
	 * @param string $slug
	 * @param int    $interval
	 */
	public function register_custom_schedule( $slug, $interval ) {
		$this->custom_schedules[ $slug ] = $interval;
	}

	/**
	 * Get a registered custom schedules.
	 *
	 * @return array
	 */
	public function get_custom_schedules() {
		return $this->custom_schedules;
	}

	/**
	 * Register an event loop.
	 *
	 * This allows for splitting up a long running process across multiple page loads.
	 *
	 * @param string $id       The event ID.
	 * @param string $schedule The schedule between loop starts. This is the maximum amount of time to wait.
	 * @param int    $wait     Time to wait in seconds between loop parts.
	 */
	public function register_loop( $id, $schedule, $wait ) {
		$this->loops[ $id ] = array(
			'schedule' => $schedule,
			'wait'     => $wait,
		);
	}

	/**
	 * Get the loop configuration.
	 *
	 * @param string $id
	 *
	 * @return array
	 */
	public function get_loop( $id ) {
		return isset( $this->loops[ $id ] ) ? $this->loops[ $id ] : array();
	}

	/**
	 * Get a lock to be used for scheduling events.
	 *
	 * @return bool
	 */
	protected function scheduling_lock() {
		return ITSEC_Lib::get_lock( self::LOCK_SCHEDULING, 5 );
	}

	/**
	 * Release the lock used for scheduling events.
	 */
	protected function scheduling_unlock() {
		ITSEC_Lib::release_lock( self::LOCK_SCHEDULING );
	}

	/**
	 * Make a job object.
	 *
	 * @param string $id
	 * @param array  $data
	 * @param array  $opts
	 *
	 * @return ITSEC_Job
	 */
	protected function make_job( $id, $data, $opts = array() ) {
		return new ITSEC_Job( $this, $id, $data, $opts );
	}

	/**
	 * Dispatch the action to execute the scheduled job.
	 *
	 * @param ITSEC_Job $job
	 */
	protected final function call_action( ITSEC_Job $job ) {
		$interactive = ITSEC_Core::is_interactive();
		ITSEC_Core::set_interactive( false );
		$this->is_running = true;

		try {
			/**
			 * Fires when a scheduled job should be executed.
			 *
			 * @param ITSEC_Job $job
			 */
			do_action( "itsec_scheduled_{$job->get_id()}", $job );
		} catch ( Exception $e ) {
			ITSEC_Log::add_fatal_error( 'scheduler', 'unhandled-exception', array(
				'exception' => (string) $e,
				'job'       => $job->get_id(),
				'data'      => $job->get_data(),
			) );
			$job->reschedule_in( 500 );
		}

		$this->is_running = false;
		ITSEC_Core::set_interactive( $interactive );
	}

	/**
	 * Generate a unique hash of the data.
	 *
	 * @param array $data
	 *
	 * @return string
	 */
	protected function hash_data( $data ) {
		return md5( serialize( $data ) );
	}

	/**
	 * Get the interval for the schedule.
	 *
	 * @param string $schedule
	 *
	 * @return int
	 */
	final public function get_schedule_interval( $schedule ) {
		switch ( $schedule ) {
			case self::S_TWICE_HOURLY:
				return HOUR_IN_SECONDS / 2;
			case self::S_HOURLY:
				return HOUR_IN_SECONDS;
			case self::S_FOUR_DAILY:
				return DAY_IN_SECONDS / 4;
			case self::S_TWICE_DAILY:
				return DAY_IN_SECONDS / 2;
			case self::S_DAILY:
				return DAY_IN_SECONDS;
			case self::S_WEEKLY:
				return WEEK_IN_SECONDS;
			case self::S_MONTHLY:
				return MONTH_IN_SECONDS;
			default:
				return isset( $this->custom_schedules[ $schedule ] ) ? $this->custom_schedules[ $schedule ] : false;
		}
	}

	/**
	 * Run code when the plugin is uninstalled.
	 */
	public function uninstall() {

	}

	/**
	 * Reset the scheduler.
	 *
	 * This unregisters all events, and re-registers them.
	 */
	public function reset() {
		$this->uninstall();
		$this->run();
		$this->register_events();
	}
}
