<?php

/**
 * Class ActionScheduler_QueueRunner
 */
class ActionScheduler_QueueRunner extends ActionScheduler_Abstract_QueueRunner {
	const WP_CRON_HOOK = 'action_scheduler_run_queue';

	const WP_CRON_SCHEDULE = 'every_minute';

	/** @var ActionScheduler_AsyncRequest_QueueRunner */
	protected $async_request;

	/** @var ActionScheduler_QueueRunner  */
	private static $runner = null;

	/** @var int  */
	private $processed_actions_count = 0;

	/**
	 * @return ActionScheduler_QueueRunner
	 * @codeCoverageIgnore
	 */
	public static function instance() {
		if ( empty(self::$runner) ) {
			$class = apply_filters('action_scheduler_queue_runner_class', 'ActionScheduler_QueueRunner');
			self::$runner = new $class();
		}
		return self::$runner;
	}

	/**
	 * ActionScheduler_QueueRunner constructor.
	 *
	 * @param ActionScheduler_Store                    $store Store object.
	 * @param ActionScheduler_FatalErrorMonitor        $monitor Monitor object.
	 * @param ActionScheduler_QueueCleaner             $cleaner Cleaner object.
	 * @param ActionScheduler_AsyncRequest_QueueRunner $async_request Async request runner object.
	 */
	public function __construct( ActionScheduler_Store $store = null, ActionScheduler_FatalErrorMonitor $monitor = null, ActionScheduler_QueueCleaner $cleaner = null, ActionScheduler_AsyncRequest_QueueRunner $async_request = null ) {
		parent::__construct( $store, $monitor, $cleaner );

		if ( is_null( $async_request ) ) {
			$async_request = new ActionScheduler_AsyncRequest_QueueRunner( $this->store );
		}

		$this->async_request = $async_request;
	}

	/**
	 * @codeCoverageIgnore
	 */
	public function init() {

		add_filter( 'cron_schedules', array( self::instance(), 'add_wp_cron_schedule' ) );

		// Check for and remove any WP Cron hook scheduled by Action Scheduler < 3.0.0, which didn't include the $context param.
		$next_timestamp = wp_next_scheduled( self::WP_CRON_HOOK );
		if ( $next_timestamp ) {
			wp_unschedule_event( $next_timestamp, self::WP_CRON_HOOK );
		}

		$cron_context = array( 'WP Cron' );

		if ( ! wp_next_scheduled( self::WP_CRON_HOOK, $cron_context ) ) {
			$schedule = apply_filters( 'action_scheduler_run_schedule', self::WP_CRON_SCHEDULE );
			wp_schedule_event( time(), $schedule, self::WP_CRON_HOOK, $cron_context );
		}

		add_action( self::WP_CRON_HOOK, array( self::instance(), 'run' ) );
		$this->hook_dispatch_async_request();
	}

	/**
	 * Hook check for dispatching an async request.
	 */
	public function hook_dispatch_async_request() {
		add_action( 'shutdown', array( $this, 'maybe_dispatch_async_request' ) );
	}

	/**
	 * Unhook check for dispatching an async request.
	 */
	public function unhook_dispatch_async_request() {
		remove_action( 'shutdown', array( $this, 'maybe_dispatch_async_request' ) );
	}

	/**
	 * Check if we should dispatch an async request to process actions.
	 *
	 * This method is attached to 'shutdown', so is called frequently. To avoid slowing down
	 * the site, it mitigates the work performed in each request by:
	 * 1. checking if it's in the admin context and then
	 * 2. haven't run on the 'shutdown' hook within the lock time (60 seconds by default)
	 * 3. haven't exceeded the number of allowed batches.
	 *
	 * The order of these checks is important, because they run from a check on a value:
	 * 1. in memory - is_admin() maps to $GLOBALS or the WP_ADMIN constant
	 * 2. in memory - transients use autoloaded options by default
	 * 3. from a database query - has_maximum_concurrent_batches() run the query
	 *    $this->store->get_claim_count() to find the current number of claims in the DB.
	 *
	 * If all of these conditions are met, then we request an async runner check whether it
	 * should dispatch a request to process pending actions.
	 */
	public function maybe_dispatch_async_request() {
		// Only start an async queue at most once every 60 seconds.
		if (
			is_admin()
			&& ! ActionScheduler::lock()->is_locked( 'async-request-runner' )
			&& ActionScheduler::lock()->set( 'async-request-runner' )
		) {
			$this->async_request->maybe_dispatch();
		}
	}

	/**
	 * Process actions in the queue. Attached to self::WP_CRON_HOOK i.e. 'action_scheduler_run_queue'
	 *
	 * The $context param of this method defaults to 'WP Cron', because prior to Action Scheduler 3.0.0
	 * that was the only context in which this method was run, and the self::WP_CRON_HOOK hook had no context
	 * passed along with it. New code calling this method directly, or by triggering the self::WP_CRON_HOOK,
	 * should set a context as the first parameter. For an example of this, refer to the code seen in
	 * @see ActionScheduler_AsyncRequest_QueueRunner::handle()
	 *
	 * @param string $context Optional identifier for the context in which this action is being processed, e.g. 'WP CLI' or 'WP Cron'
	 *        Generally, this should be capitalised and not localised as it's a proper noun.
	 * @return int The number of actions processed.
	 */
	public function run( $context = 'WP Cron' ) {
		ActionScheduler_Compatibility::raise_memory_limit();
		ActionScheduler_Compatibility::raise_time_limit( $this->get_time_limit() );
		do_action( 'action_scheduler_before_process_queue' );
		$this->run_cleanup();

		$this->processed_actions_count = 0;
		if ( false === $this->has_maximum_concurrent_batches() ) {
			do {
				$batch_size                     = apply_filters( 'action_scheduler_queue_runner_batch_size', 25 );
				$processed_actions_in_batch     = $this->do_batch( $batch_size, $context );
				$this->processed_actions_count += $processed_actions_in_batch;
			} while ( $processed_actions_in_batch > 0 && ! $this->batch_limits_exceeded( $this->processed_actions_count ) ); // keep going until we run out of actions, time, or memory.
		}

		do_action( 'action_scheduler_after_process_queue' );
		return $this->processed_actions_count;
	}

	/**
	 * Process a batch of actions pending in the queue.
	 *
	 * Actions are processed by claiming a set of pending actions then processing each one until either the batch
	 * size is completed, or memory or time limits are reached, defined by @see $this->batch_limits_exceeded().
	 *
	 * @param int    $size The maximum number of actions to process in the batch.
	 * @param string $context Optional identifier for the context in which this action is being processed, e.g. 'WP CLI' or 'WP Cron'
	 *                        Generally, this should be capitalised and not localised as it's a proper noun.
	 * @return int The number of actions processed.
	 */
	protected function do_batch( $size = 100, $context = '' ) {
		$claim = $this->store->stake_claim($size);
		$this->monitor->attach($claim);
		$processed_actions = 0;

		foreach ( $claim->get_actions() as $action_id ) {
			// bail if we lost the claim.
			if ( ! in_array( $action_id, $this->store->find_actions_by_claim_id( $claim->get_id() ) ) ) {
				break;
			}
			$this->process_action( $action_id, $context );
			$processed_actions++;

			if ( $this->batch_limits_exceeded( $processed_actions + $this->processed_actions_count ) ) {
				break;
			}
		}
		$this->store->release_claim($claim);
		$this->monitor->detach();
		$this->clear_caches();
		return $processed_actions;
	}

	/**
	 * Flush the cache if possible (intended for use after a batch of actions has been processed).
	 *
	 * This is useful because running large batches can eat up memory and because invalid data can accrue in the
	 * runtime cache, which may lead to unexpected results.
	 */
	protected function clear_caches() {
		/*
		 * Calling wp_cache_flush_runtime() lets us clear the runtime cache without invalidating the external object
		 * cache, so we will always prefer this method (as compared to calling wp_cache_flush()) when it is available.
		 *
		 * However, this function was only introduced in WordPress 6.0. Additionally, the preferred way of detecting if
		 * it is supported changed in WordPress 6.1 so we use two different methods to decide if we should utilize it.
		 */
		$flushing_runtime_cache_explicitly_supported = function_exists( 'wp_cache_supports' ) && wp_cache_supports( 'flush_runtime' );
		$flushing_runtime_cache_implicitly_supported = ! function_exists( 'wp_cache_supports' ) && function_exists( 'wp_cache_flush_runtime' );

		if ( $flushing_runtime_cache_explicitly_supported || $flushing_runtime_cache_implicitly_supported ) {
			wp_cache_flush_runtime();
		} elseif (
			! wp_using_ext_object_cache()
			/**
			 * When an external object cache is in use, and when wp_cache_flush_runtime() is not available, then
			 * normally the cache will not be flushed after processing a batch of actions (to avoid a performance
			 * penalty for other processes).
			 *
			 * This filter makes it possible to override this behavior and always flush the cache, even if an external
			 * object cache is in use.
			 *
			 * @since 1.0
			 *
			 * @param bool $flush_cache If the cache should be flushed.
			 */
			|| apply_filters( 'action_scheduler_queue_runner_flush_cache', false )
		) {
			wp_cache_flush();
		}
	}

	/**
	 * Add schedule to WP cron.
	 *
	 * @param array<string, array<string, int|string>> $schedules Schedules.
	 * @return array<string, array<string, int|string>>
	 */
	public function add_wp_cron_schedule( $schedules ) {
		$schedules['every_minute'] = array(
			'interval' => 60, // in seconds.
			'display'  => __( 'Every minute', 'action-scheduler' ),
		);

		return $schedules;
	}
}
