<?php
/**
 * Sync sender.
 *
 * @package automattic/jetpack-sync
 */

namespace Automattic\Jetpack\Sync;

use Automattic\Jetpack\Constants;

/**
 * This class grabs pending actions from the queue and sends them
 */
class Sender {
	/**
	 * Name of the option that stores the time of the next sync.
	 *
	 * @access public
	 *
	 * @var string
	 */
	const NEXT_SYNC_TIME_OPTION_NAME = 'jetpack_next_sync_time';

	/**
	 * Sync timeout after a WPCOM error.
	 *
	 * @access public
	 *
	 * @var int
	 */
	const WPCOM_ERROR_SYNC_DELAY = 60;

	/**
	 * Sync timeout after a queue has been locked.
	 *
	 * @access public
	 *
	 * @var int
	 */
	const QUEUE_LOCKED_SYNC_DELAY = 10;

	/**
	 * Maximum bytes to checkout without exceeding the memory limit.
	 *
	 * @access private
	 *
	 * @var int
	 */
	private $dequeue_max_bytes;

	/**
	 * Maximum bytes in a single encoded item.
	 *
	 * @access private
	 *
	 * @var int
	 */
	private $upload_max_bytes;

	/**
	 * Maximum number of sync items in a single action.
	 *
	 * @access private
	 *
	 * @var int
	 */
	private $upload_max_rows;

	/**
	 * Maximum time for perfirming a checkout of items from the queue (in seconds).
	 *
	 * @access private
	 *
	 * @var int
	 */
	private $max_dequeue_time;

	/**
	 * How many seconds to wait after sending sync items after exceeding the sync wait threshold (in seconds).
	 *
	 * @access private
	 *
	 * @var int
	 */
	private $sync_wait_time;

	/**
	 * How much maximum time to wait for the checkout to finish (in seconds).
	 *
	 * @access private
	 *
	 * @var int
	 */
	private $sync_wait_threshold;

	/**
	 * How much maximum time to wait for the sync items to be queued for sending (in seconds).
	 *
	 * @access private
	 *
	 * @var int
	 */
	private $enqueue_wait_time;

	/**
	 * Incremental sync queue object.
	 *
	 * @access private
	 *
	 * @var Automattic\Jetpack\Sync\Queue
	 */
	private $sync_queue;

	/**
	 * Full sync queue object.
	 *
	 * @access private
	 *
	 * @var Automattic\Jetpack\Sync\Queue
	 */
	private $full_sync_queue;

	/**
	 * Codec object for encoding and decoding sync items.
	 *
	 * @access private
	 *
	 * @var Automattic\Jetpack\Sync\Codec_Interface
	 */
	private $codec;

	/**
	 * The current user before we change or clear it.
	 *
	 * @access private
	 *
	 * @var \WP_User
	 */
	private $old_user;

	/**
	 * Container for the singleton instance of this class.
	 *
	 * @access private
	 * @static
	 *
	 * @var Automattic\Jetpack\Sync\Sender
	 */
	private static $instance;

	/**
	 * Retrieve the singleton instance of this class.
	 *
	 * @access public
	 * @static
	 *
	 * @return Automattic\Jetpack\Sync\Sender
	 */
	public static function get_instance() {
		if ( null === self::$instance ) {
			self::$instance = new self();
		}

		return self::$instance;
	}

	/**
	 * Constructor.
	 * This is necessary because you can't use "new" when you declare instance properties >:(
	 *
	 * @access protected
	 * @static
	 */
	protected function __construct() {
		$this->set_defaults();
		$this->init();
	}

	/**
	 * Initialize the sender.
	 * Prepares the current user and initializes all sync modules.
	 *
	 * @access private
	 */
	private function init() {
		add_action( 'jetpack_sync_before_send_queue_sync', array( $this, 'maybe_set_user_from_token' ), 1 );
		add_action( 'jetpack_sync_before_send_queue_sync', array( $this, 'maybe_clear_user_from_token' ), 20 );
		add_filter( 'jetpack_xmlrpc_methods', array( $this, 'register_jetpack_xmlrpc_methods' ) );
		foreach ( Modules::get_modules() as $module ) {
			$module->init_before_send();
		}
	}

	/**
	 * Detect if this is a XMLRPC request with a valid signature.
	 * If so, changes the user to the new one.
	 *
	 * @access public
	 */
	public function maybe_set_user_from_token() {
		$verified_user = \Jetpack::connection()->verify_xml_rpc_signature();
		if ( Constants::is_true( 'XMLRPC_REQUEST' ) &&
			! is_wp_error( $verified_user )
			&& $verified_user
		) {
			$old_user       = wp_get_current_user();
			$this->old_user = isset( $old_user->ID ) ? $old_user->ID : 0;
			wp_set_current_user( $verified_user['user_id'] );
		}
	}

	/**
	 * If we used to have a previous current user, revert back to it.
	 *
	 * @access public
	 */
	public function maybe_clear_user_from_token() {
		if ( isset( $this->old_user ) ) {
			wp_set_current_user( $this->old_user );
		}
	}

	/**
	 * Retrieve the next sync time.
	 *
	 * @access public
	 *
	 * @param string $queue_name Name of the queue.
	 * @return float Timestamp of the next sync.
	 */
	public function get_next_sync_time( $queue_name ) {
		return (float) get_option( self::NEXT_SYNC_TIME_OPTION_NAME . '_' . $queue_name, 0 );
	}

	/**
	 * Set the next sync time.
	 *
	 * @access public
	 *
	 * @param int    $time       Timestamp of the next sync.
	 * @param string $queue_name Name of the queue.
	 * @return boolean True if update was successful, false otherwise.
	 */
	public function set_next_sync_time( $time, $queue_name ) {
		return update_option( self::NEXT_SYNC_TIME_OPTION_NAME . '_' . $queue_name, $time, true );
	}

	/**
	 * Trigger a full sync.
	 *
	 * @access public
	 *
	 * @return boolean|\WP_Error True if this sync sending was successful, error object otherwise.
	 */
	public function do_full_sync() {
		if ( ! Modules::get_module( 'full-sync' ) ) {
			return;
		}
		$this->continue_full_sync_enqueue();
		return $this->do_sync_and_set_delays( $this->full_sync_queue );
	}

	/**
	 * Enqueue the next sync items for sending.
	 * Will not be done if the current request is a WP import one.
	 * Will be delayed until the next sync time comes.
	 *
	 * @access private
	 */
	private function continue_full_sync_enqueue() {
		if ( defined( 'WP_IMPORTING' ) && WP_IMPORTING ) {
			return false;
		}

		if ( $this->get_next_sync_time( 'full-sync-enqueue' ) > microtime( true ) ) {
			return false;
		}

		Modules::get_module( 'full-sync' )->continue_enqueuing();

		$this->set_next_sync_time( time() + $this->get_enqueue_wait_time(), 'full-sync-enqueue' );
	}

	/**
	 * Trigger incremental sync.
	 *
	 * @access public
	 *
	 * @return boolean|\WP_Error True if this sync sending was successful, error object otherwise.
	 */
	public function do_sync() {
		return $this->do_sync_and_set_delays( $this->sync_queue );
	}

	/**
	 * Trigger sync for a certain sync queue.
	 * Responsible for setting next sync time.
	 * Will not be delayed if the current request is a WP import one.
	 * Will be delayed until the next sync time comes.
	 *
	 * @access public
	 *
	 * @param Automattic\Jetpack\Sync\Queue $queue Queue object.
	 * @return boolean|\WP_Error True if this sync sending was successful, error object otherwise.
	 */
	public function do_sync_and_set_delays( $queue ) {
		// Don't sync if importing.
		if ( defined( 'WP_IMPORTING' ) && WP_IMPORTING ) {
			return new \WP_Error( 'is_importing' );
		}

		if ( ! Settings::is_sender_enabled( $queue->id ) ) {
			return new \WP_Error( 'sender_disabled_for_queue_' . $queue->id );
		}

		// Don't sync if we are throttled.
		if ( $this->get_next_sync_time( $queue->id ) > microtime( true ) ) {
			return new \WP_Error( 'sync_throttled' );
		}

		$start_time = microtime( true );

		Settings::set_is_syncing( true );

		$sync_result = $this->do_sync_for_queue( $queue );

		Settings::set_is_syncing( false );

		$exceeded_sync_wait_threshold = ( microtime( true ) - $start_time ) > (float) $this->get_sync_wait_threshold();

		if ( is_wp_error( $sync_result ) ) {
			if ( 'unclosed_buffer' === $sync_result->get_error_code() ) {
				$this->set_next_sync_time( time() + self::QUEUE_LOCKED_SYNC_DELAY, $queue->id );
			}
			if ( 'wpcom_error' === $sync_result->get_error_code() ) {
				$this->set_next_sync_time( time() + self::WPCOM_ERROR_SYNC_DELAY, $queue->id );
			}
		} elseif ( $exceeded_sync_wait_threshold ) {
			// If we actually sent data and it took a while, wait before sending again.
			$this->set_next_sync_time( time() + $this->get_sync_wait_time(), $queue->id );
		}

		return $sync_result;
	}

	/**
	 * Retrieve the next sync items to send.
	 *
	 * @access public
	 *
	 * @param Automattic\Jetpack\Sync\Queue_Buffer $buffer Queue buffer object.
	 * @param boolean                              $encode Whether to encode the items.
	 * @return array Sync items to send.
	 */
	public function get_items_to_send( $buffer, $encode = true ) {
		// Track how long we've been processing so we can avoid request timeouts.
		$start_time    = microtime( true );
		$upload_size   = 0;
		$items_to_send = array();
		$items         = $buffer->get_items();
		// Set up current screen to avoid errors rendering content.
		require_once ABSPATH . 'wp-admin/includes/class-wp-screen.php';
		require_once ABSPATH . 'wp-admin/includes/screen.php';
		set_current_screen( 'sync' );
		$skipped_items_ids = array();
		/**
		 * We estimate the total encoded size as we go by encoding each item individually.
		 * This is expensive, but the only way to really know :/
		 */
		foreach ( $items as $key => $item ) {
			// Suspending cache addition help prevent overloading in memory cache of large sites.
			wp_suspend_cache_addition( true );
			/**
			 * Modify the data within an action before it is serialized and sent to the server
			 * For example, during full sync this expands Post ID's into full Post objects,
			 * so that we don't have to serialize the whole object into the queue.
			 *
			 * @since 4.2.0
			 *
			 * @param array The action parameters
			 * @param int The ID of the user who triggered the action
			 */
			$item[1] = apply_filters( 'jetpack_sync_before_send_' . $item[0], $item[1], $item[2] );
			wp_suspend_cache_addition( false );
			if ( false === $item[1] ) {
				$skipped_items_ids[] = $key;
				continue;
			}
			$encoded_item = $encode ? $this->codec->encode( $item ) : $item;
			$upload_size += strlen( $encoded_item );
			if ( $upload_size > $this->upload_max_bytes && count( $items_to_send ) > 0 ) {
				break;
			}
			$items_to_send[ $key ] = $encoded_item;
			if ( microtime( true ) - $start_time > $this->max_dequeue_time ) {
				break;
			}
		}

		return array( $items_to_send, $skipped_items_ids, $items, microtime( true ) - $start_time );
	}

	/**
	 * If supported, flush all response data to the client and finish the request.
	 * This allows for time consuming tasks to be performed without leaving the connection open.
	 *
	 * @access private
	 */
	private function fastcgi_finish_request() {
		if ( function_exists( 'fastcgi_finish_request' ) && version_compare( phpversion(), '7.0.16', '>=' ) ) {
			fastcgi_finish_request();
		}
	}

	/**
	 * Perform sync for a certain sync queue.
	 *
	 * @access public
	 *
	 * @param Automattic\Jetpack\Sync\Queue $queue Queue object.
	 * @return boolean|\WP_Error True if this sync sending was successful, error object otherwise.
	 */
	public function do_sync_for_queue( $queue ) {
		do_action( 'jetpack_sync_before_send_queue_' . $queue->id );
		if ( $queue->size() === 0 ) {
			return new \WP_Error( 'empty_queue_' . $queue->id );
		}
		/**
		 * Now that we're sure we are about to sync, try to ignore user abort
		 * so we can avoid getting into a bad state.
		 */
		if ( function_exists( 'ignore_user_abort' ) ) {
			ignore_user_abort( true );
		}

		/* Don't make the request block till we finish, if possible. */
		if ( Constants::is_true( 'REST_REQUEST' ) || Constants::is_true( 'XMLRPC_REQUEST' ) ) {
			$this->fastcgi_finish_request();
		}

		$checkout_start_time = microtime( true );

		$buffer = $queue->checkout_with_memory_limit( $this->dequeue_max_bytes, $this->upload_max_rows );

		if ( ! $buffer ) {
			// Buffer has no items.
			return new \WP_Error( 'empty_buffer' );
		}

		if ( is_wp_error( $buffer ) ) {
			return $buffer;
		}

		$checkout_duration = microtime( true ) - $checkout_start_time;

		list( $items_to_send, $skipped_items_ids, $items, $preprocess_duration ) = $this->get_items_to_send( $buffer, true );
		if ( ! empty( $items_to_send ) ) {
			/**
			 * Fires when data is ready to send to the server.
			 * Return false or WP_Error to abort the sync (e.g. if there's an error)
			 * The items will be automatically re-sent later
			 *
			 * @since 4.2.0
			 *
			 * @param array $data The action buffer
			 * @param string $codec The codec name used to encode the data
			 * @param double $time The current time
			 * @param string $queue The queue used to send ('sync' or 'full_sync')
			 */
			Settings::set_is_sending( true );
			$processed_item_ids = apply_filters( 'jetpack_sync_send_data', $items_to_send, $this->codec->name(), microtime( true ), $queue->id, $checkout_duration, $preprocess_duration );
			Settings::set_is_sending( false );
		} else {
			$processed_item_ids = $skipped_items_ids;
			$skipped_items_ids  = array();
		}

		if ( ! $processed_item_ids || is_wp_error( $processed_item_ids ) ) {
			$checked_in_item_ids = $queue->checkin( $buffer );
			if ( is_wp_error( $checked_in_item_ids ) ) {
				// phpcs:ignore WordPress.PHP.DevelopmentFunctions.error_log_error_log
				error_log( 'Error checking in buffer: ' . $checked_in_item_ids->get_error_message() );
				$queue->force_checkin();
			}
			if ( is_wp_error( $processed_item_ids ) ) {
				return new \WP_Error( 'wpcom_error', $processed_item_ids->get_error_code() );
			}
			// Returning a wpcom_error is a sign to the caller that we should wait a while before syncing again.
			return new \WP_Error( 'wpcom_error', 'jetpack_sync_send_data_false' );
		} else {
			// Detect if the last item ID was an error.
			$had_wp_error = is_wp_error( end( $processed_item_ids ) );
			if ( $had_wp_error ) {
				$wp_error = array_pop( $processed_item_ids );
			}
			// Also checkin any items that were skipped.
			if ( count( $skipped_items_ids ) > 0 ) {
				$processed_item_ids = array_merge( $processed_item_ids, $skipped_items_ids );
			}
			$processed_items = array_intersect_key( $items, array_flip( $processed_item_ids ) );
			/**
			 * Allows us to keep track of all the actions that have been sent.
			 * Allows us to calculate the progress of specific actions.
			 *
			 * @since 4.2.0
			 *
			 * @param array $processed_actions The actions that we send successfully.
			 */
			do_action( 'jetpack_sync_processed_actions', $processed_items );
			$queue->close( $buffer, $processed_item_ids );
			// Returning a WP_Error is a sign to the caller that we should wait a while before syncing again.
			if ( $had_wp_error ) {
				return new \WP_Error( 'wpcom_error', $wp_error->get_error_code() );
			}
		}
		return true;
	}

	/**
	 * Returns any object that is able to be synced.
	 *
	 * @access public
	 *
	 * @param array $args the synchronized object parameters.
	 * @return string Encoded sync object.
	 */
	public function sync_object( $args ) {
		// For example: posts, post, 5.
		list( $module_name, $object_type, $id ) = $args;

		$sync_module = Modules::get_module( $module_name );
		$codec       = $this->get_codec();

		return $codec->encode( $sync_module->get_object_by_id( $object_type, $id ) );
	}

	/**
	 * Register additional sync XML-RPC methods available to Jetpack for authenticated users.
	 *
	 * @access public
	 * @since 7.8
	 *
	 * @param array $jetpack_methods XML-RPC methods available to the Jetpack Server.
	 * @return array Filtered XML-RPC methods.
	 */
	public function register_jetpack_xmlrpc_methods( $jetpack_methods ) {
		$jetpack_methods['jetpack.syncObject'] = array( $this, 'sync_object' );
		return $jetpack_methods;
	}

	/**
	 * Get the incremental sync queue object.
	 *
	 * @access public
	 *
	 * @return Automattic\Jetpack\Sync\Queue Queue object.
	 */
	public function get_sync_queue() {
		return $this->sync_queue;
	}

	/**
	 * Get the full sync queue object.
	 *
	 * @access public
	 *
	 * @return Automattic\Jetpack\Sync\Queue Queue object.
	 */
	public function get_full_sync_queue() {
		return $this->full_sync_queue;
	}

	/**
	 * Get the codec object.
	 *
	 * @access public
	 *
	 * @return Automattic\Jetpack\Sync\Codec_Interface Codec object.
	 */
	public function get_codec() {
		return $this->codec;
	}

	/**
	 * Determine the codec object.
	 * Use gzip deflate if supported.
	 *
	 * @access public
	 */
	public function set_codec() {
		if ( function_exists( 'gzinflate' ) ) {
			$this->codec = new JSON_Deflate_Array_Codec();
		} else {
			$this->codec = new Simple_Codec();
		}
	}

	/**
	 * Compute and send all the checksums.
	 *
	 * @access public
	 */
	public function send_checksum() {
		$store = new Replicastore();
		do_action( 'jetpack_sync_checksum', $store->checksum_all() );
	}

	/**
	 * Reset the incremental sync queue.
	 *
	 * @access public
	 */
	public function reset_sync_queue() {
		$this->sync_queue->reset();
	}

	/**
	 * Reset the full sync queue.
	 *
	 * @access public
	 */
	public function reset_full_sync_queue() {
		$this->full_sync_queue->reset();
	}

	/**
	 * Set the maximum bytes to checkout without exceeding the memory limit.
	 *
	 * @access public
	 *
	 * @param int $size Maximum bytes to checkout.
	 */
	public function set_dequeue_max_bytes( $size ) {
		$this->dequeue_max_bytes = $size;
	}

	/**
	 * Set the maximum bytes in a single encoded item.
	 *
	 * @access public
	 *
	 * @param int $max_bytes Maximum bytes in a single encoded item.
	 */
	public function set_upload_max_bytes( $max_bytes ) {
		$this->upload_max_bytes = $max_bytes;
	}

	/**
	 * Set the maximum number of sync items in a single action.
	 *
	 * @access public
	 *
	 * @param int $max_rows Maximum number of sync items.
	 */
	public function set_upload_max_rows( $max_rows ) {
		$this->upload_max_rows = $max_rows;
	}

	/**
	 * Set the sync wait time (in seconds).
	 *
	 * @access public
	 *
	 * @param int $seconds Sync wait time.
	 */
	public function set_sync_wait_time( $seconds ) {
		$this->sync_wait_time = $seconds;
	}

	/**
	 * Get current sync wait time (in seconds).
	 *
	 * @access public
	 *
	 * @return int Sync wait time.
	 */
	public function get_sync_wait_time() {
		return $this->sync_wait_time;
	}

	/**
	 * Set the enqueue wait time (in seconds).
	 *
	 * @access public
	 *
	 * @param int $seconds Enqueue wait time.
	 */
	public function set_enqueue_wait_time( $seconds ) {
		$this->enqueue_wait_time = $seconds;
	}

	/**
	 * Get current enqueue wait time (in seconds).
	 *
	 * @access public
	 *
	 * @return int Enqueue wait time.
	 */
	public function get_enqueue_wait_time() {
		return $this->enqueue_wait_time;
	}

	/**
	 * Set the sync wait threshold (in seconds).
	 *
	 * @access public
	 *
	 * @param int $seconds Sync wait threshold.
	 */
	public function set_sync_wait_threshold( $seconds ) {
		$this->sync_wait_threshold = $seconds;
	}

	/**
	 * Get current sync wait threshold (in seconds).
	 *
	 * @access public
	 *
	 * @return int Sync wait threshold.
	 */
	public function get_sync_wait_threshold() {
		return $this->sync_wait_threshold;
	}

	/**
	 * Set the maximum time for perfirming a checkout of items from the queue (in seconds).
	 *
	 * @access public
	 *
	 * @param int $seconds Maximum dequeue time.
	 */
	public function set_max_dequeue_time( $seconds ) {
		$this->max_dequeue_time = $seconds;
	}

	/**
	 * Initialize the sync queues, codec and set the default settings.
	 *
	 * @access public
	 */
	public function set_defaults() {
		$this->sync_queue      = new Queue( 'sync' );
		$this->full_sync_queue = new Queue( 'full_sync' );
		$this->set_codec();

		// Saved settings.
		Settings::set_importing( null );
		$settings = Settings::get_settings();
		$this->set_dequeue_max_bytes( $settings['dequeue_max_bytes'] );
		$this->set_upload_max_bytes( $settings['upload_max_bytes'] );
		$this->set_upload_max_rows( $settings['upload_max_rows'] );
		$this->set_sync_wait_time( $settings['sync_wait_time'] );
		$this->set_enqueue_wait_time( $settings['enqueue_wait_time'] );
		$this->set_sync_wait_threshold( $settings['sync_wait_threshold'] );
		$this->set_max_dequeue_time( Defaults::get_max_sync_execution_time() );
	}

	/**
	 * Reset sync queues, modules and settings.
	 *
	 * @access public
	 */
	public function reset_data() {
		$this->reset_sync_queue();
		$this->reset_full_sync_queue();

		foreach ( Modules::get_modules() as $module ) {
			$module->reset_data();
		}

		foreach ( array( 'sync', 'full_sync', 'full-sync-enqueue' ) as $queue_name ) {
			delete_option( self::NEXT_SYNC_TIME_OPTION_NAME . '_' . $queue_name );
		}

		Settings::reset_data();
	}

	/**
	 * Perform cleanup at the event of plugin uninstallation.
	 *
	 * @access public
	 */
	public function uninstall() {
		// Lets delete all the other fun stuff like transient and option and the sync queue.
		$this->reset_data();

		// Delete the full sync status.
		delete_option( 'jetpack_full_sync_status' );

		// Clear the sync cron.
		wp_clear_scheduled_hook( 'jetpack_sync_cron' );
		wp_clear_scheduled_hook( 'jetpack_sync_full_cron' );
	}
}