<?php
/**
 * WP Asynchronous Tasks
 * Version: 1.0
 * Description: Creates an abstract class to execute asynchronous tasks
 * Author: 10up, Eric Mann, Luke Gedeon, John P. Bloch
 * License: MIT
 * Note: Modified to return metadata at the end of the launch function
 *
 * @package WP_Smush
 */

if ( ! defined( 'WPINC' ) ) {
	die;
}

/**
 * Class WP_Async_Task_Smush
 */
abstract class WP_Async_Task_Smush {

	/**
	 * Constant identifier for a task that should be available to logged-in users
	 *
	 * See constructor documentation for more details.
	 */
	const LOGGED_IN = 1;

	/**
	 * Constant identifier for a task that should be available to logged-out users
	 *
	 * See constructor documentation for more details.
	 */
	const LOGGED_OUT = 2;

	/**
	 * Constant identifier for a task that should be available to all users regardless of auth status
	 *
	 * See constructor documentation for more details.
	 */
	const BOTH = 3;

	/**
	 * This is the argument count for the main action set in the constructor. It
	 * is set to an arbitrarily high value of twenty, but can be overridden if
	 * necessary
	 *
	 * @var int
	 */
	protected $argument_count = 20;

	/**
	 * Priority to fire intermediate action.
	 *
	 * @var int
	 */
	protected $priority = 10;

	/**
	 * Action name.
	 *
	 * @var string
	 */
	protected $action;

	/**
	 * Request body data.
	 *
	 * @var array
	 */
	protected $_body_data;

	/**
	 * Constructor to wire up the necessary actions
	 *
	 * Which hooks the asynchronous postback happens on can be set by the
	 * $auth_level parameter. There are essentially three options: logged in users
	 * only, logged out users only, or both. Set this when you instantiate an
	 * object by using one of the three class constants to do so:
	 *  - LOGGED_IN
	 *  - LOGGED_OUT
	 *  - BOTH
	 * $auth_level defaults to BOTH
	 *
	 * @throws Exception If the class' $action value hasn't been set.
	 *
	 * @param int $auth_level The authentication level to use (see above).
	 */
	public function __construct( $auth_level = self::BOTH ) {
		if ( empty( $this->action ) ) {
			throw new Exception( 'Action not defined for class ' . __CLASS__ );
		}
		// Handle the actual action.
		add_action( $this->action, array( $this, 'launch' ), (int) $this->priority, (int) $this->argument_count );

		add_action( "admin_post_wp_async_$this->action", array( $this, 'handle_postback' ) );
	}

	/**
	 * Add the shutdown action for launching the real postback if we don't
	 * get an exception thrown by prepare_data().
	 *
	 * @uses func_get_args() To grab any arguments passed by the action
	 */
	public function launch() {
		$data = func_get_args();
		try {
			$data = $this->prepare_data( $data );
		} catch ( Exception $e ) {
			error_log(
				sprintf(
					'Async Smush: Error in prepare_data function in %s at line %s: %s',
					__FILE__,
					__LINE__,
					$e->getMessage()
				)
			);
			return;
		}

		$data['action'] = "wp_async_$this->action";
		$data['_nonce'] = $this->create_async_nonce();

		$this->_body_data = $data;

		$shutdown_action = has_action( 'shutdown', array( $this, 'process_request' ) );

		// Do not use this, as in case of importing, only the last image gets processed
		// It's very important that all the Media uploads, are handled via shutdown action, else, sometimes the image meta updated
		// by smush is earlier, and then original meta update causes discrepancy.
		if ( ( ( ! empty( $_POST['action'] ) && 'upload-attachment' === $_POST['action'] ) || ( ! empty( $_POST ) && isset( $_POST['post_id'] ) && $_POST['post_id'] ) ) && ! $shutdown_action ) {
			add_action( 'shutdown', array( $this, 'process_request' ) );
		} else {
			// Send a ajax request to process image and return image metadata, added for compatibility with plugins like
			// WP All Import, and RSS aggregator, which upload multiple images at once.
			$this->process_request();
		}

		// If we have image metadata return it.
		if ( ! empty( $data['metadata'] ) ) {
			return $data['metadata'];
		}
	}

	/**
	 * Launch the request on the WordPress shutdown hook
	 *
	 * On VIP we got into data races due to the postback sometimes completing
	 * faster than the data could propogate to the database server cluster.
	 * This made WordPress get empty data sets from the database without
	 * failing. On their advice, we're moving the actual firing of the async
	 * postback to the shutdown hook. Supposedly that will ensure that the
	 * data at least has time to get into the object cache.
	 *
	 * @uses $_COOKIE        To send a cookie header for async postback
	 * @uses apply_filters()
	 * @uses admin_url()
	 * @uses wp_remote_post()
	 */
	public function process_request() {
		if ( ! empty( $this->_body_data ) ) {
			$cookies = array();
			foreach ( $_COOKIE as $name => $value ) {
				$cookies[] = "$name=" . urlencode( is_array( $value ) ? serialize( $value ) : $value );
			}

			// @todo: We've set sslverify to false
			$request_args = array(
				'timeout'   => apply_filters( 'smush_async_time_out', 0 ),
				'blocking'  => false,
				'sslverify' => false,
				'body'      => $this->_body_data,
				'headers'   => array(
					'cookie' => implode( '; ', $cookies ),
				),
			);

			$url = admin_url( 'admin-post.php' );

			wp_remote_post( $url, $request_args );
		}
	}

	/**
	 * Verify the postback is valid, then fire any scheduled events.
	 *
	 * @uses $_POST['_nonce']
	 * @uses is_user_logged_in()
	 * @uses add_filter()
	 * @uses wp_die()
	 */
	public function handle_postback() {
		if ( isset( $_POST['_nonce'] ) && $this->verify_async_nonce( $_POST['_nonce'] ) ) {
			$this->run_action();
		}

		add_filter( 'wp_die_handler', array( $this, 'handle_die' ) );
		wp_die();
	}

	/**
	 * Handle Die
	 */
	public function handle_die() {
		die();
	}

	/**
	 * Create a random, one time use token.
	 *
	 * Based entirely on wp_create_nonce() but does not tie the nonce to the
	 * current logged-in user.
	 *
	 * @uses wp_nonce_tick()
	 * @uses wp_hash()
	 *
	 * @return string The one-time use token
	 */
	protected function create_async_nonce() {
		$action = $this->get_nonce_action();
		$i      = wp_nonce_tick();

		return substr( wp_hash( $i . $action . get_class( $this ), 'nonce' ), - 12, 10 );
	}

	/**
	 * Verify that the correct nonce was used within the time limit.
	 *
	 * @uses wp_nonce_tick()
	 * @uses wp_hash()
	 *
	 * @param string $nonce Nonce to be verified.
	 *
	 * @return bool Whether the nonce check passed or failed
	 */
	protected function verify_async_nonce( $nonce ) {
		$action = $this->get_nonce_action();
		$i      = wp_nonce_tick();

		// Nonce generated 0-12 hours ago.
		if ( substr( wp_hash( $i . $action . get_class( $this ), 'nonce' ), - 12, 10 ) == $nonce ) {
			return 1;
		}

		// Nonce generated 12-24 hours ago.
		if ( substr( wp_hash( ( $i - 1 ) . $action . get_class( $this ), 'nonce' ), - 12, 10 ) == $nonce ) {
			return 2;
		}

		// Invalid nonce.
		return false;
	}

	/**
	 * Get a nonce action based on the $action property of the class
	 *
	 * @return string The nonce action for the current instance
	 */
	protected function get_nonce_action() {
		$action = $this->action;
		if ( substr( $action, 0, 7 ) === 'nopriv_' ) {
			$action = substr( $action, 7 );
		}
		$action = "wp_async_$action";

		return $action;
	}

	/**
	 * Prepare any data to be passed to the asynchronous postback
	 *
	 * The array this function receives will be a numerically keyed array from
	 * func_get_args(). It is expected that you will return an associative array
	 * so that the $_POST values used in the asynchronous call will make sense.
	 *
	 * The array you send back may or may not have anything to do with the data
	 * passed into this method. It all depends on the implementation details and
	 * what data is needed in the asynchronous postback.
	 *
	 * Do not set values for 'action' or '_nonce', as those will get overwritten
	 * later in launch().
	 *
	 * @throws Exception If the postback should not occur for any reason.
	 *
	 * @param array $data The raw data received by the launch method.
	 *
	 * @return array The prepared data
	 */
	abstract protected function prepare_data( $data );

	/**
	 * Run the do_action function for the asynchronous postback.
	 *
	 * This method needs to fetch and sanitize any and all data from the $_POST
	 * superglobal and provide them to the do_action call.
	 *
	 * The action should be constructed as "wp_async_task_$this->action"
	 */
	abstract protected function run_action();

}
