<?php
/**
 * WP Multisite WaaS Async Calls implementation.
 *
 * @package WP_Ultimo
 * @subpackage Async_Calls
 * @since 2.0.7
 */

namespace WP_Ultimo;

use \WP_Ultimo\Dependencies\Amp\Iterator;
use \WP_Ultimo\Dependencies\Amp\Sync\LocalSemaphore;
use \WP_Ultimo\Dependencies\Amp\Sync\ConcurrentIterator;
use \WP_Ultimo\Dependencies\Amp\Http\Client\Request;
use \WP_Ultimo\Dependencies\Amp\Http\Client\Connection\DefaultConnectionPool;
use \WP_Ultimo\Dependencies\Amp\Socket\ClientTlsContext;
use \WP_Ultimo\Dependencies\Amp\Socket\ConnectContext;
use \WP_Ultimo\Dependencies\Amp\Http\Client\HttpClientBuilder;

// Exit if accessed directly
defined('ABSPATH') || exit;

/**
 * WP Multisite WaaS Async Calls implementation.
 *
 * @since 2.0.7
 */
class Async_Calls {

	/**
	 * Keeps a registry of the listeners.
	 *
	 * @var array
	 */
	static $registry = array();

	/**
	 * Registers a new listener.
	 *
	 * @since 2.0.7
	 *
	 * @param string   $id The id of the listener.
	 * @param callable $callable A callback to be run.
	 * @param mixed    ...$args Arguments to be passed to the callback.
	 * @return void
	 */
	public static function register_listener($id, $callable, ...$args) {

		self::$registry[$id] = array(
			'callable' => $callable,
			'args'     => $args,
		);

	}  // end register_listener;

	/**
	 * Install the registered listeners.
	 *
	 * @since 2.0.7
	 * @return void
	 */
	public static function install_listeners() {

		foreach (self::$registry as $id => $listener) {

			add_action("wp_ajax_wu_async_call_listener_{$id}", function() use ($listener) {

				try {

					$results = call_user_func_array($listener['callable'], $listener['args']);

				} catch (\Throwable $th) {

					wp_send_json_error($th);

				} // end try;

				wp_send_json_success($results);

				exit;

			});

		} // end foreach;

	} // end install_listeners;

	/**
	 * Build the base URL for the listener calls.
	 *
	 * @since 2.0.7
	 *
	 * @param string $id The listener id.
	 * @param array  $args The additional args passed to the URL.
	 * @return string
	 */
	public static function build_base_url($id, $args) {

		return add_query_arg($args, admin_url('admin-ajax.php'));

	} // end build_base_url;

	/**
	 * Build the final URL to be called.
	 *
	 * @since 2.0.7
	 *
	 * @param string $id The listener id.
	 * @param int    $total The total number of records.
	 * @param int    $chunk_size The chunk size.
	 * @param array  $args Additional arguments to be passed.
	 * @return array The list of paginates URLs to call.
	 */
	public static function build_url_list($id, $total, $chunk_size, $args = array()) {

		$pages = ceil($total / $chunk_size);

		$urls = array();

		for ($i = 1; $i <= $pages; $i++) {

			$urls[] = self::build_base_url($id, array_merge($args, array(
				'action'   => "wu_async_call_listener_$id",
				'parallel' => 1,
				'page'     => $i,
				'per_page' => $chunk_size,
			)));

		} // end for;

		return $urls;

	} // end build_url_list;

	/**
	 * Builds and returns the client that will handle the calls.
	 *
	 * @since 2.0.7
	 * @return \WP_Ultimo\Dependencies\Amp\Http\Client\HttpClient;
	 */
	public static function get_client() {

		$client_tls_context = new ClientTlsContext('');

		$connect_base_context = new ConnectContext;

		$tls_context = $client_tls_context->withoutPeerVerification();

		$connect_context = $connect_base_context->withTlsContext($tls_context);

		$builder = new HttpClientBuilder;

		return $builder->usingPool(new DefaultConnectionPool(null, $connect_context))->build();

	} // end get_client;

	/**
	 * Run the parallel queue after everything is correctly enqueued.
	 *
	 * @since 2.0.7
	 *
	 * @param string  $id The listener id.
	 * @param array   $args Additional arguments to be passed.
	 * @param int     $total The total number of records.
	 * @param integer $chunk_size The chunk size to use.
	 * @param integer $parallel_threads The number of parallel threads to be run.
	 * @return true|\WP_Error
	 */
	public static function run($id, $args, $total, $chunk_size = 10, $parallel_threads = 3) {

		$client = self::get_client();

		$urls = self::build_url_list($id, $total, $chunk_size, $args);

		$coroutine = \WP_Ultimo\Dependencies\Amp\call(static function() use ($id, $total, $chunk_size, $parallel_threads, $client, $urls) {

			$results = array();

			$chunker = new LocalSemaphore($parallel_threads);

			yield ConcurrentIterator\each(Iterator\fromIterable($urls), $chunker, function($url) use (&$results, $client) {

				try {

					$request = new Request($url);

					$request->setTcpConnectTimeout(1000 * 1000);

					$request->setTlsHandshakeTimeout(1000 * 1000);

					$request->setTransferTimeout(1000 * 1000);

					$request->setHeader('cookie', wu_get_isset($_SERVER, 'HTTP_COOKIE', ''));

					$response = yield $client->request($request);

					$body = yield $response->getBody()->buffer();

					$results[$url] = json_decode($body);

				} catch (\Throwable $e) {

					throw $e;

				} // end try;

			});

			return self::condense_results($results); // phpcs:ignore

		});

		$responses = \WP_Ultimo\Dependencies\Amp\Promise\wait($coroutine);

		return $responses;

	} // end run;

	/**
	 * Condense multiple results into one single result.
	 *
	 * @since 2.0.7
	 *
	 * @param array $results The different results returned by multiple calls.
	 * @return true|\WP_Error
	 */
	public static function condense_results($results) {

		foreach ($results as $result) {

			$status = wu_get_isset($result, 'success', false);

			if ($status === false) {

				return $result;

			} // end if;

		} // end foreach;

		return true;

	} // end condense_results;

} // end class Async_Calls;