<?php
/**
 * Background sending with retries.
 *
 * @package PingPush
 */

defined( 'ABSPATH' ) || exit;

/**
 * Queues notifications so page loads are never blocked by the Pushover API.
 *
 * Uses Action Scheduler when another plugin (e.g. WooCommerce) provides it,
 * otherwise WP-Cron plus a non-blocking cron spawn at the end of the request.
 */
class PingPush_Queue {

	const HOOK        = 'pingpush_send';
	const GROUP       = 'pingpush';
	const MAX_RETRIES = 3;

	/**
	 * Whether this request queued something via WP-Cron.
	 *
	 * @var bool
	 */
	private static $spawn = false;

	/**
	 * True while an HTTP request to Pushover is in flight (guards custom hooks from looping).
	 *
	 * @var bool
	 */
	private static $sending = false;

	/**
	 * Whether a send is in progress.
	 *
	 * @return bool
	 */
	public static function is_sending() {
		return self::$sending;
	}

	/**
	 * Register the send handler.
	 */
	public static function init() {
		add_action( self::HOOK, array( __CLASS__, 'handle' ), 10, 2 );
		add_action( 'shutdown', array( __CLASS__, 'maybe_spawn_cron' ) );
	}

	/**
	 * Whether Action Scheduler is usable.
	 *
	 * @return bool
	 */
	public static function has_action_scheduler() {
		return function_exists( 'as_enqueue_async_action' )
			&& function_exists( 'as_schedule_single_action' )
			&& did_action( 'action_scheduler_init' );
	}

	/**
	 * Queue a payload.
	 *
	 * @param array $payload Prepared message (no credentials).
	 * @param int   $attempt Attempt number (0 = first).
	 * @param int   $delay   Seconds to wait.
	 */
	public static function push( array $payload, $attempt = 0, $delay = 0 ) {
		$payload['id'] = $payload['id'] ?? wp_generate_uuid4();
		$args          = array( $payload, (int) $attempt );

		if ( self::has_action_scheduler() ) {
			if ( $delay > 0 ) {
				as_schedule_single_action( time() + $delay, self::HOOK, $args, self::GROUP );
			} else {
				as_enqueue_async_action( self::HOOK, $args, self::GROUP );
			}
			return;
		}

		$scheduled = wp_schedule_single_event( time() + max( 0, (int) $delay ), self::HOOK, $args, true );
		if ( is_wp_error( $scheduled ) || false === $scheduled ) {
			// Cron unavailable: send now rather than lose the alert.
			self::handle( $payload, $attempt );
			return;
		}
		if ( 0 === (int) $delay ) {
			self::$spawn = true;
		}
	}

	/**
	 * Kick WP-Cron (non-blocking loopback) so low-traffic sites send right away.
	 */
	public static function maybe_spawn_cron() {
		if ( self::$spawn && ! wp_doing_cron() && function_exists( 'spawn_cron' ) && ! ( defined( 'DISABLE_WP_CRON' ) && DISABLE_WP_CRON ) ) {
			spawn_cron();
		}
	}

	/**
	 * Send a queued payload.
	 *
	 * @param array $payload Payload.
	 * @param int   $attempt Attempt.
	 */
	public static function handle( $payload, $attempt = 0 ) {
		if ( ! is_array( $payload ) ) {
			return;
		}

		$settings = PingPush_Settings::get();
		$event    = (string) ( $payload['event'] ?? '' );
		$title    = (string) ( $payload['title'] ?? '' );

		if ( empty( $settings['token'] ) || empty( $settings['user_key'] ) ) {
			PingPush_Logger::add( $event, $title, 'failed', 0, __( 'Pushover keys are not set.', 'pingpush' ) );
			return;
		}

		self::$sending = true;
		$result        = PingPush_API::send( $settings['token'], $settings['user_key'], $payload );
		self::$sending = false;

		if ( $result['ok'] ) {
			$detail = '';
			if ( null !== $result['remaining'] ) {
				/* translators: %d: messages remaining this month. */
				$detail = sprintf( __( '%d messages left this month', 'pingpush' ), $result['remaining'] );
				update_option( 'pingpush_quota_remaining', (int) $result['remaining'], false );
			}
			PingPush_Logger::add( $event, $title, 'sent', $result['code'], $detail );
			return;
		}

		if ( $result['retry'] && $attempt < self::MAX_RETRIES ) {
			$delays = array( 60, 300, 900 );
			$delay  = $delays[ min( $attempt, count( $delays ) - 1 ) ];
			/* translators: 1: error, 2: seconds. */
			PingPush_Logger::add( $event, $title, 'retrying', $result['code'], sprintf( __( '%1$s Retrying in %2$d seconds.', 'pingpush' ), $result['error'], $delay ) );
			self::push( $payload, $attempt + 1, $delay );
			return;
		}

		PingPush_Logger::add( $event, $title, 'failed', $result['code'], $result['error'] );
	}
}