<?php
/**
 * Retry queue. If PostaraMail can't be reached (or answers with a temporary
 * error) the signup is kept here and retried every 15 minutes, so a short
 * outage never loses a subscriber.
 */

if ( ! defined( 'ABSPATH' ) ) {
	exit;
}

class PostaraMail_Queue {

	const OPTION   = 'postaramail_queue';
	const HOOK     = 'postaramail_retry';
	const MAX_ITEM = 500;
	const MAX_TRY  = 12;

	public static function init() {
		add_filter( 'cron_schedules', array( __CLASS__, 'schedules' ) );
		add_action( self::HOOK, array( __CLASS__, 'process' ) );
		// Scheduling reads the translated schedule label, so it waits until WordPress has loaded translations (init).
		add_action( 'init', array( __CLASS__, 'ensure_events' ) );
	}

	/** Makes sure the repeating background tasks exist (safety net if an event was lost, for example after a migration). */
	public static function ensure_events() {
		$events = array(
			self::HOOK                => 300,
			PostaraMail_Sync::HOOK    => 180,
			PostaraMail_Pending::HOOK => 120,
		);
		foreach ( $events as $hook => $delay ) {
			if ( ! wp_next_scheduled( $hook ) ) {
				wp_schedule_event( time() + $delay, 'postaramail_15min', $hook );
			}
		}
	}

	public static function schedules( $schedules ) {
		$schedules['postaramail_15min'] = array(
			'interval' => 15 * MINUTE_IN_SECONDS,
			'display'  => 'Every 15 minutes (PostaraMail)', // Plain text on purpose: cron may ask for schedules before translations load.
		);
		return $schedules;
	}

	public static function activate() {
		// Nothing to do here: ensure_events() schedules the tasks on the next page load, after translations are available.
	}

	public static function deactivate() {
		wp_clear_scheduled_hook( self::HOOK );
	}

	public static function all() {
		$q = get_option( self::OPTION, array() );
		return is_array( $q ) ? $q : array();
	}

	public static function count() {
		return count( self::all() );
	}

	public static function push( $item ) {
		$q = self::all();
		if ( count( $q ) >= self::MAX_ITEM ) {
			array_shift( $q ); // Drop the oldest rather than growing forever.
		}
		$item['tries'] = 0;
		$item['added'] = time();
		$q[]           = $item;
		update_option( self::OPTION, $q, false );
	}

	/** Queue now and ask WordPress to run cron soon (used where blocking would be rude, e.g. checkout). */
	public static function push_and_spawn( $item ) {
		self::push( $item );
		wp_schedule_single_event( time() + 5, self::HOOK );
		if ( function_exists( 'spawn_cron' ) ) {
			spawn_cron();
		}
	}

	public static function process() {
		if ( get_transient( 'postaramail_queue_lock' ) ) {
			return;
		}
		set_transient( 'postaramail_queue_lock', 1, 120 );

		$queue = self::all();
		$keep  = array();
		$done  = 0;

		foreach ( $queue as $item ) {
			if ( $done >= 25 ) {
				$keep[] = $item; // Next run.
				continue;
			}
			++$done;
			$r = PostaraMail_Subscriber::send( $item );
			if ( $r['ok'] ) {
				continue; // Delivered.
			}
			if ( $r['retry'] ) {
				$item['tries'] = (int) $item['tries'] + 1;
				$too_old       = ( time() - (int) $item['added'] ) > 3 * DAY_IN_SECONDS;
				if ( $item['tries'] >= self::MAX_TRY || $too_old ) {
					PostaraMail_Subscriber::remember_error( $r['message'] ? $r['message'] : $r['code'] );
					continue; // Give up on this one.
				}
				$keep[] = $item;
				continue;
			}
			// Permanent answer from the API (for example the plan limit): don't retry, but tell the admin.
			PostaraMail_Subscriber::remember_error( $r['message'] ? $r['message'] : $r['code'] );
		}

		update_option( self::OPTION, $keep, false );
		delete_transient( 'postaramail_queue_lock' );
	}
}