class PollingCron
{

    /**
     * Cron event name
     */
    const EVENT_NAME = 'AmazonPayPolling';

    /**
     * AmazonPay module object
     *
     * @var AmazonPay
     */
    private $module;

    /**
     * Sets `$module` member var with dependency injection.
     *
     * @author Evan D Shaw <evandanielshaw@gmail.com>
     * @param AmazonPay $module
     * @return void
     */
    public function __construct(AmazonPay $module) {
        $this->module = $module;
    }

    /**
     * Clear cron event
     *
     * @author Evan D Shaw <evandanielshaw@gmail.com>
     * @return void
     */
    public function clearEvent() {
        wp_clear_scheduled_hook(self::EVENT_NAME);
    }

    /**
     * Schedules polling cron if not already scheduled
     *
     * @author Evan D Shaw <evandanielshaw@gmail.com>
     * @return bool
     */
    public function scheduleEvent() {
        add_action(self::EVENT_NAME, [$this, 'updateAllOrders']);
        $cron = wp_next_scheduled(self::EVENT_NAME);
        if ($cron) {
            return false;
        }

        $unixts = (new DateTime('now', new DateTimeZone('UTC')))->getTimestamp();

        return wp_schedule_event($unixts, 'hourly', self::EVENT_NAME);
    }

    /**
     * Loops through all Amazon Pay orders and updates transaction states accordingly
     *
     * @author Evan D Shaw <evandanielshaw@gmail.com>
     * @return void
     * @throws InvalidArgumentException Thrown by `OrderMeta` constructor if order doesn't exist.
     */
    public function updateAllOrders() {
        $orderIds = $this->getAllAmazonPayOrders();
        foreach ($orderIds as $oa) {
            $orderId = (int)$oa['order_id'];
            $ometa = new Models\OrderMeta($orderId);
            // order state is updated automatically by these API calls
            if ($ometa->getChargeId() !== null) {
                $chargeState = $ometa->getChargeState();
                if (!$chargeState->isCanceled() && !$chargeState->isCaptured()) {
                    (new API\Charge\Get($this->module, $ometa))->get($ometa->getChargeId());
                }
            }
            if ($ometa->getRefundId() !== null) {
                (new API\Refund\Get($this->module, $ometa))->get($ometa->getRefundId());
            }
        }
    }

    /**
     * Returns all order IDs associated with an Amazon Pay order
     *
     * @author Evan D Shaw <evandanielshaw@gmail.com>
     * @global \wpdb $wpdb
     * @return array
     */
    public function getAllAmazonPayOrders() {
        global $wpdb;

        $order_meta_table_name = $wpdb->prefix . 'usces_order_meta';
        $query = $wpdb->prepare(
            "SELECT order_id
            FROM {$order_meta_table_name}
            WHERE meta_key = %s
            ORDER BY order_id ASC",
            Models\OrderMeta::CHARGE_PERMISSION_ID
        );
        $orderIds = $wpdb->get_results($query, ARRAY_A);
        if (empty($orderIds)) {
            return [];
        }

        return $orderIds;
    }
}