<?php
/**
 * Email queue runner.
 *
 * @package HostKhata
 */

namespace HostKhata\Domain\Email;

defined( 'ABSPATH' ) || exit;

use HostKhata\Core\Hookable;
use HostKhata\Database\Repositories\EmailRepository;
use HostKhata\Settings\Settings;
use WP_Error;

/**
 * Sends queued emails in small batches from WP-Cron, with retries.
 *
 * A failed email is tried again after 15, 30 and 45 minutes, then marked as
 * failed; an admin can retry it by hand.
 *
 * @since 0.1.0
 */
final class QueueRunner implements Hookable {

	const HOOK         = 'hostkhata_send_email_queue';
	const SCHEDULE     = 'hostkhata_five_minutes';
	const MAX_ATTEMPTS = 4;
	const LOG_DAYS     = 90;

	/**
	 * Queue.
	 *
	 * @var EmailRepository
	 */
	private $emails;

	/**
	 * Settings.
	 *
	 * @var Settings
	 */
	private $settings;

	/**
	 * Alternative body for the message being sent.
	 *
	 * @var string
	 */
	private $alt_body = '';

	/**
	 * Last error reported by wp_mail().
	 *
	 * @var string
	 */
	private $last_error = '';

	/**
	 * Constructor.
	 *
	 * @param EmailRepository $emails   Queue.
	 * @param Settings        $settings Settings.
	 */
	public function __construct( EmailRepository $emails, Settings $settings ) {
		$this->emails   = $emails;
		$this->settings = $settings;
	}

	/**
	 * {@inheritdoc}
	 */
	public function register(): void {
		add_filter( 'cron_schedules', array( $this, 'add_schedule' ) ); // phpcs:ignore WordPress.WP.CronInterval.CronSchedulesInterval -- Five minutes keeps the queue moving without hammering shared hosting.
		add_action( 'init', array( $this, 'schedule' ) );
		add_action( self::HOOK, array( $this, 'run' ) );
		add_filter( 'hostkhata_cron_hooks', array( $this, 'cron_hooks' ) );
		add_action( 'wp_mail_failed', array( $this, 'remember_error' ) );
	}

	/**
	 * Adds the five-minute schedule.
	 *
	 * @since 0.1.0
	 *
	 * @param array<string, array<string, mixed>> $schedules Schedules.
	 * @return array<string, array<string, mixed>>
	 */
	public function add_schedule( array $schedules ): array {
		$schedules[ self::SCHEDULE ] = array(
			'interval' => 5 * MINUTE_IN_SECONDS,
			'display'  => __( 'Every five minutes', 'hostkhata' ),
		);

		return $schedules;
	}

	/**
	 * Schedules the cron event once.
	 *
	 * @since 0.1.0
	 *
	 * @return void
	 */
	public function schedule(): void {
		if ( ! wp_next_scheduled( self::HOOK ) ) {
			wp_schedule_event( time() + MINUTE_IN_SECONDS, self::SCHEDULE, self::HOOK );
		}
	}

	/**
	 * Registers the hook for unscheduling on deactivation.
	 *
	 * @since 0.1.0
	 *
	 * @param string[] $hooks Hooks.
	 * @return string[]
	 */
	public function cron_hooks( array $hooks ): array {
		$hooks[] = self::HOOK;

		return $hooks;
	}

	/**
	 * Remembers why wp_mail() failed.
	 *
	 * @since 0.1.0
	 *
	 * @param WP_Error $error Error.
	 * @return void
	 */
	public function remember_error( WP_Error $error ): void {
		$this->last_error = $error->get_error_message();
	}

	/**
	 * Sends one batch.
	 *
	 * @since 0.1.0
	 *
	 * @return array{sent: int, failed: int, retry: int}
	 */
	public function run(): array {
		$result = array(
			'sent'   => 0,
			'failed' => 0,
			'retry'  => 0,
		);

		foreach ( $this->emails->claim_due( (int) $this->settings->get( 'email_batch_size' ) ) as $email ) {
			$error = $this->send( $email );

			if ( '' === $error ) {
				$this->emails->log( $email, 'sent' );
				$this->emails->delete( $email['id'] );
				++$result['sent'];
			} elseif ( $email['attempts'] >= self::MAX_ATTEMPTS ) {
				$this->emails->update(
					$email['id'],
					array(
						'status'     => 'failed',
						'last_error' => $error,
					)
				);
				$this->emails->log( $email, 'failed', $error );
				++$result['failed'];
			} else {
				$this->emails->update(
					$email['id'],
					array(
						'status'         => 'pending',
						'last_error'     => $error,
						'send_after_gmt' => gmdate( 'Y-m-d H:i:s', time() + $email['attempts'] * 15 * MINUTE_IN_SECONDS ),
					)
				);
				++$result['retry'];
			}
		}

		$this->emails->purge_log( self::LOG_DAYS );

		/** This action is documented in src/Domain/Billing/BillingRunner.php. */
		do_action( 'hostkhata_cron_ran', 'email_queue', $result );

		return $result;
	}

	/**
	 * Puts a failed email back on the queue.
	 *
	 * @since 0.1.0
	 *
	 * @param int $id Queue id.
	 * @return bool False when the email is not failed.
	 */
	public function retry( int $id ): bool {
		$email = $this->emails->find( $id );

		if ( null === $email || 'failed' !== $email['status'] ) {
			return false;
		}

		return $this->emails->update(
			$id,
			array(
				'status'         => 'pending',
				'attempts'       => 0,
				'send_after_gmt' => gmdate( 'Y-m-d H:i:s' ),
			)
		);
	}

	/**
	 * Sends one email.
	 *
	 * @param array<string, mixed> $email Queue row.
	 * @return string Empty on success, otherwise the error message.
	 */
	private function send( array $email ): string {
		$from_name    = (string) $this->settings->get( 'email_from_name' );
		$from_address = (string) $this->settings->get( 'email_from_address' );
		$headers      = array( 'Content-Type: text/html; charset=UTF-8' );

		if ( is_email( $from_address ) ) {
			$headers[] = sprintf( 'From: %s <%s>', str_replace( array( "\r", "\n", '<', '>' ), '', $from_name ), $from_address );
		}

		$to = '' !== $email['to_name'] ? sprintf( '%s <%s>', str_replace( array( "\r", "\n", '<', '>', ',' ), '', $email['to_name'] ), $email['to_email'] ) : $email['to_email'];

		$this->alt_body   = $email['body_text'];
		$this->last_error = '';

		add_action( 'phpmailer_init', array( $this, 'add_alt_body' ) );

		$sent = wp_mail( $to, $email['subject'], $email['body_html'], $headers );

		remove_action( 'phpmailer_init', array( $this, 'add_alt_body' ) );

		if ( $sent ) {
			return '';
		}

		return '' !== $this->last_error ? $this->last_error : __( 'The mail server did not accept the message.', 'hostkhata' );
	}

	/**
	 * Adds the plain-text alternative to the message being sent.
	 *
	 * @since 0.1.0
	 *
	 * @param \PHPMailer\PHPMailer\PHPMailer $mailer Mailer.
	 * @return void
	 */
	public function add_alt_body( $mailer ): void {
		$mailer->AltBody = $this->alt_body; // phpcs:ignore WordPress.NamingConventions.ValidVariableName.UsedPropertyNotSnakeCase -- PHPMailer property.
	}
}