Retry Failed Emails

<?php

add_action( 'groundhogg/event/failed', 'gh_retry_failed_email_events', 10, 2 );

const GH_FAILED_EMAIL_MAX_RETRIES = 3;
const GH_FAILED_EMAIL_RETRY_DELAY = 60 * 3; //3 minutes

/**
 * Hooks in after an event fails and if the error code is wp_mail_failed retry the event in a few minutes
 *
 * @param  \Groundhogg\Event  $event
 *
 * @return void
 */
function gh_retry_failed_email_events( \Groundhogg\Event $event, WP_Error $error ) {

	// not a failed email
	if ( $error->get_error_code() !== 'wp_mail_failed' ) {
		return;
	}
	
	// optionally target specific error messages
	$msg = $error->get_error_message();
	if ( 
		! str_contains( $msg, 'some error message' )
	) {
		return;
	}

	$retries = $event->get_arg( '_retries', 0 );

	if ( $retries >= GH_FAILED_EMAIL_MAX_RETRIES ) {
		return;
	}

	$event->update( [
		'status' => \Groundhogg\Event::WAITING,
		'time'   => time() + GH_FAILED_EMAIL_RETRY_DELAY,
	] );

	$event->set_args( [ '_retries' => $retries + 1 ] );
}