add email newsletter filter (is being added in 3.1.38)

gistfile1.txt

//this goes in includes/admin-files/event_newsletter.php at line 49 (approx)
<li>
   <select name="filter">
       <option value="all"><?php _e("All attendees of this event", "event_espresso"); ?></opton>
       <option value="completed"><?php _e("Completed payment status attendees", "event_espresso"); ?></opton>
       <option value="incomplete"><?php _e("Incomplete payment status attendees", "event_espresso"); ?></opton>
       <option value="pending"><?php _e("Pending payment status attendees", "event_espresso"); ?></opton>           
   </select>
</li>

// line 6 of that same file changes to:
espresso_event_reminder($event_id, $_POST['email_subject'], $_POST['email_text'], $email_name, $_POST['filter']);

// This is a pluggable function in email.php, so you can put this function into uploads/espresso/custom_functions.php:
function espresso_event_reminder($event_id, $email_subject='', $email_text='', $email_id=0, $filter="all") {
	global $wpdb, $org_options;
	do_action('action_hook_espresso_log', __FILE__, __FUNCTION__, '');
	$count = 0;
              switch ($filter) {
                  case "completed":
                      $sql_filter = " AND payment_status='Completed'";
                      break;
                  case "incomplete":
                      $sql_filter = " AND payment_status='Incomplete'";
                      break;
                  case "pending":
                      $sql_filter = " AND payment_status='Pending'";
                      break;
                  default:
                      $sql_filter = "";
              }
	$SQL = 'SELECT * FROM ' . EVENTS_ATTENDEE_TABLE . ' WHERE event_id =%d' . $sql_filter . ' GROUP BY lname, fname';
              
	$attendees = $wpdb->get_results( $wpdb->prepare( $SQL, $event_id ));
	
	if ($wpdb->num_rows > 0) {
		foreach ($attendees as $attendee) {
			$attendee_id = $attendee->id;
			event_espresso_email_confirmations(array('attendee_id' => $attendee_id, 'send_admin_email' => 'false', 'send_attendee_email' => 'true', 'custom_data' => array('email_type' => 'reminder', 'email_subject' => $email_subject, 'email_text' => $email_text, 'email_id' => $email_id)));
			$count++;
		}
		?>
		<div id="message" class="updated fade">
			<p><strong>
					<?php echo sprintf(_n('Email Sent to 1 person successfully.', 'Email Sent to %d people successfully.', $count, 'event_espresso'), $count); ?>
				</strong></p>
		</div>
		<?php
		return;
	} else {
		?>
		<div id="message" class="error fade">
			<p><strong>
					<?php _e('No attendee records available.', 'event_espresso'); ?>
				</strong></p>
		</div>
		<?php
	}
}