Noptin_Background_Mailer::fetch_subscriber_from_query( $item )

	public function fetch_subscriber_from_query( $item ) {

		// Ensure that the query is an array...
		$subscriber_query = ( ! is_array( $item['subscribers_query'] ) ) ? array() : $item['subscribers_query'];

		// ... and it has a meta query too.
		if ( empty( $subscriber_query['meta_query'] ) ) {
			$subscriber_query['meta_query'] = array();
		}

		$subscriber_query['meta_query']['relation'] = 'AND';

		// Avoid sending the same campaign twice.
		$subscriber_query['meta_query'][] = array(
			'key'     => '_campaign_' . $item['key'],
			'compare' => 'NOT EXISTS',
		);

		// Retrieve the id...
		$subscriber_query['fields'] = array( 'id' );

		// ... of the next subscriber...
		$subscriber_query['number'] = 1;

		// who is active.
		$subscriber_query['subscriber_status'] = 'active';

		// We do not need to count the total number of subscribers.
		$subscriber_query['count_total'] = false;

		// Filters the query used to find the next recipient of a mass mail.
		$query = apply_filters( 'noptin_background_mailer_subscriber_query', $subscriber_query, $item );

		// Run the query...
		$subscriber = new Noptin_Subscriber_Query( $query );
		$result     = $subscriber->get_results();

		// ... and return the result.
		return empty( $result ) ? null : $result[0];

	}