Appointments+ Feature: Select a random service provider

Random Worker.php

add_filter('app_pre_confirmation_reply', 'select_random_provider');

function select_random_provider($reply_array)
{
// Return if worker is already selected
	if(''!==$reply_array['worker'])
		return $reply_array;

// Read in the $value params from the $_POST request
global $appointments;
	$appointments = new Appointments();
	$value = isset($_POST['value']) ? $_POST['value']:"";

		$values 		= explode( ":", $_POST["value"] );
		$location 		= $values[0];
		$service 		= $values[1];
		$worker 		= $values[2];
		$start 			= $values[3];
		$end 			= $values[4];
		$post_id		= $values[5];

	$html = "";
	$available_workers = array();
// Get all workers who can perform this service and are available during the current week
	$all_workers = $appointments->get_workers_by_service($service);
	$week= date( "W", $start );

	foreach ($all_workers as $w) {
		$available = true;
		// Check if this worker has other appointments in this slot
		$apps = $appointments->get_reserve_apps_by_worker(" ", $w->ID, $week );
			foreach ( $apps as $app ) {
				if ( $start >= strtotime( $app->start )
				  && $end <= strtotime( $app->end ) )
						$available = false;
			}
			// If the worker is add him to our pool of available workers
			if($available)
				array_push($available_workers,$w);

	}

// Choose a worker randomly from the pool
$worker = array_rand($available_workers);
$worker_id = $available_workers[$worker]->ID; 

// A script that handles AJAX responses and injects the random service provider into the final value param
$script = <<<EOT
			<script type="text/javascript">
				jQuery(document).ready(function($) {
				var final_value = $(".appointments-confirmation-final-value")
				tmp = final_value.val().split(':')
				tmp[2]={$worker_id}
				final_value.val(tmp.join(":"))
				})
			</script>
EOT;

// Add this script to the $reply_array
	$html .= $script;
	$reply_array['worker'] =  $html;
	// Hook for further development if needed
	apply_filters('random_service_provider',$reply_array)

	return $reply_array;
}

You can just copy/paste the above code into your functions.php or a site specific plugin if you use one