<?php
abstract class AbstractCarrier {

    protected $connection;
    protected $channel;
    protected $queueName;

    public function __construct($queueName, $host = 'localhost', $port = 5672, $username = 'guest', $password = 'guest') {

        $this->queueName = $queueName;

        $this->connection = new AMQPStreamConnection($host, $port, $username, $password);
        $this->channel = $this->connection->channel();
        $this->channel->queue_declare($queueName, false, false, false, false);

    }

    /**
     * This method is called by the script that implements the carrier. It is blocking.
     * The call to basic_consume calls the 'receivedParcel' method which is implmented by the subclasses
     */
    public function waitForMail() {
        $this->channel->basic_consume($this->queueName, $this->queueName, false,false,false,false, [$this, 'receivedParcel']);

        while (count($this->channel->callbacks)) {
            $this->channel->wait();
        }
        $this->channel->close();
        $this->connection->close();
    }

    /* Stub to be implemented by sub classes */
    protected function receivedParcel($msg){}

}