AMQP-CPP/include/deferredget.h

/**
 *  DeferredGet.h
 *
 *  @author Emiel Bruijntjes <emiel.bruijntjes@copernica.com>
 *  @copyright 2014 Copernica BV
 */

/**
 *  Include guard
 */
#pragma once

/**
 *  Dependencies
 */
#include "deferredconsumerbase.h"

/**
 *  Set up namespace
 */
namespace AMQP {

/**
 *  Class definition
 *
 *  This class implements the 'shared_from_this' functionality, because
 *  it grabs a self-pointer when the callback is running, otherwise the onFinalize()
 *  is called before the actual message is consumed.
 */
class DeferredGet : public DeferredConsumerBase
{
private:
    /**
     *  Callback in case the queue is empty
     *  @var    EmptyCallback
     */
    EmptyCallback _emptyCallback;

    /**
     *  Callback with the number of messages still in the queue
     *  @var    SizeCallback
     */
    SizeCallback _sizeCallback;

    /**
     *  Report success for a get operation
     *
     *  @param  messagecount    Number of messages left in the queue
     *  @param  deliveryTag     Delivery tag of the message coming in
     *  @param  redelivered     Was the message redelivered?
     */
    const std::shared_ptr<Deferred> &reportSuccess(uint32_t messagecount, uint64_t deliveryTag, bool redelivered) override;

    /**
     *  Report success when queue was empty
     *  @return Deferred
     */
    virtual const std::shared_ptr<Deferred> &reportSuccess() const override;

    /**
     *  Emit a message
     *
     *  @param  message The message to emit
     *  @param  deliveryTag The delivery tag (for ack()ing)
     *  @param  redelivered Is this a redelivered message
     */
    void emit(Message &&message, uint64_t deliveryTag, bool redelivered) const override;

    /**
     *  The channel implementation may call our
     *  private members and construct us
     */
    friend class ChannelImpl;
    friend class ConsumedMessage;

public:
    /**
     *  Protected constructor that can only be called
     *  from within the channel implementation
     *
     *  Note: this constructor _should_ be protected, but because make_shared
     *  will then not work, we have decided to make it public after all,
     *  because the work-around would result in not-so-easy-to-read code.
     *
     *  @param  channel     the channel implementation
     *  @param  failed      are we already failed?
     */
    DeferredGet(ChannelImpl *channel, bool failed = false) :
        DeferredConsumerBase(failed, channel) {}

public:
    /**
     *  Register a function to be called when a message arrives
     *  This fuction is also available as onReceived() and onMessage() because I always forget which name I gave to it
     *  @param  callback
     */
    DeferredGet &onSuccess(const MessageCallback &callback)
    {
        // store the callback
        _messageCallback = callback;

        // allow chaining
        return *this;
    }

    /**
     *  Register a function to be called if no message could be fetched
     *  @param  callback    the callback to execute
     */
    DeferredGet &onEmpty(const EmptyCallback &callback)
    {
        // store callback
        _emptyCallback = callback;

        // allow chaining
        return *this;
    }

    /**
     *  Register a function to be called when size information is known
     *  @param  callback    the callback to execute
     */
    DeferredGet &onSize(const SizeCallback &callback)
    {
        // store callback
        _sizeCallback = callback;

        // allow chaining
        return *this;
    }
};

/**
 *  End of namespace
 */
}