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transmission/qt/RpcQueue.h

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/*
* This file Copyright (C) 2016 Mnemosyne LLC
*
* It may be used under the GNU GPL versions 2 or 3
* or any future license endorsed by Mnemosyne LLC.
*
* $Id$
*/
#pragma once
#include <functional>
#include <type_traits>
#include <QFutureInterface>
#include <QFutureWatcher>
#include <QObject>
#include <QPair>
#include <QQueue>
#include "RpcClient.h"
class RpcQueue: public QObject
{
Q_OBJECT
public:
explicit RpcQueue (QObject * parent = nullptr);
void setTolerateErrors (bool tolerateErrors = true) { myTolerateErrors = tolerateErrors; }
template <typename Func>
void add (Func func)
{
myQueue.enqueue (qMakePair (normalizeFunc (func),
ErrorHandlerFunction ()));
}
template <typename Func, typename ErrorHandler>
void add (Func func, ErrorHandler errorHandler)
{
myQueue.enqueue (qMakePair (normalizeFunc (func),
normalizeErrorHandler (errorHandler)));
}
RpcResponseFuture future ();
// The first function in queue is ran synchronously
// (hence it may be e. g. a lambda capturing local variables by reference).
void run ();
private:
// Internally queued function. Takes the last response future, makes a
// request and returns a new response future.
typedef std::function<RpcResponseFuture (const RpcResponseFuture&)> QueuedFunction;
// Internally stored error handler function. Takes the last response future and returns nothing.
typedef std::function<void (const RpcResponseFuture&)> ErrorHandlerFunction;
private slots:
void stepFinished ();
private:
void runNext (const RpcResponseFuture& response);
// These overloads convert various forms of input closures to what we store internally.
// normal closure, takes response and returns new future
template <typename Func,
typename std::enable_if<std::is_same<typename std::result_of<Func (const RpcResponse&)>::type, RpcResponseFuture>::value>::type * = nullptr>
QueuedFunction normalizeFunc (const Func& func)
{
return [func] (const RpcResponseFuture& r) { return func (r.result ()); };
}
// closure without argument (first step), takes nothing and returns new future
template <typename Func,
typename std::enable_if<std::is_same<typename std::result_of<Func ()>::type, RpcResponseFuture>::value>::type * = nullptr>
QueuedFunction normalizeFunc (const Func& func)
{
return [func] (const RpcResponseFuture&) { return func (); };
}
// closure without return value ("auxiliary"), takes response and returns nothing -- internally we reuse the last future
template <typename Func,
typename std::enable_if<std::is_same<typename std::result_of<Func (const RpcResponse&)>::type, void>::value>::type * = nullptr>
QueuedFunction normalizeFunc (const Func& func)
{
return [func] (const RpcResponseFuture& r) { func (r.result ()); return r; };
}
// closure without argument and return value, takes nothing and returns nothing -- next function will also get nothing
template <typename Func,
typename std::enable_if<std::is_same<typename std::result_of<Func ()>::type, void>::value>::type * = nullptr>
QueuedFunction normalizeFunc (const Func& func)
{
return [func] (const RpcResponseFuture& r) { func (); return r; };
}
// normal error handler, takes last response
template <typename Func,
typename std::enable_if<std::is_same<typename std::result_of<Func (const RpcResponse&)>::type, void>::value>::type * = nullptr>
ErrorHandlerFunction normalizeErrorHandler (const Func& func)
{
return [func] (const RpcResponseFuture& r) { func (r.result ()); };
}
// error handler without an argument, takes nothing
template <typename Func,
typename std::enable_if<std::is_same<typename std::result_of<Func ()>::type, void>::value>::type * = nullptr>
ErrorHandlerFunction normalizeErrorHandler (const Func& func)
{
return [func] (const RpcResponseFuture& r) { func (); };
}
private:
bool myTolerateErrors;
QFutureInterface<RpcResponse> myPromise;
QQueue<QPair<QueuedFunction, ErrorHandlerFunction>> myQueue;
ErrorHandlerFunction myNextErrorHandler;
QFutureWatcher<RpcResponse> myFutureWatcher;
};