continue_with.h

/*
    SPDX-FileCopyrightText: 2014-2016 Ivan Cukic <ivan.cukic(at)kde.org>
 
    SPDX-License-Identifier: LGPL-2.1-only OR LGPL-3.0-only OR LicenseRef-KDE-Accepted-LGPL
*/
 
#ifndef UTILS_CONTINUE_WITH_H
#define UTILS_CONTINUE_WITH_H
 
#include <QDebug>
#include <QFuture>
#include <QFutureWatcher>
 
#include <optional>
 
#ifdef ENABLE_QJSVALUE_CONTINUATION
#include <QJSValue>
#endif
 
namespace kamd
{
namespace utils
{
namespace detail
{ //_
#ifdef ENABLE_QJSVALUE_CONTINUATION
inline void test_continuation(const QJSValue &continuation)
{
    if (!continuation.isCallable()) {
        qWarning() << "Passed handler is not callable: " << continuation.toString();
    }
}
 
template<typename _ReturnType>
inline void pass_value(const QFuture<_ReturnType> &future, QJSValue continuation)
{
    auto result = continuation.call({future.result()});
    if (result.isError()) {
        qWarning() << "Handler returned this error: " << result.toString();
    }
}
 
inline void pass_value(const QFuture<void> &future, QJSValue continuation)
{
    Q_UNUSED(future);
    auto result = continuation.call({});
    if (result.isError()) {
        qWarning() << "Handler returned this error: " << result.toString();
    }
}
#endif
 
template<typename _Continuation>
inline void test_continuation(_Continuation &&continuation)
{
    Q_UNUSED(continuation);
}
 
template<typename _ReturnType, typename _Continuation>
inline void pass_value(const QFuture<_ReturnType> &future, _Continuation &&continuation)
{
    using namespace kamd::utils;
    continuation(future.resultCount() > 0 ? std::optional(future.result()) : std::nullopt);
}
 
template<typename _Continuation>
inline void pass_value(_Continuation &&continuation)
{
    continuation();
}
 
} //^ namespace detail
 
template<typename _ReturnType, typename _Continuation>
inline void continue_with(const QFuture<_ReturnType> &future, _Continuation &&continuation)
{
    detail::test_continuation(continuation);
 
    auto watcher = new QFutureWatcher<_ReturnType>();
    QObject::connect(watcher, &QFutureWatcherBase::finished, [=]() mutable {
        detail::pass_value(future, continuation);
    });
 
    watcher->setFuture(future);
}
 
} // namespace utils
} // namespace kamd
 
#endif /* !UTILS_CONTINUE_WITH_H */