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#ifndef QPROMISE_H
#define QPROMISE_H

#include <QtCore/qglobal.h>
#include <QtCore/qfuture.h>

#include <utility>

QT_REQUIRE_CONFIG(future);

QT_BEGIN_NAMESPACE

template<typename T>
class QPromise
{
    static_assert (std::is_copy_constructible_v<T>
                   || std::is_move_constructible_v<T>
                   || std::is_same_v<T, void>,
                   "Type with copy or move constructors or type void is required");
public:
    QPromise() = default;
    Q_DISABLE_COPY(QPromise)
    QPromise(QPromise<T> &&other) : d(other.d)
    {
        other.d = QFutureInterface<T>();
    }
    QPromise(QFutureInterface<T> &other) : d(other) {}
    QPromise& operator=(QPromise<T> &&other)
    {
        QPromise<T> tmp(std::move(other));
        tmp.swap(*this);
        return *this;
    }
    ~QPromise()
    {
        const int state = d.loadState();
        // If QFutureInterface has no state, there is nothing to be done
        if (state == static_cast<int>(QFutureInterfaceBase::State::NoState))
            return;
        // Otherwise, if computation is not finished at this point, cancel
        // potential waits
        if (!(state & QFutureInterfaceBase::State::Finished)) {
            d.cancel();
            finish();  // required to finalize the state
        }
    }

    // Core QPromise APIs
    QFuture<T> future() const { return d.future(); }
    template<typename U, typename = QtPrivate::EnableIfSameOrConvertible<U, T>>
    bool addResult(U &&result, int index = -1)
    {
        return d.reportResult(std::forward<U>(result), index);
    }
#ifndef QT_NO_EXCEPTIONS
    void setException(const QException &e) { d.reportException(e); }
    void setException(std::exception_ptr e) { d.reportException(e); }
#endif
    void start() { d.reportStarted(); }
    void finish() { d.reportFinished(); }

    void suspendIfRequested() { d.suspendIfRequested(); }

    bool isCanceled() const { return d.isCanceled(); }

    // Progress methods
    void setProgressRange(int minimum, int maximum) { d.setProgressRange(minimum, maximum); }
    void setProgressValue(int progressValue) { d.setProgressValue(progressValue); }
    void setProgressValueAndText(int progressValue, const QString &progressText)
    {
        d.setProgressValueAndText(progressValue, progressText);
    }

    void swap(QPromise<T> &other) noexcept
    {
        qSwap(this->d, other.d);
    }

#if defined(Q_CLANG_QDOC)  // documentation-only simplified signatures
    bool addResult(const T &result, int index = -1) { }
    bool addResult(T &&result, int index = -1) { }
#endif
private:
    mutable QFutureInterface<T> d = QFutureInterface<T>();
};

template<typename T>
inline void swap(QPromise<T> &a, QPromise<T> &b) noexcept
{
    a.swap(b);
}

QT_END_NAMESPACE

#endif  // QPROMISE_H