/*
 * BluezQt - Asynchronous BlueZ wrapper library
 *
 * SPDX-FileCopyrightText: 2019 Manuel Weichselbaumer <mincequi@web.de>
 *
 * SPDX-License-Identifier: LGPL-2.1-only OR LGPL-3.0-only OR LicenseRef-KDE-Accepted-LGPL
 */

#pragma once

#include <QDBusPendingReply>

#include "pendingcall.h"

namespace BluezQt
{
using namespace std::placeholders;

/**
 * @class BluezQt::TPendingCall tpendingcall.h <BluezQt/TPendingCall>
 *
 * Pending method call (template version).
 *
 * This class represents a pending method call. It is a convenient wrapper
 * around QDBusPendingReply and QDBusPendingCallWatcher.
 * The TPendingCall is a template class whose parameters are the types that will
 * be used to extract the contents of the reply's data.
 */

// KF6 TODO: convert all PendingCalls to TPendingCall (or convert existing PendingCall class to templated version).
template<class... T>
class TPendingCall : public PendingCall
{
private:
    template<int Index, typename Ty, typename... Ts>
    struct Select {
        using Type = typename Select<Index - 1, Ts...>::Type;
    };
    template<typename Ty, typename... Ts>
    struct Select<0, Ty, Ts...> {
        using Type = Ty;
    };

public:
    /**
     * Returns a return value at given index of the call.
     *
     * Returns the return value at position Index (which is a template parameter) cast to type Type.
     * This function uses template code to determine the proper Type type, according to the type
     * list used in the construction of this object.
     *
     * @return return value at index
     */
    template<int Index>
    inline const typename Select<Index, T...>::Type valueAt() const
    {
        using ResultType = typename Select<Index, T...>::Type;
        return qdbus_cast<ResultType>(m_reply.argumentAt(Index), nullptr);
    }

private:
    TPendingCall(const QDBusPendingCall &call, QObject *parent = nullptr)
        : PendingCall(call, std::bind(&TPendingCall::process, this, _1, _2, _3), parent)
    {
    }

    void process(QDBusPendingCallWatcher *watcher, ErrorProcessor errorProcessor, QVariantList *values)
    {
        m_reply = *watcher;
        errorProcessor(m_reply.error());
        if (m_reply.isError()) {
            return;
        }

        for (int i = 0; i < m_reply.count(); ++i) {
            values->append(m_reply.argumentAt(i));
        }
    }

    QDBusPendingReply<T...> m_reply;

    friend class MediaTransport;
};

} // namespace BluezQt
