dbus.h

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/**********************************************************************
 * LeechCraft - modular cross-platform feature rich internet client.
 * Copyright (C) 2006-2014  Georg Rudoy
 *
 * Distributed under the Boost Software License, Version 1.0.
 * (See accompanying file LICENSE or copy at https://www.boost.org/LICENSE_1_0.txt)
 **********************************************************************/

#pragma once

#include <coroutine>
#include <memory>
#include <tuple>
#include <QDBusPendingCallWatcher>
#include <QDBusPendingReply>
#include <util/sll/either.h>
#include <util/sll/void.h>

namespace LC::Util::detail
{
    template<typename... Rets>
    struct DBusAwaiter
    {
        QDBusPendingReply<Rets...> Reply_;
        std::unique_ptr<QDBusPendingCallWatcher> Watcher_;

        DBusAwaiter (const QDBusPendingReply<Rets...>& reply)
        : Reply_ { reply }
        {
        }

        bool await_ready () const noexcept
        {
            return Reply_.isFinished ();
        }

        void await_suspend (std::coroutine_handle<> handle) noexcept
        {
            Watcher_ = std::make_unique<QDBusPendingCallWatcher> (Reply_);
            QObject::connect (Watcher_.get (),
                    &QDBusPendingCallWatcher::finished,
                    handle);
        }

        template<typename = void>
        struct SuccessType;

        template<typename T> requires (sizeof... (Rets) == 0)
        struct SuccessType<T> { using Type = Void; };

        template<typename T> requires (sizeof... (Rets) == 1)
        struct SuccessType<T> { using Type = Rets... [0]; };

        template<typename T> requires (sizeof... (Rets) > 1)
        struct SuccessType<T> { using Type = std::tuple<Rets...>; };

        using SuccessType_t = SuccessType<>::Type;

        Either<QDBusError, SuccessType_t> await_resume () const noexcept
        {
            if (Reply_.isError ())
                return { AsLeft, Reply_.error () };

            if constexpr (sizeof... (Rets) == 0)
                return { Void {} };
            else if constexpr (sizeof... (Rets) == 1)
                return { Reply_.value () };
            else
                return [&]<size_t... Idxs> (std::index_sequence<Idxs...>) -> std::tuple<Rets...>
                {
                    return { Reply_.template argumentAt<Idxs> ()... };
                } (std::make_index_sequence<sizeof... (Rets)> {});
        }
    };
}

namespace LC
{
    template<typename... Rets>
    Util::detail::DBusAwaiter<Rets...> operator co_await (const QDBusPendingReply<Rets...>& reply)
    {
        return { reply };
    }
}

namespace LC::Util
{
    template<typename... Rets>
    detail::DBusAwaiter<Rets...> Typed (const QDBusPendingCall& asyncCall)
    {
        return { asyncCall };
    }
}