/*
 * Copyright (c) 2021 Huawei Device Co., Ltd.
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#ifndef UTILS_INCLUDE_PROMISE_H
#define UTILS_INCLUDE_PROMISE_H

#include <condition_variable>
#include <thread>

#include <refbase.h>

namespace OHOS {
template<class T>
class Promise : public RefBase {
public:
    Promise() = default;
    Promise(const T& t);
    virtual ~Promise() = default;

    virtual bool IsResolved() const;
    virtual const T &Await();
    virtual void Then(std::function<void(const T &t)> func);
    virtual bool Resolve(const T &t);

private:
    bool resolved = false;
    std::mutex mutex;
    std::condition_variable cv;
    T value{};

    std::function<void(const T &t)> onComplete = nullptr;
};

template<class T>
Promise<T>::Promise(const T& t)
{
    value = t;
    resolved = true;
}

template<class T>
bool Promise<T>::IsResolved() const
{
    return resolved;
}

template<class T>
const T &Promise<T>::Await()
{
    if (resolved == false) {
        std::unique_lock<std::mutex> lock(mutex);
        cv.wait(lock, [this]() { return resolved == true; });
    }
    return value;
}

template<class T>
void Promise<T>::Then(std::function<void(const T &t)> func)
{
    std::unique_lock<std::mutex> lock(mutex);
    if (resolved == false) {
        onComplete = func;
    } else {
        func(value);
    }
}

template<class T>
bool Promise<T>::Resolve(const T &t)
{
    if (resolved == false) {
        std::unique_lock<std::mutex> lock(mutex);
        if (resolved == false) {
            value = t;
            resolved = true;
            cv.notify_all();
            if (onComplete != nullptr) {
                onComplete(value);
            }
            return true;
        }
    }
    return false;
}
} // namespace OHOS

#endif // UTILS_INCLUDE_PROMISE_H