// Copyright 2021 The Dawn Authors
//
// 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 DAWNNATIVE_ASYC_TASK_H_
#define DAWNNATIVE_ASYC_TASK_H_

#include <functional>
#include <memory>
#include <mutex>
#include <unordered_map>

#include "common/RefCounted.h"

namespace dawn::platform {
    class WaitableEvent;
    class WorkerTaskPool;
}  // namespace dawn::platform

namespace dawn::native {

    // TODO(crbug.com/dawn/826): we'll add additional things to AsyncTask in the future, like
    // Cancel() and RunNow(). Cancelling helps avoid running the task's body when we are just
    // shutting down the device. RunNow() could be used for more advanced scenarios, for example
    // always doing ShaderModule initial compilation asynchronously, but being able to steal the
    // task if we need it for synchronous pipeline compilation.
    using AsyncTask = std::function<void()>;

    class AsyncTaskManager {
      public:
        explicit AsyncTaskManager(dawn::platform::WorkerTaskPool* workerTaskPool);

        void PostTask(AsyncTask asyncTask);
        void WaitAllPendingTasks();
        bool HasPendingTasks();

      private:
        class WaitableTask : public RefCounted {
          public:
            AsyncTask asyncTask;
            AsyncTaskManager* taskManager;
            std::unique_ptr<dawn::platform::WaitableEvent> waitableEvent;
        };

        static void DoWaitableTask(void* task);
        void HandleTaskCompletion(WaitableTask* task);

        std::mutex mPendingTasksMutex;
        std::unordered_map<WaitableTask*, Ref<WaitableTask>> mPendingTasks;
        dawn::platform::WorkerTaskPool* mWorkerTaskPool;
    };

}  // namespace dawn::native

#endif