// Copyright 2021 The Dawn & Tint Authors
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are met:
//
// 1. Redistributions of source code must retain the above copyright notice, this
//    list of conditions and the following disclaimer.
//
// 2. Redistributions in binary form must reproduce the above copyright notice,
//    this list of conditions and the following disclaimer in the documentation
//    and/or other materials provided with the distribution.
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//    contributors may be used to endorse or promote products derived from
//    this software without specific prior written permission.
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#ifndef SRC_DAWN_NATIVE_ASYNCTASK_H_
#define SRC_DAWN_NATIVE_ASYNCTASK_H_

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

#include "absl/container/flat_hash_map.h"
#include "dawn/common/Ref.h"
#include "dawn/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:
        WaitableTask();
        ~WaitableTask() override;

        AsyncTask asyncTask;
        AsyncTaskManager* taskManager;
        std::unique_ptr<dawn::platform::WaitableEvent> waitableEvent;
    };

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

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

}  // namespace dawn::native

#endif  // SRC_DAWN_NATIVE_ASYNCTASK_H_
