// Copyright 2019 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.

#include <windows.h>

#include "dawn/utils/Timer.h"

namespace utils {

class WindowsTimer : public Timer {
  public:
    WindowsTimer() : Timer(), mRunning(false), mFrequency(0) {}

    ~WindowsTimer() override = default;

    void Start() override {
        LARGE_INTEGER curTime;
        QueryPerformanceCounter(&curTime);
        mStartTime = curTime.QuadPart;

        // Cache the frequency
        GetFrequency();

        mRunning = true;
    }

    void Stop() override {
        LARGE_INTEGER curTime;
        QueryPerformanceCounter(&curTime);
        mStopTime = curTime.QuadPart;

        mRunning = false;
    }

    double GetElapsedTime() const override {
        LONGLONG endTime;
        if (mRunning) {
            LARGE_INTEGER curTime;
            QueryPerformanceCounter(&curTime);
            endTime = curTime.QuadPart;
        } else {
            endTime = mStopTime;
        }

        return static_cast<double>(endTime - mStartTime) / mFrequency;
    }

    double GetAbsoluteTime() override {
        LARGE_INTEGER curTime;
        QueryPerformanceCounter(&curTime);

        return static_cast<double>(curTime.QuadPart) / GetFrequency();
    }

  private:
    LONGLONG GetFrequency() {
        if (mFrequency == 0) {
            LARGE_INTEGER frequency = {};
            QueryPerformanceFrequency(&frequency);

            mFrequency = frequency.QuadPart;
        }

        return mFrequency;
    }

    bool mRunning;
    LONGLONG mStartTime;
    LONGLONG mStopTime;
    LONGLONG mFrequency;
};

Timer* CreateTimer() {
    return new WindowsTimer();
}

}  // namespace utils