/*
 * Copyright 2018 The Android Open Source Project
 *
 * 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.
 */

#pragma once

#include <chrono>
#include <memory>
#include <mutex>
#include <list>
#include <vector>
#include <atomic>
#include <condition_variable>

#include <EGL/egl.h>
#include <EGL/eglext.h>

#include <jni.h>

#include "swappy/swappy.h"
#include "swappy/swappy_extra.h"

#include "Thread.h"

namespace swappy {

class ChoreographerFilter;
class ChoreographerThread;
class EGL;
class FrameStatistics;

using EGLDisplay = void *;
using EGLSurface = void *;

using namespace std::chrono_literals;

class Swappy {
  private:
    // Allows construction with std::unique_ptr from a static method, but disallows construction
    // outside of the class since no one else can construct a ConstructorTag
    struct ConstructorTag {
    };
  public:
    Swappy(JavaVM *vm,
           std::chrono::nanoseconds refreshPeriod,
           std::chrono::nanoseconds appOffset,
           std::chrono::nanoseconds sfOffset,
           ConstructorTag tag);

    static void init(JNIEnv *env, jobject jactivity);

    static void onChoreographer(int64_t frameTimeNanos);

    static bool swap(EGLDisplay display, EGLSurface surface);

    static void init(JavaVM *vm,
                     std::chrono::nanoseconds refreshPeriod,
                     std::chrono::nanoseconds appOffset,
                     std::chrono::nanoseconds sfOffset);

    // Pass callbacks for tracing within the swap function
    static void addTracer(const SwappyTracer *tracer);

    static uint64_t getSwapIntervalNS();

    static void setAutoSwapInterval(bool enabled);

    static void setAutoPipelineMode(bool enabled);

    static void overrideAutoSwapInterval(uint64_t swap_ns);

    static void enableStats(bool enabled);
    static void recordFrameStart(EGLDisplay display, EGLSurface surface);
    static void getStats(Swappy_Stats *stats);
    static bool isEnabled();
    static void destroyInstance();

private:
    class FrameDuration {
    public:
        FrameDuration() = default;

        FrameDuration(std::chrono::nanoseconds cpuTime, std::chrono::nanoseconds gpuTime) :
            mCpuTime(cpuTime), mGpuTime(gpuTime) {
            mCpuTime = std::min(mCpuTime, MAX_DURATION);
            mGpuTime = std::min(mGpuTime, MAX_DURATION);
        }

        std::chrono::nanoseconds getCpuTime() const { return mCpuTime; }
        std::chrono::nanoseconds getGpuTime() const { return mGpuTime; }
        std::chrono::nanoseconds getTime(bool pipeline) const {
            if (pipeline) {
                return std::max(mCpuTime, mGpuTime);
            }

            return mCpuTime + mGpuTime;
        }

        FrameDuration& operator+=(const FrameDuration& other) {
            mCpuTime += other.mCpuTime;
            mGpuTime += other.mGpuTime;
            return *this;
        }

        FrameDuration& operator-=(const FrameDuration& other) {
            mCpuTime -= other.mCpuTime;
            mGpuTime -= other.mGpuTime;
            return *this;
        }

        friend FrameDuration operator/(FrameDuration lhs, int rhs) {
            lhs.mCpuTime /= rhs;
            lhs.mGpuTime /= rhs;
            return lhs;
        }
    private:
        std::chrono::nanoseconds mCpuTime = std::chrono::nanoseconds(0);
        std::chrono::nanoseconds mGpuTime = std::chrono::nanoseconds(0);

        static constexpr std::chrono::nanoseconds MAX_DURATION =
                std::chrono::milliseconds(100);
    };

    static Swappy *getInstance();

    bool enabled() const { return !mDisableSwappy; }

    EGL *getEgl();

    bool swapInternal(EGLDisplay display, EGLSurface surface);

    void addTracerCallbacks(SwappyTracer tracer);

    void preSwapBuffersCallbacks();
    void postSwapBuffersCallbacks();
    void preWaitCallbacks();
    void postWaitCallbacks();
    void startFrameCallbacks();
    void swapIntervalChangedCallbacks();

    void onSettingsChanged();

    void handleChoreographer();
    std::chrono::nanoseconds wakeClient();

    void startFrame();

    void waitUntil(int32_t frameNumber);

    void waitOneFrame();

    // Waits for the next frame, considering both Choreographer and the prior frame's completion
    bool waitForNextFrame(EGLDisplay display);

    // Destroys the previous sync fence (if any) and creates a new one for this frame
    void resetSyncFence(EGLDisplay display);

    // Computes the desired presentation time based on the swap interval and sets it
    // using eglPresentationTimeANDROID
    bool setPresentationTime(EGLDisplay display, EGLSurface surface);

    void updateSwapDuration(std::chrono::nanoseconds duration);

    void addFrameDuration(FrameDuration duration);

    bool updateSwapInterval();

    void swapFaster(const FrameDuration& averageFrameTime,
                    const std::chrono::nanoseconds& upperBound,
                    const std::chrono::nanoseconds& lowerBound,
                    const int32_t& newSwapInterval) REQUIRES(mFrameDurationsMutex);

    void swapSlower(const FrameDuration& averageFrameTime,
                      const std::chrono::nanoseconds& upperBound,
                      const std::chrono::nanoseconds& lowerBound,
                      const int32_t& newSwapInterval) REQUIRES(mFrameDurationsMutex);

    bool mDisableSwappy = false;

    int32_t nanoToSwapInterval(std::chrono::nanoseconds);

    std::atomic<std::chrono::nanoseconds> mSwapDuration;

    static std::mutex sInstanceMutex;
    static std::unique_ptr<Swappy> sInstance;

    std::atomic<int32_t> mSwapInterval;
    std::atomic<int32_t> mAutoSwapInterval;
    int mAutoSwapIntervalThreshold = 0;

    std::mutex mWaitingMutex;
    std::condition_variable mWaitingCondition;
    std::chrono::steady_clock::time_point mCurrentFrameTimestamp = std::chrono::steady_clock::now();
    int32_t mCurrentFrame = 0;

    std::mutex mEglMutex;
    std::shared_ptr<EGL> mEgl;

    int32_t mTargetFrame = 0;
    std::chrono::steady_clock::time_point mPresentationTime = std::chrono::steady_clock::now();
    bool mPipelineMode = false;

    const std::chrono::nanoseconds mRefreshPeriod;
    std::unique_ptr<ChoreographerFilter> mChoreographerFilter;

    bool mUsingExternalChoreographer = false;
    std::unique_ptr<ChoreographerThread> mChoreographerThread;

    template <typename ...T>
    using Tracer = std::function<void (T...)>;

    struct SwappyTracerCallbacks {
        std::list<Tracer<>> preWait;
        std::list<Tracer<>> postWait;
        std::list<Tracer<>> preSwapBuffers;
        std::list<Tracer<long>> postSwapBuffers;
        std::list<Tracer<int32_t, long>> startFrame;
        std::list<Tracer<>> swapIntervalChanged;
    };

    SwappyTracerCallbacks mInjectedTracers;

    std::mutex mFrameDurationsMutex;
    std::vector<FrameDuration> mFrameDurations GUARDED_BY(mFrameDurationsMutex);
    FrameDuration mFrameDurationsSum GUARDED_BY(mFrameDurationsMutex);
    static constexpr int mFrameDurationSamples = 10;
    bool mAutoSwapIntervalEnabled GUARDED_BY(mFrameDurationsMutex) = true;
    bool mPipelineModeAutoMode GUARDED_BY(mFrameDurationsMutex) = true;
    static constexpr std::chrono::nanoseconds FRAME_HYSTERESIS = 3ms;
    std::chrono::steady_clock::time_point mSwapTime;
    std::chrono::steady_clock::time_point mStartFrameTime;
    std::unique_ptr<FrameStatistics> mFrameStatistics;

    const std::chrono::nanoseconds mSfOffset;
};

} //namespace swappy