/*
 * Copyright (C) 2020 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 <optional>
#include <thread>

#include "host/frontend/webrtc/cvd_video_frame_buffer.h"
#include "host/frontend/webrtc/libdevice/video_sink.h"
#include "host/frontend/webrtc/screenshot_handler.h"
#include "host/libs/screen_connector/screen_connector.h"

namespace cuttlefish {
/**
 * ScreenConnectorImpl will generate this, and enqueue
 *
 * It's basically a (processed) frame, so it:
 *   must be efficiently std::move-able
 * Also, for the sake of algorithm simplicity:
 *   must be default-constructable & assignable
 *
 */
struct WebRtcScProcessedFrame : public ScreenConnectorFrameInfo {
  // must support move semantic
  std::unique_ptr<CvdVideoFrameBuffer> buf_;
  std::unique_ptr<WebRtcScProcessedFrame> Clone() {
    // copy internal buffer, not move
    CvdVideoFrameBuffer* new_buffer = new CvdVideoFrameBuffer(*(buf_.get()));
    auto cloned_frame = std::make_unique<WebRtcScProcessedFrame>();
    cloned_frame->buf_ = std::unique_ptr<CvdVideoFrameBuffer>(new_buffer);
    return cloned_frame;
  }
};

namespace webrtc_streaming {
class Streamer;
}  // namespace webrtc_streaming

class DisplayHandler {
 public:
  using ScreenConnector = cuttlefish::ScreenConnector<WebRtcScProcessedFrame>;
  using GenerateProcessedFrameCallback =
      ScreenConnector::GenerateProcessedFrameCallback;
  using WebRtcScProcessedFrame = cuttlefish::WebRtcScProcessedFrame;

  DisplayHandler(webrtc_streaming::Streamer& streamer,
                 ScreenshotHandler& screenshot_handler,
                 ScreenConnector& screen_connector);
  ~DisplayHandler();

  [[noreturn]] void Loop();

  // If std::nullopt, send last frame for all displays.
  void SendLastFrame(std::optional<uint32_t> display_number);

  void AddDisplayClient();
  void RemoveDisplayClient();

 private:
  struct BufferInfo {
    std::chrono::system_clock::time_point last_sent_time_stamp;
    std::shared_ptr<webrtc_streaming::VideoFrameBuffer> buffer;
  };
  enum class RepeaterState {
    RUNNING,
    STOPPED,
  };

  GenerateProcessedFrameCallback GetScreenConnectorCallback();
  void SendBuffers(std::map<uint32_t, std::shared_ptr<BufferInfo>> buffers);
  void RepeatFramesPeriodically();

  std::map<uint32_t, std::shared_ptr<webrtc_streaming::VideoSink>>
      display_sinks_;
  webrtc_streaming::Streamer& streamer_;
  ScreenshotHandler& screenshot_handler_;
  ScreenConnector& screen_connector_;
  std::map<uint32_t, std::shared_ptr<BufferInfo>> display_last_buffers_;
  std::mutex last_buffers_mutex_;
  std::mutex send_mutex_;
  std::thread frame_repeater_;
  // Protected by repeater_state_mutex
  RepeaterState repeater_state_ = RepeaterState::RUNNING;
  // Protected by repeater_state_mutex
  int num_active_clients_ = 0;
  std::mutex repeater_state_mutex_;
  std::condition_variable repeater_state_condvar_;
};
}  // namespace cuttlefish