// Copyright 2013 The Flutter Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef FLUTTER_SHELL_PLATFORM_FUCHSIA_DEFAULT_SESSION_CONNECTION_H_
#define FLUTTER_SHELL_PLATFORM_FUCHSIA_DEFAULT_SESSION_CONNECTION_H_

#include <fuchsia/scenic/scheduling/cpp/fidl.h>
#include <fuchsia/ui/scenic/cpp/fidl.h>
#include <lib/fidl/cpp/interface_handle.h>
#include <lib/ui/scenic/cpp/session.h>

#include "flutter/flow/scene_update_context.h"
#include "flutter/fml/closure.h"
#include "flutter/fml/macros.h"

namespace flutter_runner {

using on_frame_presented_event =
    std::function<void(fuchsia::scenic::scheduling::FramePresentedInfo)>;

// The component residing on the raster thread that is responsible for
// maintaining the Scenic session connection and presenting node updates.
class DefaultSessionConnection final : public flutter::SessionWrapper {
 public:
  DefaultSessionConnection(
      std::string debug_label,
      fidl::InterfaceHandle<fuchsia::ui::scenic::Session> session,
      fml::closure session_error_callback,
      on_frame_presented_event on_frame_presented_callback,
      zx_handle_t vsync_event_handle,
      uint64_t max_frames_in_flight);

  ~DefaultSessionConnection();

  scenic::Session* get() override { return &session_wrapper_; }
  void Present() override;

  static fml::TimePoint CalculateNextLatchPoint(
      fml::TimePoint present_requested_time,
      fml::TimePoint now,
      fml::TimePoint last_latch_point_targeted,
      fml::TimeDelta flutter_frame_build_time,
      fml::TimeDelta vsync_interval,
      std::deque<std::pair<fml::TimePoint, fml::TimePoint>>&
          future_presentation_infos);

 private:
  scenic::Session session_wrapper_;

  on_frame_presented_event on_frame_presented_callback_;

  zx_handle_t vsync_event_handle_;

  fml::TimePoint last_latch_point_targeted_ =
      fml::TimePoint::FromEpochDelta(fml::TimeDelta::Zero());
  fml::TimePoint present_requested_time_ =
      fml::TimePoint::FromEpochDelta(fml::TimeDelta::Zero());

  std::deque<std::pair<fml::TimePoint, fml::TimePoint>>
      future_presentation_infos_ = {};

  bool initialized_ = false;

  // A flow event trace id for following |Session::Present| calls into
  // Scenic.  This will be incremented each |Session::Present| call.  By
  // convention, the Scenic side will also contain its own trace id that
  // begins at 0, and is incremented each |Session::Present| call.
  uint64_t next_present_trace_id_ = 0;
  uint64_t next_present_session_trace_id_ = 0;
  uint64_t processed_present_session_trace_id_ = 0;

  // The maximum number of frames Flutter sent to Scenic that it can have
  // outstanding at any time. This is equivalent to how many times it has
  // called Present2() before receiving an OnFramePresented() event.
  const int kMaxFramesInFlight;
  int frames_in_flight_ = 0;

  int frames_in_flight_allowed_ = 0;

  bool present_session_pending_ = false;

  void PresentSession();

  static void ToggleSignal(zx_handle_t handle, bool raise);

  FML_DISALLOW_COPY_AND_ASSIGN(DefaultSessionConnection);
};

}  // namespace flutter_runner

#endif  // FLUTTER_SHELL_PLATFORM_FUCHSIA_DEFAULT_SESSION_CONNECTION_H_