// Copyright 2017 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "components/viz/common/surfaces/parent_local_surface_id_allocator.h"

#include "base/rand_util.h"
#include "base/trace_event/trace_event.h"
#include "third_party/perfetto/include/perfetto/tracing/track_event_args.h"

namespace viz {

constexpr LocalSurfaceId g_invalid_local_surface_id;

ParentLocalSurfaceIdAllocator::ParentLocalSurfaceIdAllocator()
    : current_local_surface_id_(kInvalidParentSequenceNumber,
                                kInitialChildSequenceNumber,
                                base::UnguessableToken::Create()) {}

bool ParentLocalSurfaceIdAllocator::UpdateFromChild(
    const LocalSurfaceId& child_local_surface_id) {
  const LocalSurfaceId& current_local_surface_id = current_local_surface_id_;
  const LocalSurfaceId& child_allocated_local_surface_id =
      child_local_surface_id;

  // If the child has not incremented its child sequence number then there is
  // nothing to do here. This allocator already has the latest LocalSurfaceId.
  if (current_local_surface_id.child_sequence_number() >=
      child_allocated_local_surface_id.child_sequence_number()) {
    return false;
  }

  is_invalid_ = false;
  if (current_local_surface_id.parent_sequence_number() >
      child_allocated_local_surface_id.parent_sequence_number()) {
    // If the current LocalSurfaceId has a newer parent sequence number
    // than the one provided by the child, then the merged LocalSurfaceId
    // is actually a new LocalSurfaceId and so we report its allocation time
    // as now.
    TRACE_EVENT2(
        TRACE_DISABLED_BY_DEFAULT("viz.surface_id_flow"),
        "ParentLocalSurfaceIdAllocator::UpdateFromChild New Allocation",
        "current", current_local_surface_id_.ToString(), "child",
        child_local_surface_id.ToString());
  } else {
    TRACE_EVENT2(
        TRACE_DISABLED_BY_DEFAULT("viz.surface_id_flow"),
        "ParentLocalSurfaceIdAllocator::UpdateFromChild Synchronization",
        "current", current_local_surface_id_.ToString(), "child",
        child_local_surface_id.ToString());
  }

  current_local_surface_id_.child_sequence_number_ =
      child_allocated_local_surface_id.child_sequence_number_;

  TRACE_EVENT(
      TRACE_DISABLED_BY_DEFAULT("viz.surface_id_flow"),
      "LocalSurfaceId.Embed.Flow",
      perfetto::Flow::Global(current_local_surface_id_.embed_trace_id()),
      "step", "UpdateFromChild", "local_surface_id",
      current_local_surface_id_.ToString());

  return true;
}

void ParentLocalSurfaceIdAllocator::Invalidate(
    bool also_invalidate_allocation_group) {
  is_invalid_ = true;
  if (also_invalidate_allocation_group) {
    current_local_surface_id_.embed_token_ = base::UnguessableToken::Create();
  }
}

void ParentLocalSurfaceIdAllocator::GenerateId() {
  if (is_allocation_suppressed_)
    return;
  is_invalid_ = false;

  ++current_local_surface_id_.parent_sequence_number_;

  TRACE_EVENT(
      TRACE_DISABLED_BY_DEFAULT("viz.surface_id_flow"),
      "LocalSurfaceId.Embed.Flow",
      perfetto::Flow::Global(current_local_surface_id_.embed_trace_id()),
      "step", "ParentLocalSurfaceIdAllocator::GenerateId", "local_surface_id",
      current_local_surface_id_.ToString());

  TRACE_EVENT(
      TRACE_DISABLED_BY_DEFAULT("viz.surface_id_flow"),
      "LocalSurfaceId.Submission.Flow",
      perfetto::Flow::Global(current_local_surface_id_.submission_trace_id()),
      "step", "ParentLocalSurfaceIdAllocator::GenerateId", "local_surface_id",
      current_local_surface_id_.ToString());
}

const LocalSurfaceId& ParentLocalSurfaceIdAllocator::GetCurrentLocalSurfaceId()
    const {
  if (is_invalid_)
    return g_invalid_local_surface_id;
  return current_local_surface_id_;
}

bool ParentLocalSurfaceIdAllocator::HasValidLocalSurfaceId() const {
  return !is_invalid_ && current_local_surface_id_.is_valid();
}

const base::UnguessableToken& ParentLocalSurfaceIdAllocator::GetEmbedToken()
    const {
  return current_local_surface_id_.embed_token();
}

// static
const LocalSurfaceId& ParentLocalSurfaceIdAllocator::InvalidLocalSurfaceId() {
  return g_invalid_local_surface_id;
}

}  // namespace viz