quiche/quic/moqt/moqt_object_subscriber.cc

// Copyright 2024 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file

#include "quiche/quic/moqt/moqt_object_subscriber.h"

#include <algorithm>
#include <cstdint>
#include <cstring>
#include <memory>
#include <optional>
#include <utility>

#include "absl/status/status.h"
#include "absl/strings/string_view.h"
#include "quiche/quic/core/quic_alarm.h"
#include "quiche/quic/core/quic_alarm_factory.h"
#include "quiche/quic/core/quic_clock.h"
#include "quiche/quic/core/quic_time.h"
#include "quiche/quic/moqt/moqt_fetch_task.h"
#include "quiche/quic/moqt/moqt_key_value_pair.h"
#include "quiche/quic/moqt/moqt_messages.h"
#include "quiche/quic/moqt/moqt_object.h"
#include "quiche/quic/moqt/moqt_session_callbacks.h"
#include "quiche/quic/moqt/moqt_types.h"
#include "quiche/common/platform/api/quiche_bug_tracker.h"
#include "quiche/common/quiche_mem_slice.h"
#include "quiche/web_transport/web_transport.h"

namespace moqt {

namespace {

constexpr quic::QuicTimeDelta kMinPublishDoneTimeout =
    quic::QuicTimeDelta::FromSeconds(1);
constexpr quic::QuicTimeDelta kMaxPublishDoneTimeout =
    quic::QuicTimeDelta::FromSeconds(10);

}  // namespace

LiveSubscriber::~LiveSubscriber() {
  if (publish_done_alarm_ != nullptr) {
    publish_done_alarm_->PermanentCancel();
  }
  if (visitor_ != nullptr) {
    // The application expects OnPublishDone even if the Session has gone away.
    visitor_->OnPublishDone(full_track_name());
  }
}

void LiveSubscriber::OnObjectOrOk(const SubscribeOkData& data) {
  if (parameters().subscription_filter.has_value()) {
    parameters().subscription_filter->OnLargestObject(
        data.parameters.largest_object);
  }
  publisher_object_delivery_timeout_ =
      data.properties.object_delivery_timeout();
  publisher_subgroup_delivery_timeout_ =
      data.properties.subgroup_delivery_timeout();
  // TODO(martinduke): Is there anything to do with EXPIRES?
  default_publisher_priority_ = data.properties.default_publisher_priority();
  dynamic_groups_ = data.properties.dynamic_groups();
  visitor_->OnReply(full_track_name(), data);
  error_is_allowed_ = false;
}

void LiveSubscriber::OnStreamOpened(webtransport::StreamVisitor*) {
  ++currently_open_streams_;
  if (publish_done_alarm_ != nullptr && publish_done_alarm_->IsSet()) {
    publish_done_alarm_->Cancel();
  }
}

void LiveSubscriber::OnStreamClosed(absl::Status status,
                                    std::optional<DataStreamIndex> index) {
  ++streams_closed_;
  --currently_open_streams_;
  QUICHE_DCHECK_GE(currently_open_streams_, -1);
  if (index.has_value() && visitor_ != nullptr) {
    // If index is nullopt, there was not an object received on the stream.
    if (status.ok()) {
      visitor_->OnStreamFin(full_track_name(), *index);
    } else {
      visitor_->OnStreamReset(full_track_name(), *index);
    }
  }
  if (all_streams_closed()) {
    request_stream()->Fin();
    // Fin will destroy the class.
    return;
  }
  if (publish_done_alarm_ == nullptr) {
    return;
  }
  MaybeSetPublishDoneAlarm();
}

void LiveSubscriber::OnPublishDone(uint64_t stream_count,
                                   const quic::QuicClock* clock,
                                   quic::QuicAlarmFactory* alarm_factory) {
  total_streams_ = stream_count;
  clock_ = clock;
  if (all_streams_closed()) {
    request_stream()->Fin();
    // Fin will destroy the class.
    return;
  }
  publish_done_alarm_ = std::unique_ptr<quic::QuicAlarm>(
      alarm_factory->CreateAlarm(new PublishDoneDelegate(weak_ptr())));
  MaybeSetPublishDoneAlarm();
}

void LiveSubscriber::MaybeSetPublishDoneAlarm() {
  if (currently_open_streams_ == 0 && total_streams_.has_value() &&
      clock_ != nullptr) {
    quic::QuicTimeDelta timeout =
        std::max(object_delivery_timeout(), subgroup_delivery_timeout());
    timeout = std::min(timeout, kMaxPublishDoneTimeout);
    timeout = std::max(timeout, kMinPublishDoneTimeout);
    publish_done_alarm_->Set(clock_->ApproximateNow() + timeout);
  }
}

void LiveSubscriber::OnJoiningFetchReady(
    std::unique_ptr<MoqtFetchTask> fetch_task) {
  fetch_task_ = std::move(fetch_task);
  fetch_task_->SetObjectAvailableCallback([this]() { FetchObjects(); });
}

void LiveSubscriber::FetchObjects() {
  if (fetch_task_ == nullptr) {
    return;
  }
  if (visitor_ == nullptr || !fetch_task_->GetStatus().ok()) {
    fetch_task_.reset();
    return;
  }
  while (true) {
    PublishedObject object;
    switch (fetch_task_->GetNextObject(object)) {
      case MoqtFetchTask::GetNextObjectResult::kSuccess:
        if (object.metadata.payload_length == 0) {
          QUICHE_DCHECK_EQ(fetch_object_offset_, 0);
          visitor_->OnObjectFragment(full_track_name(), object.metadata, "", 0);
          break;
        }
        for (size_t i = 0; i < object.payload.size(); ++i) {
          if (fetch_object_offset_ > 0 && object.payload[i].empty()) {
            QUICHE_BUG(LiveSubscriber_empty_payload)
                << "Empty payload for partial object "
                << object.metadata.location;
            continue;
          }
          visitor_->OnObjectFragment(full_track_name(), object.metadata,
                                     object.payload[i].AsStringView(),
                                     fetch_object_offset_);
          fetch_object_offset_ += object.payload[i].length();
          if (fetch_object_offset_ == object.metadata.payload_length) {
            fetch_object_offset_ = 0;
            break;
          }
        }
        break;
      case MoqtFetchTask::GetNextObjectResult::kError:
      case MoqtFetchTask::GetNextObjectResult::kEof:
        fetch_task_.reset();
        return;
      case MoqtFetchTask::GetNextObjectResult::kPending:
        return;
    }
  }
}

void LiveSubscriber::SendObjectAck(uint64_t group_id, uint64_t object_id,
                                   quic::QuicTimeDelta delta_from_deadline) {
  request_stream()->SendOrBufferMessageOrFatal(
      request_stream()->framer()->SerializeObjectAck(
          {group_id, object_id, delta_from_deadline}));
}

UpstreamFetchTask::~UpstreamFetchTask() {
  // Set status_ so that callbacks into UpstreamFetchTask exit early.
  status_ = absl::CancelledError("UpstreamFetchTask destroyed");
  if (task_destroyed_callback_) {
    std::move(task_destroyed_callback_)();
  }
}

MoqtFetchTask::GetNextObjectResult UpstreamFetchTask::GetNextObject(
    PublishedObject& output) {
  if (!next_object_.has_value()) {
    if (!status_.ok()) {
      return kError;
    }
    if (eof_) {
      return kEof;
    }
    need_object_available_callback_ = true;
    return kPending;
  }
  if (next_object_->payload_length > 0 && payload_.empty()) {
    need_object_available_callback_ = true;
    return kPending;
  }
  while (!payload_.empty()) {
    payload_offset_ += payload_.front().length();
    output.payload.push_back(std::move(payload_.front()));
    payload_.pop_front();
  }
  output.metadata.location =
      Location(next_object_->group_id, next_object_->object_id);
  output.metadata.subgroup = next_object_->subgroup_id;
  output.metadata.status = next_object_->object_status;
  output.metadata.publisher_priority = next_object_->publisher_priority;
  output.metadata.payload_length = next_object_->payload_length;
  output.fin_after_this = false;
  if (payload_offset_ == next_object_->payload_length) {
    next_object_.reset();
    payload_offset_ = 0;
    payload_length_ = 0;
  }
  if (can_read_callback_) {
    can_read_callback_();
  }
  return kSuccess;
}

void UpstreamFetchTask::NewObject(const MoqtObject& message) {
  next_object_ = message;
  while (!payload_.empty()) {
    payload_.pop_front();
  };
  payload_offset_ = 0;
  payload_length_ = 0;
}

void UpstreamFetchTask::AppendPayloadToObject(absl::string_view payload) {
  QUICHE_BUG_IF(quic_bug_AppendPayloadToObjectCalledEarly,
                !next_object_.has_value())
      << "AppendPayloadToObject called without an object";
  QUICHE_BUG_IF(quic_bug_AlreadyGotPayload, next_object_->payload_length == 0)
      << "AppendPayloadToObject called after payload was already full";
  // Copy |payload| to the right spot in the buffer.
  payload_length_ += payload.length();
  payload_.push_back(quiche::QuicheMemSlice::Copy(payload));
}

void UpstreamFetchTask::NotifyNewObject() {
  if (need_object_available_callback_ && object_available_callback_) {
    need_object_available_callback_ = false;
    object_available_callback_();
  }
}

void UpstreamFetchTask::OnStreamAndFetchClosed(absl::Status status) {
  if (eof_ || !status_.ok()) {
    return;
  }
  // Delete callbacks, because IncomingDataStream and FetchRequestStream are
  // gone.
  can_read_callback_ = nullptr;
  task_destroyed_callback_ = nullptr;
  status_ = status;
  eof_ = status.ok();
  if (need_object_available_callback_ &&
      object_available_callback_ != nullptr) {
    need_object_available_callback_ = false;
    object_available_callback_();
  }
}

}  // namespace moqt