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/*

 *  Copyright (c) 2021 The WebRTC project authors. All Rights Reserved.

 *  Use of this source code is governed by a BSD-style license

 *  that can be found in the LICENSE file in the root of the source

 *  tree. An additional intellectual property rights grant can be found

 *  in the file PATENTS.  All contributing project authors may

 *  be found in the AUTHORS file in the root of the source tree.

*/

#ifndef NET_DCSCTP_TX_SEND_QUEUE_H_

#define NET_DCSCTP_TX_SEND_QUEUE_H_

#include <cstdint>

#include <limits>

#include <optional>

#include <utility>

#include <vector>

#include "api/array_view.h"

#include "api/units/timestamp.h"

#include "net/dcsctp/common/internal_types.h"

#include "net/dcsctp/packet/data.h"

#include "net/dcsctp/public/types.h"

namespace dcsctp {

class SendQueue {

 public:

  // Container for a data chunk that is produced by the SendQueue

  struct DataToSend {

    DataToSend(OutgoingMessageId message_id, Data data)

        : message_id(message_id), data(std::move(data)) {}

    OutgoingMessageId message_id;

    // The data to send, including all parameters.

    Data data;

    // Partial reliability - RFC3758

    MaxRetransmits max_retransmissions = MaxRetransmits::NoLimit();

    webrtc::Timestamp expires_at = webrtc::Timestamp::PlusInfinity();

    // Lifecycle - set for the last fragment, and `LifecycleId::NotSet()` for

    // all other fragments.

    LifecycleId lifecycle_id = LifecycleId::NotSet();

};

  virtual ~SendQueue() = default;

  // TODO(boivie): This interface is obviously missing an "Add" function, but

  // that is postponed a bit until the story around how to model message

  // prioritization, which is important for any advanced stream scheduler, is

  // further clarified.

  // Produce a chunk to be sent.

//

  // `max_size` refers to how many payload bytes that may be produced, not

  // including any headers.

  virtual std::optional<DataToSend> Produce(webrtc::Timestamp now,

                                            size_t max_size) = 0;

  // Discards a partially sent message identified by the parameters

  // `stream_id` and `message_id`. The `message_id` comes from the returned

  // information when having called `Produce`. A partially sent message means

  // that it has had at least one fragment of it returned when `Produce` was

  // called prior to calling this method).

//

  // This is used when a message has been found to be expired (by the partial

  // reliability extension), and the retransmission queue will signal the

  // receiver that any partially received message fragments should be skipped.

  // This means that any remaining fragments in the Send Queue must be removed

  // as well so that they are not sent.

//

  // This function returns true if this message had unsent fragments still in

  // the queue that were discarded, and false if there were no such fragments.

  virtual bool Discard(StreamID stream_id, OutgoingMessageId message_id) = 0;

  // Prepares the stream to be reset. This is used to close a WebRTC data

  // channel and will be signaled to the other side.

//

  // Concretely, it discards all whole (not partly sent) messages in the given

  // stream and pauses that stream so that future added messages aren't

  // produced until `ResumeStreams` is called.

//

  // TODO(boivie): Investigate if it really should discard any message at all.

  // RFC8831 only mentions that "[RFC6525] also guarantees that all the messages

  // are delivered (or abandoned) before the stream is reset."

//

  // This method can be called multiple times to add more streams to be

  // reset, and paused while they are resetting. This is the first part of the

  // two-phase commit protocol to reset streams, where the caller completes the

  // procedure by either calling `CommitResetStreams` or `RollbackResetStreams`.

  virtual void PrepareResetStream(StreamID stream_id) = 0;

  // Indicates if there are any streams that are ready to be reset.

  virtual bool HasStreamsReadyToBeReset() const = 0;

  // Returns a list of streams that are ready to be included in an outgoing

  // stream reset request. Any streams that are returned here must be included

  // in an outgoing stream reset request, and there must not be concurrent

  // requests. Before calling this method again, you must have called

  virtual std::vector<StreamID> GetStreamsReadyToBeReset() = 0;

  // Called to commit to reset the streams returned by

  // `GetStreamsReadyToBeReset`. It will reset the stream sequence numbers

  // (SSNs) and message identifiers (MIDs) and resume the paused streams.

  virtual void CommitResetStreams() = 0;

  // Called to abort the resetting of streams returned by

  // `GetStreamsReadyToBeReset`. Will resume the paused streams without

  // resetting the stream sequence numbers (SSNs) or message identifiers (MIDs).

  // Note that the non-partial messages that were discarded when calling

  // `PrepareResetStreams` will not be recovered, to better match the intention

  // from the sender to "close the channel".

  virtual void RollbackResetStreams() = 0;

  // Resets all message identifier counters (MID, SSN) and makes all partially

  // messages be ready to be re-sent in full. This is used when the peer has

  // been detected to have restarted and is used to try to minimize the amount

  // of data loss. However, data loss cannot be completely guaranteed when a

  // peer restarts.

  virtual void Reset() = 0;

  // Returns the amount of buffered data. This doesn't include packets that are

  // e.g. inflight.

  virtual size_t buffered_amount(StreamID stream_id) const = 0;

  // Returns the total amount of buffer data, for all streams.

  virtual size_t total_buffered_amount() const = 0;

  // Returns the limit for the `OnBufferedAmountLow` event. Default value is 0.

  virtual size_t buffered_amount_low_threshold(StreamID stream_id) const = 0;

  // Sets a limit for the `OnBufferedAmountLow` event.

  virtual void SetBufferedAmountLowThreshold(StreamID stream_id,

                                             size_t bytes) = 0;

  // Configures the send queue to support interleaved message sending as

  // described in RFC8260. Every send queue starts with this value set as

  // disabled, but can later change it when the capabilities of the connection

  // have been negotiated. This affects the behavior of the `Produce` method.

  virtual void EnableMessageInterleaving(bool enabled) = 0;

};

}  // namespace dcsctp

#endif  // NET_DCSCTP_TX_SEND_QUEUE_H_