// Copyright 2021 The Pigweed Authors
//
// 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
//
//     https://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.

// This file defines the ServerReaderWriter, ServerReader, and ServerWriter
// classes for the raw RPC interface. These classes are used for bidirectional,
// client, and server streaming RPCs.
#pragma once

#include "pw_bytes/span.h"
#include "pw_rpc/internal/responder.h"

namespace pw::rpc {
namespace internal {

// Forward declarations for internal classes needed in friend statements.
class RawMethod;

namespace test::raw {

template <typename, auto, uint32_t, size_t, size_t>
class ServerStreamingContext;
template <typename, auto, uint32_t, size_t, size_t>
class ClientStreamingContext;
template <typename, auto, uint32_t, size_t, size_t>
class BidirectionalStreamingContext;

}  // namespace test::raw
}  // namespace internal

class RawServerReader;
class RawServerWriter;

// The RawServerReaderWriter is used to send and receive messages in a raw
// bidirectional streaming RPC.
class RawServerReaderWriter : private internal::Responder {
 public:
  constexpr RawServerReaderWriter() : RawServerReaderWriter(kHasClientStream) {}

  RawServerReaderWriter(RawServerReaderWriter&&) = default;
  RawServerReaderWriter& operator=(RawServerReaderWriter&&) = default;

  using internal::Responder::open;

  // Functions for setting the callbacks.
  using internal::Responder::set_on_client_stream_end;
  using internal::Responder::set_on_error;
  using internal::Responder::set_on_next;

  // Returns a buffer in which a response payload can be built.
  ByteSpan PayloadBuffer() { return AcquirePayloadBuffer(); }

  // Releases a buffer acquired from PayloadBuffer() without sending any data.
  void ReleaseBuffer() {
    ReleasePayloadBuffer()
        .IgnoreError();  // TODO(pwbug/387): Handle Status properly
  }

  // Sends a response packet with the given raw payload. The payload can either
  // be in the buffer previously acquired from PayloadBuffer(), or an arbitrary
  // external buffer.
  Status Write(ConstByteSpan response);

  Status Finish(Status status = OkStatus()) {
    return CloseAndSendResponse(status);
  }

 protected:
  using internal::Responder::HasClientStream;
  using internal::Responder::kHasClientStream;
  using internal::Responder::kNoClientStream;

  RawServerReaderWriter(internal::ServerCall& call,
                        HasClientStream has_client_stream = kHasClientStream)
      : internal::Responder(call, has_client_stream) {}

  constexpr RawServerReaderWriter(HasClientStream has_client_stream)
      : internal::Responder(has_client_stream) {}

  using internal::Responder::CloseAndSendResponse;

 private:
  friend class internal::RawMethod;

  template <typename, auto, uint32_t, size_t, size_t>
  friend class internal::test::raw::BidirectionalStreamingContext;
};

// The RawServerReader is used to receive messages and send a response in a
// raw client streaming RPC.
class RawServerReader : private RawServerReaderWriter {
 public:
  constexpr RawServerReader() : RawServerReaderWriter(kHasClientStream) {}

  RawServerReader(RawServerReader&&) = default;
  RawServerReader& operator=(RawServerReader&&) = default;

  using RawServerReaderWriter::open;

  using RawServerReaderWriter::set_on_client_stream_end;
  using RawServerReaderWriter::set_on_error;
  using RawServerReaderWriter::set_on_next;

  using RawServerReaderWriter::PayloadBuffer;

  Status Finish(ConstByteSpan response, Status status = OkStatus()) {
    return CloseAndSendResponse(response, status);
  }

 private:
  friend class internal::RawMethod;  // Needed for conversions from ReaderWriter

  template <typename, auto, uint32_t, size_t, size_t>
  friend class internal::test::raw::ClientStreamingContext;

  using RawServerReaderWriter::HasClientStream;

  RawServerReader(internal::ServerCall& call)
      : RawServerReaderWriter(call, kHasClientStream) {}
};

// The RawServerWriter is used to send responses in a raw server streaming RPC.
class RawServerWriter : private RawServerReaderWriter {
 public:
  constexpr RawServerWriter() : RawServerReaderWriter(kNoClientStream) {}

  RawServerWriter(RawServerWriter&&) = default;
  RawServerWriter& operator=(RawServerWriter&&) = default;

  using RawServerReaderWriter::open;

  using RawServerReaderWriter::set_on_error;

  using RawServerReaderWriter::Finish;
  using RawServerReaderWriter::PayloadBuffer;
  using RawServerReaderWriter::ReleaseBuffer;
  using RawServerReaderWriter::Write;

 private:
  friend class RawServerReaderWriter;  // Needed for conversions.

  template <typename, auto, uint32_t, size_t, size_t>
  friend class internal::test::raw::ServerStreamingContext;

  friend class internal::RawMethod;

  using RawServerReaderWriter::HasClientStream;

  RawServerWriter(internal::ServerCall& call)
      : RawServerReaderWriter(call, kNoClientStream) {}
};

}  // namespace pw::rpc