/* Copyright 2023 The OpenXLA 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

    http://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.
==============================================================================*/

#ifndef XLA_BACKENDS_CPU_COLLECTIVES_IN_PROCESS_COMMUNICATOR_H_
#define XLA_BACKENDS_CPU_COLLECTIVES_IN_PROCESS_COMMUNICATOR_H_

#include <cstddef>
#include <optional>
#include <string>

#include "absl/status/status.h"
#include "absl/status/statusor.h"
#include "absl/strings/str_cat.h"
#include "absl/types/span.h"
#include "xla/core/collectives/communicator.h"
#include "xla/core/collectives/rank_id.h"
#include "xla/service/collective_ops_utils.h"
#include "xla/stream_executor/device_memory.h"
#include "xla/util.h"
#include "xla/xla_data.pb.h"

namespace xla::cpu {

// XLA communicator that implements collective operations using shared memory
// and works only within a single process.
class InProcessCommunicator : public Communicator {
 public:
  InProcessCommunicator(size_t rank, size_t num_ranks);

  absl::Status AllReduce(se::DeviceMemoryBase send_buffer,
                         se::DeviceMemoryBase recv_buffer, PrimitiveType dtype,
                         size_t count, ReductionKind reduction_kind,
                         const Executor& executor) override;

  absl::Status CollectivePermute(se::DeviceMemoryBase send_buffer,
                                 se::DeviceMemoryBase recv_buffer,
                                 PrimitiveType dtype, size_t count,
                                 std::optional<RankId> source_rank,
                                 absl::Span<const RankId> target_ranks,
                                 const Executor& executor) override;

  absl::Status AllToAll(absl::Span<const se::DeviceMemoryBase> send_buffers,
                        absl::Span<const se::DeviceMemoryBase> recv_buffers,
                        PrimitiveType dtype, size_t count,
                        const Executor& executor) override;

  absl::Status AllGather(se::DeviceMemoryBase send_buffer,
                         se::DeviceMemoryBase recv_buffer, PrimitiveType dtype,
                         size_t count, const Executor& executor) override;

  absl::Status ReduceScatter(se::DeviceMemoryBase send_buffer,
                             se::DeviceMemoryBase recv_buffer,
                             PrimitiveType dtype, size_t count,
                             ReductionKind reduction_kind,
                             const Executor& executor) override;

  absl::Status Broadcast(se::DeviceMemoryBase, se::DeviceMemoryBase,
                         PrimitiveType, size_t, RankId,
                         const Executor&) override {
    return Unimplemented("Broadcast is not implemented");
  }

  absl::Status Send(se::DeviceMemoryBase, PrimitiveType, size_t, RankId,
                    const Executor&) override {
    return Unimplemented("Send is not implemented");
  }

  absl::Status Recv(se::DeviceMemoryBase, PrimitiveType, size_t, RankId,
                    const Executor&) override {
    return Unimplemented("Recv is not implemented");
  }

  absl::StatusOr<size_t> NumRanks() const override { return num_ranks_; }

  std::string ToString() const override {
    return absl::StrCat("InProcessCommunicator [rank: ", rank_,
                        " num_ranks: ", num_ranks_, "]");
  }

 private:
  size_t rank_;
  size_t num_ranks_;
};

}  // namespace xla::cpu

#endif  // XLA_BACKENDS_CPU_COLLECTIVES_IN_PROCESS_COMMUNICATOR_H_