// Copyright (c) 2021 PaddlePaddle Authors. All Rights Reserved.
//
// 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.

#include "paddle/fluid/distributed/fleet_executor/compute_interceptor.h"

#include "paddle/fluid/distributed/fleet_executor/task_node.h"

namespace paddle {
namespace distributed {

ComputeInterceptor::ComputeInterceptor(int64_t interceptor_id, TaskNode* node)
    : Interceptor(interceptor_id, node) {
  PrepareDeps();
  RegisterMsgHandle([this](const InterceptorMessage& msg) { Compute(msg); });
}

void ComputeInterceptor::PrepareDeps() {
  auto& upstream = GetTaskNode()->upstream();
  auto& downstream = GetTaskNode()->downstream();

  // TODO(wangxi): get from task node
  int64_t in_buff_size = std::numeric_limits<int64_t>::max();
  int64_t out_buff_size = 2;

  for (auto up_id : upstream) {
    in_readys_.emplace(up_id, std::make_pair(in_buff_size, 0));
    in_stops_.emplace(up_id, false);
  }
  for (auto down_id : downstream) {
    out_buffs_.emplace(down_id, std::make_pair(out_buff_size, 0));
  }
}

void ComputeInterceptor::IncreaseReady(int64_t up_id) {
  auto it = in_readys_.find(up_id);
  PADDLE_ENFORCE_NE(it, in_readys_.end(),
                    platform::errors::NotFound(
                        "Cannot find upstream=%lld in in_readys.", up_id));

  auto max_ready_size = it->second.first;
  auto ready_size = it->second.second;
  ready_size += 1;
  PADDLE_ENFORCE_LE(ready_size, max_ready_size,
                    platform::errors::OutOfRange(
                        "upstream=%lld ready_size must <= max_ready_size, but "
                        "now ready_size=%lld, max_ready_size=%lld",
                        up_id, ready_size, max_ready_size));
  it->second.second = ready_size;
}

void ComputeInterceptor::DecreaseBuff(int64_t down_id) {
  auto it = out_buffs_.find(down_id);
  PADDLE_ENFORCE_NE(it, out_buffs_.end(),
                    platform::errors::NotFound(
                        "Cannot find downstream=%lld in out_buffs.", down_id));
  auto used_size = it->second.second;
  used_size -= 1;
  PADDLE_ENFORCE_GE(
      used_size, 0,
      platform::errors::OutOfRange(
          "downstream=%lld used buff size must >= 0, but now equal %lld",
          down_id, used_size));
  it->second.second = used_size;
}

bool ComputeInterceptor::IsInputReady() {
  for (auto& ins : in_readys_) {
    auto ready_size = ins.second.second;
    // not ready, return false
    if (ready_size == 0) return false;
  }
  return true;
}

bool ComputeInterceptor::CanWriteOutput() {
  for (auto& outs : out_buffs_) {
    auto max_buffer_size = outs.second.first;
    auto used_size = outs.second.second;
    // full, return false
    if (used_size == max_buffer_size) return false;
  }
  return true;
}

void ComputeInterceptor::SendDataReadyToDownStream() {
  for (auto& outs : out_buffs_) {
    auto down_id = outs.first;
    auto max_buff_size = outs.second.first;
    auto used_size = outs.second.second;
    used_size += 1;
    PADDLE_ENFORCE_LE(
        used_size, max_buff_size,
        platform::errors::OutOfRange("downstream=%lld used buff size must <= "
                                     "max_buff_size, but now used_size=%lld, "
                                     "max_buff_size=%lld",
                                     down_id, used_size, max_buff_size));
    outs.second.second = used_size;

    InterceptorMessage ready_msg;
    ready_msg.set_message_type(DATA_IS_READY);
    VLOG(3) << "ComputeInterceptor Send data_is_ready msg to " << down_id;
    Send(down_id, ready_msg);
  }
}

void ComputeInterceptor::ReplyCompletedToUpStream() {
  for (auto& ins : in_readys_) {
    auto up_id = ins.first;
    auto ready_size = ins.second.second;
    ready_size -= 1;
    PADDLE_ENFORCE_GE(
        ready_size, 0,
        platform::errors::OutOfRange(
            "upstream=%lld ready_size must >= 0, but now got %lld", up_id,
            ready_size));
    ins.second.second = ready_size;

    InterceptorMessage reply_msg;
    reply_msg.set_message_type(DATE_IS_USELESS);
    VLOG(3) << "ComputeInterceptor Reply data_is_useless msg to " << up_id;
    Send(up_id, reply_msg);
  }
}

void ComputeInterceptor::Run() {
  while (IsInputReady() && CanWriteOutput()) {
    VLOG(3) << "id=" << GetInterceptorId() << " ComputeInterceptor running";
    // TODO(wangxi): add op run

    // send to downstream and increase buff used
    SendDataReadyToDownStream();
    // reply to upstream and decrease ready data
    ReplyCompletedToUpStream();
  }
}

void ComputeInterceptor::ReceivedStop(int64_t up_id) {
  received_stop_ = true;

  // source node has no upstream, stop is send by carrier or others
  if (up_id == -1) return;

  auto it = in_stops_.find(up_id);
  PADDLE_ENFORCE_NE(it, in_stops_.end(),
                    platform::errors::NotFound(
                        "Cannot find upstream=%lld in in_stops.", up_id));
  PADDLE_ENFORCE_EQ(
      it->second, false,
      platform::errors::AlreadyExists("Already received stop from %lld, stop "
                                      "cannot be send more than once."));
  it->second = true;
}

void ComputeInterceptor::TryStop() {
  if (!received_stop_) return;

  // can stop only when all upstream is stop and
  // downstream complete
  for (auto& in_stop : in_stops_) {
    if (!in_stop.second) return;
  }
  for (auto& out_buff : out_buffs_) {
    auto used_size = out_buff.second.second;
    if (used_size != 0) return;
  }

  // send stop to downstream
  for (auto& out : out_buffs_) {
    auto down_id = out.first;
    InterceptorMessage stop;
    stop.set_message_type(STOP);
    Send(down_id, stop);
  }
  stop_ = true;
}

void ComputeInterceptor::HandleStop(const InterceptorMessage& msg) {
  ReceivedStop(msg.src_id());

  TryStop();
}

void ComputeInterceptor::Compute(const InterceptorMessage& msg) {
  if (msg.message_type() == DATA_IS_READY) {
    IncreaseReady(msg.src_id());
    Run();
  } else if (msg.message_type() == DATE_IS_USELESS) {
    DecreaseBuff(msg.src_id());
    Run();
  }

  TryStop();
}

REGISTER_INTERCEPTOR(Compute, ComputeInterceptor);

}  // namespace distributed
}  // namespace paddle