#   Copyright (c) 2022 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.

import paddle
from paddle.fluid.framework import dygraph_only
from .base.topology import ParallelMode
from paddle.distributed import fleet
from types import MethodType
from paddle.fluid import core
from paddle.fluid.dygraph import to_variable
import numpy as np
from paddle import _C_ops, _legacy_C_ops


def distributed_scaler(scaler):

    def unscale_method(self, optimizer):
        if not self._enable:
            return
        if getattr(optimizer, '_param_groups', None) and isinstance(
                optimizer._param_groups[0], dict):
            param_grads = []
            param_grads_fp16 = []
            param_grads_fp32 = []
            for group in optimizer._param_groups:
                for param in group['params']:
                    if param._grad_ivar() is not None:
                        param_grads.append(param._grad_ivar())
                        if param._grad_ivar(
                        ).dtype == core.VarDesc.VarType.FP16:
                            param_grads_fp16.append(param._grad_ivar())
                        else:
                            param_grads_fp32.append(param._grad_ivar())
        else:
            param_grads = [
                param._grad_ivar() for param in optimizer._parameter_list
                if param._grad_ivar() is not None
            ]
            param_grads_fp16 = [
                param._grad_ivar() for param in optimizer._parameter_list
                if (param._grad_ivar() is not None) and (
                    param._grad_ivar().dtype == core.VarDesc.VarType.FP16)
            ]
            param_grads_fp32 = [
                param._grad_ivar() for param in optimizer._parameter_list
                if (param._grad_ivar() is not None) and (
                    param._grad_ivar().dtype == core.VarDesc.VarType.FP32)
            ]
        temp_found_inf_fp16 = to_variable(np.array([0]).astype(np.bool_))
        temp_found_inf_fp32 = to_variable(np.array([0]).astype(np.bool_))
        if len(param_grads_fp16):
            _legacy_C_ops.check_finite_and_unscale(param_grads_fp16,
                                                   self._scale,
                                                   param_grads_fp16,
                                                   temp_found_inf_fp16)
        if len(param_grads_fp32):
            _legacy_C_ops.check_finite_and_unscale(param_grads_fp32,
                                                   self._scale,
                                                   param_grads_fp32,
                                                   temp_found_inf_fp32)

        self._found_inf = 1 if temp_found_inf_fp16 or temp_found_inf_fp32 else 0
        is_found_inf = paddle.to_tensor([self._found_inf], dtype="int32")

        # TODO(shenliang03) Since dp allreduce in the optimizer is
        # after the gradscaler, check_finite needs to synchronize global
        # information. In the future, we should use check_group to speed.
        paddle.distributed.all_reduce(is_found_inf,
                                      op=paddle.distributed.ReduceOp.MAX,
                                      group=None)
        self._found_inf = is_found_inf.numpy()[0]

    # Only data_parallel doesn't need to modify scaler
    fleet_env = fleet.fleet
    if fleet_env._hcg.get_parallel_mode() is not ParallelMode.DATA_PARALLEL:
        scaler._unscale = MethodType(unscale_method, scaler)

    return scaler