# Copyright 2020 Huawei Technologies Co., Ltd
#
# 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.
# ============================================================================
"""Bert for pretraining."""
import numpy as np

import mindspore.nn as nn
from mindspore.common.initializer import initializer, TruncatedNormal
from mindspore.ops import operations as P
from mindspore.ops import functional as F
from mindspore.ops import composite as C
from mindspore.common.tensor import Tensor
from mindspore.common.parameter import Parameter, ParameterTuple
from mindspore.common import dtype as mstype
from mindspore.nn.wrap.grad_reducer import DistributedGradReducer
from mindspore.context import ParallelMode
from mindspore.communication.management import get_group_size
from mindspore import context
from mindspore.ops import _selected_ops
from .bert_model import BertModel

GRADIENT_CLIP_TYPE = 1
GRADIENT_CLIP_VALUE = 1.0

clip_grad = C.MultitypeFuncGraph("clip_grad")


# pylint: disable=consider-using-in
@clip_grad.register("Number", "Number", "Tensor")
def _clip_grad(clip_type, clip_value, grad):
    """
    Clip gradients.

    Inputs:
        clip_type (int): The way to clip, 0 for 'value', 1 for 'norm'.
        clip_value (float): Specifies how much to clip.
        grad (tuple[Tensor]): Gradients.

    Outputs:
        tuple[Tensor], clipped gradients.
    """
    if clip_type != 0 and clip_type != 1:
        return grad
    dt = F.dtype(grad)
    if clip_type == 0:
        new_grad = C.clip_by_value(grad, F.cast(F.tuple_to_array((-clip_value,)), dt),
                                   F.cast(F.tuple_to_array((clip_value,)), dt))
    else:
        new_grad = nn.ClipByNorm()(grad, F.cast(F.tuple_to_array((clip_value,)), dt))
    return new_grad


class GetMaskedLMOutput(nn.Cell):
    """
    Get masked lm output.

    Args:
        config (BertConfig): The config of BertModel.

    Returns:
        Tensor, masked lm output.
    """
    def __init__(self, config):
        super(GetMaskedLMOutput, self).__init__()
        self.width = config.hidden_size
        self.reshape = P.Reshape()
        self.gather = P.GatherV2()

        weight_init = TruncatedNormal(config.initializer_range)
        self.dense = nn.Dense(self.width,
                              config.hidden_size,
                              weight_init=weight_init,
                              activation=config.hidden_act).to_float(config.compute_type)
        self.layernorm = nn.LayerNorm((config.hidden_size,)).to_float(config.compute_type)
        self.output_bias = Parameter(
            initializer(
                'zero',
                config.vocab_size),
            name='output_bias')
        self.matmul = P.MatMul(transpose_b=True)
        self.log_softmax = nn.LogSoftmax(axis=-1)
        self.shape_flat_offsets = (-1, 1)
        self.rng = Tensor(np.array(range(0, config.batch_size)).astype(np.int32))
        self.last_idx = (-1,)
        self.shape_flat_sequence_tensor = (config.batch_size * config.seq_length, self.width)
        self.seq_length_tensor = Tensor(np.array((config.seq_length,)).astype(np.int32))
        self.cast = P.Cast()
        self.compute_type = config.compute_type
        self.dtype = config.dtype

    def construct(self,
                  input_tensor,
                  output_weights,
                  positions):
        flat_offsets = self.reshape(
            self.rng * self.seq_length_tensor, self.shape_flat_offsets)
        flat_position = self.reshape(positions + flat_offsets, self.last_idx)
        flat_sequence_tensor = self.reshape(input_tensor, self.shape_flat_sequence_tensor)
        input_tensor = self.gather(flat_sequence_tensor, flat_position, 0)
        input_tensor = self.cast(input_tensor, self.compute_type)
        output_weights = self.cast(output_weights, self.compute_type)
        input_tensor = self.dense(input_tensor)
        input_tensor = self.layernorm(input_tensor)
        logits = self.matmul(input_tensor, output_weights)
        logits = self.cast(logits, self.dtype)
        logits = logits + self.output_bias
        log_probs = self.log_softmax(logits)
        return log_probs


class GetNextSentenceOutput(nn.Cell):
    """
    Get next sentence output.

    Args:
        config (BertConfig): The config of Bert.

    Returns:
        Tensor, next sentence output.
    """
    def __init__(self, config):
        super(GetNextSentenceOutput, self).__init__()
        self.log_softmax = _selected_ops.LogSoftmax()
        weight_init = TruncatedNormal(config.initializer_range)
        self.dense = nn.Dense(config.hidden_size, 2,
                              weight_init=weight_init, has_bias=True).to_float(config.compute_type)
        self.dtype = config.dtype
        self.cast = P.Cast()

    def construct(self, input_tensor):
        logits = self.dense(input_tensor)
        logits = self.cast(logits, self.dtype)
        log_prob = self.log_softmax(logits)
        return log_prob


class BertPreTraining(nn.Cell):
    """
    Bert pretraining network.

    Args:
        config (BertConfig): The config of BertModel.
        is_training (bool): Specifies whether to use the training mode.
        use_one_hot_embeddings (bool): Specifies whether to use one-hot for embeddings.

    Returns:
        Tensor, prediction_scores, seq_relationship_score.
    """
    def __init__(self, config, is_training, use_one_hot_embeddings):
        super(BertPreTraining, self).__init__()
        self.bert = BertModel(config, is_training, use_one_hot_embeddings)
        self.cls1 = GetMaskedLMOutput(config)
        self.cls2 = GetNextSentenceOutput(config)

    def construct(self, input_ids, input_mask, token_type_id,
                  masked_lm_positions):
        sequence_output, pooled_output, embedding_table = \
            self.bert(input_ids, token_type_id, input_mask)
        prediction_scores = self.cls1(sequence_output,
                                      embedding_table,
                                      masked_lm_positions)
        seq_relationship_score = self.cls2(pooled_output)
        return prediction_scores, seq_relationship_score


class BertPretrainingLoss(nn.Cell):
    """
    Provide bert pre-training loss.

    Args:
        config (BertConfig): The config of BertModel.

    Returns:
        Tensor, total loss.
    """
    def __init__(self, config):
        super(BertPretrainingLoss, self).__init__()
        self.vocab_size = config.vocab_size
        self.onehot = P.OneHot()
        self.on_value = Tensor(1.0, mstype.float32)
        self.off_value = Tensor(0.0, mstype.float32)
        self.reduce_sum = P.ReduceSum()
        self.reduce_mean = P.ReduceMean()
        self.reshape = P.Reshape()
        self.last_idx = (-1,)
        self.neg = P.Neg()
        self.cast = P.Cast()

    def construct(self, prediction_scores, seq_relationship_score, masked_lm_ids,
                  masked_lm_weights, next_sentence_labels):
        """Defines the computation performed."""
        label_ids = self.reshape(masked_lm_ids, self.last_idx)
        label_weights = self.cast(self.reshape(masked_lm_weights, self.last_idx), mstype.float32)
        one_hot_labels = self.onehot(label_ids, self.vocab_size, self.on_value, self.off_value)

        per_example_loss = self.neg(self.reduce_sum(prediction_scores * one_hot_labels, self.last_idx))
        numerator = self.reduce_sum(label_weights * per_example_loss, ())
        denominator = self.reduce_sum(label_weights, ()) + self.cast(F.tuple_to_array((1e-5,)), mstype.float32)
        masked_lm_loss = numerator / denominator

        # next_sentence_loss
        labels = self.reshape(next_sentence_labels, self.last_idx)
        one_hot_labels = self.onehot(labels, 2, self.on_value, self.off_value)
        per_example_loss = self.neg(self.reduce_sum(
            one_hot_labels * seq_relationship_score, self.last_idx))
        next_sentence_loss = self.reduce_mean(per_example_loss, self.last_idx)

        # total_loss
        total_loss = masked_lm_loss + next_sentence_loss

        return total_loss


class BertNetworkWithLoss(nn.Cell):
    """
    Provide bert pre-training loss through network.

    Args:
        config (BertConfig): The config of BertModel.
        is_training (bool): Specifies whether to use the training mode.
        use_one_hot_embeddings (bool): Specifies whether to use one-hot for embeddings. Default: False.

    Returns:
        Tensor, the loss of the network.
    """
    def __init__(self, config, is_training, use_one_hot_embeddings=False):
        super(BertNetworkWithLoss, self).__init__()
        self.bert = BertPreTraining(config, is_training, use_one_hot_embeddings)
        self.loss = BertPretrainingLoss(config)
        self.cast = P.Cast()

    def construct(self,
                  input_ids,
                  input_mask,
                  token_type_id,
                  next_sentence_labels,
                  masked_lm_positions,
                  masked_lm_ids,
                  masked_lm_weights):
        prediction_scores, seq_relationship_score = \
            self.bert(input_ids, input_mask, token_type_id, masked_lm_positions)
        total_loss = self.loss(prediction_scores, seq_relationship_score,
                               masked_lm_ids, masked_lm_weights, next_sentence_labels)
        return self.cast(total_loss, mstype.float32)


class BertTrainOneStepCell(nn.Cell):
    """
    Encapsulation class of bert network training.

    Append an optimizer to the training network after that the construct
    function can be called to create the backward graph.

    Args:
        network (Cell): The training network. Note that loss function should have been added.
        optimizer (Optimizer): Optimizer for updating the weights.
        sens (Number): The adjust parameter. Default: 1.0.
    """
    def __init__(self, network, optimizer, sens=1.0):
        super(BertTrainOneStepCell, self).__init__(auto_prefix=False)
        self.network = network
        self.weights = ParameterTuple(network.trainable_params())
        self.optimizer = optimizer
        self.grad = C.GradOperation(get_by_list=True, sens_param=True)
        self.sens = sens
        self.reducer_flag = False
        self.parallel_mode = context.get_auto_parallel_context("parallel_mode")
        if self.parallel_mode in [ParallelMode.DATA_PARALLEL, ParallelMode.HYBRID_PARALLEL]:
            self.reducer_flag = True
        self.grad_reducer = None
        if self.reducer_flag:
            mean = context.get_auto_parallel_context("gradients_mean")
            degree = get_group_size()
            self.grad_reducer = DistributedGradReducer(optimizer.parameters, mean, degree)

        self.cast = P.Cast()
        self.hyper_map = C.HyperMap()

    def set_sens(self, value):
        self.sens = value

    def construct(self,
                  input_ids,
                  input_mask,
                  token_type_id,
                  next_sentence_labels,
                  masked_lm_positions,
                  masked_lm_ids,
                  masked_lm_weights):
        """Defines the computation performed."""
        weights = self.weights

        loss = self.network(input_ids,
                            input_mask,
                            token_type_id,
                            next_sentence_labels,
                            masked_lm_positions,
                            masked_lm_ids,
                            masked_lm_weights)
        grads = self.grad(self.network, weights)(input_ids,
                                                 input_mask,
                                                 token_type_id,
                                                 next_sentence_labels,
                                                 masked_lm_positions,
                                                 masked_lm_ids,
                                                 masked_lm_weights,
                                                 self.cast(F.tuple_to_array((self.sens,)),
                                                           mstype.float32))
        grads = self.hyper_map(F.partial(clip_grad, GRADIENT_CLIP_TYPE, GRADIENT_CLIP_VALUE), grads)
        if self.reducer_flag:
            # apply grad reducer on grads
            grads = self.grad_reducer(grads)
        succ = self.optimizer(grads)
        return F.depend(loss, succ)


grad_scale = C.MultitypeFuncGraph("grad_scale")
reciprocal = P.Reciprocal()


@grad_scale.register("Tensor", "Tensor")
def tensor_grad_scale(scale, grad):
    return grad * reciprocal(scale)


class BertTrainOneStepWithLossScaleCell(nn.Cell):
    """
    Encapsulation class of bert network training.

    Append an optimizer to the training network after that the construct
    function can be called to create the backward graph.

    Args:
        network (Cell): The training network. Note that loss function should have been added.
        optimizer (Optimizer): Optimizer for updating the weights.
        scale_update_cell (Cell): Cell to do the loss scale. Default: None.
    """
    def __init__(self, network, optimizer, scale_update_cell=None):
        super(BertTrainOneStepWithLossScaleCell, self).__init__(auto_prefix=False)
        self.network = network
        self.weights = ParameterTuple(network.trainable_params())
        self.optimizer = optimizer
        self.grad = C.GradOperation(get_by_list=True,
                                    sens_param=True)
        self.reducer_flag = False
        self.allreduce = P.AllReduce()
        self.parallel_mode = context.get_auto_parallel_context("parallel_mode")
        if self.parallel_mode in [ParallelMode.DATA_PARALLEL, ParallelMode.HYBRID_PARALLEL]:
            self.reducer_flag = True
        self.grad_reducer = F.identity
        self.degree = 1
        if self.reducer_flag:
            self.degree = get_group_size()
            self.grad_reducer = DistributedGradReducer(optimizer.parameters, False, self.degree)
        self.is_distributed = (self.parallel_mode != ParallelMode.STAND_ALONE)
        self.cast = P.Cast()
        self.alloc_status = P.NPUAllocFloatStatus()
        self.get_status = P.NPUGetFloatStatus()
        self.clear_before_grad = P.NPUClearFloatStatus()
        self.reduce_sum = P.ReduceSum(keep_dims=False)
        self.depend_parameter_use = P.ControlDepend(depend_mode=1)
        self.base = Tensor(1, mstype.float32)
        self.less_equal = P.LessEqual()
        self.hyper_map = C.HyperMap()
        self.loss_scale = None
        self.loss_scaling_manager = scale_update_cell
        if scale_update_cell:
            self.loss_scale = Parameter(Tensor(scale_update_cell.get_loss_scale(), dtype=mstype.float32),
                                        name="loss_scale")

    @C.add_flags(has_effect=True)
    def construct(self,
                  input_ids,
                  input_mask,
                  token_type_id,
                  next_sentence_labels,
                  masked_lm_positions,
                  masked_lm_ids,
                  masked_lm_weights,
                  sens=None):
        """Defines the computation performed."""
        weights = self.weights
        loss = self.network(input_ids,
                            input_mask,
                            token_type_id,
                            next_sentence_labels,
                            masked_lm_positions,
                            masked_lm_ids,
                            masked_lm_weights)
        if sens is None:
            scaling_sens = self.loss_scale
        else:
            scaling_sens = sens
        # alloc status and clear should be right before gradoperation
        init = self.alloc_status()
        self.clear_before_grad(init)
        grads = self.grad(self.network, weights)(input_ids,
                                                 input_mask,
                                                 token_type_id,
                                                 next_sentence_labels,
                                                 masked_lm_positions,
                                                 masked_lm_ids,
                                                 masked_lm_weights,
                                                 self.cast(scaling_sens,
                                                           mstype.float32))
        # apply grad reducer on grads
        grads = self.grad_reducer(grads)
        grads = self.hyper_map(F.partial(grad_scale, scaling_sens * self.degree), grads)
        grads = self.hyper_map(F.partial(clip_grad, GRADIENT_CLIP_TYPE, GRADIENT_CLIP_VALUE), grads)
        self.get_status(init)
        flag_sum = self.reduce_sum(init, (0,))
        if self.is_distributed:
            # sum overflow flag over devices
            flag_reduce = self.allreduce(flag_sum)
            cond = self.less_equal(self.base, flag_reduce)
        else:
            cond = self.less_equal(self.base, flag_sum)
        overflow = cond
        if sens is None:
            overflow = self.loss_scaling_manager(self.loss_scale, cond)
        if overflow:
            succ = False
        else:
            succ = self.optimizer(grads)
        ret = (loss, cond, scaling_sens)
        return F.depend(ret, succ)
