# coding=utf-8
# Copyright 2021 The OneFlow 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 oneflow as flow
from oneflow import nn

from libai.layers import Linear, build_activation


class T5MLP(nn.Module):
    def __init__(
        self,
        hidden_size,
        ffn_hidden_size,
        output_dropout_prob=0.0,
        init_method=nn.init.xavier_normal_,
        output_layer_init_method=None,
        *,
        layer_idx=0,
    ):
        super().__init__()
        self.output_dropout_prob = output_dropout_prob

        if output_layer_init_method is None:
            output_layer_init_method = init_method

        self.dense_h_to_4h = Linear(
            hidden_size,
            ffn_hidden_size,
            bias=False,
            parallel="col",
            skip_bias_add=False,
            init_method=init_method,
            layer_idx=layer_idx,
        )

        self.activation_func = build_activation("relu")

        self.dense_4h_to_h = Linear(
            ffn_hidden_size,
            hidden_size,
            bias=False,
            parallel="row",
            skip_bias_add=False,
            init_method=output_layer_init_method,
            layer_idx=layer_idx,
        )

        self.dropout = nn.Dropout(self.output_dropout_prob)

    def forward(self, hidden_states):
        intermediate = self.dense_h_to_4h(hidden_states)
        intermediate = self.activation_func(intermediate)
        output = self.dense_4h_to_h(intermediate)
        output = self.dropout(output)
        return output


class MT5MLP(nn.Module):
    def __init__(
        self,
        hidden_size,
        ffn_hidden_size,
        output_dropout_prob=0.0,
        init_method=nn.init.xavier_normal_,
        output_layer_init_method=None,
        *,
        layer_idx=0,
    ):
        super().__init__()
        self.output_dropout_prob = output_dropout_prob

        if output_layer_init_method is None:
            output_layer_init_method = init_method

        self.wi_0 = Linear(
            hidden_size,
            ffn_hidden_size,
            bias=False,
            parallel="col",
            skip_bias_add=False,
            init_method=init_method,
            layer_idx=layer_idx,
        )

        self.wi_1 = Linear(
            hidden_size,
            ffn_hidden_size,
            bias=False,
            parallel="col",
            skip_bias_add=False,
            init_method=init_method,
            layer_idx=layer_idx,
        )

        self.wo = Linear(
            ffn_hidden_size,
            hidden_size,
            bias=False,
            parallel="row",
            skip_bias_add=False,
            init_method=output_layer_init_method,
            layer_idx=layer_idx,
        )

        self.dropout = nn.Dropout(self.output_dropout_prob)

    def forward(self, hidden_states):
        wi_0_out = self.wi_0(hidden_states)
        hidden_linear = self.wi_1(hidden_states)
        hidden_states = flow._C.fused_fast_gelu_mul(wi_0_out, hidden_linear)
        output = self.wo(hidden_states)
        output = self.dropout(output)
        return output