# Copyright (c) 2020 PaddlePaddle Authors. All Rights Reserve.
#
# 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
import paddle.nn as nn
import paddle.nn.functional as F
 
 
class FusedLeakyReLU(nn.Layer):
    def __init__(self, channel, bias=True, negative_slope=0.2, scale=2 ** 0.5):
        super().__init__()
 
        if bias:
            self.bias = self.create_parameter((channel,), default_initializer=nn.initializer.Constant(0.0))
 
        else:
            self.bias = None
 
        self.negative_slope = negative_slope
        self.scale = scale
 
    def forward(self, input):
        return fused_leaky_relu(input, self.bias, self.negative_slope, self.scale)
 
 
def fused_leaky_relu(input, bias=None, negative_slope=0.2, scale=2 ** 0.5):
    if bias is not None:
        rest_dim = [1] * (input.ndim - bias.ndim - 1)
        return (
            F.leaky_relu(
                input + bias.reshape((1, bias.shape[0], *rest_dim)), negative_slope=0.2
            )
            * scale
        )
 
    else:
        return F.leaky_relu(input, negative_slope=0.2) * scale
