# Copyright (c) 2020 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
import paddle.nn as nn
import paddle.nn.functional as F


def SyncBatchNorm(*args, **kwargs):
    """In cpu environment nn.SyncBatchNorm does not have kernel so use nn.BatchNorm instead"""
    if paddle.get_device() == 'cpu':
        return nn.BatchNorm(*args, **kwargs)
    else:
        return nn.SyncBatchNorm(*args, **kwargs)


class ConvBNReLU(nn.Layer):
    def __init__(self,
                 in_channels,
                 out_channels,
                 kernel_size,
                 padding='same',
                 **kwargs):
        super().__init__()

        self._conv = nn.Conv2D(
            in_channels, out_channels, kernel_size, padding=padding, **kwargs)

        self._batch_norm = SyncBatchNorm(out_channels)

    def forward(self, x):
        x = self._conv(x)
        x = self._batch_norm(x)
        x = F.relu(x)
        return x


class ConvBN(nn.Layer):
    def __init__(self,
                 in_channels,
                 out_channels,
                 kernel_size,
                 padding='same',
                 **kwargs):
        super().__init__()
        self._conv = nn.Conv2D(
            in_channels, out_channels, kernel_size, padding=padding, **kwargs)
        self._batch_norm = SyncBatchNorm(out_channels)

    def forward(self, x):
        x = self._conv(x)
        x = self._batch_norm(x)
        return x

