# 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 math
import os

import paddle
import paddle.nn as nn
import paddle.nn.functional as F
from paddle.nn import Conv2d
from paddle.nn import SyncBatchNorm as BatchNorm

from paddleseg.cvlibs import manager
from paddleseg import utils
from paddleseg.cvlibs import param_init
from paddleseg.utils import logger
from paddleseg.models.common import layer_libs, activation

__all__ = [
    "fcn_hrnet_w18_small_v1", "fcn_hrnet_w18_small_v2", "fcn_hrnet_w18",
    "fcn_hrnet_w30", "fcn_hrnet_w32", "fcn_hrnet_w40", "fcn_hrnet_w44",
    "fcn_hrnet_w48", "fcn_hrnet_w60", "fcn_hrnet_w64"
]


@manager.MODELS.add_component
class FCN(nn.Layer):
    """
    Fully Convolutional Networks for Semantic Segmentation.
    https://arxiv.org/abs/1411.4038

    Args:
        num_classes (int): the unique number of target classes.

        backbone (paddle.nn.Layer): backbone networks.

        model_pretrained (str): the path of pretrained model.

        backbone_indices (tuple): one values in the tuple indicte the indices of output of backbone.Default -1.

        backbone_channels (tuple): the same length with "backbone_indices". It indicates the channels of corresponding index.

        channels (int): channels after conv layer before the last one.
    """

    def __init__(self,
                 num_classes,
                 backbone,
                 backbone_pretrained=None,
                 model_pretrained=None,
                 backbone_indices=(-1, ),
                 backbone_channels=(270, ),
                 channels=None):
        super(FCN, self).__init__()

        self.num_classes = num_classes
        self.backbone_pretrained = backbone_pretrained
        self.model_pretrained = model_pretrained
        self.backbone_indices = backbone_indices
        if channels is None:
            channels = backbone_channels[0]

        self.backbone = backbone
        self.conv_last_2 = ConvBNLayer(
            in_channels=backbone_channels[0],
            out_channels=channels,
            kernel_size=1,
            stride=1)
        self.conv_last_1 = Conv2d(
            in_channels=channels,
            out_channels=self.num_classes,
            kernel_size=1,
            stride=1,
            padding=0)
        if self.training:
            self.init_weight()

    def forward(self, x):
        input_shape = x.shape[2:]
        fea_list = self.backbone(x)
        x = fea_list[self.backbone_indices[0]]
        x = self.conv_last_2(x)
        logit = self.conv_last_1(x)
        logit = F.resize_bilinear(logit, input_shape)
        return [logit]

    def init_weight(self):
        params = self.parameters()
        for param in params:
            param_name = param.name
            if 'batch_norm' in param_name:
                if 'w_0' in param_name:
                    param_init.constant_init(param, value=1.0)
                elif 'b_0' in param_name:
                    param_init.constant_init(param, value=0.0)
            if 'conv' in param_name and 'w_0' in param_name:
                param_init.normal_init(param, scale=0.001)

        if self.model_pretrained is not None:
            if os.path.exists(self.model_pretrained):
                utils.load_pretrained_model(self, self.model_pretrained)
            else:
                raise Exception('Pretrained model is not found: {}'.format(
                    self.model_pretrained))
        elif self.backbone_pretrained is not None:
            if os.path.exists(self.backbone_pretrained):
                utils.load_pretrained_model(self.backbone,
                                            self.backbone_pretrained)
            else:
                raise Exception('Pretrained model is not found: {}'.format(
                    self.backbone_pretrained))
        else:
            logger.warning('No pretrained model to load, train from scratch')


class ConvBNLayer(nn.Layer):
    def __init__(self,
                 in_channels,
                 out_channels,
                 kernel_size,
                 stride=1,
                 groups=1,
                 act="relu"):
        super(ConvBNLayer, self).__init__()

        self._conv = Conv2d(
            in_channels=in_channels,
            out_channels=out_channels,
            kernel_size=kernel_size,
            stride=stride,
            padding=(kernel_size - 1) // 2,
            groups=groups,
            bias_attr=False)
        self._batch_norm = BatchNorm(out_channels)
        self.act = activation.Activation(act=act)

    def forward(self, input):
        y = self._conv(input)
        y = self._batch_norm(y)
        y = self.act(y)
        return y


@manager.MODELS.add_component
def fcn_hrnet_w18_small_v1(*args, **kwargs):
    return FCN(backbone='HRNet_W18_Small_V1', backbone_channels=(240), **kwargs)


@manager.MODELS.add_component
def fcn_hrnet_w18_small_v2(*args, **kwargs):
    return FCN(backbone='HRNet_W18_Small_V2', backbone_channels=(270), **kwargs)


@manager.MODELS.add_component
def fcn_hrnet_w18(*args, **kwargs):
    return FCN(backbone='HRNet_W18', backbone_channels=(270), **kwargs)


@manager.MODELS.add_component
def fcn_hrnet_w30(*args, **kwargs):
    return FCN(backbone='HRNet_W30', backbone_channels=(450), **kwargs)


@manager.MODELS.add_component
def fcn_hrnet_w32(*args, **kwargs):
    return FCN(backbone='HRNet_W32', backbone_channels=(480), **kwargs)


@manager.MODELS.add_component
def fcn_hrnet_w40(*args, **kwargs):
    return FCN(backbone='HRNet_W40', backbone_channels=(600), **kwargs)


@manager.MODELS.add_component
def fcn_hrnet_w44(*args, **kwargs):
    return FCN(backbone='HRNet_W44', backbone_channels=(660), **kwargs)


@manager.MODELS.add_component
def fcn_hrnet_w48(*args, **kwargs):
    return FCN(backbone='HRNet_W48', backbone_channels=(720), **kwargs)


@manager.MODELS.add_component
def fcn_hrnet_w60(*args, **kwargs):
    return FCN(backbone='HRNet_W60', backbone_channels=(900), **kwargs)


@manager.MODELS.add_component
def fcn_hrnet_w64(*args, **kwargs):
    return FCN(backbone='HRNet_W64', backbone_channels=(960), **kwargs)
