from __future__ import absolute_import
from __future__ import division
from __future__ import print_function

import math
import torch.nn as nn
from collections import OrderedDict
from functools import partial

from lib.models.tools.module_helper import ModuleHelper 



class GlobalAvgPool2d(nn.Module):
    def __init__(self):
        """Global average pooling over the input's spatial dimensions"""
        super(GlobalAvgPool2d, self).__init__()

    def forward(self, inputs):
        in_size = inputs.size()
        return inputs.view((in_size[0], in_size[1], -1)).mean(dim=2)


class IdentityResidualBlock(nn.Module):
    def __init__(self,
                 in_channels,
                 channels,
                 stride=1,
                 dilation=1,
                 groups=1,
                 bn_type=None,
                 dropout=None):
        """Configurable identity-mapping residual block

        Parameters
        ----------
        in_channels : int
            Number of input channels.
        channels : list of int
            Number of channels in the internal feature maps. Can either have two or three elements: if three construct
            a residual block with two `3 x 3` convolutions, otherwise construct a bottleneck block with `1 x 1`, then
            `3 x 3` then `1 x 1` convolutions.
        stride : int
            Stride of the first `3 x 3` convolution
        dilation : int
            Dilation to apply to the `3 x 3` convolutions.
        groups : int
            Number of convolution groups. This is used to create ResNeXt-style blocks and is only compatible with
            bottleneck blocks.
        bn_type : callable
            Function to create normalization / activation Module.
        dropout: callable
            Function to create Dropout Module.
        """
        super(IdentityResidualBlock, self).__init__()

        # Check parameters for inconsistencies
        if len(channels) != 2 and len(channels) != 3:
            raise ValueError("channels must contain either two or three values")
        if len(channels) == 2 and groups != 1:
            raise ValueError("groups > 1 are only valid if len(channels) == 3")

        is_bottleneck = len(channels) == 3
        need_proj_conv = stride != 1 or in_channels != channels[-1]

        self.bn1 = ModuleHelper.BNReLU(in_channels, bn_type=bn_type)
        if not is_bottleneck:
            layers = [
                ("conv1", nn.Conv2d(in_channels, channels[0], 3, stride=stride, padding=dilation, bias=False,
                                    dilation=dilation)),
                ("bn2", ModuleHelper.BNReLU(channels[0], bn_type=bn_type)),
                ("conv2", nn.Conv2d(channels[0], channels[1], 3, stride=1, padding=dilation, bias=False,
                                    dilation=dilation))
            ]
            if dropout is not None:
                layers = layers[0:2] + [("dropout", dropout())] + layers[2:]
        else:
            layers = [
                ("conv1", nn.Conv2d(in_channels, channels[0], 1, stride=stride, padding=0, bias=False)),
                ("bn2", ModuleHelper.BNReLU(channels[0], bn_type=bn_type)),
                ("conv2", nn.Conv2d(channels[0], channels[1], 3, stride=1, padding=dilation, bias=False,
                                    groups=groups, dilation=dilation)),
                ("bn3", ModuleHelper.BNReLU(channels[1], bn_type=bn_type)),
                ("conv3", nn.Conv2d(channels[1], channels[2], 1, stride=1, padding=0, bias=False))
            ]
            if dropout is not None:
                layers = layers[0:4] + [("dropout", dropout())] + layers[4:]
        self.convs = nn.Sequential(OrderedDict(layers))

        if need_proj_conv:
            self.proj_conv = nn.Conv2d(in_channels, channels[-1], 1, stride=stride, padding=0, bias=False)

    def forward(self, x):
        if hasattr(self, "proj_conv"):
            bn1 = self.bn1(x)
            shortcut = self.proj_conv(bn1)
        else:
            shortcut = x.clone()
            bn1 = self.bn1(x)

        out = self.convs(bn1)
        out.add_(shortcut)

        return out


class WiderResNetA2(nn.Module):
    def __init__(self,
                 structure=[3, 3, 6, 3, 1, 1],
                 bn_type=None,
                 classes=0,
                 dilation=True):
        """Wider ResNet with pre-activation (identity mapping) blocks

        This variant uses down-sampling by max-pooling in the first two blocks and by strided convolution in the others.

        Parameters
        ----------
        structure : list of int
            Number of residual blocks in each of the six modules of the network.
        bn_type : callable
            Function to create normalization / activation Module.
        classes : int
            If not `0` also include global average pooling and a fully-connected layer with `classes` outputs at the end
            of the network.
        dilation : bool
            If `True` apply dilation to the last three modules and change the down-sampling factor from 32 to 8.
        """
        super(WiderResNetA2, self).__init__()
        self.structure = structure
        self.dilation = dilation

        if len(structure) != 6:
            raise ValueError("Expected a structure with six values")

        # Initial layers
        self.mod1 = nn.Sequential(OrderedDict([
            ("conv1", nn.Conv2d(3, 64, 3, stride=1, padding=1, bias=False))
        ]))

        # Groups of residual blocks
        in_channels = 64
        channels = [(128, 128), (256, 256), (512, 512), (512, 1024), (512, 1024, 2048), (1024, 2048, 4096)]
        for mod_id, num in enumerate(structure):
            # Create blocks for module
            blocks = []
            for block_id in range(num):
                if not dilation:
                    dil = 1
                    stride = 2 if block_id == 0 and 2 <= mod_id <= 4 else 1
                else:
                    if mod_id == 3:
                        dil = 2
                    elif mod_id > 3:
                        dil = 4
                    else:
                        dil = 1
                    stride = 2 if block_id == 0 and mod_id == 2 else 1

                if mod_id == 4:
                    drop = None
                elif mod_id == 5:
                    drop = None
                else:
                    drop = None

                blocks.append((
                    "block%d" % (block_id + 1),
                    IdentityResidualBlock(in_channels, channels[mod_id], bn_type=bn_type, stride=stride, dilation=dil,
                                          dropout=drop)
                ))

                # Update channels and p_keep
                in_channels = channels[mod_id][-1]

            # Create module
            if mod_id < 2:
                self.add_module("pool%d" % (mod_id + 2), nn.MaxPool2d(3, stride=2, padding=1, ceil_mode=True))
            self.add_module("mod%d" % (mod_id + 2), nn.Sequential(OrderedDict(blocks)))

        self.bn_out = ModuleHelper.BNReLU(in_channels, bn_type=bn_type)


    def forward(self, img):
        tuple_features = list()
        out = self.mod1(img)
        out = self.mod2(self.pool2(out))
        out = self.mod3(self.pool3(out))
        out = self.mod4(out)
        tuple_features.append(out)
        out = self.mod5(out)
        tuple_features.append(out)
        out = self.mod6(out)
        tuple_features.append(out)
        out = self.mod7(out)
        out = self.bn_out(out)
        tuple_features.append(out)
        return tuple_features