# Fast Fourier Convolution NeurIPS 2020
# original implementation https://github.com/pkumivision/FFC/blob/main/model_zoo/ffc.py
# paper https://proceedings.neurips.cc/paper/2020/file/2fd5d41ec6cfab47e32164d5624269b1-Paper.pdf

import numpy as np
import torch
import torch.nn as nn
import torch.nn.functional as F

from saicinpainting.training.modules.base import get_activation, BaseDiscriminator
from saicinpainting.training.modules.spatial_transform import LearnableSpatialTransformWrapper
from saicinpainting.training.modules.squeeze_excitation import SELayer
from saicinpainting.utils import get_shape


class FFCSE_block(nn.Module):

    def __init__(self, channels, ratio_g):
        super(FFCSE_block, self).__init__()
        in_cg = int(channels * ratio_g)
        in_cl = channels - in_cg
        r = 16

        self.avgpool = nn.AdaptiveAvgPool2d((1, 1))
        self.conv1 = nn.Conv2d(channels, channels // r,
                               kernel_size=1, bias=True)
        self.relu1 = nn.ReLU(inplace=True)
        self.conv_a2l = None if in_cl == 0 else nn.Conv2d(
            channels // r, in_cl, kernel_size=1, bias=True)
        self.conv_a2g = None if in_cg == 0 else nn.Conv2d(
            channels // r, in_cg, kernel_size=1, bias=True)
        self.sigmoid = nn.Sigmoid()

    def forward(self, x):
        x = x if type(x) is tuple else (x, 0)
        id_l, id_g = x

        x = id_l if type(id_g) is int else torch.cat([id_l, id_g], dim=1)
        x = self.avgpool(x)
        x = self.relu1(self.conv1(x))

        x_l = 0 if self.conv_a2l is None else id_l * \
            self.sigmoid(self.conv_a2l(x))
        x_g = 0 if self.conv_a2g is None else id_g * \
            self.sigmoid(self.conv_a2g(x))
        return x_l, x_g


class FourierUnit(nn.Module):

    def __init__(self, in_channels, out_channels, groups=1, spatial_scale_factor=None, spatial_scale_mode='bilinear',
                 spectral_pos_encoding=False, use_se=False, se_kwargs=None, ffc3d=False, fft_norm='ortho'):
        # bn_layer not used
        super(FourierUnit, self).__init__()
        self.groups = groups

        self.conv_layer = torch.nn.Conv2d(in_channels=in_channels * 2 + (2 if spectral_pos_encoding else 0),
                                          out_channels=out_channels * 2,
                                          kernel_size=1, stride=1, padding=0, groups=self.groups, bias=False)
        self.bn = torch.nn.BatchNorm2d(out_channels * 2)
        self.relu = torch.nn.ReLU(inplace=True)

        # squeeze and excitation block
        self.use_se = use_se
        if use_se:
            if se_kwargs is None:
                se_kwargs = {}
            self.se = SELayer(self.conv_layer.in_channels, **se_kwargs)

        self.spatial_scale_factor = spatial_scale_factor
        self.spatial_scale_mode = spatial_scale_mode
        self.spectral_pos_encoding = spectral_pos_encoding
        self.ffc3d = ffc3d
        self.fft_norm = fft_norm

    def forward(self, x):
        batch = x.shape[0]

        if self.spatial_scale_factor is not None:
            orig_size = x.shape[-2:]
            x = F.interpolate(x, scale_factor=self.spatial_scale_factor, mode=self.spatial_scale_mode, align_corners=False)

        r_size = x.size()
        # (batch, c, h, w/2+1, 2)
        fft_dim = (-3, -2, -1) if self.ffc3d else (-2, -1)
        ffted = torch.fft.rfftn(x, dim=fft_dim, norm=self.fft_norm)
        ffted = torch.stack((ffted.real, ffted.imag), dim=-1)
        ffted = ffted.permute(0, 1, 4, 2, 3).contiguous()  # (batch, c, 2, h, w/2+1)
        ffted = ffted.view((batch, -1,) + ffted.size()[3:])

        if self.spectral_pos_encoding:
            height, width = ffted.shape[-2:]
            coords_vert = torch.linspace(0, 1, height)[None, None, :, None].expand(batch, 1, height, width).to(ffted)
            coords_hor = torch.linspace(0, 1, width)[None, None, None, :].expand(batch, 1, height, width).to(ffted)
            ffted = torch.cat((coords_vert, coords_hor, ffted), dim=1)

        if self.use_se:
            ffted = self.se(ffted)

        ffted = self.conv_layer(ffted)  # (batch, c*2, h, w/2+1)
        ffted = self.relu(self.bn(ffted))

        ffted = ffted.view((batch, -1, 2,) + ffted.size()[2:]).permute(
            0, 1, 3, 4, 2).contiguous()  # (batch,c, t, h, w/2+1, 2)
        ffted = torch.complex(ffted[..., 0], ffted[..., 1])

        ifft_shape_slice = x.shape[-3:] if self.ffc3d else x.shape[-2:]
        output = torch.fft.irfftn(ffted, s=ifft_shape_slice, dim=fft_dim, norm=self.fft_norm)

        if self.spatial_scale_factor is not None:
            output = F.interpolate(output, size=orig_size, mode=self.spatial_scale_mode, align_corners=False)

        return output


class SeparableFourierUnit(nn.Module):

    def __init__(self, in_channels, out_channels, groups=1, kernel_size=3):
        # bn_layer not used
        super(SeparableFourierUnit, self).__init__()
        self.groups = groups
        row_out_channels = out_channels // 2
        col_out_channels = out_channels - row_out_channels
        self.row_conv = torch.nn.Conv2d(in_channels=in_channels * 2,
                                        out_channels=row_out_channels * 2,
                                        kernel_size=(kernel_size, 1),  # kernel size is always like this, but the data will be transposed
                                        stride=1, padding=(kernel_size // 2, 0),
                                        padding_mode='reflect',
                                        groups=self.groups, bias=False)
        self.col_conv = torch.nn.Conv2d(in_channels=in_channels * 2,
                                        out_channels=col_out_channels * 2,
                                        kernel_size=(kernel_size, 1),  # kernel size is always like this, but the data will be transposed
                                        stride=1, padding=(kernel_size // 2, 0),
                                        padding_mode='reflect',
                                        groups=self.groups, bias=False)
        self.row_bn = torch.nn.BatchNorm2d(row_out_channels * 2)
        self.col_bn = torch.nn.BatchNorm2d(col_out_channels * 2)
        self.relu = torch.nn.ReLU(inplace=True)

    def process_branch(self, x, conv, bn):
        batch = x.shape[0]

        r_size = x.size()
        # (batch, c, h, w/2+1, 2)
        ffted = torch.fft.rfft(x, norm="ortho")
        ffted = torch.stack((ffted.real, ffted.imag), dim=-1)
        ffted = ffted.permute(0, 1, 4, 2, 3).contiguous()  # (batch, c, 2, h, w/2+1)
        ffted = ffted.view((batch, -1,) + ffted.size()[3:])

        ffted = self.relu(bn(conv(ffted)))

        ffted = ffted.view((batch, -1, 2,) + ffted.size()[2:]).permute(
            0, 1, 3, 4, 2).contiguous()  # (batch,c, t, h, w/2+1, 2)
        ffted = torch.complex(ffted[..., 0], ffted[..., 1])

        output = torch.fft.irfft(ffted, s=x.shape[-1:], norm="ortho")
        return output


    def forward(self, x):
        rowwise = self.process_branch(x, self.row_conv, self.row_bn)
        colwise = self.process_branch(x.permute(0, 1, 3, 2), self.col_conv, self.col_bn).permute(0, 1, 3, 2)
        out = torch.cat((rowwise, colwise), dim=1)
        return out


class SpectralTransform(nn.Module):

    def __init__(self, in_channels, out_channels, stride=1, groups=1, enable_lfu=True, separable_fu=False, **fu_kwargs):
        # bn_layer not used
        super(SpectralTransform, self).__init__()
        self.enable_lfu = enable_lfu
        if stride == 2:
            self.downsample = nn.AvgPool2d(kernel_size=(2, 2), stride=2)
        else:
            self.downsample = nn.Identity()

        self.stride = stride
        self.conv1 = nn.Sequential(
            nn.Conv2d(in_channels, out_channels //
                      2, kernel_size=1, groups=groups, bias=False),
            nn.BatchNorm2d(out_channels // 2),
            nn.ReLU(inplace=True)
        )
        fu_class = SeparableFourierUnit if separable_fu else FourierUnit
        self.fu = fu_class(
            out_channels // 2, out_channels // 2, groups, **fu_kwargs)
        if self.enable_lfu:
            self.lfu = fu_class(
                out_channels // 2, out_channels // 2, groups)
        self.conv2 = torch.nn.Conv2d(
            out_channels // 2, out_channels, kernel_size=1, groups=groups, bias=False)

    def forward(self, x):

        x = self.downsample(x)
        x = self.conv1(x)
        output = self.fu(x)

        if self.enable_lfu:
            n, c, h, w = x.shape
            split_no = 2
            split_s = h // split_no
            xs = torch.cat(torch.split(
                x[:, :c // 4], split_s, dim=-2), dim=1).contiguous()
            xs = torch.cat(torch.split(xs, split_s, dim=-1),
                           dim=1).contiguous()
            xs = self.lfu(xs)
            xs = xs.repeat(1, 1, split_no, split_no).contiguous()
        else:
            xs = 0

        output = self.conv2(x + output + xs)

        return output


class FFC(nn.Module):

    def __init__(self, in_channels, out_channels, kernel_size,
                 ratio_gin, ratio_gout, stride=1, padding=0,
                 dilation=1, groups=1, bias=False, enable_lfu=True,
                 padding_type='reflect', gated=False, **spectral_kwargs):
        super(FFC, self).__init__()

        assert stride == 1 or stride == 2, "Stride should be 1 or 2."
        self.stride = stride

        in_cg = int(in_channels * ratio_gin)
        in_cl = in_channels - in_cg
        out_cg = int(out_channels * ratio_gout)
        out_cl = out_channels - out_cg
        #groups_g = 1 if groups == 1 else int(groups * ratio_gout)
        #groups_l = 1 if groups == 1 else groups - groups_g

        self.ratio_gin = ratio_gin
        self.ratio_gout = ratio_gout
        self.global_in_num = in_cg

        module = nn.Identity if in_cl == 0 or out_cl == 0 else nn.Conv2d
        self.convl2l = module(in_cl, out_cl, kernel_size,
                              stride, padding, dilation, groups, bias, padding_mode=padding_type)
        module = nn.Identity if in_cl == 0 or out_cg == 0 else nn.Conv2d
        self.convl2g = module(in_cl, out_cg, kernel_size,
                              stride, padding, dilation, groups, bias, padding_mode=padding_type)
        module = nn.Identity if in_cg == 0 or out_cl == 0 else nn.Conv2d
        self.convg2l = module(in_cg, out_cl, kernel_size,
                              stride, padding, dilation, groups, bias, padding_mode=padding_type)
        module = nn.Identity if in_cg == 0 or out_cg == 0 else SpectralTransform
        self.convg2g = module(
            in_cg, out_cg, stride, 1 if groups == 1 else groups // 2, enable_lfu, **spectral_kwargs)

        self.gated = gated
        module = nn.Identity if in_cg == 0 or out_cl == 0 or not self.gated else nn.Conv2d
        self.gate = module(in_channels, 2, 1)

    def forward(self, x):
        x_l, x_g = x if type(x) is tuple else (x, 0)
        out_xl, out_xg = 0, 0

        if self.gated:
            total_input_parts = [x_l]
            if torch.is_tensor(x_g):
                total_input_parts.append(x_g)
            total_input = torch.cat(total_input_parts, dim=1)

            gates = torch.sigmoid(self.gate(total_input))
            g2l_gate, l2g_gate = gates.chunk(2, dim=1)
        else:
            g2l_gate, l2g_gate = 1, 1

        if self.ratio_gout != 1:
            out_xl = self.convl2l(x_l) + self.convg2l(x_g) * g2l_gate
        if self.ratio_gout != 0:
            out_xg = self.convl2g(x_l) * l2g_gate + self.convg2g(x_g)

        return out_xl, out_xg


class FFC_BN_ACT(nn.Module):

    def __init__(self, in_channels, out_channels,
                 kernel_size, ratio_gin, ratio_gout,
                 stride=1, padding=0, dilation=1, groups=1, bias=False,
                 norm_layer=nn.BatchNorm2d, activation_layer=nn.Identity,
                 padding_type='reflect',
                 enable_lfu=True, **kwargs):
        super(FFC_BN_ACT, self).__init__()
        self.ffc = FFC(in_channels, out_channels, kernel_size,
                       ratio_gin, ratio_gout, stride, padding, dilation,
                       groups, bias, enable_lfu, padding_type=padding_type, **kwargs)
        lnorm = nn.Identity if ratio_gout == 1 else norm_layer
        gnorm = nn.Identity if ratio_gout == 0 else norm_layer
        global_channels = int(out_channels * ratio_gout)
        self.bn_l = lnorm(out_channels - global_channels)
        self.bn_g = gnorm(global_channels)

        lact = nn.Identity if ratio_gout == 1 else activation_layer
        gact = nn.Identity if ratio_gout == 0 else activation_layer
        self.act_l = lact(inplace=True)
        self.act_g = gact(inplace=True)

    def forward(self, x):
        x_l, x_g = self.ffc(x)
        x_l = self.act_l(self.bn_l(x_l))
        x_g = self.act_g(self.bn_g(x_g))
        return x_l, x_g


class FFCResnetBlock(nn.Module):
    def __init__(self, dim, padding_type, norm_layer, activation_layer=nn.ReLU, dilation=1,
                 spatial_transform_kwargs=None, inline=False, **conv_kwargs):
        super().__init__()
        self.conv1 = FFC_BN_ACT(dim, dim, kernel_size=3, padding=dilation, dilation=dilation,
                                norm_layer=norm_layer,
                                activation_layer=activation_layer,
                                padding_type=padding_type,
                                **conv_kwargs)
        self.conv2 = FFC_BN_ACT(dim, dim, kernel_size=3, padding=dilation, dilation=dilation,
                                norm_layer=norm_layer,
                                activation_layer=activation_layer,
                                padding_type=padding_type,
                                **conv_kwargs)
        if spatial_transform_kwargs is not None:
            self.conv1 = LearnableSpatialTransformWrapper(self.conv1, **spatial_transform_kwargs)
            self.conv2 = LearnableSpatialTransformWrapper(self.conv2, **spatial_transform_kwargs)
        self.inline = inline

    def forward(self, x):
        if self.inline:
            x_l, x_g = x[:, :-self.conv1.ffc.global_in_num], x[:, -self.conv1.ffc.global_in_num:]
        else:
            x_l, x_g = x if type(x) is tuple else (x, 0)

        id_l, id_g = x_l, x_g

        x_l, x_g = self.conv1((x_l, x_g))
        x_l, x_g = self.conv2((x_l, x_g))

        x_l, x_g = id_l + x_l, id_g + x_g
        out = x_l, x_g
        if self.inline:
            out = torch.cat(out, dim=1)
        return out


class ConcatTupleLayer(nn.Module):
    def forward(self, x):
        assert isinstance(x, tuple)
        x_l, x_g = x
        assert torch.is_tensor(x_l) or torch.is_tensor(x_g)
        if not torch.is_tensor(x_g):
            return x_l
        return torch.cat(x, dim=1)


class FFCResNetGenerator(nn.Module):
    def __init__(self, input_nc, output_nc, ngf=64, n_downsampling=3, n_blocks=9, norm_layer=nn.BatchNorm2d,
                 padding_type='reflect', activation_layer=nn.ReLU,
                 up_norm_layer=nn.BatchNorm2d, up_activation=nn.ReLU(True),
                 init_conv_kwargs={}, downsample_conv_kwargs={}, resnet_conv_kwargs={},
                 spatial_transform_layers=None, spatial_transform_kwargs={},
                 add_out_act=True, max_features=1024, out_ffc=False, out_ffc_kwargs={}):
        assert (n_blocks >= 0)
        super().__init__()

        model = [nn.ReflectionPad2d(3),
                 FFC_BN_ACT(input_nc, ngf, kernel_size=7, padding=0, norm_layer=norm_layer,
                            activation_layer=activation_layer, **init_conv_kwargs)]

        ### downsample
        for i in range(n_downsampling):
            mult = 2 ** i
            if i == n_downsampling - 1:
                cur_conv_kwargs = dict(downsample_conv_kwargs)
                cur_conv_kwargs['ratio_gout'] = resnet_conv_kwargs.get('ratio_gin', 0)
            else:
                cur_conv_kwargs = downsample_conv_kwargs
            model += [FFC_BN_ACT(min(max_features, ngf * mult),
                                 min(max_features, ngf * mult * 2),
                                 kernel_size=3, stride=2, padding=1,
                                 norm_layer=norm_layer,
                                 activation_layer=activation_layer,
                                 **cur_conv_kwargs)]

        mult = 2 ** n_downsampling
        feats_num_bottleneck = min(max_features, ngf * mult)

        ### resnet blocks
        for i in range(n_blocks):
            cur_resblock = FFCResnetBlock(feats_num_bottleneck, padding_type=padding_type, activation_layer=activation_layer,
                                          norm_layer=norm_layer, **resnet_conv_kwargs)
            if spatial_transform_layers is not None and i in spatial_transform_layers:
                cur_resblock = LearnableSpatialTransformWrapper(cur_resblock, **spatial_transform_kwargs)
            model += [cur_resblock]

        model += [ConcatTupleLayer()]

        ### upsample
        for i in range(n_downsampling):
            mult = 2 ** (n_downsampling - i)
            model += [nn.ConvTranspose2d(min(max_features, ngf * mult),
                                         min(max_features, int(ngf * mult / 2)),
                                         kernel_size=3, stride=2, padding=1, output_padding=1),
                      up_norm_layer(min(max_features, int(ngf * mult / 2))),
                      up_activation]

        if out_ffc:
            model += [FFCResnetBlock(ngf, padding_type=padding_type, activation_layer=activation_layer,
                                     norm_layer=norm_layer, inline=True, **out_ffc_kwargs)]

        model += [nn.ReflectionPad2d(3),
                  nn.Conv2d(ngf, output_nc, kernel_size=7, padding=0)]
        if add_out_act:
            model.append(get_activation('tanh' if add_out_act is True else add_out_act))
        self.model = nn.Sequential(*model)

    def forward(self, input):
        return self.model(input)


class FFCNLayerDiscriminator(BaseDiscriminator):
    def __init__(self, input_nc, ndf=64, n_layers=3, norm_layer=nn.BatchNorm2d, max_features=512,
                 init_conv_kwargs={}, conv_kwargs={}):
        super().__init__()
        self.n_layers = n_layers

        def _act_ctor(inplace=True):
            return nn.LeakyReLU(negative_slope=0.2, inplace=inplace)

        kw = 3
        padw = int(np.ceil((kw-1.0)/2))
        sequence = [[FFC_BN_ACT(input_nc, ndf, kernel_size=kw, padding=padw, norm_layer=norm_layer,
                                activation_layer=_act_ctor, **init_conv_kwargs)]]

        nf = ndf
        for n in range(1, n_layers):
            nf_prev = nf
            nf = min(nf * 2, max_features)

            cur_model = [
                FFC_BN_ACT(nf_prev, nf,
                           kernel_size=kw, stride=2, padding=padw,
                           norm_layer=norm_layer,
                           activation_layer=_act_ctor,
                           **conv_kwargs)
            ]
            sequence.append(cur_model)

        nf_prev = nf
        nf = min(nf * 2, 512)

        cur_model = [
            FFC_BN_ACT(nf_prev, nf,
                       kernel_size=kw, stride=1, padding=padw,
                       norm_layer=norm_layer,
                       activation_layer=lambda *args, **kwargs: nn.LeakyReLU(*args, negative_slope=0.2, **kwargs),
                       **conv_kwargs),
            ConcatTupleLayer()
        ]
        sequence.append(cur_model)

        sequence += [[nn.Conv2d(nf, 1, kernel_size=kw, stride=1, padding=padw)]]

        for n in range(len(sequence)):
            setattr(self, 'model'+str(n), nn.Sequential(*sequence[n]))

    def get_all_activations(self, x):
        res = [x]
        for n in range(self.n_layers + 2):
            model = getattr(self, 'model' + str(n))
            res.append(model(res[-1]))
        return res[1:]

    def forward(self, x):
        act = self.get_all_activations(x)
        feats = []
        for out in act[:-1]:
            if isinstance(out, tuple):
                if torch.is_tensor(out[1]):
                    out = torch.cat(out, dim=1)
                else:
                    out = out[0]
            feats.append(out)
        return act[-1], feats