# ------------------------------------------------------------------------
# Modified from https://github.com/megvii-research/NAFNet/blob/main/basicsr/models/archs/NAFNet_arch.py
# Copyright (c) 2022 megvii-model. All Rights Reserved.
# ------------------------------------------------------------------------

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

from .arch_util import LayerNorm2d


class SimpleGate(nn.Module):

    def forward(self, x):
        x1, x2 = x.chunk(2, dim=1)
        return x1 * x2


class NAFBlock(nn.Module):

    def __init__(self, c, DW_Expand=2, FFN_Expand=2, drop_out_rate=0.):
        super().__init__()
        dw_channel = c * DW_Expand
        self.conv1 = nn.Conv2d(
            in_channels=c,
            out_channels=dw_channel,
            kernel_size=1,
            padding=0,
            stride=1,
            groups=1,
            bias=True)
        self.conv2 = nn.Conv2d(
            in_channels=dw_channel,
            out_channels=dw_channel,
            kernel_size=3,
            padding=1,
            stride=1,
            groups=dw_channel,
            bias=True)
        self.conv3 = nn.Conv2d(
            in_channels=dw_channel // 2,
            out_channels=c,
            kernel_size=1,
            padding=0,
            stride=1,
            groups=1,
            bias=True)

        # Simplified Channel Attention
        self.sca = nn.Sequential(
            nn.AdaptiveAvgPool2d(1),
            nn.Conv2d(
                in_channels=dw_channel // 2,
                out_channels=dw_channel // 2,
                kernel_size=1,
                padding=0,
                stride=1,
                groups=1,
                bias=True),
        )

        # SimpleGate
        self.sg = SimpleGate()

        ffn_channel = FFN_Expand * c
        self.conv4 = nn.Conv2d(
            in_channels=c,
            out_channels=ffn_channel,
            kernel_size=1,
            padding=0,
            stride=1,
            groups=1,
            bias=True)
        self.conv5 = nn.Conv2d(
            in_channels=ffn_channel // 2,
            out_channels=c,
            kernel_size=1,
            padding=0,
            stride=1,
            groups=1,
            bias=True)

        self.norm1 = LayerNorm2d(c)
        self.norm2 = LayerNorm2d(c)

        self.dropout1 = nn.Dropout(
            drop_out_rate) if drop_out_rate > 0. else nn.Identity()
        self.dropout2 = nn.Dropout(
            drop_out_rate) if drop_out_rate > 0. else nn.Identity()

        self.beta = nn.Parameter(torch.zeros((1, c, 1, 1)), requires_grad=True)
        self.gamma = nn.Parameter(
            torch.zeros((1, c, 1, 1)), requires_grad=True)

    def forward(self, inp):
        x = inp

        x = self.norm1(x)

        x = self.conv1(x)
        x = self.conv2(x)
        x = self.sg(x)
        x = x * self.sca(x)
        x = self.conv3(x)

        x = self.dropout1(x)

        y = inp + x * self.beta

        x = self.conv4(self.norm2(y))
        x = self.sg(x)
        x = self.conv5(x)

        x = self.dropout2(x)

        return y + x * self.gamma


class NAFNet(nn.Module):

    def __init__(self,
                 img_channel=3,
                 width=16,
                 middle_blk_num=1,
                 enc_blk_nums=[],
                 dec_blk_nums=[]):
        super().__init__()

        self.intro = nn.Conv2d(
            in_channels=img_channel,
            out_channels=width,
            kernel_size=3,
            padding=1,
            stride=1,
            groups=1,
            bias=True)
        self.ending = nn.Conv2d(
            in_channels=width,
            out_channels=img_channel,
            kernel_size=3,
            padding=1,
            stride=1,
            groups=1,
            bias=True)

        self.encoders = nn.ModuleList()
        self.decoders = nn.ModuleList()
        self.middle_blks = nn.ModuleList()
        self.ups = nn.ModuleList()
        self.downs = nn.ModuleList()

        chan = width
        for num in enc_blk_nums:
            self.encoders.append(
                nn.Sequential(*[NAFBlock(chan) for _ in range(num)]))
            self.downs.append(nn.Conv2d(chan, 2 * chan, 2, 2))
            chan = chan * 2

        self.middle_blks = \
            nn.Sequential(
                *[NAFBlock(chan) for _ in range(middle_blk_num)]
            )

        for num in dec_blk_nums:
            self.ups.append(
                nn.Sequential(
                    nn.Conv2d(chan, chan * 2, 1, bias=False),
                    nn.PixelShuffle(2)))
            chan = chan // 2
            self.decoders.append(
                nn.Sequential(*[NAFBlock(chan) for _ in range(num)]))

        self.padder_size = 2**len(self.encoders)

    def forward(self, inp):
        B, C, H, W = inp.shape
        inp = self.check_image_size(inp)

        x = self.intro(inp)

        encs = []

        for encoder, down in zip(self.encoders, self.downs):
            x = encoder(x)
            encs.append(x)
            x = down(x)

        x = self.middle_blks(x)

        for decoder, up, enc_skip in zip(self.decoders, self.ups, encs[::-1]):
            x = up(x)
            x = x + enc_skip
            x = decoder(x)

        x = self.ending(x)
        x = x + inp

        return x[:, :, :H, :W]

    def check_image_size(self, x):
        _, _, h, w = x.size()
        mod_pad_h = (self.padder_size
                     - h % self.padder_size) % self.padder_size
        mod_pad_w = (self.padder_size
                     - w % self.padder_size) % self.padder_size
        x = F.pad(x, (0, mod_pad_w, 0, mod_pad_h))
        return x


class PSNRLoss(nn.Module):

    def __init__(self, loss_weight=1.0, reduction='mean', toY=False):
        super(PSNRLoss, self).__init__()
        assert reduction == 'mean'
        self.loss_weight = loss_weight
        self.scale = 10 / np.log(10)
        self.toY = toY
        self.coef = torch.tensor([65.481, 128.553, 24.966]).reshape(1, 3, 1, 1)
        self.first = True

    def forward(self, pred, target):
        assert len(pred.size()) == 4
        if self.toY:
            if self.first:
                self.coef = self.coef.to(pred.device)
                self.first = False

            pred = (pred * self.coef).sum(dim=1).unsqueeze(dim=1) + 16.
            target = (target * self.coef).sum(dim=1).unsqueeze(dim=1) + 16.

            pred, target = pred / 255., target / 255.
            pass
        assert len(pred.size()) == 4

        return self.loss_weight * self.scale * torch.log((
            (pred - target)**2).mean(dim=(1, 2, 3)) + 1e-8).mean()