# pylint: skip-file
# model: SRFormer
# SRFormer: Permuted Self-Attention for Single Image Super-Resolution

import math
import re

import torch
import torch.nn as nn
import torch.nn.functional as F
import torch.utils.checkpoint as checkpoint

from .timm.helpers import to_2tuple
from .timm.weight_init import trunc_normal_


class emptyModule(nn.Module):
    def __init__(self):
        super().__init__()

    def forward(self, x):
        return x


def drop_path(x, drop_prob: float = 0.0, training: bool = False):
    """Drop paths (Stochastic Depth) per sample (when applied in main path of residual blocks).

    From: https://github.com/rwightman/pytorch-image-models/blob/master/timm/models/layers/drop.py
    """
    if drop_prob == 0.0 or not training:
        return x
    keep_prob = 1 - drop_prob
    shape = (x.shape[0],) + (1,) * (
        x.ndim - 1
    )  # work with diff dim tensors, not just 2D ConvNets
    random_tensor = keep_prob + torch.rand(shape, dtype=x.dtype, device=x.device)
    random_tensor.floor_()  # binarize
    output = x.div(keep_prob) * random_tensor
    return output


class DropPath(nn.Module):
    """Drop paths (Stochastic Depth) per sample  (when applied in main path of residual blocks).

    From: https://github.com/rwightman/pytorch-image-models/blob/master/timm/models/layers/drop.py
    """

    def __init__(self, drop_prob=None):
        super(DropPath, self).__init__()
        self.drop_prob = drop_prob

    def forward(self, x):
        return drop_path(x, self.drop_prob, self.training)


class dwconv(nn.Module):
    def __init__(self, hidden_features):
        super(dwconv, self).__init__()
        self.depthwise_conv = nn.Sequential(
            nn.Conv2d(
                hidden_features,
                hidden_features,
                kernel_size=5,
                stride=1,
                padding=2,
                dilation=1,
                groups=hidden_features,
            ),
            nn.GELU(),
        )
        self.hidden_features = hidden_features

    def forward(self, x, x_size):
        x = (
            x.transpose(1, 2)
            .view(x.shape[0], self.hidden_features, x_size[0], x_size[1])
            .contiguous()
        )  # b Ph*Pw c
        x = self.depthwise_conv(x)
        x = x.flatten(2).transpose(1, 2).contiguous()
        return x


class ConvFFN(nn.Module):
    def __init__(
        self,
        in_features,
        hidden_features=None,
        out_features=None,
        act_layer=nn.GELU,
        drop=0.0,
    ):
        super().__init__()
        out_features = out_features or in_features
        hidden_features = hidden_features or in_features
        self.fc1 = nn.Linear(in_features, hidden_features)
        self.act = act_layer()
        self.before_add = emptyModule()
        self.after_add = emptyModule()
        self.dwconv = dwconv(hidden_features=hidden_features)
        self.fc2 = nn.Linear(hidden_features, out_features)
        self.drop = nn.Dropout(drop)

    def forward(self, x, x_size):
        x = self.fc1(x)
        x = self.act(x)
        x = self.before_add(x)
        x = x + self.dwconv(x, x_size)
        x = self.after_add(x)
        x = self.drop(x)
        x = self.fc2(x)
        x = self.drop(x)
        return x


def window_partition(x, window_size):
    """
    Args:
        x: (b, h, w, c)
        window_size (int): window size

    Returns:
        windows: (num_windows*b, window_size, window_size, c)
    """
    b, h, w, c = x.shape
    x = x.view(b, h // window_size, window_size, w // window_size, window_size, c)
    windows = (
        x.permute(0, 1, 3, 2, 4, 5).contiguous().view(-1, window_size, window_size, c)
    )
    return windows


def window_reverse(windows, window_size, h, w):
    """
    Args:
        windows: (num_windows*b, window_size, window_size, c)
        window_size (int): Window size
        h (int): Height of image
        w (int): Width of image

    Returns:
        x: (b, h, w, c)
    """
    b = int(windows.shape[0] / (h * w / window_size / window_size))
    x = windows.view(
        b, h // window_size, w // window_size, window_size, window_size, -1
    )
    x = x.permute(0, 1, 3, 2, 4, 5).contiguous().view(b, h, w, -1)
    return x


class PSA(nn.Module):
    r"""Window based multi-head self attention (W-MSA) module with relative position bias.
    It supports both of shifted and non-shifted window.

    Args:
        dim (int): Number of input channels.
        window_size (tuple[int]): The height and width of the window.
        num_heads (int): Number of attention heads.
        qkv_bias (bool, optional):  If True, add a learnable bias to query, key, value. Default: True
        qk_scale (float | None, optional): Override default qk scale of head_dim ** -0.5 if set
        attn_drop (float, optional): Dropout ratio of attention weight. Default: 0.0
        proj_drop (float, optional): Dropout ratio of output. Default: 0.0
    """

    def __init__(
        self,
        dim,
        window_size,
        num_heads,
        qkv_bias=True,
        qk_scale=None,
        attn_drop=0.0,
        proj_drop=0.0,
    ):
        super().__init__()
        self.dim = dim
        self.window_size = window_size  # Wh, Ww
        self.permuted_window_size = (window_size[0] // 2, window_size[1] // 2)
        self.num_heads = num_heads
        head_dim = dim // num_heads
        self.scale = qk_scale or head_dim**-0.5

        # define a parameter table of relative position bias
        self.relative_position_bias_table = nn.Parameter(
            torch.zeros(
                (2 * self.permuted_window_size[0] - 1)
                * (2 * self.permuted_window_size[1] - 1),
                num_heads,
            )
        )  # 2*Wh-1 * 2*Ww-1, nH

        # get pair-wise aligned relative position index for each token inside the window
        coords_h = torch.arange(self.permuted_window_size[0])
        coords_w = torch.arange(self.permuted_window_size[1])
        coords = torch.stack(torch.meshgrid([coords_h, coords_w]))  # 2, Wh, Ww
        coords_flatten = torch.flatten(coords, 1)  # 2, Wh*Ww
        relative_coords = (
            coords_flatten[:, :, None] - coords_flatten[:, None, :]
        )  # 2, Wh*Ww, Wh*Ww
        relative_coords = relative_coords.permute(
            1, 2, 0
        ).contiguous()  # Wh*Ww, Wh*Ww, 2
        relative_coords[:, :, 0] += (
            self.permuted_window_size[0] - 1
        )  # shift to start from 0
        relative_coords[:, :, 1] += self.permuted_window_size[1] - 1
        relative_coords[:, :, 0] *= 2 * self.permuted_window_size[1] - 1
        aligned_relative_position_index = relative_coords.sum(-1)  # Wh*Ww, Wh*Ww
        aligned_relative_position_index = (
            aligned_relative_position_index.reshape(
                self.permuted_window_size[0],
                self.permuted_window_size[1],
                1,
                1,
                self.permuted_window_size[0] * self.permuted_window_size[1],
            )
            .repeat(1, 1, 2, 2, 1)
            .permute(0, 2, 1, 3, 4)
            .reshape(
                4 * self.permuted_window_size[0] * self.permuted_window_size[1],
                self.permuted_window_size[0] * self.permuted_window_size[1],
            )
        )  #  FN*FN,WN*WN
        self.register_buffer(
            "aligned_relative_position_index", aligned_relative_position_index
        )
        # compresses the channel dimension of KV
        self.kv = nn.Linear(dim, dim // 2, bias=qkv_bias)
        self.q = nn.Linear(dim, dim, bias=qkv_bias)
        self.attn_drop = nn.Dropout(attn_drop)
        self.proj = nn.Linear(dim, dim)
        self.proj_drop = nn.Dropout(proj_drop)

        trunc_normal_(self.relative_position_bias_table, std=0.02)
        self.softmax = nn.Softmax(dim=-1)

    def forward(self, x, mask=None):
        """
        Args:
            x: input features with shape of (num_windows*b, n, c)
            mask: (0/-inf) mask with shape of (num_windows, Wh*Ww, Wh*Ww) or None
        """
        b_, n, c = x.shape
        # compress the channel dimension of KV :(num_windows*b, num_heads, n//4, c//num_heads)
        kv = (
            self.kv(x)
            .reshape(
                b_,
                self.permuted_window_size[0],
                2,
                self.permuted_window_size[1],
                2,
                2,
                c // 4,
            )
            .permute(0, 1, 3, 5, 2, 4, 6)
            .reshape(b_, n // 4, 2, self.num_heads, c // self.num_heads)
            .permute(2, 0, 3, 1, 4)
        )
        k, v = kv[0], kv[1]
        # keep the channel dimension of Q: (num_windows*b, num_heads, n, c//num_heads)
        q = (
            self.q(x)
            .reshape(b_, n, 1, self.num_heads, c // self.num_heads)
            .permute(2, 0, 3, 1, 4)[0]
        )
        q = q * self.scale
        attn = q @ k.transpose(-2, -1)  # (num_windows*b, num_heads, n, n//4)

        relative_position_bias = self.relative_position_bias_table[
            self.aligned_relative_position_index.view(-1)
        ].view(
            self.window_size[0] * self.window_size[1],
            self.permuted_window_size[0] * self.permuted_window_size[1],
            -1,
        )  # (n, n//4)
        relative_position_bias = relative_position_bias.permute(
            2, 0, 1
        ).contiguous()  # (num_heads, n, n//4)
        attn = attn + relative_position_bias.unsqueeze(0)

        if mask is not None:
            nw = mask.shape[0]
            attn = attn.view(b_ // nw, nw, self.num_heads, n, n // 4) + mask.unsqueeze(
                1
            ).unsqueeze(0)
            attn = attn.view(-1, self.num_heads, n, n // 4)
            attn = self.softmax(attn)
        else:
            attn = self.softmax(attn)

        attn = self.attn_drop(attn)

        x = (attn @ v).transpose(1, 2).reshape(b_, n, c)
        x = self.proj(x)
        x = self.proj_drop(x)
        return x

    def extra_repr(self) -> str:
        return f"dim={self.dim}, window_size={self.permuted_window_size}, num_heads={self.num_heads}"

    def flops(self, n):
        # calculate flops for 1 window with token length of n
        flops = 0
        # qkv = self.qkv(x)
        flops += n * self.dim * 1.5 * self.dim
        # attn = (q @ k.transpose(-2, -1))
        flops += self.num_heads * n * (self.dim // self.num_heads) * n / 4
        #  x = (attn @ v)
        flops += self.num_heads * n * n / 4 * (self.dim // self.num_heads)
        # x = self.proj(x)
        flops += n * self.dim * self.dim
        return flops


class PSA_Block(nn.Module):
    r"""Swin Transformer Block.

    Args:
        dim (int): Number of input channels.
        input_resolution (tuple[int]): Input resolution.
        num_heads (int): Number of attention heads.
        window_size (int): Window size.
        shift_size (int): Shift size for SW-MSA.
        mlp_ratio (float): Ratio of mlp hidden dim to embedding dim.
        qkv_bias (bool, optional): If True, add a learnable bias to query, key, value. Default: True
        qk_scale (float | None, optional): Override default qk scale of head_dim ** -0.5 if set.
        drop (float, optional): Dropout rate. Default: 0.0
        attn_drop (float, optional): Attention dropout rate. Default: 0.0
        drop_path (float, optional): Stochastic depth rate. Default: 0.0
        act_layer (nn.Module, optional): Activation layer. Default: nn.GELU
        norm_layer (nn.Module, optional): Normalization layer.  Default: nn.LayerNorm
    """

    def __init__(
        self,
        dim,
        input_resolution,
        num_heads,
        window_size=7,
        shift_size=0,
        mlp_ratio=4.0,
        qkv_bias=True,
        qk_scale=None,
        drop=0.0,
        attn_drop=0.0,
        drop_path=0.0,
        act_layer=nn.GELU,
        norm_layer=nn.LayerNorm,
    ):
        super().__init__()
        self.dim = dim
        self.input_resolution = input_resolution
        self.num_heads = num_heads
        self.window_size = window_size
        self.permuted_window_size = window_size // 2
        self.shift_size = shift_size
        self.mlp_ratio = mlp_ratio
        if min(self.input_resolution) <= self.window_size:
            # if window size is larger than input resolution, we don't partition windows
            self.shift_size = 0
            self.window_size = min(self.input_resolution)
        assert (
            0 <= self.shift_size < self.window_size
        ), "shift_size must in 0-window_size"
        self.norm1 = norm_layer(dim)

        self.attn = PSA(
            dim,
            window_size=to_2tuple(self.window_size),
            num_heads=num_heads,
            qkv_bias=qkv_bias,
            qk_scale=qk_scale,
            attn_drop=attn_drop,
            proj_drop=drop,
        )

        self.drop_path = DropPath(drop_path) if drop_path > 0.0 else nn.Identity()

        self.norm2 = norm_layer(dim)
        mlp_hidden_dim = int(dim * mlp_ratio)
        self.mlp = ConvFFN(
            in_features=dim,
            hidden_features=mlp_hidden_dim,
            act_layer=act_layer,
            drop=drop,
        )

        if self.shift_size > 0:
            attn_mask = self.calculate_mask(self.input_resolution)
        else:
            attn_mask = None
        self.register_buffer("attn_mask", attn_mask)

        # emptyModule for Power Spectrum Based Evaluation
        self.after_norm1 = emptyModule()
        self.after_attention = emptyModule()
        self.residual_after_attention = emptyModule()
        self.after_norm2 = emptyModule()
        self.after_mlp = emptyModule()
        self.residual_after_mlp = emptyModule()

    def calculate_mask(self, x_size):
        # calculate mask for original windows
        h, w = x_size
        img_mask = torch.zeros((1, h, w, 1))  # 1 h w 1
        h_slices = (
            slice(0, -self.window_size),
            slice(-self.window_size, -self.shift_size),
            slice(-self.shift_size, None),
        )
        w_slices = (
            slice(0, -self.window_size),
            slice(-self.window_size, -self.shift_size),
            slice(-self.shift_size, None),
        )
        cnt = 0
        for h in h_slices:
            for w in w_slices:
                img_mask[:, h, w, :] = cnt
                cnt += 1

        mask_windows = window_partition(
            img_mask, self.window_size
        )  # nw, window_size, window_size, 1
        mask_windows = mask_windows.view(-1, self.window_size * self.window_size)
        # calculate mask for permuted windows
        h, w = x_size
        permuted_window_mask = torch.zeros((1, h // 2, w // 2, 1))  # 1 h w 1
        h_slices = (
            slice(0, -self.permuted_window_size),
            slice(-self.permuted_window_size, -self.shift_size // 2),
            slice(-self.shift_size // 2, None),
        )
        w_slices = (
            slice(0, -self.permuted_window_size),
            slice(-self.permuted_window_size, -self.shift_size // 2),
            slice(-self.shift_size // 2, None),
        )
        cnt = 0
        for h in h_slices:
            for w in w_slices:
                permuted_window_mask[:, h, w, :] = cnt
                cnt += 1

        permuted_windows = window_partition(
            permuted_window_mask, self.permuted_window_size
        )
        permuted_windows = permuted_windows.view(
            -1, self.permuted_window_size * self.permuted_window_size
        )
        # calculate attention mask
        attn_mask = mask_windows.unsqueeze(2) - permuted_windows.unsqueeze(1)
        attn_mask = attn_mask.masked_fill(attn_mask != 0, float(-100.0)).masked_fill(
            attn_mask == 0, float(0.0)
        )

        return attn_mask

    def forward(self, x, x_size):
        h, w = x_size
        b, _, c = x.shape
        # assert seq_len == h * w, "input feature has wrong size"

        shortcut = x
        x = self.norm1(x)
        x = self.after_norm1(x)
        x = x.view(b, h, w, c)

        # cyclic shift
        if self.shift_size > 0:
            shifted_x = torch.roll(
                x, shifts=(-self.shift_size, -self.shift_size), dims=(1, 2)
            )
        else:
            shifted_x = x

        # partition windows
        x_windows = window_partition(
            shifted_x, self.window_size
        )  # nw*b, window_size, window_size, c
        x_windows = x_windows.view(
            -1, self.window_size * self.window_size, c
        )  # nw*b, window_size*window_size, c

        # W-MSA/SW-MSA (to be compatible for testing on images whose shapes are the multiple of window size
        if self.input_resolution == x_size:
            attn_windows = self.attn(
                x_windows, mask=self.attn_mask
            )  # nw*b, window_size*window_size, c
        else:
            attn_windows = self.attn(
                x_windows, mask=self.calculate_mask(x_size).to(x.device)
            )

        # merge windows
        attn_windows = attn_windows.view(-1, self.window_size, self.window_size, c)
        shifted_x = window_reverse(attn_windows, self.window_size, h, w)  # b h' w' c

        # reverse cyclic shift
        if self.shift_size > 0:
            x = torch.roll(
                shifted_x, shifts=(self.shift_size, self.shift_size), dims=(1, 2)
            )
        else:
            x = shifted_x
        x = x.view(b, h * w, c)
        x = self.after_attention(x)
        # FFN
        x = shortcut + self.drop_path(x)
        x = self.residual_after_attention(x)
        x = self.residual_after_mlp(
            x
            + self.drop_path(
                self.after_mlp(self.mlp(self.after_norm2(self.norm2(x)), x_size))
            )
        )

        return x

    def extra_repr(self) -> str:
        return (
            f"dim={self.dim}, input_resolution={self.input_resolution}, num_heads={self.num_heads}, "
            f"window_size={self.window_size}, shift_size={self.shift_size}, mlp_ratio={self.mlp_ratio}"
        )

    def flops(self):
        flops = 0
        h, w = self.input_resolution
        # norm1
        flops += self.dim * h * w
        # W-MSA/SW-MSA
        nw = h * w / self.window_size / self.window_size
        flops += nw * self.attn.flops(self.window_size * self.window_size)
        # mlp
        flops += 2 * h * w * self.dim * self.dim * self.mlp_ratio
        flops += h * w * self.dim * 25
        # norm2
        flops += self.dim * h * w
        return flops


class PatchMerging(nn.Module):
    r"""Patch Merging Layer.

    Args:
        input_resolution (tuple[int]): Resolution of input feature.
        dim (int): Number of input channels.
        norm_layer (nn.Module, optional): Normalization layer.  Default: nn.LayerNorm
    """

    def __init__(self, input_resolution, dim, norm_layer=nn.LayerNorm):
        super().__init__()
        self.input_resolution = input_resolution
        self.dim = dim
        self.reduction = nn.Linear(4 * dim, 2 * dim, bias=False)
        self.norm = norm_layer(4 * dim)

    def forward(self, x):
        """
        x: b, h*w, c
        """
        h, w = self.input_resolution
        b, seq_len, c = x.shape
        assert seq_len == h * w, "input feature has wrong size"
        assert h % 2 == 0 and w % 2 == 0, f"x size ({h}*{w}) are not even."

        x = x.view(b, h, w, c)

        x0 = x[:, 0::2, 0::2, :]  # b h/2 w/2 c
        x1 = x[:, 1::2, 0::2, :]  # b h/2 w/2 c
        x2 = x[:, 0::2, 1::2, :]  # b h/2 w/2 c
        x3 = x[:, 1::2, 1::2, :]  # b h/2 w/2 c
        x = torch.cat([x0, x1, x2, x3], -1)  # b h/2 w/2 4*c
        x = x.view(b, -1, 4 * c)  # b h/2*w/2 4*c

        x = self.norm(x)
        x = self.reduction(x)

        return x

    def extra_repr(self) -> str:
        return f"input_resolution={self.input_resolution}, dim={self.dim}"

    def flops(self):
        h, w = self.input_resolution
        flops = h * w * self.dim
        flops += (h // 2) * (w // 2) * 4 * self.dim * 2 * self.dim
        return flops


class BasicLayer(nn.Module):
    """A basic Swin Transformer layer for one stage.

    Args:
        dim (int): Number of input channels.
        input_resolution (tuple[int]): Input resolution.
        depth (int): Number of blocks.
        num_heads (int): Number of attention heads.
        window_size (int): Local window size.
        mlp_ratio (float): Ratio of mlp hidden dim to embedding dim.
        qkv_bias (bool, optional): If True, add a learnable bias to query, key, value. Default: True
        qk_scale (float | None, optional): Override default qk scale of head_dim ** -0.5 if set.
        drop (float, optional): Dropout rate. Default: 0.0
        attn_drop (float, optional): Attention dropout rate. Default: 0.0
        drop_path (float | tuple[float], optional): Stochastic depth rate. Default: 0.0
        norm_layer (nn.Module, optional): Normalization layer. Default: nn.LayerNorm
        downsample (nn.Module | None, optional): Downsample layer at the end of the layer. Default: None
        use_checkpoint (bool): Whether to use checkpointing to save memory. Default: False.
    """

    def __init__(
        self,
        dim,
        input_resolution,
        depth,
        num_heads,
        window_size,
        mlp_ratio=4.0,
        qkv_bias=True,
        qk_scale=None,
        drop=0.0,
        attn_drop=0.0,
        drop_path=0.0,
        norm_layer=nn.LayerNorm,
        downsample=None,
        use_checkpoint=False,
    ):
        super().__init__()
        self.dim = dim
        self.input_resolution = input_resolution
        self.depth = depth
        self.use_checkpoint = use_checkpoint

        # build blocks
        self.blocks = nn.ModuleList(
            [
                PSA_Block(
                    dim=dim,
                    input_resolution=input_resolution,
                    num_heads=num_heads,
                    window_size=window_size,
                    shift_size=0 if (i % 2 == 0) else window_size // 2,
                    mlp_ratio=mlp_ratio,
                    qkv_bias=qkv_bias,
                    qk_scale=qk_scale,
                    drop=drop,
                    attn_drop=attn_drop,
                    drop_path=drop_path[i]
                    if isinstance(drop_path, list)
                    else drop_path,
                    norm_layer=norm_layer,
                )
                for i in range(depth)
            ]
        )

        # patch merging layer
        if downsample is not None:
            self.downsample = downsample(
                input_resolution, dim=dim, norm_layer=norm_layer
            )
        else:
            self.downsample = None

    def forward(self, x, x_size):
        for blk in self.blocks:
            if self.use_checkpoint:
                x = checkpoint.checkpoint(blk, x)
            else:
                x = blk(x, x_size)
        if self.downsample is not None:
            x = self.downsample(x)
        return x

    def extra_repr(self) -> str:
        return f"dim={self.dim}, input_resolution={self.input_resolution}, depth={self.depth}"

    def flops(self):
        flops = 0
        for blk in self.blocks:
            flops += blk.flops()
        if self.downsample is not None:
            flops += self.downsample.flops()
        return flops


class PSA_Group(nn.Module):
    """Residual Swin Transformer Block (PSA_Group).

    Args:
        dim (int): Number of input channels.
        input_resolution (tuple[int]): Input resolution.
        depth (int): Number of blocks.
        num_heads (int): Number of attention heads.
        window_size (int): Local window size.
        mlp_ratio (float): Ratio of mlp hidden dim to embedding dim.
        qkv_bias (bool, optional): If True, add a learnable bias to query, key, value. Default: True
        qk_scale (float | None, optional): Override default qk scale of head_dim ** -0.5 if set.
        drop (float, optional): Dropout rate. Default: 0.0
        attn_drop (float, optional): Attention dropout rate. Default: 0.0
        drop_path (float | tuple[float], optional): Stochastic depth rate. Default: 0.0
        norm_layer (nn.Module, optional): Normalization layer. Default: nn.LayerNorm
        downsample (nn.Module | None, optional): Downsample layer at the end of the layer. Default: None
        use_checkpoint (bool): Whether to use checkpointing to save memory. Default: False.
        img_size: Input image size.
        patch_size: Patch size.
        resi_connection: The convolutional block before residual connection.
    """

    def __init__(
        self,
        dim,
        input_resolution,
        depth,
        num_heads,
        window_size,
        mlp_ratio=4.0,
        qkv_bias=True,
        qk_scale=None,
        drop=0.0,
        attn_drop=0.0,
        drop_path=0.0,
        norm_layer=nn.LayerNorm,
        downsample=None,
        use_checkpoint=False,
        img_size=224,
        patch_size=4,
        resi_connection="1conv",
    ):
        super(PSA_Group, self).__init__()

        self.dim = dim
        self.input_resolution = input_resolution

        self.residual_group = BasicLayer(
            dim=dim,
            input_resolution=input_resolution,
            depth=depth,
            num_heads=num_heads,
            window_size=window_size,
            mlp_ratio=mlp_ratio,
            qkv_bias=qkv_bias,
            qk_scale=qk_scale,
            drop=drop,
            attn_drop=attn_drop,
            drop_path=drop_path,
            norm_layer=norm_layer,
            downsample=downsample,
            use_checkpoint=use_checkpoint,
        )

        if resi_connection == "1conv":
            self.conv = nn.Conv2d(dim, dim, 3, 1, 1)
        elif resi_connection == "3conv":
            # to save parameters and memory
            self.conv = nn.Sequential(
                nn.Conv2d(dim, dim // 4, 3, 1, 1),
                nn.LeakyReLU(negative_slope=0.2, inplace=True),
                nn.Conv2d(dim // 4, dim // 4, 1, 1, 0),
                nn.LeakyReLU(negative_slope=0.2, inplace=True),
                nn.Conv2d(dim // 4, dim, 3, 1, 1),
            )

        self.patch_embed = PatchEmbed(
            img_size=img_size,
            patch_size=patch_size,
            in_chans=0,
            embed_dim=dim,
            norm_layer=None,
        )

        self.patch_unembed = PatchUnEmbed(
            img_size=img_size,
            patch_size=patch_size,
            in_chans=0,
            embed_dim=dim,
            norm_layer=None,
        )

        self.before_PSA_Group_conv = emptyModule()
        self.after_PSA_Group_conv = emptyModule()
        self.after_PSA_Group_Residual = emptyModule()

    def forward(self, x, x_size):
        return self.after_PSA_Group_Residual(
            self.after_PSA_Group_conv(
                self.patch_embed(
                    self.conv(
                        self.patch_unembed(
                            self.before_PSA_Group_conv(self.residual_group(x, x_size)),
                            x_size,
                        )
                    )
                )
            )
            + x
        )

    def flops(self):
        flops = 0
        flops += self.residual_group.flops()
        h, w = self.input_resolution
        flops += h * w * self.dim * self.dim * 9
        flops += self.patch_embed.flops()
        flops += self.patch_unembed.flops()

        return flops


class PatchEmbed(nn.Module):
    r"""Image to Patch Embedding

    Args:
        img_size (int): Image size.  Default: 224.
        patch_size (int): Patch token size. Default: 4.
        in_chans (int): Number of input image channels. Default: 3.
        embed_dim (int): Number of linear projection output channels. Default: 96.
        norm_layer (nn.Module, optional): Normalization layer. Default: None
    """

    def __init__(
        self,
        img_size=224,
        window_size=22,
        patch_size=4,
        in_chans=3,
        embed_dim=96,
        norm_layer=None,
    ):
        super().__init__()
        if img_size % window_size != 0:
            img_size = img_size + (window_size - img_size % window_size)
        img_size = to_2tuple(img_size)
        patch_size = to_2tuple(patch_size)
        patches_resolution = [
            img_size[0] // patch_size[0],
            img_size[1] // patch_size[1],
        ]
        self.img_size = img_size
        self.patch_size = patch_size
        self.patches_resolution = patches_resolution
        self.num_patches = patches_resolution[0] * patches_resolution[1]

        self.in_chans = in_chans
        self.embed_dim = embed_dim

        if norm_layer is not None:
            self.norm = norm_layer(embed_dim)
        else:
            self.norm = None

    def forward(self, x):
        x = x.flatten(2).transpose(1, 2)  # b Ph*Pw c
        if self.norm is not None:
            x = self.norm(x)
        return x

    def flops(self):
        flops = 0
        h, w = self.img_size
        if self.norm is not None:
            flops += h * w * self.embed_dim
        return flops


class PatchUnEmbed(nn.Module):
    r"""Image to Patch Unembedding

    Args:
        img_size (int): Image size.  Default: 224.
        patch_size (int): Patch token size. Default: 4.
        in_chans (int): Number of input image channels. Default: 3.
        embed_dim (int): Number of linear projection output channels. Default: 96.
        norm_layer (nn.Module, optional): Normalization layer. Default: None
    """

    def __init__(
        self,
        img_size=224,
        window_size=24,
        patch_size=4,
        in_chans=3,
        embed_dim=96,
        norm_layer=None,
    ):
        super().__init__()
        if img_size % window_size != 0:
            img_size = img_size + (window_size - img_size % window_size)
        img_size = to_2tuple(img_size)
        patch_size = to_2tuple(patch_size)
        patches_resolution = [
            img_size[0] // patch_size[0],
            img_size[1] // patch_size[1],
        ]
        self.img_size = img_size
        self.patch_size = patch_size
        self.patches_resolution = patches_resolution
        self.num_patches = patches_resolution[0] * patches_resolution[1]
        self.in_chans = in_chans
        self.embed_dim = embed_dim

    def forward(self, x, x_size):
        x = x.transpose(1, 2).view(
            x.shape[0], self.embed_dim, x_size[0], x_size[1]
        )  # b Ph*Pw c
        return x

    def flops(self):
        flops = 0
        return flops


class Upsample(nn.Sequential):
    """Upsample module.

    Args:
        scale (int): Scale factor. Supported scales: 2^n and 3.
        num_feat (int): Channel number of intermediate features.
    """

    def __init__(self, scale, num_feat):
        m = []
        if (scale & (scale - 1)) == 0:  # scale = 2^n
            for _ in range(int(math.log(scale, 2))):
                m.append(nn.Conv2d(num_feat, 4 * num_feat, 3, 1, 1))
                m.append(nn.PixelShuffle(2))
        elif scale == 3:
            m.append(nn.Conv2d(num_feat, 9 * num_feat, 3, 1, 1))
            m.append(nn.PixelShuffle(3))
        else:
            raise ValueError(
                f"scale {scale} is not supported. Supported scales: 2^n and 3."
            )
        super(Upsample, self).__init__(*m)


class UpsampleOneStep(nn.Sequential):
    """UpsampleOneStep module (the difference with Upsample is that it always only has 1conv + 1pixelshuffle)
       Used in lightweight SR to save parameters.

    Args:
        scale (int): Scale factor. Supported scales: 2^n and 3.
        num_feat (int): Channel number of intermediate features.

    """

    def __init__(self, scale, num_feat, num_out_ch, input_resolution=None):
        self.num_feat = num_feat
        self.input_resolution = input_resolution
        m = []
        m.append(nn.Conv2d(num_feat, (scale**2) * num_out_ch, 3, 1, 1))
        m.append(nn.PixelShuffle(scale))
        super(UpsampleOneStep, self).__init__(*m)

    def flops(self):
        h, w = self.input_resolution
        flops = h * w * self.num_feat * 3 * 9
        return flops


class SRFormer(nn.Module):
    r"""SRFormer
        A PyTorch implement of : `SRFormer: Permuted Self-Attention for Single Image Super-Resolution`, based on Swin Transformer.

    Args:
        img_size (int | tuple(int)): Input image size. Default 64
        patch_size (int | tuple(int)): Patch size. Default: 1
        in_chans (int): Number of input image channels. Default: 3
        embed_dim (int): Patch embedding dimension. Default: 96
        depths (tuple(int)): Depth of each Swin Transformer layer.
        num_heads (tuple(int)): Number of attention heads in different layers.
        window_size (int): Window size. Default: 7
        mlp_ratio (float): Ratio of mlp hidden dim to embedding dim. Default: 4
        qkv_bias (bool): If True, add a learnable bias to query, key, value. Default: True
        qk_scale (float): Override default qk scale of head_dim ** -0.5 if set. Default: None
        drop_rate (float): Dropout rate. Default: 0
        attn_drop_rate (float): Attention dropout rate. Default: 0
        drop_path_rate (float): Stochastic depth rate. Default: 0.1
        norm_layer (nn.Module): Normalization layer. Default: nn.LayerNorm.
        ape (bool): If True, add absolute position embedding to the patch embedding. Default: False
        patch_norm (bool): If True, add normalization after patch embedding. Default: True
        use_checkpoint (bool): Whether to use checkpointing to save memory. Default: False
        upscale: Upscale factor. 2/3/4/8 for image SR, 1 for denoising and compress artifact reduction
        img_range: Image range. 1. or 255.
        upsampler: The reconstruction reconstruction module. 'pixelshuffle'/'pixelshuffledirect'/'nearest+conv'/None
        resi_connection: The convolutional block before residual connection. '1conv'/'3conv'
    """

    def __init__(self, state_dict):
        super(SRFormer, self).__init__()

        # Default
        img_size = 64
        patch_size = 1
        in_chans = 3
        embed_dim = 96
        depths = (6, 6, 6, 6)
        num_heads = (6, 6, 6, 6)
        window_size = 7
        mlp_ratio = 4.0
        qkv_bias = True
        qk_scale = None
        drop_rate = 0.0
        attn_drop_rate = 0.0
        drop_path_rate = 0.1
        norm_layer = nn.LayerNorm
        ape = False
        patch_norm = True
        use_checkpoint = False
        upscale = 2
        img_range = 1.0
        upsampler = ""
        resi_connection = "1conv"

        self.model_arch = "SRFormer"
        self.sub_type = "SR"
        self.state = state_dict

        state_keys = list(state_dict.keys())

        if "conv_before_upsample.0.weight" in state_keys:
            if "conv_up1.weight" in state_keys:
                upsampler = "nearest+conv"
            else:
                upsampler = "pixelshuffle"
        elif "upsample.0.weight" in state_keys:
            upsampler = "pixelshuffledirect"
        else:
            upsampler = ""

        num_feat = (
            state_dict.get("conv_before_upsample.0.weight", None).shape[1]
            if state_dict.get("conv_before_upsample.weight", None)
            else 64
        )

        num_in_ch = state_dict["conv_first.weight"].shape[1]
        in_chans = num_in_ch
        if "conv_last.weight" in state_keys:
            num_out_ch = state_dict["conv_last.weight"].shape[0]
        else:
            num_out_ch = num_in_ch

        upscale = 1
        if upsampler == "nearest+conv":
            upsample_keys = [
                x for x in state_keys if "conv_up" in x and "bias" not in x
            ]

            for upsample_key in upsample_keys:
                upscale *= 2
        elif upsampler == "pixelshuffle":
            upsample_keys = [
                x
                for x in state_keys
                if "upsample" in x and "conv" not in x and "bias" not in x
            ]
            for upsample_key in upsample_keys:
                shape = state_dict[upsample_key].shape[0]
                upscale *= math.sqrt(shape // num_feat)
            upscale = int(upscale)
        elif upsampler == "pixelshuffledirect":
            upscale = int(
                math.sqrt(state_dict["upsample.0.bias"].shape[0] // num_out_ch)
            )

        max_layer_num = 0
        max_block_num = 0
        for key in state_keys:
            result = re.match(
                r"layers.(\d*).residual_group.blocks.(\d*).norm1.weight", key
            )
            if result:
                layer_num, block_num = result.groups()
                max_layer_num = max(max_layer_num, int(layer_num))
                max_block_num = max(max_block_num, int(block_num))

        depths = [max_block_num + 1 for _ in range(max_layer_num + 1)]

        if (
            "layers.0.residual_group.blocks.0.attn.relative_position_bias_table"
            in state_keys
        ):
            num_heads_num = state_dict[
                "layers.0.residual_group.blocks.0.attn.relative_position_bias_table"
            ].shape[-1]
            num_heads = [num_heads_num for _ in range(max_layer_num + 1)]
        else:
            num_heads = depths

        embed_dim = state_dict["conv_first.weight"].shape[0]

        mlp_ratio = float(
            state_dict["layers.0.residual_group.blocks.0.mlp.fc1.bias"].shape[0]
            / embed_dim
        )

        if "layers.0.conv.4.weight" in state_keys:
            resi_connection = "3conv"
        else:
            resi_connection = "1conv"

        window_size = int(
            math.sqrt(
                state_dict[
                    "layers.0.residual_group.blocks.0.attn.aligned_relative_position_index"
                ].shape[0]
            )
        )

        if "layers.0.residual_group.blocks.1.attn_mask" in state_keys:
            img_size = int(
                (
                    math.sqrt(
                        state_dict["layers.0.residual_group.blocks.1.attn_mask"].shape[
                            0
                        ]
                    )
                )
                * 16
            )

        self.in_nc = num_in_ch
        self.out_nc = num_out_ch
        self.num_feat = num_feat
        self.embed_dim = embed_dim
        self.num_heads = num_heads
        self.depths = depths
        self.window_size = window_size
        self.mlp_ratio = mlp_ratio
        self.scale = upscale
        self.upsampler = upsampler
        self.img_size = img_size
        self.img_range = img_range
        self.resi_connection = resi_connection

        self.supports_fp16 = False  # Too much weirdness to support this at the moment
        self.supports_bfp16 = True
        self.min_size_restriction = 16

        num_in_ch = in_chans
        num_out_ch = in_chans
        num_feat = 64
        self.img_range = img_range
        if in_chans == 3:
            rgb_mean = (0.4488, 0.4371, 0.4040)
            self.mean = torch.Tensor(rgb_mean).view(1, 3, 1, 1)
        else:
            self.mean = torch.zeros(1, 1, 1, 1)
        self.upscale = upscale
        self.upsampler = upsampler
        self.window_size = window_size
        # ------------------------- 1, shallow feature extraction ------------------------- #
        self.conv_first = nn.Conv2d(num_in_ch, embed_dim, 3, 1, 1)

        # ------------------------- 2, deep feature extraction ------------------------- #
        self.num_layers = len(depths)
        self.embed_dim = embed_dim
        self.ape = ape
        self.patch_norm = patch_norm
        self.num_features = embed_dim
        self.mlp_ratio = mlp_ratio

        # split image into non-overlapping patches
        self.patch_embed = PatchEmbed(
            img_size=img_size,
            window_size=window_size,
            patch_size=patch_size,
            in_chans=embed_dim,
            embed_dim=embed_dim,
            norm_layer=norm_layer if self.patch_norm else None,
        )
        num_patches = self.patch_embed.num_patches
        patches_resolution = self.patch_embed.patches_resolution
        self.patches_resolution = patches_resolution

        # merge non-overlapping patches into image
        self.patch_unembed = PatchUnEmbed(
            img_size=img_size,
            window_size=window_size,
            patch_size=patch_size,
            in_chans=embed_dim,
            embed_dim=embed_dim,
            norm_layer=norm_layer if self.patch_norm else None,
        )

        # absolute position embedding
        if self.ape:
            self.absolute_pos_embed = nn.Parameter(
                torch.zeros(1, num_patches, embed_dim)
            )
            trunc_normal_(self.absolute_pos_embed, std=0.02)

        self.pos_drop = nn.Dropout(p=drop_rate)

        # stochastic depth
        dpr = [
            x.item() for x in torch.linspace(0, drop_path_rate, sum(depths))
        ]  # stochastic depth decay rule

        # build Permuted Self Attention Group  (PSA_Group)
        self.layers = nn.ModuleList()
        for i_layer in range(self.num_layers):
            layer = PSA_Group(
                dim=embed_dim,
                input_resolution=(patches_resolution[0], patches_resolution[1]),
                depth=depths[i_layer],
                num_heads=num_heads[i_layer],
                window_size=window_size,
                mlp_ratio=self.mlp_ratio,
                qkv_bias=qkv_bias,
                qk_scale=qk_scale,
                drop=drop_rate,
                attn_drop=attn_drop_rate,
                drop_path=dpr[
                    sum(depths[:i_layer]) : sum(depths[: i_layer + 1])
                ],  # no impact on SR results
                norm_layer=norm_layer,
                downsample=None,
                use_checkpoint=use_checkpoint,
                img_size=img_size,
                patch_size=patch_size,
                resi_connection=resi_connection,
            )
            self.layers.append(layer)
        self.norm = norm_layer(self.num_features)

        # build the last conv layer in deep feature extraction
        if resi_connection == "1conv":
            self.conv_after_body = nn.Conv2d(embed_dim, embed_dim, 3, 1, 1)
        elif resi_connection == "3conv":
            # to save parameters and memory
            self.conv_after_body = nn.Sequential(
                nn.Conv2d(embed_dim, embed_dim // 4, 3, 1, 1),
                nn.LeakyReLU(negative_slope=0.2, inplace=True),
                nn.Conv2d(embed_dim // 4, embed_dim // 4, 1, 1, 0),
                nn.LeakyReLU(negative_slope=0.2, inplace=True),
                nn.Conv2d(embed_dim // 4, embed_dim, 3, 1, 1),
            )

        # ------------------------- 3, high quality image reconstruction ------------------------- #
        if self.upsampler == "pixelshuffle":
            # for classical SR
            self.conv_before_upsample = nn.Sequential(
                nn.Conv2d(embed_dim, num_feat, 3, 1, 1), nn.LeakyReLU(inplace=True)
            )
            self.upsample = Upsample(upscale, num_feat)
            self.conv_last = nn.Conv2d(num_feat, num_out_ch, 3, 1, 1)
        elif self.upsampler == "pixelshuffledirect":
            # for lightweight SR (to save parameters)
            self.upsample = UpsampleOneStep(
                upscale,
                embed_dim,
                num_out_ch,
                (patches_resolution[0], patches_resolution[1]),
            )
        elif self.upsampler == "nearest+conv":
            # for real-world SR (less artifacts)
            assert self.upscale == 4, "only support x4 now."
            self.conv_before_upsample = nn.Sequential(
                nn.Conv2d(embed_dim, num_feat, 3, 1, 1), nn.LeakyReLU(inplace=True)
            )
            self.conv_up1 = nn.Conv2d(num_feat, num_feat, 3, 1, 1)
            self.conv_up2 = nn.Conv2d(num_feat, num_feat, 3, 1, 1)
            self.conv_hr = nn.Conv2d(num_feat, num_feat, 3, 1, 1)
            self.conv_last = nn.Conv2d(num_feat, num_out_ch, 3, 1, 1)
            self.lrelu = nn.LeakyReLU(negative_slope=0.2, inplace=True)
        else:
            # for image denoising and JPEG compression artifact reduction
            self.conv_last = nn.Conv2d(embed_dim, num_out_ch, 3, 1, 1)

        self.apply(self._init_weights)

        self.load_state_dict(state_dict, strict=True)

    def _init_weights(self, m):
        if isinstance(m, nn.Linear):
            trunc_normal_(m.weight, std=0.02)
            if isinstance(m, nn.Linear) and m.bias is not None:
                nn.init.constant_(m.bias, 0)
        elif isinstance(m, nn.LayerNorm):
            nn.init.constant_(m.bias, 0)
            nn.init.constant_(m.weight, 1.0)

    @torch.jit.ignore
    def no_weight_decay(self):
        return {"absolute_pos_embed"}

    @torch.jit.ignore
    def no_weight_decay_keywords(self):
        return {"relative_position_bias_table"}

    def forward_features(self, x):
        x_size = (x.shape[2], x.shape[3])
        x = self.patch_embed(x)
        if self.ape:
            x = x + self.absolute_pos_embed
        x = self.pos_drop(x)

        for layer in self.layers:
            x = layer(x, x_size)

        x = self.norm(x)  # b seq_len c
        x = self.patch_unembed(x, x_size)

        return x

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

    def forward(self, x):
        H, W = x.shape[2:]
        x = self.check_image_size(x)
        self.mean = self.mean.type_as(x)
        x = (x - self.mean) * self.img_range

        if self.upsampler == "pixelshuffle":
            # for classical SR
            x = self.conv_first(x)
            x = self.conv_after_body(self.forward_features(x)) + x
            x = self.conv_before_upsample(x)
            x = self.conv_last(self.upsample(x))
        elif self.upsampler == "pixelshuffledirect":
            # for lightweight SR
            x = self.conv_first(x)
            x = self.conv_after_body(self.forward_features(x)) + x
            x = self.upsample(x)
        elif self.upsampler == "nearest+conv":
            # for real-world SR
            x = self.conv_first(x)
            x = self.conv_after_body(self.forward_features(x)) + x
            x = self.conv_before_upsample(x)
            x = self.lrelu(
                self.conv_up1(
                    torch.nn.functional.interpolate(x, scale_factor=2, mode="nearest")
                )
            )
            x = self.lrelu(
                self.conv_up2(
                    torch.nn.functional.interpolate(x, scale_factor=2, mode="nearest")
                )
            )
            x = self.conv_last(self.lrelu(self.conv_hr(x)))
        else:
            # for image denoising and JPEG compression artifact reduction
            x_first = self.conv_first(x)
            res = self.conv_after_body(self.forward_features(x_first)) + x_first
            x = x + self.conv_last(res)

        x = x / self.img_range + self.mean

        return x[:, :, : H * self.upscale, : W * self.upscale]

    def flops(self):
        flops = 0
        h, w = self.patches_resolution
        flops += h * w * 3 * self.embed_dim * 9
        flops += self.patch_embed.flops()
        for layer in self.layers:
            flops += layer.flops()
        flops += h * w * 9 * self.embed_dim * self.embed_dim
        flops += self.upsample.flops()
        return flops