import torch
import torch.nn as nn
import torch.nn.functional as F


class RLN(nn.Module):
	r"""Revised LayerNorm"""
	def __init__(self, dim, eps=1e-5, detach_grad=False):
		super(RLN, self).__init__()
		self.eps = eps
		self.detach_grad = detach_grad

		self.weight = nn.Parameter(torch.ones((1, dim, 1, 1)))
		self.bias = nn.Parameter(torch.zeros((1, dim, 1, 1)))

		self.meta1 = nn.Conv2d(1, dim, 1)
		self.meta2 = nn.Conv2d(1, dim, 1)

	def forward(self, input):
		mean = torch.mean(input, dim=(1, 2, 3), keepdim=True)
		std = torch.sqrt((input - mean).pow(2).mean(dim=(1, 2, 3), keepdim=True) + self.eps)

		normalized_input = (input - mean) / std

		if self.detach_grad:
			rescale, rebias = self.meta1(std.detach()), self.meta2(mean.detach())
		else:
			rescale, rebias = self.meta1(std), self.meta2(mean)

		out = normalized_input * self.weight + self.bias
		return out, rescale, rebias


class Mlp(nn.Module):
	def __init__(self, network_depth, in_features, hidden_features=None, out_features=None):
		super().__init__()
		out_features = out_features or in_features
		hidden_features = hidden_features or in_features

		self.network_depth = network_depth

		self.mlp = nn.Sequential(
			nn.Conv2d(in_features, hidden_features, 1),
			nn.ReLU(True),
			nn.Conv2d(hidden_features, out_features, 1)
		)

	def forward(self, x):
		return self.mlp(x)


def window_partition(x, window_size):
	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**2, C)
	return windows


def window_reverse(windows, window_size, H, W):
	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


def get_relative_positions(window_size):
	coords_h = torch.arange(window_size)
	coords_w = torch.arange(window_size)

	coords = torch.stack(torch.meshgrid([coords_h, coords_w], indexing="ij"))  # 2, Wh, Ww
	coords_flatten = torch.flatten(coords, 1)  # 2, Wh*Ww
	relative_positions = coords_flatten[:, :, None] - coords_flatten[:, None, :]  # 2, Wh*Ww, Wh*Ww

	relative_positions = relative_positions.permute(1, 2, 0).contiguous()  # Wh*Ww, Wh*Ww, 2
	relative_positions_log  = torch.sign(relative_positions) * torch.log(1. + relative_positions.abs())

	return relative_positions_log


class WindowAttention(nn.Module):
	def __init__(self, dim, window_size, num_heads):

		super().__init__()
		self.dim = dim
		self.window_size = window_size  # Wh, Ww
		self.num_heads = num_heads
		head_dim = dim // num_heads
		self.scale = head_dim ** -0.5

		relative_positions = get_relative_positions(self.window_size)
		self.register_buffer("relative_positions", relative_positions)
		self.meta = nn.Sequential(
			nn.Linear(2, 256, bias=True),
			nn.ReLU(True),
			nn.Linear(256, num_heads, bias=True)
		)

		self.softmax = nn.Softmax(dim=-1)

	def forward(self, qkv):
		B_, N, _ = qkv.shape

		qkv = qkv.reshape(B_, N, 3, self.num_heads, self.dim // self.num_heads).permute(2, 0, 3, 1, 4)

		q, k, v = qkv[0], qkv[1], qkv[2]  # make torchscript happy (cannot use tensor as tuple)

		q = q * self.scale
		attn = (q @ k.transpose(-2, -1))

		relative_position_bias = self.meta(self.relative_positions)
		relative_position_bias = relative_position_bias.permute(2, 0, 1).contiguous()  # nH, Wh*Ww, Wh*Ww
		attn = attn + relative_position_bias.unsqueeze(0)

		attn = self.softmax(attn)

		x = (attn @ v).transpose(1, 2).reshape(B_, N, self.dim)
		return x


class Attention(nn.Module):
	def __init__(self, network_depth, dim, num_heads, window_size, shift_size, use_attn=False, conv_type=None):
		super().__init__()
		self.dim = dim
		self.head_dim = int(dim // num_heads)
		self.num_heads = num_heads

		self.window_size = window_size
		self.shift_size = shift_size

		self.network_depth = network_depth
		self.use_attn = use_attn
		self.conv_type = conv_type

		if self.conv_type == 'Conv':
			self.conv = nn.Sequential(
				nn.Conv2d(dim, dim, kernel_size=3, padding=1, padding_mode='reflect'),
				nn.ReLU(True),
				nn.Conv2d(dim, dim, kernel_size=3, padding=1, padding_mode='reflect')
			)

		if self.conv_type == 'DWConv':
			self.conv = nn.Conv2d(dim, dim, kernel_size=5, padding=2, groups=dim, padding_mode='reflect')

		if self.conv_type == 'DWConv' or self.use_attn:
			self.V = nn.Conv2d(dim, dim, 1)
			self.proj = nn.Conv2d(dim, dim, 1)

		if self.use_attn:
			self.QK = nn.Conv2d(dim, dim * 2, 1)
			self.attn = WindowAttention(dim, window_size, num_heads)

	def check_size(self, x, shift=False):
		_, _, 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

		if shift:
			x = F.pad(x, (self.shift_size, (self.window_size-self.shift_size+mod_pad_w) % self.window_size,
						  self.shift_size, (self.window_size-self.shift_size+mod_pad_h) % self.window_size), mode='reflect')
		else:
			x = F.pad(x, (0, mod_pad_w, 0, mod_pad_h), 'reflect')
		return x

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

		if self.conv_type == 'DWConv' or self.use_attn:
			V = self.V(X)

		if self.use_attn:
			QK = self.QK(X)
			QKV = torch.cat([QK, V], dim=1)

			# shift
			shifted_QKV = self.check_size(QKV, self.shift_size > 0)
			Ht, Wt = shifted_QKV.shape[2:]

			# partition windows
			shifted_QKV = shifted_QKV.permute(0, 2, 3, 1)
			qkv = window_partition(shifted_QKV, self.window_size)  # nW*B, window_size**2, C

			attn_windows = self.attn(qkv)

			# merge windows
			shifted_out = window_reverse(attn_windows, self.window_size, Ht, Wt)  # B H' W' C

			# reverse cyclic shift
			out = shifted_out[:, self.shift_size:(self.shift_size+H), self.shift_size:(self.shift_size+W), :]
			attn_out = out.permute(0, 3, 1, 2)

			if self.conv_type in ['Conv', 'DWConv']:
				conv_out = self.conv(V)
				out = self.proj(conv_out + attn_out)
			else:
				out = self.proj(attn_out)

		else:
			if self.conv_type == 'Conv':
				out = self.conv(X)				# no attention and use conv, no projection
			elif self.conv_type == 'DWConv':
				out = self.proj(self.conv(V))

		return out


class TransformerBlock(nn.Module):
	def __init__(self, network_depth, dim, num_heads, mlp_ratio=4.,
				 norm_layer=nn.LayerNorm, mlp_norm=False,
				 window_size=8, shift_size=0, use_attn=True, conv_type=None):
		super().__init__()
		self.use_attn = use_attn
		self.mlp_norm = mlp_norm

		self.norm1 = norm_layer(dim) if use_attn else nn.Identity()
		self.attn = Attention(network_depth, dim, num_heads=num_heads, window_size=window_size,
							  shift_size=shift_size, use_attn=use_attn, conv_type=conv_type)

		self.norm2 = norm_layer(dim) if use_attn and mlp_norm else nn.Identity()
		self.mlp = Mlp(network_depth, dim, hidden_features=int(dim * mlp_ratio))

	def forward(self, x):
		identity = x
		if self.use_attn: x, rescale, rebias = self.norm1(x)
		x = self.attn(x)
		if self.use_attn: x = x * rescale + rebias
		x = identity + x

		identity = x
		if self.use_attn and self.mlp_norm: x, rescale, rebias = self.norm2(x)
		x = self.mlp(x)
		if self.use_attn and self.mlp_norm: x = x * rescale + rebias
		x = identity + x
		return x


class BasicLayer(nn.Module):
	def __init__(self, network_depth, dim, depth, num_heads, mlp_ratio=4.,
				 norm_layer=nn.LayerNorm, window_size=8,
				 attn_ratio=0., attn_loc='last', conv_type=None):

		super().__init__()
		self.dim = dim
		self.depth = depth

		attn_depth = attn_ratio * depth

		if attn_loc == 'last':
			use_attns = [i >= depth-attn_depth for i in range(depth)]
		elif attn_loc == 'first':
			use_attns = [i < attn_depth for i in range(depth)]
		elif attn_loc == 'middle':
			use_attns = [i >= (depth-attn_depth)//2 and i < (depth+attn_depth)//2 for i in range(depth)]

		# build blocks
		self.blocks = nn.ModuleList([
			TransformerBlock(network_depth=network_depth,
							 dim=dim, 
							 num_heads=num_heads,
							 mlp_ratio=mlp_ratio,
							 norm_layer=norm_layer,
							 window_size=window_size,
							 shift_size=0 if (i % 2 == 0) else window_size // 2,
							 use_attn=use_attns[i], conv_type=conv_type)
			for i in range(depth)])

	def forward(self, x):
		for blk in self.blocks:
			x = blk(x)
		return x


class PatchEmbed(nn.Module):
	def __init__(self, patch_size=4, in_chans=3, embed_dim=96, kernel_size=None):
		super().__init__()
		self.in_chans = in_chans
		self.embed_dim = embed_dim

		if kernel_size is None:
			kernel_size = patch_size

		self.proj = nn.Conv2d(in_chans, embed_dim, kernel_size=kernel_size, stride=patch_size,
							  padding=(kernel_size-patch_size+1)//2, padding_mode='reflect')

	def forward(self, x):
		x = self.proj(x)
		return x


class PatchUnEmbed(nn.Module):
	def __init__(self, patch_size=4, out_chans=3, embed_dim=96, kernel_size=None):
		super().__init__()
		self.out_chans = out_chans
		self.embed_dim = embed_dim

		if kernel_size is None:
			kernel_size = 1

		self.proj = nn.Sequential(
			nn.Conv2d(embed_dim, out_chans*patch_size**2, kernel_size=kernel_size,
					  padding=kernel_size//2, padding_mode='reflect'),
			nn.PixelShuffle(patch_size)
		)

	def forward(self, x):
		x = self.proj(x)
		return x


class SKFusion(nn.Module):
	def __init__(self, dim, height=2, reduction=8):
		super(SKFusion, self).__init__()
		
		self.height = height
		d = max(int(dim/reduction), 4)
		
		self.avg_pool = nn.AdaptiveAvgPool2d(1)
		self.mlp = nn.Sequential(
			nn.Conv2d(dim, d, 1, bias=False), 
			nn.ReLU(),
			nn.Conv2d(d, dim*height, 1, bias=False)
		)
		
		self.softmax = nn.Softmax(dim=1)

	def forward(self, in_feats):
		B, C, H, W = in_feats[0].shape
		
		in_feats = torch.cat(in_feats, dim=1)
		in_feats = in_feats.view(B, self.height, C, H, W)
		
		feats_sum = torch.sum(in_feats, dim=1)
		attn = self.mlp(self.avg_pool(feats_sum))
		attn = self.softmax(attn.view(B, self.height, C, 1, 1))

		out = torch.sum(in_feats*attn, dim=1)
		return out      


class DehazeFormer(nn.Module):
	def __init__(self, in_chans=3, out_chans=3, window_size=8,
				 embed_dims=[24, 48, 96, 48, 24],
				 mlp_ratios=[2., 2., 4., 2., 2.],
				 depths=[4, 4, 8, 4, 4],
				 num_heads=[2, 4, 6, 4, 2],
				 attn_ratio=[1., 1., 1., 1., 1.],
				 conv_type=['DWConv', 'DWConv', 'DWConv', 'DWConv', 'DWConv'],
				 norm_layer=[RLN, RLN, RLN, RLN, RLN]):
		super(DehazeFormer, self).__init__()

		# setting
		self.patch_size = 4
		self.window_size = window_size
		self.mlp_ratios = mlp_ratios

		# split image into non-overlapping patches
		self.patch_embed = PatchEmbed(
			patch_size=1, in_chans=in_chans, embed_dim=embed_dims[0], kernel_size=3)

		# backbone
		self.layer1 = BasicLayer(network_depth=sum(depths), dim=embed_dims[0], depth=depths[0],
					   			 num_heads=num_heads[0], mlp_ratio=mlp_ratios[0],
					   			 norm_layer=norm_layer[0], window_size=window_size,
					   			 attn_ratio=attn_ratio[0], attn_loc='last', conv_type=conv_type[0])

		self.patch_merge1 = PatchEmbed(
			patch_size=2, in_chans=embed_dims[0], embed_dim=embed_dims[1])

		self.skip1 = nn.Conv2d(embed_dims[0], embed_dims[0], 1)

		self.layer2 = BasicLayer(network_depth=sum(depths), dim=embed_dims[1], depth=depths[1],
								 num_heads=num_heads[1], mlp_ratio=mlp_ratios[1],
								 norm_layer=norm_layer[1], window_size=window_size,
								 attn_ratio=attn_ratio[1], attn_loc='last', conv_type=conv_type[1])

		self.patch_merge2 = PatchEmbed(
			patch_size=2, in_chans=embed_dims[1], embed_dim=embed_dims[2])

		self.skip2 = nn.Conv2d(embed_dims[1], embed_dims[1], 1)

		self.layer3 = BasicLayer(network_depth=sum(depths), dim=embed_dims[2], depth=depths[2],
								 num_heads=num_heads[2], mlp_ratio=mlp_ratios[2],
								 norm_layer=norm_layer[2], window_size=window_size,
								 attn_ratio=attn_ratio[2], attn_loc='last', conv_type=conv_type[2])

		self.patch_split1 = PatchUnEmbed(
			patch_size=2, out_chans=embed_dims[3], embed_dim=embed_dims[2])

		assert embed_dims[1] == embed_dims[3]
		self.fusion1 = SKFusion(embed_dims[3])

		self.layer4 = BasicLayer(network_depth=sum(depths), dim=embed_dims[3], depth=depths[3],
								 num_heads=num_heads[3], mlp_ratio=mlp_ratios[3],
								 norm_layer=norm_layer[3], window_size=window_size,
								 attn_ratio=attn_ratio[3], attn_loc='last', conv_type=conv_type[3])

		self.patch_split2 = PatchUnEmbed(
			patch_size=2, out_chans=embed_dims[4], embed_dim=embed_dims[3])

		assert embed_dims[0] == embed_dims[4]
		self.fusion2 = SKFusion(embed_dims[4])			

		self.layer5 = BasicLayer(network_depth=sum(depths), dim=embed_dims[4], depth=depths[4],
					   			 num_heads=num_heads[4], mlp_ratio=mlp_ratios[4],
					   			 norm_layer=norm_layer[4], window_size=window_size,
					   			 attn_ratio=attn_ratio[4], attn_loc='last', conv_type=conv_type[4])

		# merge non-overlapping patches into image
		self.patch_unembed = PatchUnEmbed(
			patch_size=1, out_chans=out_chans, embed_dim=embed_dims[4], kernel_size=3)

	def forward(self, x):
		x = self.patch_embed(x)
		x = self.layer1(x)
		skip1 = x

		x = self.patch_merge1(x)
		x = self.layer2(x)
		skip2 = x

		x = self.patch_merge2(x)
		x = self.layer3(x)
		x = self.patch_split1(x)

		x = self.fusion1([x, self.skip2(skip2)]) + x
		x = self.layer4(x)
		x = self.patch_split2(x)

		x = self.fusion2([x, self.skip1(skip1)]) + x
		x = self.layer5(x)
		x = self.patch_unembed(x)
		return x


class MCT(nn.Module):
	def __init__(self):
		super(MCT, self).__init__()
		self.ts = 256
		self.l = 8

		self.dims = 3 * 3 * self.l

		self.basenet = DehazeFormer(3, self.dims)

	def get_coord(self, x):
		B, _, H, W = x.size()

		coordh, coordw = torch.meshgrid([torch.linspace(-1,1,H), torch.linspace(-1,1,W)], indexing="ij")
		coordh = coordh.unsqueeze(0).unsqueeze(1).repeat(B,1,1,1)
		coordw = coordw.unsqueeze(0).unsqueeze(1).repeat(B,1,1,1)

		return coordw.detach(), coordh.detach()

	def mapping(self, x, param):
		# curves
		curve = torch.stack(torch.chunk(param, 3, dim=1), dim=1)
		curve_list = list(torch.chunk(curve, 3, dim=2))

		# grid: x, y, z -> w, h, d  ~[-1 ,1]
		x_list = list(torch.chunk(x.detach(), 3, dim=1))
		coordw, coordh = self.get_coord(x)
		grid_list = [torch.stack([coordw, coordh, x_i], dim=4) for x_i in x_list]

		# mapping
		out = sum([F.grid_sample(curve_i, grid_i, 'bilinear', 'border', True) \
				   for curve_i, grid_i in zip(curve_list, grid_list)]).squeeze(2)

		return out		# no Tanh is much better than using Tanh

	def forward(self, x):
		# param input
		x_d = F.interpolate(x, (self.ts, self.ts), mode='area')
		param = self.basenet(x_d)
		out = self.mapping(x, param)
		return out