# ---------------------------------------------------------------
# Copyright (c) 2021, NVIDIA Corporation. All rights reserved.
#
# This work is licensed under the NVIDIA Source Code License
# ---------------------------------------------------------------
import math
import torch
import torch.nn as nn
from functools import partial

from timm.models.layers import DropPath, to_2tuple, trunc_normal_


class Mlp(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.dwconv = DWConv(hidden_features)
        self.act = act_layer()
        self.fc2 = nn.Linear(hidden_features, out_features)
        self.drop = nn.Dropout(drop)

        self.apply(self._init_weights)

    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)
        elif isinstance(m, nn.Conv2d):
            fan_out = m.kernel_size[0] * m.kernel_size[1] * m.out_channels
            fan_out //= m.groups
            m.weight.data.normal_(0, math.sqrt(2.0 / fan_out))
            if m.bias is not None:
                m.bias.data.zero_()

    def forward(self, x, H, W):
        x = self.fc1(x)
        x = self.dwconv(x, H, W)
        x = self.act(x)
        x = self.drop(x)
        x = self.fc2(x)
        x = self.drop(x)
        return x


class Attention(nn.Module):
    def __init__(
        self,
        dim,
        num_heads=8,
        qkv_bias=False,
        qk_scale=None,
        attn_drop=0.0,
        proj_drop=0.0,
        sr_ratio=1,
    ):
        super().__init__()
        assert (
            dim % num_heads == 0
        ), f"dim {dim} should be divided by num_heads {num_heads}."

        self.dim = dim
        self.num_heads = num_heads
        head_dim = dim // num_heads
        self.scale = qk_scale or head_dim ** -0.5

        self.q = nn.Linear(dim, dim, bias=qkv_bias)
        self.kv = nn.Linear(dim, dim * 2, bias=qkv_bias)
        self.attn_drop = nn.Dropout(attn_drop)
        self.proj = nn.Linear(dim, dim)
        self.proj_drop = nn.Dropout(proj_drop)

        self.sr_ratio = sr_ratio
        if sr_ratio > 1:
            self.sr = nn.Conv2d(dim, dim, kernel_size=sr_ratio, stride=sr_ratio)
            self.norm = nn.LayerNorm(dim)

        self.apply(self._init_weights)

    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)
        elif isinstance(m, nn.Conv2d):
            fan_out = m.kernel_size[0] * m.kernel_size[1] * m.out_channels
            fan_out //= m.groups
            m.weight.data.normal_(0, math.sqrt(2.0 / fan_out))
            if m.bias is not None:
                m.bias.data.zero_()

    def forward(self, x, H, W):
        B, N, C = x.shape
        q = (
            self.q(x)
            .reshape(B, N, self.num_heads, C // self.num_heads)
            .permute(0, 2, 1, 3)
        )

        if self.sr_ratio > 1:
            x_ = x.permute(0, 2, 1).reshape(B, C, H, W)
            x_ = self.sr(x_).reshape(B, C, -1).permute(0, 2, 1)
            x_ = self.norm(x_)
            kv = (
                self.kv(x_)
                .reshape(B, -1, 2, self.num_heads, C // self.num_heads)
                .permute(2, 0, 3, 1, 4)
            )
        else:
            kv = (
                self.kv(x)
                .reshape(B, -1, 2, self.num_heads, C // self.num_heads)
                .permute(2, 0, 3, 1, 4)
            )
        k, v = kv[0], kv[1]

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


class Block(nn.Module):
    def __init__(
        self,
        dim,
        num_heads,
        mlp_ratio=4.0,
        qkv_bias=False,
        qk_scale=None,
        drop=0.0,
        attn_drop=0.0,
        drop_path=0.0,
        act_layer=nn.GELU,
        norm_layer=nn.LayerNorm,
        sr_ratio=1,
    ):
        super().__init__()
        self.norm1 = norm_layer(dim)
        self.attn = Attention(
            dim,
            num_heads=num_heads,
            qkv_bias=qkv_bias,
            qk_scale=qk_scale,
            attn_drop=attn_drop,
            proj_drop=drop,
            sr_ratio=sr_ratio,
        )
        # NOTE: drop path for stochastic depth, we shall see if this is better than dropout here
        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 = Mlp(
            in_features=dim,
            hidden_features=mlp_hidden_dim,
            act_layer=act_layer,
            drop=drop,
        )

        self.apply(self._init_weights)

    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)
        elif isinstance(m, nn.Conv2d):
            fan_out = m.kernel_size[0] * m.kernel_size[1] * m.out_channels
            fan_out //= m.groups
            m.weight.data.normal_(0, math.sqrt(2.0 / fan_out))
            if m.bias is not None:
                m.bias.data.zero_()

    def forward(self, x, H, W):
        x = x + self.drop_path(self.attn(self.norm1(x), H, W))
        x = x + self.drop_path(self.mlp(self.norm2(x), H, W))

        return x


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

    def __init__(self, img_size=224, patch_size=7, stride=4, in_chans=3, embed_dim=768):
        super().__init__()
        img_size = to_2tuple(img_size)
        patch_size = to_2tuple(patch_size)

        self.img_size = img_size
        self.patch_size = patch_size
        self.H, self.W = img_size[0] // patch_size[0], img_size[1] // patch_size[1]
        self.num_patches = self.H * self.W
        self.proj = nn.Conv2d(
            in_chans,
            embed_dim,
            kernel_size=patch_size,
            stride=stride,
            padding=(patch_size[0] // 2, patch_size[1] // 2),
        )
        self.norm = nn.LayerNorm(embed_dim)

        self.apply(self._init_weights)

    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)
        elif isinstance(m, nn.Conv2d):
            fan_out = m.kernel_size[0] * m.kernel_size[1] * m.out_channels
            fan_out //= m.groups
            m.weight.data.normal_(0, math.sqrt(2.0 / fan_out))
            if m.bias is not None:
                m.bias.data.zero_()

    def forward(self, x):
        x = self.proj(x)
        _, _, H, W = x.shape
        x = x.flatten(2).transpose(1, 2)
        x = self.norm(x)

        return x, H, W


class MixVisionTransformer(nn.Module):
    def __init__(
        self,
        img_size=224,
        patch_size=16,
        in_chans=3,
        num_classes=1000,
        embed_dims=[64, 128, 256, 512],
        num_heads=[1, 2, 4, 8],
        mlp_ratios=[4, 4, 4, 4],
        qkv_bias=False,
        qk_scale=None,
        drop_rate=0.0,
        attn_drop_rate=0.0,
        drop_path_rate=0.0,
        norm_layer=nn.LayerNorm,
        depths=[3, 4, 6, 3],
        sr_ratios=[8, 4, 2, 1],
    ):
        super().__init__()
        self.num_classes = num_classes
        self.depths = depths

        # patch_embed
        self.patch_embed1 = OverlapPatchEmbed(
            img_size=img_size,
            patch_size=7,
            stride=4,
            in_chans=in_chans,
            embed_dim=embed_dims[0],
        )
        self.patch_embed2 = OverlapPatchEmbed(
            img_size=img_size // 4,
            patch_size=3,
            stride=2,
            in_chans=embed_dims[0],
            embed_dim=embed_dims[1],
        )
        self.patch_embed3 = OverlapPatchEmbed(
            img_size=img_size // 8,
            patch_size=3,
            stride=2,
            in_chans=embed_dims[1],
            embed_dim=embed_dims[2],
        )
        self.patch_embed4 = OverlapPatchEmbed(
            img_size=img_size // 16,
            patch_size=3,
            stride=2,
            in_chans=embed_dims[2],
            embed_dim=embed_dims[3],
        )

        # transformer encoder
        dpr = [
            x.item() for x in torch.linspace(0, drop_path_rate, sum(depths))
        ]  # stochastic depth decay rule
        cur = 0
        self.block1 = nn.ModuleList(
            [
                Block(
                    dim=embed_dims[0],
                    num_heads=num_heads[0],
                    mlp_ratio=mlp_ratios[0],
                    qkv_bias=qkv_bias,
                    qk_scale=qk_scale,
                    drop=drop_rate,
                    attn_drop=attn_drop_rate,
                    drop_path=dpr[cur + i],
                    norm_layer=norm_layer,
                    sr_ratio=sr_ratios[0],
                )
                for i in range(depths[0])
            ]
        )
        self.norm1 = norm_layer(embed_dims[0])

        cur += depths[0]
        self.block2 = nn.ModuleList(
            [
                Block(
                    dim=embed_dims[1],
                    num_heads=num_heads[1],
                    mlp_ratio=mlp_ratios[1],
                    qkv_bias=qkv_bias,
                    qk_scale=qk_scale,
                    drop=drop_rate,
                    attn_drop=attn_drop_rate,
                    drop_path=dpr[cur + i],
                    norm_layer=norm_layer,
                    sr_ratio=sr_ratios[1],
                )
                for i in range(depths[1])
            ]
        )
        self.norm2 = norm_layer(embed_dims[1])

        cur += depths[1]
        self.block3 = nn.ModuleList(
            [
                Block(
                    dim=embed_dims[2],
                    num_heads=num_heads[2],
                    mlp_ratio=mlp_ratios[2],
                    qkv_bias=qkv_bias,
                    qk_scale=qk_scale,
                    drop=drop_rate,
                    attn_drop=attn_drop_rate,
                    drop_path=dpr[cur + i],
                    norm_layer=norm_layer,
                    sr_ratio=sr_ratios[2],
                )
                for i in range(depths[2])
            ]
        )
        self.norm3 = norm_layer(embed_dims[2])

        cur += depths[2]
        self.block4 = nn.ModuleList(
            [
                Block(
                    dim=embed_dims[3],
                    num_heads=num_heads[3],
                    mlp_ratio=mlp_ratios[3],
                    qkv_bias=qkv_bias,
                    qk_scale=qk_scale,
                    drop=drop_rate,
                    attn_drop=attn_drop_rate,
                    drop_path=dpr[cur + i],
                    norm_layer=norm_layer,
                    sr_ratio=sr_ratios[3],
                )
                for i in range(depths[3])
            ]
        )
        self.norm4 = norm_layer(embed_dims[3])

        # classification head
        # self.head = nn.Linear(embed_dims[3], num_classes) if num_classes > 0 else nn.Identity()

        self.apply(self._init_weights)

    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)
        elif isinstance(m, nn.Conv2d):
            fan_out = m.kernel_size[0] * m.kernel_size[1] * m.out_channels
            fan_out //= m.groups
            m.weight.data.normal_(0, math.sqrt(2.0 / fan_out))
            if m.bias is not None:
                m.bias.data.zero_()

    def init_weights(self, pretrained=None):
        pass

    def reset_drop_path(self, drop_path_rate):
        dpr = [x.item() for x in torch.linspace(0, drop_path_rate, sum(self.depths))]
        cur = 0
        for i in range(self.depths[0]):
            self.block1[i].drop_path.drop_prob = dpr[cur + i]

        cur += self.depths[0]
        for i in range(self.depths[1]):
            self.block2[i].drop_path.drop_prob = dpr[cur + i]

        cur += self.depths[1]
        for i in range(self.depths[2]):
            self.block3[i].drop_path.drop_prob = dpr[cur + i]

        cur += self.depths[2]
        for i in range(self.depths[3]):
            self.block4[i].drop_path.drop_prob = dpr[cur + i]

    def freeze_patch_emb(self):
        self.patch_embed1.requires_grad = False

    @torch.jit.ignore
    def no_weight_decay(self):
        return {
            "pos_embed1",
            "pos_embed2",
            "pos_embed3",
            "pos_embed4",
            "cls_token",
        }  # has pos_embed may be better

    def get_classifier(self):
        return self.head

    def reset_classifier(self, num_classes, global_pool=""):
        self.num_classes = num_classes
        self.head = (
            nn.Linear(self.embed_dim, num_classes) if num_classes > 0 else nn.Identity()
        )

    def forward_features(self, x):
        B = x.shape[0]
        outs = []

        # stage 1
        x, H, W = self.patch_embed1(x)
        for i, blk in enumerate(self.block1):
            x = blk(x, H, W)
        x = self.norm1(x)
        x = x.reshape(B, H, W, -1).permute(0, 3, 1, 2).contiguous()
        outs.append(x)

        # stage 2
        x, H, W = self.patch_embed2(x)
        for i, blk in enumerate(self.block2):
            x = blk(x, H, W)
        x = self.norm2(x)
        x = x.reshape(B, H, W, -1).permute(0, 3, 1, 2).contiguous()
        outs.append(x)

        # stage 3
        x, H, W = self.patch_embed3(x)
        for i, blk in enumerate(self.block3):
            x = blk(x, H, W)
        x = self.norm3(x)
        x = x.reshape(B, H, W, -1).permute(0, 3, 1, 2).contiguous()
        outs.append(x)

        # stage 4
        x, H, W = self.patch_embed4(x)
        for i, blk in enumerate(self.block4):
            x = blk(x, H, W)
        x = self.norm4(x)
        x = x.reshape(B, H, W, -1).permute(0, 3, 1, 2).contiguous()
        outs.append(x)

        return outs

    def forward(self, x):
        x = self.forward_features(x)
        # x = self.head(x)

        return x


class DWConv(nn.Module):
    def __init__(self, dim=768):
        super(DWConv, self).__init__()
        self.dwconv = nn.Conv2d(dim, dim, 3, 1, 1, bias=True, groups=dim)

    def forward(self, x, H, W):
        B, N, C = x.shape
        x = x.transpose(1, 2).view(B, C, H, W)
        x = self.dwconv(x)
        x = x.flatten(2).transpose(1, 2)

        return x


# ---------------------------------------------------------------
# End of NVIDIA code
# ---------------------------------------------------------------

from ._base import EncoderMixin  # noqa E402


class MixVisionTransformerEncoder(MixVisionTransformer, EncoderMixin):
    def __init__(self, out_channels, depth=5, **kwargs):
        super().__init__(**kwargs)
        self._out_channels = out_channels
        self._depth = depth
        self._in_channels = 3

    def make_dilated(self, *args, **kwargs):
        raise ValueError("MixVisionTransformer encoder does not support dilated mode")

    def set_in_channels(self, in_channels, *args, **kwargs):
        if in_channels != 3:
            raise ValueError(
                "MixVisionTransformer encoder does not support in_channels setting other than 3"
            )

    def forward(self, x):

        # create dummy output for the first block
        B, C, H, W = x.shape
        dummy = torch.empty([B, 0, H // 2, W // 2], dtype=x.dtype, device=x.device)

        return [x, dummy] + self.forward_features(x)[: self._depth - 1]

    def load_state_dict(self, state_dict):
        state_dict.pop("head.weight", None)
        state_dict.pop("head.bias", None)
        return super().load_state_dict(state_dict)


def get_pretrained_cfg(name):
    return {
        "url": "https://github.com/qubvel/segmentation_models.pytorch/releases/download/v0.0.2/{}.pth".format(
            name
        ),
        "input_space": "RGB",
        "input_size": [3, 224, 224],
        "input_range": [0, 1],
        "mean": [0.485, 0.456, 0.406],
        "std": [0.229, 0.224, 0.225],
    }


mix_transformer_encoders = {
    "mit_b0": {
        "encoder": MixVisionTransformerEncoder,
        "pretrained_settings": {"imagenet": get_pretrained_cfg("mit_b0"),},
        "params": dict(
            out_channels=(3, 0, 32, 64, 160, 256),
            patch_size=4,
            embed_dims=[32, 64, 160, 256],
            num_heads=[1, 2, 5, 8],
            mlp_ratios=[4, 4, 4, 4],
            qkv_bias=True,
            norm_layer=partial(nn.LayerNorm, eps=1e-6),
            depths=[2, 2, 2, 2],
            sr_ratios=[8, 4, 2, 1],
            drop_rate=0.0,
            drop_path_rate=0.1,
        ),
    },
    "mit_b1": {
        "encoder": MixVisionTransformerEncoder,
        "pretrained_settings": {"imagenet": get_pretrained_cfg("mit_b1"),},
        "params": dict(
            out_channels=(3, 0, 64, 128, 320, 512),
            patch_size=4,
            embed_dims=[64, 128, 320, 512],
            num_heads=[1, 2, 5, 8],
            mlp_ratios=[4, 4, 4, 4],
            qkv_bias=True,
            norm_layer=partial(nn.LayerNorm, eps=1e-6),
            depths=[2, 2, 2, 2],
            sr_ratios=[8, 4, 2, 1],
            drop_rate=0.0,
            drop_path_rate=0.1,
        ),
    },
    "mit_b2": {
        "encoder": MixVisionTransformerEncoder,
        "pretrained_settings": {"imagenet": get_pretrained_cfg("mit_b2"),},
        "params": dict(
            out_channels=(3, 0, 64, 128, 320, 512),
            patch_size=4,
            embed_dims=[64, 128, 320, 512],
            num_heads=[1, 2, 5, 8],
            mlp_ratios=[4, 4, 4, 4],
            qkv_bias=True,
            norm_layer=partial(nn.LayerNorm, eps=1e-6),
            depths=[3, 4, 6, 3],
            sr_ratios=[8, 4, 2, 1],
            drop_rate=0.0,
            drop_path_rate=0.1,
        ),
    },
    "mit_b3": {
        "encoder": MixVisionTransformerEncoder,
        "pretrained_settings": {"imagenet": get_pretrained_cfg("mit_b3"),},
        "params": dict(
            out_channels=(3, 0, 64, 128, 320, 512),
            patch_size=4,
            embed_dims=[64, 128, 320, 512],
            num_heads=[1, 2, 5, 8],
            mlp_ratios=[4, 4, 4, 4],
            qkv_bias=True,
            norm_layer=partial(nn.LayerNorm, eps=1e-6),
            depths=[3, 4, 18, 3],
            sr_ratios=[8, 4, 2, 1],
            drop_rate=0.0,
            drop_path_rate=0.1,
        ),
    },
    "mit_b4": {
        "encoder": MixVisionTransformerEncoder,
        "pretrained_settings": {"imagenet": get_pretrained_cfg("mit_b4"),},
        "params": dict(
            out_channels=(3, 0, 64, 128, 320, 512),
            patch_size=4,
            embed_dims=[64, 128, 320, 512],
            num_heads=[1, 2, 5, 8],
            mlp_ratios=[4, 4, 4, 4],
            qkv_bias=True,
            norm_layer=partial(nn.LayerNorm, eps=1e-6),
            depths=[3, 8, 27, 3],
            sr_ratios=[8, 4, 2, 1],
            drop_rate=0.0,
            drop_path_rate=0.1,
        ),
    },
    "mit_b5": {
        "encoder": MixVisionTransformerEncoder,
        "pretrained_settings": {"imagenet": get_pretrained_cfg("mit_b5"),},
        "params": dict(
            out_channels=(3, 0, 64, 128, 320, 512),
            patch_size=4,
            embed_dims=[64, 128, 320, 512],
            num_heads=[1, 2, 5, 8],
            mlp_ratios=[4, 4, 4, 4],
            qkv_bias=True,
            norm_layer=partial(nn.LayerNorm, eps=1e-6),
            depths=[3, 6, 40, 3],
            sr_ratios=[8, 4, 2, 1],
            drop_rate=0.0,
            drop_path_rate=0.1,
        ),
    },
}
