import logging
import math
import os
from collections import OrderedDict
from typing import Callable, Optional

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

try:
    from timm.models.layers import trunc_normal_
except ImportError:
    from timm.layers import trunc_normal_  # noqa: F401

from .utils import to_2tuple

if os.getenv("ENV_TYPE") == "deepspeed":
    try:
        import deepspeed
        from deepspeed.runtime.activation_checkpointing.checkpointing import checkpoint
    except ImportError:
        print("Please 'pip install deepspeed'")
        deepspeed = None
        from torch.utils.checkpoint import checkpoint
else:
    from torch.utils.checkpoint import checkpoint

try:
    import xformers.ops as xops
except ImportError:
    xops = None
    print("Please 'pip install xformers'")


class LayerNorm(nn.LayerNorm):
    """Subclass torch's LayerNorm (with cast back to input dtype)."""

    def forward(self, x: torch.Tensor):
        orig_type = x.dtype
        x = F.layer_norm(x, self.normalized_shape, self.weight, self.bias, self.eps)
        return x.to(orig_type)


class QuickGELU(nn.Module):
    # NOTE This is slower than nn.GELU or nn.SiLU and uses more GPU memory
    def forward(self, x: torch.Tensor):
        return x * torch.sigmoid(1.702 * x)


class LayerScale(nn.Module):
    def __init__(self, dim, init_values=1e-5, inplace=False):
        super().__init__()
        self.inplace = inplace
        self.gamma = nn.Parameter(init_values * torch.ones(dim))

    def forward(self, x):
        return x.mul_(self.gamma) if self.inplace else x * self.gamma


class PatchDropout(nn.Module):
    """
    https://arxiv.org/abs/2212.00794
    """

    def __init__(self, prob, exclude_first_token=True):
        super().__init__()
        assert 0 <= prob < 1.0
        self.prob = prob
        self.exclude_first_token = exclude_first_token  # exclude CLS token
        logging.info(f"os.getenv('RoPE')={os.getenv('RoPE')}")

    def forward(self, x):
        if not self.training or self.prob == 0.0:
            return x

        if self.exclude_first_token:
            cls_tokens, x = x[:, :1], x[:, 1:]
        else:
            cls_tokens = torch.jit.annotate(torch.Tensor, x[:, :1])

        batch = x.size()[0]
        num_tokens = x.size()[1]

        batch_indices = torch.arange(batch)
        batch_indices = batch_indices[..., None]

        keep_prob = 1 - self.prob
        num_patches_keep = max(1, int(num_tokens * keep_prob))

        rand = torch.randn(batch, num_tokens)
        patch_indices_keep = rand.topk(num_patches_keep, dim=-1).indices

        x = x[batch_indices, patch_indices_keep]

        if self.exclude_first_token:
            x = torch.cat((cls_tokens, x), dim=1)

        if self.training and os.getenv("RoPE") == "1":
            return x, patch_indices_keep

        return x


class Attention(nn.Module):
    def __init__(
        self,
        dim,
        num_heads=8,
        qkv_bias=True,
        scaled_cosine=False,
        scale_heads=False,
        logit_scale_max=math.log(1.0 / 0.01),
        attn_drop=0.0,
        proj_drop=0.0,
        xattn=False,
        rope=False,
    ):
        super().__init__()
        self.scaled_cosine = scaled_cosine
        self.scale_heads = scale_heads
        assert dim % num_heads == 0, "dim should be divisible by num_heads"
        self.num_heads = num_heads
        self.head_dim = dim // num_heads
        self.scale = self.head_dim**-0.5
        self.logit_scale_max = logit_scale_max

        # keeping in_proj in this form (instead of nn.Linear) to match weight scheme of original
        self.in_proj_weight = nn.Parameter(torch.randn((dim * 3, dim)) * self.scale)
        if qkv_bias:
            self.in_proj_bias = nn.Parameter(torch.zeros(dim * 3))
        else:
            self.in_proj_bias = None

        if self.scaled_cosine:
            self.logit_scale = nn.Parameter(torch.log(10 * torch.ones((num_heads, 1, 1))))
        else:
            self.logit_scale = None
        self.attn_drop = nn.Dropout(attn_drop)
        if self.scale_heads:
            self.head_scale = nn.Parameter(torch.ones((num_heads, 1, 1)))
        else:
            self.head_scale = None
        self.out_proj = nn.Linear(dim, dim)
        self.out_drop = nn.Dropout(proj_drop)
        self.xattn = xattn
        self.xattn_drop = attn_drop
        self.rope = rope

    def forward(self, x, attn_mask: Optional[torch.Tensor] = None):
        L, N, C = x.shape
        q, k, v = F.linear(x, self.in_proj_weight, self.in_proj_bias).chunk(3, dim=-1)
        if self.xattn:
            q = q.contiguous().view(L, N, self.num_heads, -1).transpose(0, 1)
            k = k.contiguous().view(L, N, self.num_heads, -1).transpose(0, 1)
            v = v.contiguous().view(L, N, self.num_heads, -1).transpose(0, 1)

            x = xops.memory_efficient_attention(
                q,
                k,
                v,
                p=self.xattn_drop,
                scale=self.scale if self.logit_scale is None else None,
                attn_bias=xops.LowerTriangularMask() if attn_mask is not None else None,
            )
        else:
            q = q.contiguous().view(L, N * self.num_heads, -1).transpose(0, 1)
            k = k.contiguous().view(L, N * self.num_heads, -1).transpose(0, 1)
            v = v.contiguous().view(L, N * self.num_heads, -1).transpose(0, 1)

            if self.logit_scale is not None:
                attn = torch.bmm(F.normalize(q, dim=-1), F.normalize(k, dim=-1).transpose(-1, -2))
                logit_scale = torch.clamp(self.logit_scale, max=self.logit_scale_max).exp()
                attn = attn.view(N, self.num_heads, L, L) * logit_scale
                attn = attn.view(-1, L, L)
            else:
                q = q * self.scale
                attn = torch.bmm(q, k.transpose(-1, -2))

            if attn_mask is not None:
                if attn_mask.dtype == torch.bool:
                    new_attn_mask = torch.zeros_like(attn_mask, dtype=q.dtype)
                    new_attn_mask.masked_fill_(attn_mask, float("-inf"))
                    attn_mask = new_attn_mask
                attn += attn_mask

            attn = attn.softmax(dim=-1)
            attn = self.attn_drop(attn)

            x = torch.bmm(attn, v)

        if self.head_scale is not None:
            x = x.view(N, self.num_heads, L, C) * self.head_scale
            x = x.view(-1, L, C)
        x = x.transpose(0, 1).reshape(L, N, C)
        x = self.out_proj(x)
        x = self.out_drop(x)
        return x


class ResidualAttentionBlock(nn.Module):
    def __init__(
        self,
        d_model: int,
        n_head: int,
        mlp_ratio: float = 4.0,
        ls_init_value: float = None,
        act_layer: Callable = nn.GELU,
        norm_layer: Callable = LayerNorm,
        xattn: bool = False,
    ):
        super().__init__()

        self.ln_1 = norm_layer(d_model)
        if xattn:
            self.attn = Attention(d_model, n_head, xattn=True)
        else:
            self.attn = nn.MultiheadAttention(d_model, n_head)
        self.ls_1 = LayerScale(d_model, ls_init_value) if ls_init_value is not None else nn.Identity()

        self.ln_2 = norm_layer(d_model)
        mlp_width = int(d_model * mlp_ratio)
        self.mlp = nn.Sequential(
            OrderedDict(
                [
                    ("c_fc", nn.Linear(d_model, mlp_width)),
                    ("gelu", act_layer()),
                    ("c_proj", nn.Linear(mlp_width, d_model)),
                ]
            )
        )

        self.ls_2 = LayerScale(d_model, ls_init_value) if ls_init_value is not None else nn.Identity()
        self.xattn = xattn

    def attention(self, x: torch.Tensor, attn_mask: Optional[torch.Tensor] = None):
        attn_mask = attn_mask.to(x.dtype) if attn_mask is not None else None
        if self.xattn:
            return self.attn(x, attn_mask=attn_mask)
        return self.attn(x, x, x, need_weights=False, attn_mask=attn_mask)[0]

    def forward(self, x: torch.Tensor, attn_mask: Optional[torch.Tensor] = None):
        x = x + self.ls_1(self.attention(self.ln_1(x), attn_mask=attn_mask))
        x = x + self.ls_2(self.mlp(self.ln_2(x)))
        return x


class Transformer(nn.Module):
    def __init__(
        self,
        width: int,
        layers: int,
        heads: int,
        mlp_ratio: float = 4.0,
        ls_init_value: float = None,
        act_layer: Callable = nn.GELU,
        norm_layer: Callable = LayerNorm,
        xattn: bool = False,
    ):
        super().__init__()
        self.width = width
        self.layers = layers
        self.grad_checkpointing = False

        self.resblocks = nn.ModuleList(
            [
                ResidualAttentionBlock(
                    width,
                    heads,
                    mlp_ratio,
                    ls_init_value=ls_init_value,
                    act_layer=act_layer,
                    norm_layer=norm_layer,
                    xattn=xattn,
                )
                for _ in range(layers)
            ]
        )

    def get_cast_dtype(self) -> torch.dtype:
        return self.resblocks[0].mlp.c_fc.weight.dtype

    def forward(self, x: torch.Tensor, attn_mask: Optional[torch.Tensor] = None):
        for r in self.resblocks:
            if self.grad_checkpointing and not torch.jit.is_scripting():
                x = checkpoint(r, x, attn_mask)
            else:
                x = r(x, attn_mask=attn_mask)
        return x


class VisionTransformer(nn.Module):
    def __init__(
        self,
        image_size: int,
        patch_size: int,
        width: int,
        layers: int,
        heads: int,
        mlp_ratio: float,
        ls_init_value: float = None,
        patch_dropout: float = 0.0,
        global_average_pool: bool = False,
        output_dim: int = 512,
        act_layer: Callable = nn.GELU,
        norm_layer: Callable = LayerNorm,
        xattn: bool = False,
    ):
        super().__init__()
        self.image_size = to_2tuple(image_size)
        self.patch_size = to_2tuple(patch_size)
        self.grid_size = (self.image_size[0] // self.patch_size[0], self.image_size[1] // self.patch_size[1])
        self.output_dim = output_dim
        self.conv1 = nn.Conv2d(in_channels=3, out_channels=width, kernel_size=patch_size, stride=patch_size, bias=False)

        scale = width**-0.5
        self.class_embedding = nn.Parameter(scale * torch.randn(width))
        self.positional_embedding = nn.Parameter(scale * torch.randn(self.grid_size[0] * self.grid_size[1] + 1, width))

        # setting a patch_dropout of 0. would mean it is disabled and this function would be the identity fn
        self.patch_dropout = PatchDropout(patch_dropout) if patch_dropout > 0.0 else nn.Identity()
        self.ln_pre = norm_layer(width)

        self.transformer = Transformer(
            width,
            layers,
            heads,
            mlp_ratio,
            ls_init_value=ls_init_value,
            act_layer=act_layer,
            norm_layer=norm_layer,
            xattn=xattn,
        )

        self.global_average_pool = global_average_pool
        self.ln_post = norm_layer(width)
        self.proj = nn.Parameter(scale * torch.randn(width, output_dim))

    @torch.jit.ignore
    def set_grad_checkpointing(self, enable=True):
        self.transformer.grad_checkpointing = enable

    def forward(self, x: torch.Tensor, return_all_features: bool = False):
        x = self.conv1(x)  # shape = [*, width, grid, grid]
        x = x.reshape(x.shape[0], x.shape[1], -1)  # shape = [*, width, grid ** 2]
        x = x.permute(0, 2, 1)  # shape = [*, grid ** 2, width]
        x = torch.cat(
            [
                self.class_embedding.to(x.dtype)
                + torch.zeros(x.shape[0], 1, x.shape[-1], dtype=x.dtype, device=x.device),
                x,
            ],
            dim=1,
        )  # shape = [*, grid ** 2 + 1, width]
        x = x + self.positional_embedding.to(x.dtype)

        # a patch_dropout of 0. would mean it is disabled and this function would do nothing but return what was passed in
        x = self.patch_dropout(x)
        x = self.ln_pre(x)

        x = x.permute(1, 0, 2)  # NLD -> LND
        x = self.transformer(x)
        x = x.permute(1, 0, 2)  # LND -> NLD

        if not return_all_features:
            if self.global_average_pool:
                x = x.mean(dim=1)  # x = x[:,1:,:].mean(dim=1)
            else:
                x = x[:, 0]

            x = self.ln_post(x)

            if self.proj is not None:
                x = x @ self.proj

        return x


class TextTransformer(nn.Module):
    def __init__(
        self,
        context_length: int = 77,
        vocab_size: int = 49408,
        width: int = 512,
        heads: int = 8,
        layers: int = 12,
        ls_init_value: float = None,
        output_dim: int = 512,
        act_layer: Callable = nn.GELU,
        norm_layer: Callable = LayerNorm,
        xattn: bool = False,
        attn_mask: bool = True,
    ):
        super().__init__()
        self.context_length = context_length
        self.vocab_size = vocab_size
        self.width = width
        self.output_dim = output_dim

        self.token_embedding = nn.Embedding(vocab_size, width)
        self.positional_embedding = nn.Parameter(torch.empty(self.context_length, width))
        self.transformer = Transformer(
            width=width,
            layers=layers,
            heads=heads,
            ls_init_value=ls_init_value,
            act_layer=act_layer,
            norm_layer=norm_layer,
            xattn=xattn,
        )

        self.xattn = xattn
        self.ln_final = norm_layer(width)
        self.text_projection = nn.Parameter(torch.empty(width, output_dim))

        if attn_mask:
            self.register_buffer("attn_mask", self.build_attention_mask(), persistent=False)
        else:
            self.attn_mask = None

        self.init_parameters()

    def init_parameters(self):
        nn.init.normal_(self.token_embedding.weight, std=0.02)
        nn.init.normal_(self.positional_embedding, std=0.01)

        proj_std = (self.transformer.width**-0.5) * ((2 * self.transformer.layers) ** -0.5)
        attn_std = self.transformer.width**-0.5
        fc_std = (2 * self.transformer.width) ** -0.5
        for block in self.transformer.resblocks:
            nn.init.normal_(block.attn.in_proj_weight, std=attn_std)
            nn.init.normal_(block.attn.out_proj.weight, std=proj_std)
            nn.init.normal_(block.mlp.c_fc.weight, std=fc_std)
            nn.init.normal_(block.mlp.c_proj.weight, std=proj_std)

        if self.text_projection is not None:
            nn.init.normal_(self.text_projection, std=self.transformer.width**-0.5)

    @torch.jit.ignore
    def set_grad_checkpointing(self, enable=True):
        self.transformer.grad_checkpointing = enable

    def build_attention_mask(self):
        # lazily create causal attention mask, with full attention between the vision tokens
        # pytorch uses additive attention mask; fill with -inf
        mask = torch.empty(self.context_length, self.context_length)
        mask.fill_(float("-inf"))
        mask.triu_(1)  # zero out the lower diagonal
        return mask

    def forward(self, text, return_all_features: bool = False):
        cast_dtype = self.transformer.get_cast_dtype()
        x = self.token_embedding(text).to(cast_dtype)  # [batch_size, n_ctx, d_model]

        x = x + self.positional_embedding.to(cast_dtype)
        x = x.permute(1, 0, 2)  # NLD -> LND
        x = self.transformer(x, attn_mask=self.attn_mask)
        # x = self.transformer(x) # no attention mask is applied
        x = x.permute(1, 0, 2)  # LND -> NLD
        x = self.ln_final(x)

        if not return_all_features:
            # x.shape = [batch_size, n_ctx, transformer.width]
            # take features from the eot embedding (eot_token is the highest number in each sequence)
            x = x[torch.arange(x.shape[0]), text.argmax(dim=-1)] @ self.text_projection
        return x
