# Adapted from
# https://github.com/THUDM/GLM-4
"""Inference-only GLM-4v model visual encoder compatible with THUDM weights."""
from argparse import Namespace
from typing import Optional

import torch
from torch import nn
from torch.nn import LayerNorm

from vllm.attention.layer import MultiHeadAttention
from vllm.distributed import get_tensor_model_parallel_world_size
from vllm.model_executor.layers.activation import SiluAndMul, get_act_fn
from vllm.model_executor.layers.linear import (ColumnParallelLinear,
                                               MergedColumnParallelLinear,
                                               QKVParallelLinear,
                                               ReplicatedLinear,
                                               RowParallelLinear)
from vllm.model_executor.layers.quantization.base_config import (
    QuantizationConfig)


class PatchEmbedding(nn.Module):

    def __init__(self, config):
        super().__init__()
        self.proj = nn.Conv2d(config.in_channels,
                              config.hidden_size,
                              kernel_size=config.patch_size,
                              stride=config.patch_size)
        self.cls_embedding = nn.Parameter(torch.zeros(1, config.hidden_size))
        self.position_embedding = nn.Embedding(config.num_positions,
                                               config.hidden_size)

    def forward(self, images: torch.Tensor) -> torch.Tensor:
        """
        Parameters:
        images : torch.Tensor
            Input image tensor with shape (B, C, H, W)

        Returns:
        torch.Tensor
            Transformed tensor with shape (B, L, D)
        """
        images = images.to(device=self.proj.weight.device,
                           dtype=self.proj.weight.dtype)
        x = self.proj(images)
        x = x.flatten(2).transpose(1, 2)
        cls_token = self.cls_embedding.expand(x.shape[0], -1, -1)
        x = torch.cat((cls_token, x), dim=1)
        x += self.position_embedding.weight.unsqueeze(0)
        return x


class Attention(nn.Module):

    def __init__(
        self,
        config,
        quant_config: Optional[QuantizationConfig] = None,
        prefix: str = '',
    ):
        super().__init__()
        self.hidden_size = config.hidden_size
        self.tp_size = get_tensor_model_parallel_world_size()
        self.num_heads_per_rank = config.num_heads // self.tp_size
        self.head_dim = config.hidden_size // config.num_heads
        self.scale = self.head_dim**-0.5

        self.query_key_value = QKVParallelLinear(
            config.hidden_size,
            self.head_dim,
            config.num_heads,
            quant_config=quant_config,
        )
        self.dense = RowParallelLinear(
            config.hidden_size,
            config.hidden_size,
            quant_config=quant_config,
        )

        self.attn = MultiHeadAttention(self.num_heads_per_rank, self.head_dim,
                                       self.scale)
        self.output_dropout = torch.nn.Dropout(config.dropout_prob)

    def forward(self, x: torch.Tensor) -> torch.Tensor:
        qkv, _ = self.query_key_value(x)  # B, L, 3 * H * D
        q, k, v = qkv.chunk(3, dim=-1)

        out = self.attn(q, k, v)
        output, _ = self.dense(out)
        output = self.output_dropout(output)
        return output


class MLP(nn.Module):

    def __init__(
        self,
        config,
        quant_config: Optional[QuantizationConfig] = None,
    ):
        super().__init__()
        self.config = config
        self.activation_fn = get_act_fn(config.hidden_act)
        self.fc1 = ColumnParallelLinear(
            config.hidden_size,
            config.intermediate_size,
            quant_config=quant_config,
        )
        self.fc2 = RowParallelLinear(
            config.intermediate_size,
            config.hidden_size,
            quant_config=quant_config,
        )

    def forward(self, x: torch.Tensor) -> torch.Tensor:
        x, _ = self.fc1(x)
        x = self.activation_fn(x)
        x, _ = self.fc2(x)
        return x


class TransformerLayer(nn.Module):

    def __init__(
        self,
        config,
        quant_config: Optional[QuantizationConfig] = None,
        prefix: str = '',
    ):
        super().__init__()
        self.input_layernorm = LayerNorm(config.hidden_size,
                                         eps=config.layer_norm_eps)
        self.attention = Attention(config,
                                   quant_config=quant_config,
                                   prefix=f"{prefix}.attention")
        self.mlp = MLP(config, quant_config=quant_config)
        self.post_attention_layernorm = LayerNorm(config.hidden_size,
                                                  eps=config.layer_norm_eps)

    def forward(self, hidden_states):
        attention_input = hidden_states
        attention_output = self.input_layernorm(
            self.attention(attention_input))
        hidden_states = attention_input + attention_output
        mlp_input = hidden_states
        mlp_output = self.post_attention_layernorm(self.mlp(mlp_input))
        output = mlp_input + mlp_output
        return output


class Transformer(nn.Module):

    def __init__(
        self,
        config,
        quant_config: Optional[QuantizationConfig] = None,
        prefix: str = '',
    ):
        super().__init__()
        self.layers = nn.ModuleList([
            TransformerLayer(config,
                             quant_config=quant_config,
                             prefix=f"{prefix}.layer.{layer_idx}")
            for layer_idx in range(config.num_hidden_layers)
        ])

    def forward(self, hidden_states):
        for layer_module in self.layers:
            hidden_states = layer_module(hidden_states)
        return hidden_states


class GLU(nn.Module):

    def __init__(
        self,
        config,
        in_features,
        quant_config: Optional[QuantizationConfig] = None,
    ):
        """
        The original implementation is the same as:
        ```python
        self.dense_h_to_4h = ColumnParallelLinear(
            config.hidden_size,
            config.ffn_hidden_size,
            bias=False,
            quant_config=quant_config
        )

        self.gate_proj = ColumnParallelLinear(
            config.hidden_size,
            config.ffn_hidden_size,
            bias=False,
            quant_config=quant_config
        )
        ```
        ```
        gate_proj_output, _ = self.gate_proj(x)
        dense_h_to_4h_output, _ = self.dense_h_to_4h(x)
        x = torch.cat([gate_proj_output, dense_h_to_4h_output], dim=-1)
        ```

        We merge two ColumnParallelLinear into one MergedColumnParallelLinear:
        ```
        self.merged_proj = MergedColumnParallelLinear(
            config.hidden_size,
            [config.ffn_hidden_size] * 2,
            bias=False,
            quant_config=quant_config
        )
        ```
        ```
        x, _ = self.merged_proj(x)
        ```
        """
        super().__init__()
        self.linear_proj = ReplicatedLinear(in_features,
                                            config.hidden_size,
                                            bias=False,
                                            quant_config=quant_config)
        self.norm1 = nn.LayerNorm(config.hidden_size)
        self.act1 = nn.GELU()
        self.act2 = SiluAndMul()

        self.merged_proj = MergedColumnParallelLinear(
            config.hidden_size, [config.ffn_hidden_size] * 2,
            bias=False,
            quant_config=quant_config)

        self.dense_4h_to_h = RowParallelLinear(config.ffn_hidden_size,
                                               config.hidden_size,
                                               bias=False,
                                               quant_config=quant_config)

    def forward(self, x):
        x, _ = self.linear_proj(x)
        x = self.act1(self.norm1(x))
        x, _ = self.merged_proj(x)
        x = self.act2(x)
        x, _ = self.dense_4h_to_h(x)
        return x


class EVA2CLIPModel(nn.Module):

    def __init__(
        self,
        config,
        quant_config: Optional[QuantizationConfig] = None,
        prefix: str = '',
    ):
        super().__init__()
        vision_config = Namespace(**config.vision_config)
        self.patch_embedding = PatchEmbedding(vision_config)
        self.transformer = Transformer(vision_config,
                                       quant_config=quant_config,
                                       prefix=f"{prefix}.transformer")
        self.linear_proj = GLU(config,
                               in_features=config.hidden_size,
                               quant_config=quant_config)
        self.conv = nn.Conv2d(in_channels=vision_config.hidden_size,
                              out_channels=config.hidden_size,
                              kernel_size=2,
                              stride=2)
        self.boi = nn.Parameter(torch.zeros(1, 1, config.hidden_size))
        self.eoi = nn.Parameter(torch.zeros(1, 1, config.hidden_size))
        self.scaling_factor = vision_config.scaling_factor

    def forward(self, images: torch.Tensor) -> torch.Tensor:
        """
        Parameters:
        images : torch.Tensor
            Input image tensor with shape (B, C, H, W)

        Returns:
        torch.Tensor
            Transformed tensor with shape (B, L, D)
        """
        x = self.patch_embedding(images)
        x = self.transformer(x)
        x = x[:, 1:]

        b, s, h = x.shape
        grid_size = int(s**0.5)
        x = x.view(b, grid_size, grid_size, h).permute(0, 3, 1, 2)
        x = self.conv(x)

        x = x.flatten(2).transpose(1, 2)
        x = self.linear_proj(x)
        boi = self.boi.expand(x.shape[0], -1, -1)
        eoi = self.eoi.expand(x.shape[0], -1, -1)
        x = torch.cat((boi, x, eoi), dim=1)
        x = x / self.scaling_factor
        return x
