# SPDX-License-Identifier: Apache-2.0
# SPDX-FileCopyrightText: Copyright contributors to the vLLM project

# Adapted from
# https://github.com/vllm-project/vllm/blob/v0.7.3/vllm/model_executor/models/deepseek_mtp.py
from collections.abc import Iterable

import torch
import torch.nn as nn
from transformers import PretrainedConfig

from vllm.config import VllmConfig
from vllm.model_executor.layers.layernorm import RMSNorm
from vllm.model_executor.layers.linear import ReplicatedLinear
from vllm.model_executor.layers.logits_processor import LogitsProcessor
from vllm.model_executor.layers.quantization import QuantizationConfig
from vllm.model_executor.layers.quantization.utils.int8_utils import block_dequant
from vllm.model_executor.layers.vocab_parallel_embedding import (
    ParallelLMHead,
    VocabParallelEmbedding,
)
from vllm.model_executor.model_loader.weight_utils import default_weight_loader
from vllm.model_executor.models.longcat_flash import FlashConfig
from vllm.sequence import IntermediateTensors

from .deepseek_v2 import DeepseekV2DecoderLayer
from .interfaces import SupportsPP
from .utils import maybe_prefix


class LongCatMultiTokenPredictorLayer(nn.Module):
    def __init__(
        self,
        config: PretrainedConfig,
        prefix: str,
        vllm_config: VllmConfig,
        quant_config: QuantizationConfig | None = None,
    ) -> None:
        super().__init__()
        self.enorm = RMSNorm(config.hidden_size, eps=config.rms_norm_eps)
        self.hnorm = RMSNorm(config.hidden_size, eps=config.rms_norm_eps)
        self.eh_proj = ReplicatedLinear(
            2 * config.hidden_size,
            config.hidden_size,
            bias=False,
            quant_config=quant_config,
            prefix="eh_proj",
        )
        self.mtp_block = DeepseekV2DecoderLayer(vllm_config, prefix)
        self.final_layernorm = RMSNorm(config.hidden_size, eps=config.rms_norm_eps)

    def forward(
        self,
        input_ids: torch.Tensor,
        positions: torch.Tensor,
        previous_hidden_states: torch.Tensor,
        inputs_embeds: torch.Tensor | None = None,
        spec_step_index: int = 0,
    ) -> torch.Tensor:
        assert inputs_embeds is not None
        inputs_embeds = self.enorm(inputs_embeds)
        previous_hidden_states = self.hnorm(previous_hidden_states)

        hidden_states, _ = self.eh_proj(
            torch.cat([inputs_embeds, previous_hidden_states], dim=-1)
        )

        hidden_states, residual = self.mtp_block(
            positions=positions, hidden_states=hidden_states, residual=None
        )
        hidden_states, _ = self.final_layernorm(hidden_states, residual)
        return hidden_states


class LongCatMultiTokenPredictor(nn.Module):
    def __init__(
        self,
        *,
        vllm_config: VllmConfig,
        quant_config: QuantizationConfig | None = None,
        prefix: str = "",
    ):
        super().__init__()
        config = FlashConfig(**vllm_config.model_config.hf_config.__dict__)
        vllm_config.model_config.hf_config.intermediate_size = config.intermediate_size
        self.mtp_start_layer_idx = config.num_hidden_layers * 2
        self.num_mtp_layers = 1
        self.layers = torch.nn.ModuleDict(
            {
                str(idx): LongCatMultiTokenPredictorLayer(
                    config,
                    prefix=f"{prefix}.layers.{idx}",
                    vllm_config=vllm_config,
                    quant_config=quant_config,
                )
                for idx in range(
                    self.mtp_start_layer_idx,
                    self.mtp_start_layer_idx + self.num_mtp_layers,
                )
            }
        )
        self.embed_tokens = VocabParallelEmbedding(
            config.vocab_size,
            config.hidden_size,
        )

    def forward(
        self,
        input_ids: torch.Tensor,
        positions: torch.Tensor,
        previous_hidden_states: torch.Tensor,
        inputs_embeds: torch.Tensor | None = None,
        spec_step_idx: int = 0,
    ) -> torch.Tensor:
        if inputs_embeds is None:
            inputs_embeds = self.embed_tokens(input_ids)
        current_step_idx = spec_step_idx % self.num_mtp_layers
        return self.layers[str(self.mtp_start_layer_idx + current_step_idx)](
            input_ids,
            positions,
            previous_hidden_states,
            inputs_embeds,
            current_step_idx,
        )


class LongCatFlashMTP(nn.Module, SupportsPP):
    def __init__(self, *, vllm_config: VllmConfig, prefix: str = ""):
        super().__init__()
        # LongCat MTP without MoE layers
        vllm_config.model_config.hf_config.n_routed_experts = None
        self.config = FlashConfig(**vllm_config.model_config.hf_config.__dict__)
        self.quant_config = (
            None
            if "mtp" in getattr(self.config, "disable_quant_module", [])
            else vllm_config.quant_config
        )

        self.model = LongCatMultiTokenPredictor(
            vllm_config=vllm_config,
            quant_config=self.quant_config,
            prefix=maybe_prefix(prefix, "model"),
        )
        self.lm_head = ParallelLMHead(
            self.config.vocab_size,
            self.config.hidden_size,
            quant_config=self.quant_config,
            prefix=maybe_prefix(prefix, "lm_head"),
        )
        self.logits_processor = LogitsProcessor(self.config.vocab_size)

    def forward(
        self,
        input_ids: torch.Tensor,
        positions: torch.Tensor,
        hidden_states: torch.Tensor,
        intermediate_tensors: IntermediateTensors | None = None,
        inputs_embeds: torch.Tensor | None = None,
        spec_step_idx: int = 0,
    ) -> torch.Tensor:
        hidden_states = self.model(
            input_ids, positions, hidden_states, inputs_embeds, spec_step_idx
        )
        return hidden_states

    def compute_logits(
        self,
        hidden_states: torch.Tensor,
        spec_step_idx: int = 0,
    ) -> torch.Tensor | None:
        logits = self.logits_processor(self.lm_head, hidden_states)
        return logits

    def load_weights(self, weights: Iterable[tuple[str, torch.Tensor]]) -> set[str]:
        stacked_params_mapping = [
            ("gate_up_proj", "gate_proj", 0),
            ("gate_up_proj", "up_proj", 1),
            ("fused_qkv_a_proj", "q_a_proj", 0),
            ("fused_qkv_a_proj", "kv_a_proj_with_mqa", 1),
        ]

        new_to_old_names_mapping = {
            "model.mtp.embed_tokens.weight": "model.layers.0.embed_tokens.weight",
            "model.mtp.layers.0.eh_proj.weight": "eh_proj.weight",
            "model.mtp.layers.0.eh_proj.weight_scale_inv": "eh_proj.weight_scale_inv",
            "model.mtp.layers.0.enorm.m.weight": "enorm.weight",
            "model.mtp.layers.0.hnorm.m.weight": "hnorm.weight",
            "model.mtp.layers.0.input_layernorm.weight": "model.layers.0.input_layernorm.weight",  # noqa: E501
            "model.mtp.layers.0.post_attention_layernorm.weight": "model.layers.0.post_attention_layernorm.weight",  # noqa: E501
            "model.mtp.layers.0.self_attn.kv_a_layernorm.weight": "model.layers.0.self_attn.kv_a_layernorm.weight",  # noqa: E501
            "model.mtp.layers.0.self_attn.kv_a_proj_with_mqa.weight": "model.layers.0.self_attn.kv_a_proj_with_mqa.weight",  # noqa: E501
            "model.mtp.layers.0.self_attn.kv_a_proj_with_mqa.weight_scale_inv": "model.layers.0.self_attn.kv_a_proj_with_mqa.weight_scale_inv",  # noqa: E501
            "model.mtp.layers.0.self_attn.kv_b_proj.weight": "model.layers.0.self_attn.kv_b_proj.weight",  # noqa: E501
            "model.mtp.layers.0.self_attn.kv_b_proj.weight_scale_inv": "model.layers.0.self_attn.kv_b_proj.weight_scale_inv",  # noqa: E501
            "model.mtp.layers.0.self_attn.o_proj.weight": "model.layers.0.self_attn.o_proj.weight",  # noqa: E501
            "model.mtp.layers.0.self_attn.o_proj.weight_scale_inv": "model.layers.0.self_attn.o_proj.weight_scale_inv",  # noqa: E501
            "model.mtp.layers.0.self_attn.q_a_layernorm.weight": "model.layers.0.self_attn.q_a_layernorm.weight",  # noqa: E501
            "model.mtp.layers.0.self_attn.q_a_proj.weight": "model.layers.0.self_attn.q_a_proj.weight",  # noqa: E501
            "model.mtp.layers.0.self_attn.q_a_proj.weight_scale_inv": "model.layers.0.self_attn.q_a_proj.weight_scale_inv",  # noqa: E501
            "model.mtp.layers.0.self_attn.q_b_proj.weight": "model.layers.0.self_attn.q_b_proj.weight",  # noqa: E501
            "model.mtp.layers.0.self_attn.q_b_proj.weight_scale_inv": "model.layers.0.self_attn.q_b_proj.weight_scale_inv",  # noqa: E501
            "model.mtp.layers.0.transformer_layer.mlp.down_proj.weight": "model.layers.0.mlp.down_proj.weight",  # noqa: E501
            "model.mtp.layers.0.transformer_layer.mlp.down_proj.weight_scale_inv": "model.layers.0.mlp.down_proj.weight_scale_inv",  # noqa: E501
            "model.mtp.layers.0.transformer_layer.mlp.gate_proj.weight": "model.layers.0.mlp.gate_proj.weight",  # noqa: E501
            "model.mtp.layers.0.transformer_layer.mlp.gate_proj.weight_scale_inv": "model.layers.0.mlp.gate_proj.weight_scale_inv",  # noqa: E501
            "model.mtp.layers.0.transformer_layer.mlp.up_proj.weight": "model.layers.0.mlp.up_proj.weight",  # noqa: E501
            "model.mtp.layers.0.transformer_layer.mlp.up_proj.weight_scale_inv": "model.layers.0.mlp.up_proj.weight_scale_inv",  # noqa: E501
            "model.mtp.norm.weight": "final_layernorm.weight",
        }

        params_dict = dict(self.named_parameters())
        loaded_params: set[str] = set()
        for name, loaded_weight in weights:
            if "rotary_emb.inv_freq" in name:
                continue
            spec_layer = self.get_spec_layer_idx_from_weight_name(self.config, name)
            if spec_layer is None:
                continue
            name = self._rewrite_spec_layer_name(
                spec_layer, name, new_to_old_names_mapping
            )
            for param_name, weight_name, shard_id in stacked_params_mapping:
                # Skip non-stacked layers and experts (experts handled below).
                if weight_name not in name:
                    continue
                # We have mlp.experts[0].gate_proj in the checkpoint.
                # Since we handle the experts below in expert_params_mapping,
                # we need to skip here BEFORE we update the name, otherwise
                # name will be updated to mlp.experts[0].gate_up_proj, which
                # will then be updated below in expert_params_mapping
                # for mlp.experts[0].gate_gate_up_proj, which breaks load.
                if ("mlp.experts." in name) and name not in params_dict:
                    continue
                name = name.replace(weight_name, param_name)

                # QKV fusion is optional, fall back to normal
                # weight loading if it's not enabled
                if (param_name == "fused_qkv_a_proj") and name not in params_dict:
                    continue

                # Skip loading extra bias for GPTQ models.
                if name.endswith(".bias") and name not in params_dict:
                    continue

                param = params_dict[name]
                weight_loader = param.weight_loader
                weight_loader(param, loaded_weight, shard_id)
                break
            else:
                # Skip loading extra bias for GPTQ models.
                if name.endswith(".bias") and name not in params_dict:
                    continue

                # According to DeepSeek-V3 Technical Report, MTP modules
                # shares embedding layer. We only load the first weights.
                if (
                    spec_layer != self.model.mtp_start_layer_idx
                    and ".layers" not in name
                ):
                    continue

                param = params_dict[name]
                weight_loader = getattr(param, "weight_loader", default_weight_loader)
                weight_loader(param, loaded_weight)
            loaded_params.add(name)
        spec_layer_id = self.config.num_hidden_layers * 2
        self_attn = self.model.layers[str(spec_layer_id)].mtp_block.self_attn
        if hasattr(
            self.quant_config, "weight_block_size"
        ) and self_attn.kv_b_proj.weight.dtype in (
            torch.float8_e4m3fn,
            torch.float8_e4m3fnuz,
        ):
            weight_block_size = self.quant_config.weight_block_size
            if weight_block_size is not None:
                dtype = torch.get_default_dtype()
                w = block_dequant(
                    self_attn.kv_b_proj.weight,
                    self_attn.kv_b_proj.weight_scale_inv,
                    weight_block_size,
                ).to(dtype)
            else:
                w = self_attn.kv_b_proj.weight
        else:
            w = self_attn.kv_b_proj.weight
        w_kc, w_vc = w.unflatten(
            0, (-1, self_attn.qk_nope_head_dim + self_attn.v_head_dim)
        ).split([self_attn.qk_nope_head_dim, self_attn.v_head_dim], dim=1)
        self_attn.w_kc = w_kc.transpose(1, 2).contiguous().transpose(1, 2)
        self_attn.w_vc = w_vc.contiguous().transpose(1, 2)
        if self.config.mla_scale_q_lora:
            self_attn.q_a_layernorm.weight.data *= (
                self.config.hidden_size / self.config.q_lora_rank
            ) ** 0.5
        if self.config.mla_scale_kv_lora:
            self_attn.kv_a_layernorm.weight.data *= (
                self.config.hidden_size / self.config.kv_lora_rank
            ) ** 0.5
        return loaded_params

    def _rewrite_spec_layer_name(
        self, spec_layer: int, name: str, new_to_old_names_mapping: dict
    ) -> str:
        """
        Rewrite the weight name to match the format of the original model.
        Add .mtp_block for modules in transformer layer block for spec layer
        and rename shared layer weights to be top level.
        """
        if name in new_to_old_names_mapping:
            name = new_to_old_names_mapping[name]
        spec_layer_weight_names = [
            "embed_tokens",
            "enorm",
            "hnorm",
            "eh_proj",
            "shared_head",
        ]
        if (
            name.startswith("enorm")
            or name.startswith("hnorm")
            or name.startswith("eh_proj")
            or name.startswith("final_layernorm")
        ):
            name = "model.layers." + str(spec_layer) + "." + name
        shared_weight_names = ["embed_tokens"]
        spec_layer_weight = False
        shared_weight = False
        for weight_name in spec_layer_weight_names:
            if weight_name in name:
                spec_layer_weight = True
                if weight_name in shared_weight_names:
                    shared_weight = True
                break
        if not spec_layer_weight:
            # treat rest weights as weights for transformer layer block
            name = name.replace(
                "model.layers.0.", f"model.layers.{spec_layer}.mtp_block."
            )
        elif shared_weight:
            # treat shared weights as top level weights
            name = name.replace("model.layers.0.", "model.")
        return name

    def get_spec_layer_idx_from_weight_name(
        self, config: PretrainedConfig, weight_name: str
    ) -> int | None:
        if "model.mtp" in weight_name:
            return config.num_hidden_layers * 2
        return None