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

from collections.abc import Iterable
from typing import Optional

import torch
import torch.nn as nn
from transformers import LlamaConfig

from vllm.config import VllmConfig, get_current_vllm_config
from vllm.logger import init_logger
from vllm.model_executor.layers.layernorm import RMSNorm
from vllm.model_executor.layers.linear import QKVParallelLinear
from vllm.model_executor.layers.logits_processor import LogitsProcessor
from vllm.model_executor.layers.quantization.base_config import (
    QuantizationConfig)
from vllm.model_executor.layers.vocab_parallel_embedding import (
    DEFAULT_VOCAB_PADDING_SIZE, ParallelLMHead, VocabParallelEmbedding)
from vllm.model_executor.model_loader.weight_utils import default_weight_loader
from vllm.model_executor.models.llama import (LlamaDecoderLayer,
                                              LlamaForCausalLM)

from .utils import AutoWeightsLoader, maybe_prefix

logger = init_logger(__name__)


class LlamaDecoderLayer(LlamaDecoderLayer):

    def __init__(self,
                 vllm_config: VllmConfig,
                 prefix: str = "",
                 config: Optional[LlamaConfig] = None) -> None:
        super().__init__(vllm_config, prefix=prefix, config=config)

        config = config or vllm_config.model_config.hf_config
        quant_config = self.get_quant_config(vllm_config)

        # override qkv
        self.self_attn.qkv_proj = QKVParallelLinear(
            2 * self.hidden_size,
            self.self_attn.head_dim,
            self.self_attn.total_num_heads,
            self.self_attn.total_num_kv_heads,
            bias=False,
            quant_config=quant_config,
            prefix=maybe_prefix(prefix, "qkv_proj"),
        )

        self.hidden_norm = RMSNorm(config.hidden_size, eps=config.rms_norm_eps)

        if getattr(config, "norm_before_residual", False):
            self._residual_norm = self._norm_before_residual
        else:
            self._residual_norm = self._norm_after_residual

    def get_quant_config(
            self, vllm_config: VllmConfig) -> Optional[QuantizationConfig]:
        """Use drafter's quantization config instead of verifier's."""
        draft_model_config = vllm_config.speculative_config.draft_model_config
        draft_load_config = vllm_config.load_config

        return VllmConfig.get_quantization_config(
            draft_model_config,
            draft_load_config) if draft_model_config else None

    def _norm_before_residual(
            self,
            hidden_states: torch.Tensor) -> tuple[torch.Tensor, torch.Tensor]:
        hidden_states = self.hidden_norm(hidden_states)
        residual = hidden_states
        return hidden_states, residual

    def _norm_after_residual(
            self,
            hidden_states: torch.Tensor) -> tuple[torch.Tensor, torch.Tensor]:
        residual = hidden_states
        hidden_states = self.hidden_norm(hidden_states)
        return hidden_states, residual

    def forward(
        self,
        positions: torch.Tensor,
        embeds: torch.Tensor,
        hidden_states: torch.Tensor,
        residual: Optional[torch.Tensor],
    ) -> tuple[torch.Tensor, torch.Tensor]:

        embeds = self.input_layernorm(embeds)

        hidden_states, residual = self._residual_norm(
            hidden_states=hidden_states)

        hidden_states = torch.cat([embeds, hidden_states], dim=-1)
        # Self Attention
        hidden_states = self.self_attn(
            positions=positions,
            hidden_states=hidden_states,
        )

        hidden_states, residual = self.post_attention_layernorm(
            hidden_states, residual)

        # Fully Connected
        hidden_states = self.mlp(hidden_states)

        return hidden_states, residual


class LlamaModel(nn.Module):

    def __init__(
        self,
        *,
        vllm_config: VllmConfig,
        start_layer_id: int = 0,
        prefix: str = "",
    ) -> None:
        super().__init__()
        self.config = vllm_config. \
            speculative_config.draft_model_config.hf_config
        self.vocab_size = self.config.vocab_size

        current_vllm_config = get_current_vllm_config()

        self.embed_tokens = VocabParallelEmbedding(
            self.config.vocab_size,
            self.config.hidden_size,
            prefix=maybe_prefix(prefix, "embed_tokens"),
        )

        self.layers = nn.ModuleList([
            LlamaDecoderLayer(
                current_vllm_config,
                prefix=maybe_prefix(prefix, f"layers.{start_layer_id}"),
                config=self.config,
            )
        ])
        if hasattr(self.config, "target_hidden_size"):
            self.fc = torch.nn.Linear(self.config.target_hidden_size * 3,
                                      self.config.hidden_size,
                                      bias=False)
        else:
            self.fc = torch.nn.Linear(self.config.hidden_size * 3,
                                      self.config.hidden_size,
                                      bias=False)
        self.norm = RMSNorm(
            self.config.hidden_size,
            eps=self.config.rms_norm_eps,
        )

    def get_input_embeddings(self, input_ids: torch.Tensor) -> torch.Tensor:
        return self.embed_tokens(input_ids)

    def forward(
        self,
        input_ids: torch.Tensor,
        positions: torch.Tensor,
        hidden_states: torch.Tensor,
        input_embeds: Optional[torch.Tensor] = None,
    ) -> tuple[torch.Tensor, torch.Tensor]:
        if input_embeds is None:
            input_embeds = self.get_input_embeddings(input_ids)
        assert hidden_states.shape[-1] == input_embeds.shape[-1]

        residual = None
        hidden_states, residual = self.layers[0](
            positions,
            input_embeds,
            hidden_states,
            residual,
        )

        hidden_states, hidden_prenorm = self.norm(hidden_states, residual)
        return hidden_states, hidden_prenorm

    def load_weights(self, weights: Iterable[tuple[str,
                                                   torch.Tensor]]) -> set[str]:
        stacked_params_mapping = [
            # (param_name, shard_name, shard_id)
            (".qkv_proj", ".q_proj", "q"),
            (".qkv_proj", ".k_proj", "k"),
            (".qkv_proj", ".v_proj", "v"),
            (".gate_up_proj", ".gate_proj", 0),
            (".gate_up_proj", ".up_proj", 1),
        ]
        params_dict = dict(self.named_parameters())
        loaded_params: set[str] = set()
        for name, loaded_weight in weights:
            if 'midlayer.' in name:
                name = name.replace('midlayer.', 'layers.0.')
            for param_name, weight_name, shard_id in stacked_params_mapping:
                if weight_name not in name:
                    continue
                name = name.replace(weight_name, param_name)
                param = params_dict[name]
                weight_loader = param.weight_loader
                weight_loader(param, loaded_weight, shard_id)
                break
            else:
                param = params_dict[name]
                weight_loader = getattr(param, "weight_loader",
                                        default_weight_loader)
                weight_loader(param, loaded_weight)
            loaded_params.add(name)
        return loaded_params


class Eagle3LlamaForCausalLM(LlamaForCausalLM):

    def __init__(self, *, vllm_config: VllmConfig, prefix: str = ""):
        nn.Module.__init__(self)
        self.config = vllm_config. \
            speculative_config.draft_model_config.hf_config
        # Ensure draft_vocab_size is set
        # default to the base vocab size when absent
        if getattr(self.config, "draft_vocab_size", None) is None:
            base_vocab_size = getattr(self.config, "vocab_size", None)
            self.config.draft_vocab_size = base_vocab_size
        target_layer_num = vllm_config.model_config.get_num_layers(
            vllm_config.parallel_config)

        # Store target layer count in draft config for
        # proper layer_types indexing in draft models
        self.config.target_layer_count = target_layer_num
        self.model = LlamaModel(vllm_config=vllm_config,
                                prefix="model",
                                start_layer_id=target_layer_num)

        logit_scale = getattr(self.config, "logit_scale", 1.0)
        self.lm_head = ParallelLMHead(
            self.config.draft_vocab_size,
            self.config.hidden_size,
            org_num_embeddings=self.config.draft_vocab_size,
            padding_size=(DEFAULT_VOCAB_PADDING_SIZE),
            prefix=maybe_prefix(prefix, "lm_head"))
        self.logits_processor = LogitsProcessor(self.config.draft_vocab_size,
                                                scale=logit_scale)
        self.draft_id_to_target_id = nn.Parameter(
            torch.zeros(self.config.draft_vocab_size, dtype=torch.long),
            requires_grad=False,
        )

    def get_input_embeddings(self, input_ids: torch.Tensor) -> torch.Tensor:
        return self.model.get_input_embeddings(input_ids)

    def forward(
        self,
        input_ids: torch.Tensor,
        positions: torch.Tensor,
        hidden_states: torch.Tensor,
        inputs_embeds: Optional[torch.Tensor] = None,
    ) -> tuple[torch.Tensor, torch.Tensor]:
        return self.model(input_ids, positions, hidden_states, inputs_embeds)

    def compute_logits(
        self,
        hidden_states: torch.Tensor,
    ) -> Optional[torch.Tensor]:
        logits = self.logits_processor(self.lm_head, hidden_states)
        if self.draft_id_to_target_id is None:
            assert logits.shape[1] == self.config.vocab_size, \
                "Expected logits to have shape " \
                f"(*, {self.config.vocab_size}), but got {logits.shape}"
            return logits

        base = torch.arange(self.config.draft_vocab_size, device=logits.device)
        targets = base + self.draft_id_to_target_id
        logits_new = logits.new_full((
            logits.shape[0],
            self.config.vocab_size,
        ), float('-inf'))
        logits_new[:, targets] = logits
        return logits_new

    def combine_hidden_states(
        self,
        hidden_states: torch.Tensor,
    ) -> torch.Tensor:
        # combine multiple auxiliary hidden states returned by eagle3
        return self.model.fc(hidden_states)

    def load_weights(self, weights: Iterable[tuple[str, torch.Tensor]]):
        model_weights = {}
        includes_draft_id_mapping = False
        includes_embed_tokens = False
        for name, loaded_weight in weights:
            if "t2d" in name:
                continue
            if "d2t" in name:
                name = name.replace("d2t", "draft_id_to_target_id")
                includes_draft_id_mapping = True
            elif "lm_head" not in name:
                name = "model." + name
            if "embed_tokens" in name:
                includes_embed_tokens = True
            model_weights[name] = loaded_weight

        skip_substrs = []
        if not includes_draft_id_mapping:
            skip_substrs.append("draft_id_to_target_id")
        if not includes_embed_tokens:
            skip_substrs.append("embed_tokens")
        loader = AutoWeightsLoader(
            self,
            skip_prefixes=None,
            skip_substrs=skip_substrs,
        )
        loader.load_weights(model_weights.items())
