# SPDX-License-Identifier: Apache-2.0
# SPDX-FileCopyrightText: Copyright contributors to the vLLM project
"""Inference-only Snowflake Arctic model."""

from collections.abc import Iterable
from itertools import islice

import torch
from torch import nn

from vllm.attention.layer import Attention
from vllm.compilation.decorators import support_torch_compile
from vllm.config import CacheConfig, VllmConfig
from vllm.distributed import (
    get_pp_group,
    get_tensor_model_parallel_rank,
    get_tensor_model_parallel_world_size,
    tensor_model_parallel_all_reduce,
)
from vllm.logger import init_logger
from vllm.model_executor.layers.activation import SiluAndMul
from vllm.model_executor.layers.fused_moe import fused_experts, fused_topk
from vllm.model_executor.layers.layernorm import RMSNorm
from vllm.model_executor.layers.linear import (
    MergedColumnParallelLinear,
    QKVParallelLinear,
    ReplicatedLinear,
    RowParallelLinear,
)
from vllm.model_executor.layers.logits_processor import LogitsProcessor
from vllm.model_executor.layers.quantization import QuantizationConfig
from vllm.model_executor.layers.rotary_embedding import get_rope
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.utils import set_weight_attrs
from vllm.platforms import current_platform
from vllm.sequence import IntermediateTensors
from vllm.transformers_utils.configs.arctic import ArcticConfig

from .interfaces import SupportsPP, SupportsQuant
from .utils import (
    extract_layer_index,
    is_pp_missing_parameter,
    make_empty_intermediate_tensors_factory,
    make_layers,
    maybe_prefix,
)

logger = init_logger(__name__)


class ArcticMLP(nn.Module):
    def __init__(
        self,
        config: ArcticConfig,
        expert_id: int = -1,
        is_residual_mlp: bool = False,
        quant_config: QuantizationConfig | None = None,
        reduce_results: bool = True,
        prefix: str = "",
    ):
        super().__init__()
        self.hidden_size = config.hidden_size
        self.expert_id = expert_id

        self.ffn_dim = (
            config.intermediate_size if not is_residual_mlp else self.hidden_size
        )

        self.w13 = MergedColumnParallelLinear(
            self.hidden_size,
            [self.ffn_dim] * 2,
            bias=False,
            quant_config=quant_config,
            prefix=f"{prefix}.w13",
        )
        self.w2 = RowParallelLinear(
            self.ffn_dim,
            self.hidden_size,
            bias=False,
            reduce_results=reduce_results,
            quant_config=quant_config,
            prefix=f"{prefix}.w2",
        )
        if config.hidden_act != "silu":
            raise ValueError(
                f"Unsupported activation: {config.hidden_act}. "
                "Only silu is supported for now."
            )
        self.act_fn = SiluAndMul()

    def forward(self, hidden_states):
        gate_up, _ = self.w13(hidden_states)
        hidden_states = self.act_fn(gate_up)
        hidden_states, _ = self.w2(hidden_states)
        return hidden_states


class ArcticMoE(nn.Module):
    """
    Model-parallel implementation of Arctic MoE Layer.
    """

    def __init__(
        self,
        config: ArcticConfig,
        tp_size: int | None = None,
        params_dtype: torch.dtype | None = None,
        quant_config: QuantizationConfig | None = None,
        reduce_results: bool = True,
        prefix: str = "",
    ):
        super().__init__()

        layer_id = extract_layer_index(prefix)
        self.tp_size = tp_size or get_tensor_model_parallel_world_size()
        self.hidden_size = config.hidden_size
        self.num_experts = config.num_local_experts
        self.layer_id = layer_id
        self.top_k = config.num_experts_per_tok
        self.intermediate_size = config.intermediate_size // self.tp_size

        self.is_moe_layer = (layer_id + 1) % config.moe_layer_frequency == 0
        self.reduce_results = reduce_results
        # Some other parameters
        if params_dtype is None:
            params_dtype = torch.get_default_dtype()
        self.params_dtype = params_dtype

        if not self.is_moe_layer:
            self.mlp = ArcticMLP(
                config,
                quant_config=quant_config,
                reduce_results=reduce_results,
                prefix=f"{prefix}.mlp",
            )
        else:
            self.gate = ReplicatedLinear(
                self.hidden_size,
                self.num_experts,
                bias=False,
                params_dtype=self.params_dtype,
                quant_config=quant_config,
                prefix=f"{prefix}.gate",
            )
            self.ws = nn.Parameter(
                torch.empty(
                    self.num_experts,
                    2 * self.intermediate_size,
                    self.hidden_size,
                    device=current_platform.device_type,
                    dtype=self.params_dtype,
                )
            )
            self.w2s = nn.Parameter(
                torch.empty(
                    self.num_experts,
                    self.hidden_size,
                    self.intermediate_size,
                    device=current_platform.device_type,
                    dtype=self.params_dtype,
                )
            )
            set_weight_attrs(
                self.ws,
                {
                    "weight_loader": self.weight_loader,
                },
            )
            set_weight_attrs(
                self.w2s,
                {
                    "weight_loader": self.weight_loader,
                },
            )

    def weight_loader(
        self,
        param: nn.Parameter,
        loaded_weight: torch.Tensor,
        weight_name: str,
        expert_id: int,
    ):
        tp_rank = get_tensor_model_parallel_rank()
        param_data = param.data
        shard_size = self.intermediate_size
        shard = slice(tp_rank * shard_size, (tp_rank + 1) * shard_size)
        if weight_name.endswith("w1.weight"):
            param_data[expert_id, 0:shard_size, :] = loaded_weight[shard, :]
        if weight_name.endswith("w3.weight"):
            param_data[expert_id, shard_size : 2 * shard_size, :] = loaded_weight[
                shard, :
            ]
        if weight_name.endswith("w2.weight"):
            param_data[expert_id, :, :] = loaded_weight[:, shard]

    def local_moe_fused(self, hidden_states: torch.Tensor) -> torch.Tensor:
        num_tokens, hidden_size = hidden_states.shape
        hidden_states = hidden_states.view(-1, self.hidden_size)
        # router_logits: (num_tokens, n_experts)
        router_logits, _ = self.gate(hidden_states)
        do_normalize = self.top_k > 1
        topk_weights, topk_ids, token_expert_indices = fused_topk(
            hidden_states, router_logits, self.top_k, renormalize=do_normalize
        )
        final_hidden_states = fused_experts(
            hidden_states,
            self.ws,
            self.w2s,
            topk_weights,
            topk_ids,
            inplace=True,
        )
        if self.reduce_results and self.tp_size > 1:
            final_hidden_states = tensor_model_parallel_all_reduce(final_hidden_states)
        return final_hidden_states.view(num_tokens, hidden_size)

    def forward(self, hidden_states: torch.Tensor):
        if self.is_moe_layer:
            final_hidden_states = self.local_moe_fused(hidden_states)
        else:
            final_hidden_states = self.mlp(hidden_states)
        return final_hidden_states


class ArcticAttention(nn.Module):
    def __init__(
        self,
        config: ArcticConfig,
        cache_config: CacheConfig | None = None,
        quant_config: QuantizationConfig | None = None,
        prefix: str = "",
    ):
        super().__init__()
        self.config = config
        self.hidden_size = config.hidden_size

        tp_size = get_tensor_model_parallel_world_size()
        self.total_num_heads = config.num_attention_heads
        assert self.total_num_heads % tp_size == 0
        self.num_heads = self.total_num_heads // tp_size
        self.total_num_kv_heads = config.num_key_value_heads
        if self.total_num_kv_heads >= tp_size:
            assert self.total_num_kv_heads % tp_size == 0
        else:
            assert tp_size % self.total_num_kv_heads == 0
        self.num_kv_heads = max(1, self.total_num_kv_heads // tp_size)
        self.head_dim = self.hidden_size // self.total_num_heads
        self.q_size = self.num_heads * self.head_dim
        self.kv_size = self.num_kv_heads * self.head_dim

        self.max_position_embeddings = config.max_position_embeddings
        self.scaling = self.head_dim**-0.5

        self.qkv_proj = QKVParallelLinear(
            self.hidden_size,
            self.head_dim,
            self.total_num_heads,
            self.total_num_kv_heads,
            bias=False,
            quant_config=quant_config,
            prefix=f"{prefix}.qkv_proj",
        )
        self.o_proj = RowParallelLinear(
            self.total_num_heads * self.head_dim,
            self.hidden_size,
            bias=False,
            reduce_results=True,
            quant_config=quant_config,
            prefix=f"{prefix}.o_proj",
        )

        self.rotary_emb = get_rope(
            self.head_dim,
            max_position=self.max_position_embeddings,
            rope_parameters=config.rope_parameters,
            is_neox_style=True,
        )

        self.attn = Attention(
            self.num_heads,
            self.head_dim,
            self.scaling,
            num_kv_heads=self.num_kv_heads,
            cache_config=cache_config,
            quant_config=quant_config,
            prefix=f"{prefix}.attn",
        )

    def forward(
        self,
        positions: torch.Tensor,
        hidden_states: torch.Tensor,
    ) -> torch.Tensor:
        qkv, _ = self.qkv_proj(hidden_states)
        q, k, v = qkv.split([self.q_size, self.kv_size, self.kv_size], dim=-1)
        q, k = self.rotary_emb(positions, q, k)
        attn_output = self.attn(q, k, v)
        output, _ = self.o_proj(attn_output)
        return output


class ArcticDecoderLayer(nn.Module):
    def __init__(
        self,
        config: ArcticConfig,
        cache_config: CacheConfig | None = None,
        quant_config: QuantizationConfig | None = None,
        prefix: str = "",
    ) -> None:
        super().__init__()
        self.hidden_size = config.hidden_size
        layer_idx = extract_layer_index(prefix)
        is_moe_layer = (layer_idx + 1) % config.moe_layer_frequency == 0
        self.use_residual = config.use_residual and is_moe_layer
        self.self_attn = ArcticAttention(
            config,
            cache_config,
            quant_config=quant_config,
            prefix=f"{prefix}.self_attn",
        )
        self.block_sparse_moe = ArcticMoE(
            config,
            quant_config=quant_config,
            reduce_results=(not self.use_residual),
            prefix=f"{prefix}.block_sparse_moe",
        )

        self.input_layernorm = RMSNorm(config.hidden_size, eps=config.rms_norm_eps)
        self.post_attention_layernorm = RMSNorm(
            config.hidden_size, eps=config.rms_norm_eps
        )

        if self.use_residual:
            self.residual_layernorm = RMSNorm(
                config.hidden_size, eps=config.rms_norm_eps
            )
            self.residual_mlp = ArcticMLP(
                config,
                is_residual_mlp=True,
                reduce_results=False,
                prefix=f"{prefix}.residual_mlp",
            )

    def forward(
        self,
        positions: torch.Tensor,
        hidden_states: torch.Tensor,
    ) -> torch.Tensor:
        residual_input = hidden_states
        hidden_states = self.input_layernorm(hidden_states)
        hidden_states = self.self_attn(
            positions=positions,
            hidden_states=hidden_states,
        )
        hidden_states = residual_input + hidden_states

        residual_attn = hidden_states
        if self.use_residual:
            hidden_states = self.residual_layernorm(hidden_states)
            hidden_states = self.residual_mlp(hidden_states)
            residual_mlp = hidden_states
            hidden_states = self.post_attention_layernorm(residual_input)
            hidden_states = self.block_sparse_moe(hidden_states)
            hidden_states = residual_mlp + hidden_states
            hidden_states = tensor_model_parallel_all_reduce(hidden_states)
            hidden_states = residual_attn + hidden_states
        else:
            hidden_states = self.post_attention_layernorm(hidden_states)
            hidden_states = self.block_sparse_moe(hidden_states)
            hidden_states = residual_attn + hidden_states
        return hidden_states


@support_torch_compile
class ArcticModel(nn.Module):
    def __init__(self, *, vllm_config: VllmConfig, prefix: str = ""):
        super().__init__()

        config = vllm_config.model_config.hf_config
        cache_config = vllm_config.cache_config
        quant_config = vllm_config.quant_config

        self.vocab_size = config.vocab_size
        self.embed_tokens = VocabParallelEmbedding(
            self.vocab_size, config.hidden_size, org_num_embeddings=self.vocab_size
        )
        self.start_layer, self.end_layer, self.layers = make_layers(
            config.num_hidden_layers,
            lambda prefix: ArcticDecoderLayer(
                config, cache_config, quant_config, prefix=prefix
            ),
            prefix=f"{prefix}.layers",
        )
        self._attn_implementation = config._attn_implementation
        self.norm = RMSNorm(config.hidden_size, eps=config.rms_norm_eps)
        self.make_empty_intermediate_tensors = make_empty_intermediate_tensors_factory(
            ["hidden_states"], config.hidden_size
        )

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

    def forward(
        self,
        input_ids: torch.Tensor,
        positions: torch.Tensor,
        intermediate_tensors: IntermediateTensors | None,
        inputs_embeds: torch.Tensor | None = None,
    ) -> torch.Tensor | IntermediateTensors:
        if get_pp_group().is_first_rank:
            if inputs_embeds is not None:
                hidden_states = inputs_embeds
            else:
                hidden_states = self.embed_input_ids(input_ids)
        else:
            assert intermediate_tensors is not None
            hidden_states = intermediate_tensors["hidden_states"]
        for layer in islice(self.layers, self.start_layer, self.end_layer):
            hidden_states = layer(positions, hidden_states)
        if not get_pp_group().is_last_rank:
            return IntermediateTensors({"hidden_states": hidden_states})
        hidden_states = self.norm(hidden_states)
        return hidden_states


class ArcticForCausalLM(nn.Module, SupportsPP, SupportsQuant):
    packed_modules_mapping = {"qkv_proj": ["q_proj", "k_proj", "v_proj"]}

    def __init__(self, *, vllm_config: VllmConfig, prefix: str = ""):
        super().__init__()
        config = vllm_config.model_config.hf_config
        quant_config = vllm_config.quant_config
        self.config = config
        self.model = ArcticModel(
            vllm_config=vllm_config, prefix=maybe_prefix(prefix, "model")
        )
        self.vocab_size = config.vocab_size
        self.lm_head = ParallelLMHead(
            self.vocab_size,
            config.hidden_size,
            quant_config=quant_config,
            prefix=maybe_prefix(prefix, "lm_head"),
        )
        if self.config.tie_word_embeddings:
            self.lm_head.weight = self.model.embed_tokens.weight
        self.num_experts = config.num_local_experts
        self.num_experts_per_tok = config.num_experts_per_tok

        self.logits_processor = LogitsProcessor(config.vocab_size)
        self.make_empty_intermediate_tensors = (
            self.model.make_empty_intermediate_tensors
        )

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

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

    def compute_logits(
        self,
        hidden_states: torch.Tensor,
    ) -> 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 = [
            # (param_name, shard_name, shard_id)
            ("qkv_proj", "q_proj", "q"),
            ("qkv_proj", "k_proj", "k"),
            ("qkv_proj", "v_proj", "v"),
        ]

        mlp_params_mapping: list[tuple[str, str, int]] = []
        expert_params_mapping: list[tuple[str, str, int]] = []
        num_layers = self.config.num_hidden_layers

        for layer in range(num_layers):
            mlp_params_mapping.append(
                (
                    f"layers.{layer}.residual_mlp.w13.weight",
                    f"layers.{layer}.residual_mlp.w1.weight",
                    0,
                )
            )
            mlp_params_mapping.append(
                (
                    f"layers.{layer}.residual_mlp.w13.weight",
                    f"layers.{layer}.residual_mlp.w3.weight",
                    1,
                )
            )
            if layer % 2 == 0:
                # MLP layers
                mlp_params_mapping.append(
                    (
                        f"layers.{layer}.block_sparse_moe.mlp.w13.weight",
                        f"layers.{layer}.block_sparse_moe.mlp.w1.weight",
                        0,
                    )
                )
                mlp_params_mapping.append(
                    (
                        f"layers.{layer}.block_sparse_moe.mlp.w13.weight",
                        f"layers.{layer}.block_sparse_moe.mlp.w3.weight",
                        1,
                    )
                )
            else:
                # MoE layers
                for expert_id in range(self.config.num_local_experts):
                    expert_params_mapping.append(
                        ("ws", f"experts.{expert_id}.w1.weight", expert_id)
                    )
                    expert_params_mapping.append(
                        ("w2s", f"experts.{expert_id}.w2.weight", expert_id)
                    )
                    expert_params_mapping.append(
                        ("ws", f"experts.{expert_id}.w3.weight", expert_id)
                    )

        params_dict = dict(self.named_parameters())
        loaded_params: set[str] = set()

        logger.info(
            "It will take ~10 minutes loading from the 16-bit weights. "
            "Alternatively, use the prequantized 8-bit weights of arctic "
            "and set load-format to `sharded_state` will accelerate loading."
        )
        for name, loaded_weight in weights:
            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)
                # Skip loading extra bias for GPTQ models.
                if name.endswith(".bias") and name not in params_dict:
                    continue
                if is_pp_missing_parameter(name, self):
                    continue
                param = params_dict[name]
                weight_loader = param.weight_loader
                weight_loader(param, loaded_weight, shard_id)
                break
            else:
                for param_name, weight_name, shard_id in mlp_params_mapping:
                    if weight_name not in name:
                        continue
                    name = name.replace(weight_name, param_name)
                    if is_pp_missing_parameter(name, self):
                        continue
                    param = params_dict[name]
                    weight_loader = param.weight_loader
                    weight_loader(param, loaded_weight, shard_id)
                    break
                else:
                    for param_name, weight_name, shard_id in expert_params_mapping:
                        if weight_name not in name:
                            continue
                        name = name.replace(weight_name, param_name)
                        if is_pp_missing_parameter(name, self):
                            continue
                        param = params_dict[name]
                        weight_loader = param.weight_loader
                        weight_loader(
                            param, loaded_weight, weight_name, expert_id=shard_id
                        )
                        break
                    else:
                        if name.endswith(".bias") and name not in params_dict:
                            continue
                        if is_pp_missing_parameter(name, self):
                            continue
                        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
