# SPDX-License-Identifier: Apache-2.0
# Copyright (c) 2025 Huawei Technologies Co., Ltd. All Rights Reserved.
# Copyright 2023 The vLLM team.
# Copyright 2023 DeepSeek-AI and the HuggingFace Inc. team. All rights reserved.
#
# This code is based on EleutherAI's GPT-NeoX library and the GPT-NeoX
# and OPT implementations in this library. It has been modified from its
# original forms to accommodate minor architectural differences compared
# to GPT-NeoX and OPT used by the Meta AI team that trained the model.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
from typing import Optional

import torch
from torch import nn
from vllm.attention.backends.abstract import AttentionMetadata
from vllm.attention.layer import MLAAttention
from vllm.config import CacheConfig, get_current_vllm_config
from vllm.distributed import get_tensor_model_parallel_world_size
from vllm.forward_context import ForwardContext, get_forward_context
from vllm.model_executor.layers.mla import (MLAModules,
                                            MultiHeadLatentAttentionWrapper)
from vllm.model_executor.layers.quantization import QuantizationConfig
from vllm.utils.torch_utils import direct_register_custom_op

from vllm_ascend.ascend_config import get_ascend_config


class IndexerWrapper(nn.Module):
    ''' 
    A wrapper of Indexer for Deepseek v3.2.
    This wrapper is currently used to solve the fp8 hard code issue of vllm's deepseek_v2.py.
    It wraps the original Indexer, inherits its module weights
    (including wq_b, wk, weights_proj, k_norm)
    while deletes the unused topk_indices_buffer and k_cache to save memory. 
    TODO: Will be removed once original Indexer supports different quantization methods.
    '''

    def __init__(self, vllm_indexer: nn.Module) -> None:
        super().__init__()

        self.n_head: int = vllm_indexer.n_head  # 64
        self.head_dim: int = vllm_indexer.head_dim  # 128
        self.topk_tokens: int = vllm_indexer.topk_tokens  # 2048
        self.q_lora_rank: int = vllm_indexer.q_lora_rank  # 1536
        self.wq_b = vllm_indexer.wq_b
        self.wk = vllm_indexer.wk
        self.weights_proj = vllm_indexer.weights_proj
        self.k_norm = vllm_indexer.k_norm
        self.softmax_scale = vllm_indexer.softmax_scale
        vllm_indexer.topk_indices_buffer = None  # delete topk_indices_buffer
        vllm_indexer.k_cache = None  # delete k_cache

    def forward(self):
        return


class AscendMultiHeadLatentAttention(MultiHeadLatentAttentionWrapper):

    def __init__(
        self,
        hidden_size: int,
        num_heads: int,
        scale: float,
        qk_nope_head_dim: int,
        qk_rope_head_dim: int,
        v_head_dim: int,
        q_lora_rank: Optional[int],
        kv_lora_rank: int,
        mla_modules: MLAModules,
        cache_config: Optional[CacheConfig] = None,
        quant_config: Optional[QuantizationConfig] = None,
        prefix: str = "",
    ) -> None:
        nn.Module.__init__(self)
        self.hidden_size = hidden_size
        self.kv_lora_rank = kv_lora_rank
        self.qk_rope_head_dim = qk_rope_head_dim
        self.q_lora_rank = q_lora_rank
        self.qk_nope_head_dim = qk_nope_head_dim
        self.qk_head_dim = qk_nope_head_dim + qk_rope_head_dim
        self.v_head_dim = v_head_dim
        self.prefix = prefix
        hf_config = get_current_vllm_config().model_config.hf_text_config
        self.enable_shared_expert_dp = get_ascend_config(
        ).enable_shared_expert_dp
        self.tp_size = get_tensor_model_parallel_world_size()
        self.layers = hf_config.num_hidden_layers
        if mla_modules.indexer is not None:
            ascend_indexer = IndexerWrapper(mla_modules.indexer)
        else:
            ascend_indexer = None
        self.mla_attn = MLAAttention(
            num_heads=num_heads,
            scale=scale,
            qk_nope_head_dim=self.qk_nope_head_dim,
            qk_rope_head_dim=self.qk_rope_head_dim,
            v_head_dim=self.v_head_dim,
            q_lora_rank=self.q_lora_rank,
            kv_lora_rank=self.kv_lora_rank,
            kv_b_proj=mla_modules.kv_b_proj,
            cache_config=cache_config,
            quant_config=quant_config,
            prefix=f"{prefix}.attn",
            use_sparse=mla_modules.is_sparse,
            indexer=ascend_indexer,
            # extra args
            rotary_emb=mla_modules.rotary_emb,
            fused_qkv_a_proj=mla_modules.fused_qkv_a_proj,
            q_b_proj=mla_modules.q_b_proj,
            q_a_layernorm=mla_modules.q_a_layernorm,
            q_proj=mla_modules.q_proj,
            kv_a_proj_with_mqa=mla_modules.kv_a_proj_with_mqa,
            kv_a_layernorm=mla_modules.kv_a_layernorm,
            o_proj=mla_modules.o_proj,
        )

        compilation_config = get_current_vllm_config().compilation_config
        if prefix in compilation_config.static_forward_context:
            raise ValueError(f"Duplicate layer name: {prefix}")
        compilation_config.static_forward_context[prefix] = self

    def forward(
            self,
            positions: torch.Tensor,
            hidden_states: torch.Tensor,
            kv_cache: Optional[torch.Tensor] = None,
            attn_metadata: Optional[AttentionMetadata] = None) -> torch.Tensor:
        need_gather_q_kv = get_forward_context().sp_enabled
        output_shape = hidden_states.shape
        # FIXME: This does not seem right, should make sure the buffer is fixed
        output = torch.empty(output_shape,
                             dtype=hidden_states.dtype,
                             device=hidden_states.device)
        torch.ops.vllm.mla_forward(hidden_states, need_gather_q_kv, output,
                                   self.prefix)
        output = output.view(-1, output_shape[-1])
        return output


def mla_forward(
    hidden_states: torch.Tensor,
    need_gather_q_kv: bool,
    output: torch.Tensor,
    layer_name: str,
) -> None:
    forward_context: ForwardContext = get_forward_context()
    self = forward_context.no_compile_layers[layer_name]
    if forward_context.attn_metadata:
        attn_metadata = forward_context.attn_metadata[self.mla_attn.layer_name]
    else:
        attn_metadata = forward_context.attn_metadata
    kv_cache = self.mla_attn.kv_cache[forward_context.virtual_engine]
    self.mla_attn.impl.forward(self.mla_attn.layer_name, hidden_states,
                               kv_cache, attn_metadata, need_gather_q_kv,
                               output)
    return


def mla_forward_fake(
    hidden_states: torch.Tensor,
    need_gather_q_kv: bool,
    output: torch.Tensor,
    layer_name: str,
) -> None:
    return


direct_register_custom_op(
    op_name="mla_forward",
    op_func=mla_forward,
    mutates_args=["output"],
    fake_impl=mla_forward_fake,
    dispatch_key="PrivateUse1",
)
