# SPDX-License-Identifier: Apache-2.0
# SPDX-FileCopyrightText: Copyright contributors to the vLLM project
from typing import Optional

import torch

import vllm.model_executor.layers.fused_moe.modular_kernel as mk
from vllm.model_executor.layers.fused_moe.moe_permute_unpermute import (
    _moe_unpermute_and_reduce)
from vllm.model_executor.layers.fused_moe.utils import (
    moe_kernel_quantize_input)


class MoEPrepareAndFinalizeNoEP(mk.FusedMoEPrepareAndFinalize):

    def __init__(
        self,
        quant_dtype: Optional[torch.dtype] = None,
        per_channel_quant: bool = False,
        block_shape: Optional[list[int]] = None,
    ):
        super().__init__()
        self.per_channel_quant = per_channel_quant
        self.block_shape = block_shape
        self.quant_dtype = quant_dtype

    def max_num_tokens_per_rank(self) -> Optional[int]:
        return None

    def topk_indices_dtype(self) -> Optional[torch.dtype]:
        return None

    def prepare(
        self,
        a1: torch.Tensor,
        a1_scale: Optional[torch.Tensor],
        a2_scale: Optional[torch.Tensor],
        topk_weights: torch.Tensor,
        topk_ids: torch.Tensor,
        num_experts: int,
        expert_map: Optional[torch.Tensor],
        apply_router_weight_on_input: bool = False,
    ) -> tuple[torch.Tensor, Optional[torch.Tensor], Optional[torch.Tensor],
               Optional[torch.Tensor], Optional[torch.Tensor]]:

        if apply_router_weight_on_input:
            topk = topk_ids.size(1)
            # TODO: this only works for topK=1, will need to update for topK>1
            assert topk == 1, \
                "apply_router_weight_on_input is only implemented for topk=1"
            a1.mul_(topk_weights.to(a1.dtype))

        a1q, a1q_scale = moe_kernel_quantize_input(a1, a1_scale,
                                                   self.quant_dtype,
                                                   self.per_channel_quant,
                                                   self.block_shape)

        return a1q, a1q_scale, None, None, None

    def finalize(
        self,
        output: torch.Tensor,
        fused_expert_output: torch.Tensor,
        topk_weights: torch.Tensor,
        topk_ids: torch.Tensor,
        apply_router_weight_on_input: bool,
    ) -> None:
        _moe_unpermute_and_reduce(output, fused_expert_output, None,
                                  topk_weights, apply_router_weight_on_input)