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


import torch
from compressed_tensors.quantization import (
    QuantizationArgs,
    QuantizationStrategy,
)

import vllm.model_executor.layers.fused_moe.modular_kernel as mk
from vllm.distributed import get_tensor_model_parallel_world_size
from vllm.logger import init_logger
from vllm.model_executor.layers.fused_moe import (
    FusedMoeWeightScaleSupported,
    RoutedExperts,
    SharedExperts,
)
from vllm.model_executor.layers.fused_moe.config import (
    FusedMoEConfig,
    FusedMoEQuantConfig,
)
from vllm.model_executor.layers.fused_moe.oracle.fp8 import (
    convert_to_fp8_moe_kernel_format,
    make_fp8_moe_kernel,
    make_fp8_moe_quant_config,
    select_fp8_moe_backend,
)
from vllm.model_executor.layers.quantization.compressed_tensors.compressed_tensors_moe import (  # noqa E501
    CompressedTensorsMoEMethod,
)
from vllm.model_executor.layers.quantization.utils.fp8_utils import (
    process_fp8_input_tensor_strategy_moe,
    process_fp8_weight_tensor_strategy_moe,
)
from vllm.model_executor.layers.quantization.utils.quant_utils import (
    kFp8Dynamic128Sym,
    kFp8DynamicTokenSym,
    kFp8Static128BlockSym,
    kFp8StaticChannelSym,
    kFp8StaticTensorSym,
)
from vllm.model_executor.layers.quantization.utils.w8a8_utils import (
    normalize_e4m3fn_to_e4m3fnuz,
)
from vllm.model_executor.utils import replace_parameter, set_weight_attrs
from vllm.platforms import current_platform

logger = init_logger(__name__)


class CompressedTensorsW8A8Fp8MoEMethod(CompressedTensorsMoEMethod):
    """W8A8 FP8 MoE quantization using compressed tensors."""

    def __init__(
        self,
        weight_quant: QuantizationArgs,
        input_quant: QuantizationArgs,
        moe: FusedMoEConfig,
        layer_name: str | None = None,
    ):
        super().__init__(moe)
        self.weight_quant = weight_quant
        self.input_quant = input_quant

        per_tensor = (
            self.weight_quant.strategy == QuantizationStrategy.TENSOR
            and self.input_quant.strategy == QuantizationStrategy.TENSOR
        )
        per_channel = (
            self.weight_quant.strategy == QuantizationStrategy.CHANNEL
            and self.input_quant.strategy == QuantizationStrategy.TOKEN
        )
        if not (per_tensor or per_channel):
            assert self.weight_quant.strategy == QuantizationStrategy.BLOCK
            self.weight_block_size = self.weight_quant.block_structure
            assert self.weight_quant.dynamic is not None
        else:
            self.weight_block_size = None
        self.block_quant = self.weight_block_size is not None

        self.static_input_scales = not self.input_quant.dynamic
        if self.static_input_scales and per_channel:
            raise ValueError(
                "For FP8 Fused MoE layer, we require either per tensor or "
                "channelwise, dynamic per token quantization."
            )

        ct2vllm_weight = {
            QuantizationStrategy.CHANNEL: kFp8StaticChannelSym,
            QuantizationStrategy.TENSOR: kFp8StaticTensorSym,
            QuantizationStrategy.BLOCK: kFp8Static128BlockSym,
        }
        ct2vllm_act = {
            QuantizationStrategy.TOKEN: kFp8DynamicTokenSym,
            QuantizationStrategy.TENSOR: (
                kFp8StaticTensorSym if self.static_input_scales else kFp8Dynamic128Sym
            ),
        }
        weight_key = ct2vllm_weight[self.weight_quant.strategy]
        if weight_key == kFp8Static128BlockSym:
            activation_key = kFp8Dynamic128Sym
        else:
            activation_key = ct2vllm_act[self.input_quant.strategy]

        # Select Fp8 MoE backend
        self.fp8_backend, self.experts_cls = select_fp8_moe_backend(
            config=self.moe,
            weight_key=weight_key,
            activation_key=activation_key,
            allow_vllm_cutlass=True,
        )

    def create_weights(
        self,
        layer: torch.nn.Module,
        num_experts: int,
        hidden_size: int,
        intermediate_size_per_partition: int,
        params_dtype: torch.dtype,
        **extra_weight_attrs,
    ):
        layer.num_experts = num_experts
        layer.orig_dtype = params_dtype
        layer.weight_block_size = None

        params_dtype = torch.float8_e4m3fn
        w13_num_shards = 2 if self.moe.is_act_and_mul else 1

        if self.block_quant:
            assert self.weight_block_size is not None
            layer.weight_block_size = self.weight_block_size
            tp_size = get_tensor_model_parallel_world_size()
            block_n, block_k = (
                self.weight_block_size[0],
                self.weight_block_size[1],
            )
            # NOTE: To ensure proper alignment of the block-wise quantization
            # scales, the output_size of the weights for both the gate and up
            # layers must be divisible by block_n.
            # Required by column parallel or enabling merged weights
            if intermediate_size_per_partition % block_n != 0:
                raise ValueError(
                    f"The output_size of gate's and up's weight = "
                    f"{intermediate_size_per_partition} is not divisible by "
                    f"weight quantization block_n = {block_n}."
                )
            if tp_size > 1 and intermediate_size_per_partition % block_k != 0:
                # Required by row parallel
                raise ValueError(
                    f"The input_size of down's weight = "
                    f"{intermediate_size_per_partition} is not divisible by "
                    f"weight quantization block_k = {block_k}."
                )

        # WEIGHTS
        w13_weight = torch.nn.Parameter(
            torch.empty(
                num_experts,
                w13_num_shards * intermediate_size_per_partition,
                hidden_size,
                dtype=params_dtype,
            ),
            requires_grad=False,
        )
        layer.register_parameter("w13_weight", w13_weight)
        set_weight_attrs(w13_weight, extra_weight_attrs)

        w2_weight = torch.nn.Parameter(
            torch.empty(
                num_experts,
                hidden_size,
                intermediate_size_per_partition,
                dtype=params_dtype,
            ),
            requires_grad=False,
        )
        layer.register_parameter("w2_weight", w2_weight)
        set_weight_attrs(w2_weight, extra_weight_attrs)

        # WEIGHT_SCALES
        if self.weight_quant.strategy == QuantizationStrategy.TENSOR:
            # For gated MoE, allocate 2 scales for w1 and w3 respectively.
            # They will be combined to a single scale after weight loading.
            # For non-gated MoE, allocate 1 scale for w13.
            w13_weight_scale = torch.nn.Parameter(
                torch.ones(num_experts, w13_num_shards, dtype=torch.float32),
                requires_grad=False,
            )
            layer.register_parameter("w13_weight_scale", w13_weight_scale)
            w2_weight_scale = torch.nn.Parameter(
                torch.ones(num_experts, dtype=torch.float32), requires_grad=False
            )
            layer.register_parameter("w2_weight_scale", w2_weight_scale)
            # Add PER-TENSOR quantization for RoutedExperts.weight_loader.
            extra_weight_attrs.update(
                {"quant_method": FusedMoeWeightScaleSupported.TENSOR.value}
            )
            set_weight_attrs(w13_weight_scale, extra_weight_attrs)
            set_weight_attrs(w2_weight_scale, extra_weight_attrs)

        elif self.weight_quant.strategy == QuantizationStrategy.CHANNEL:
            w13_weight_scale = torch.nn.Parameter(
                torch.ones(
                    num_experts,
                    w13_num_shards * intermediate_size_per_partition,
                    1,
                    dtype=torch.float32,
                ),
                requires_grad=False,
            )
            layer.register_parameter("w13_weight_scale", w13_weight_scale)
            w2_weight_scale = torch.nn.Parameter(
                torch.ones(num_experts, hidden_size, 1, dtype=torch.float32),
                requires_grad=False,
            )
            layer.register_parameter("w2_weight_scale", w2_weight_scale)
            # Add PER-CHANNEL quantization for RoutedExperts.weight_loader.
            extra_weight_attrs.update(
                {"quant_method": FusedMoeWeightScaleSupported.CHANNEL.value}
            )
            set_weight_attrs(w13_weight_scale, extra_weight_attrs)
            set_weight_attrs(w2_weight_scale, extra_weight_attrs)

        elif self.weight_quant.strategy == QuantizationStrategy.BLOCK:
            w13_weight_scale = torch.nn.Parameter(
                torch.ones(
                    num_experts,
                    w13_num_shards
                    * ((intermediate_size_per_partition + block_n - 1) // block_n),
                    (hidden_size + block_k - 1) // block_k,
                    dtype=torch.float32,
                ),
                requires_grad=False,
            )
            layer.register_parameter("w13_weight_scale", w13_weight_scale)
            w2_weight_scale = torch.nn.Parameter(
                torch.ones(
                    num_experts,
                    (hidden_size + block_n - 1) // block_n,
                    (intermediate_size_per_partition + block_k - 1) // block_k,
                    dtype=torch.float32,
                ),
                requires_grad=False,
            )
            layer.register_parameter("w2_weight_scale", w2_weight_scale)
            # Add PER-CHANNEL quantization for RoutedExperts.weight_loader.
            extra_weight_attrs.update(
                {"quant_method": FusedMoeWeightScaleSupported.BLOCK.value}
            )
            set_weight_attrs(w13_weight_scale, extra_weight_attrs)
            set_weight_attrs(w2_weight_scale, extra_weight_attrs)

        # INPUT_SCALES
        if self.static_input_scales:
            w13_input_scale = torch.nn.Parameter(
                torch.ones(num_experts, dtype=torch.float32), requires_grad=False
            )
            layer.register_parameter("w13_input_scale", w13_input_scale)
            set_weight_attrs(w13_input_scale, extra_weight_attrs)

            w2_input_scale = torch.nn.Parameter(
                torch.ones(num_experts, dtype=torch.float32), requires_grad=False
            )
            layer.register_parameter("w2_input_scale", w2_input_scale)
            set_weight_attrs(w2_input_scale, extra_weight_attrs)
        else:
            layer.w13_input_scale = None
            layer.w2_input_scale = None

    def process_weights_after_loading(self, layer: RoutedExperts) -> None:
        # Allow for accessing weights and scales in standard way.
        w13 = layer.w13_weight
        w2 = layer.w2_weight
        w13_scale = layer.w13_weight_scale
        w2_scale = layer.w2_weight_scale
        w13_input_scale = layer.w13_input_scale
        w2_input_scale = layer.w2_input_scale

        # MI300x and MI325x use FNUZ format for FP8. Convert if needed.
        if current_platform.is_fp8_fnuz():
            w13, w13_scale, w13_input_scale = normalize_e4m3fn_to_e4m3fnuz(
                w13, w13_scale, w13_input_scale
            )
            w2, w2_scale, w2_input_scale = normalize_e4m3fn_to_e4m3fnuz(
                w2, w2_scale, w2_input_scale
            )

        # Per tensor kernels require single activation scale. Use the max.
        if self.static_input_scales:
            assert self.input_quant.strategy == QuantizationStrategy.TENSOR
            assert w13_input_scale is not None and w2_input_scale is not None
            w13_input_scale, w2_input_scale = process_fp8_input_tensor_strategy_moe(
                w13_input_scale, w2_input_scale
            )
            replace_parameter(layer, "w13_input_scale", w13_input_scale)
            replace_parameter(layer, "w2_input_scale", w2_input_scale)

        # Per-tensor kernels use a single scale, for W13, but on disk there
        # is a separate scale for W1 and W3. Requantize with the max scale.
        if self.weight_quant.strategy == QuantizationStrategy.TENSOR:
            w13, w13_scale = process_fp8_weight_tensor_strategy_moe(
                w13,
                w13_scale,
                shard_size=layer.intermediate_size_per_partition,
                num_experts=layer.local_num_experts,
                is_act_and_mul=self.moe.is_act_and_mul,
            )

        w13, w2, w13_scale, w2_scale = convert_to_fp8_moe_kernel_format(
            fp8_backend=self.fp8_backend,
            layer=layer,
            w13=w13,
            w2=w2,
            w13_scale=w13_scale,
            w2_scale=w2_scale,
            w13_input_scale=w13_input_scale,
            w2_input_scale=w2_input_scale,
        )

        # Replace parameters with updated versions. Note that this helper
        # function ensures the replacement is compatible with RL weight reloads.
        replace_parameter(layer, "w13_weight", w13)
        replace_parameter(layer, "w2_weight", w2)
        replace_parameter(layer, "w13_weight_scale", w13_scale)
        replace_parameter(layer, "w2_weight_scale", w2_scale)

        # Setup modular kernel for TP case and naive DP/EP case.
        # In non-naive DP/EP case, we will create a ModularKernelMethod.
        # TODO(rob): unify these so FP8MoEMethod owns the ModularKernel
        # in both cases.
        self.moe_quant_config = self.get_fused_moe_quant_config(layer)
        if self.moe_quant_config:
            assert self.experts_cls is not None
            self.moe_kernel = make_fp8_moe_kernel(
                moe_quant_config=self.moe_quant_config,
                moe_config=self.moe,
                fp8_backend=self.fp8_backend,
                experts_cls=self.experts_cls,
                routing_tables=layer._expert_routing_tables(),
            )

    def maybe_make_prepare_finalize(
        self,
        routing_tables: tuple[torch.Tensor, torch.Tensor, torch.Tensor] | None = None,
    ) -> mk.FusedMoEPrepareAndFinalizeModular | None:
        raise ValueError(
            f"{self.__class__.__name__} uses the new modular kernel initialization "
            "logic. This function should not be called."
        )

    def get_fused_moe_quant_config(self, layer: torch.nn.Module) -> FusedMoEQuantConfig:
        is_per_token = self.input_quant.strategy == QuantizationStrategy.TOKEN
        return make_fp8_moe_quant_config(
            fp8_backend=self.fp8_backend,
            w1_scale=layer.w13_weight_scale,
            w2_scale=layer.w2_weight_scale,
            a1_scale=layer.w13_input_scale,
            a2_scale=layer.w2_input_scale,
            per_act_token_quant=is_per_token,
            per_out_ch_quant=is_per_token,
            block_shape=self.weight_block_size,
            swiglu_limit=getattr(layer, "swiglu_limit", None),
        )

    def apply_monolithic(
        self,
        layer: RoutedExperts,
        x: torch.Tensor,
        router_logits: torch.Tensor,
        input_ids: torch.Tensor | None = None,
    ) -> torch.Tensor:
        assert self.moe_kernel is not None
        return self.moe_kernel.apply_monolithic(
            x,
            layer.w13_weight,
            layer.w2_weight,
            router_logits,
            activation=layer.activation,
            global_num_experts=layer.global_num_experts,
            expert_map=layer.expert_map,
            apply_router_weight_on_input=layer.apply_router_weight_on_input,
            num_expert_group=layer.num_expert_group,
            topk_group=layer.topk_group,
            e_score_correction_bias=layer.e_score_correction_bias,
            routed_scaling_factor=layer.routed_scaling_factor,
        )

    def apply(
        self,
        layer: RoutedExperts,
        x: torch.Tensor,
        topk_weights: torch.Tensor,
        topk_ids: torch.Tensor,
        shared_experts: SharedExperts | None,
        shared_experts_input: torch.Tensor | None,
    ) -> torch.Tensor:
        assert not self.is_monolithic
        assert self.moe_kernel is not None
        return self.moe_kernel.apply(
            x,
            layer.w13_weight,
            layer.w2_weight,
            topk_weights,
            topk_ids,
            activation=layer.activation,
            global_num_experts=layer.global_num_experts,
            expert_map=layer.expert_map,
            apply_router_weight_on_input=layer.apply_router_weight_on_input,
            shared_experts=shared_experts,
            shared_experts_input=shared_experts_input,
        )

    @property
    def supports_eplb(self) -> bool:
        return True
