# SPDX-License-Identifier: Apache-2.0

from typing import Callable, Optional

import torch
from compressed_tensors.quantization import QuantizationStrategy

from vllm.model_executor.layers.quantization.compressed_tensors.schemes import (
    CompressedTensorsScheme)
from vllm.model_executor.layers.quantization.utils.marlin_utils_fp8 import (
    apply_fp8_marlin_linear, prepare_fp8_layer_for_marlin)
from vllm.model_executor.layers.quantization.utils.w8a8_utils import (
    convert_to_channelwise)
from vllm.model_executor.parameter import (ChannelQuantScaleParameter,
                                           ModelWeightParameter,
                                           PerTensorScaleParameter)

__all__ = ["CompressedTensorsW8A16Fp8"]

SUPPORTED_STRATEGIES = [
    QuantizationStrategy.CHANNEL, QuantizationStrategy.TENSOR
]


class CompressedTensorsW8A16Fp8(CompressedTensorsScheme):

    def __init__(self, strategy: str, is_static_input_scheme: bool):
        self.strategy = strategy
        self.is_static_input_scheme = is_static_input_scheme

    @classmethod
    def get_min_capability(cls) -> int:
        # ampere and up
        return 80

    # W8A8-Fp8 kernels support only per-tensor and per-channel cases.
    # So if we have a fused module (QKV, MLP) with per tensor scales,
    # we expand each scale to its shard's channels.
    def process_weights_after_loading(self, layer) -> None:
        if self.strategy == QuantizationStrategy.TENSOR:
            ws_channelwise = convert_to_channelwise(layer.weight_scale,
                                                    layer.logical_widths)
            layer.weight_scale = torch.nn.Parameter(ws_channelwise,
                                                    requires_grad=False)
        else:
            # required by torch.compile to be torch.nn.Parameter
            layer.weight_scale = torch.nn.Parameter(layer.weight_scale.data,
                                                    requires_grad=False)

        # Weights must be transposed for marlin
        layer.weight = torch.nn.Parameter(layer.weight.t(),
                                          requires_grad=False)

        if self.is_static_input_scheme:
            # required by torch.compile to be torch.nn.Parameter
            layer.input_scale = torch.nn.Parameter(layer.input_scale.data,
                                                   requires_grad=False)
        prepare_fp8_layer_for_marlin(layer)

    def create_weights(self, layer: torch.nn.Module, input_size: int,
                       output_partition_sizes: list[int],
                       input_size_per_partition: int,
                       params_dtype: torch.dtype, weight_loader: Callable,
                       **kwargs):

        output_size_per_partition = sum(output_partition_sizes)
        layer.logical_widths = output_partition_sizes
        layer.input_size_per_partition = input_size_per_partition
        layer.output_size_per_partition = output_size_per_partition
        layer.orig_dtype = params_dtype
        layer.weight_block_size = None

        # WEIGHT
        weight = ModelWeightParameter(data=torch.empty(
            output_size_per_partition,
            input_size_per_partition,
            dtype=torch.float8_e4m3fn),
                                      input_dim=1,
                                      output_dim=0,
                                      weight_loader=weight_loader)
        layer.register_parameter("weight", weight)

        # WEIGHT SCALE
        if self.strategy == QuantizationStrategy.CHANNEL:
            weight_scale = ChannelQuantScaleParameter(
                data=torch.empty((sum(output_partition_sizes), 1),
                                 dtype=torch.float32),
                output_dim=0,
                weight_loader=weight_loader)
        elif self.strategy == QuantizationStrategy.TENSOR:
            weight_scale = PerTensorScaleParameter(data=torch.empty(
                len(output_partition_sizes), dtype=torch.float32),
                                                   weight_loader=weight_loader)
        else:
            raise ValueError(
                f"Unsupported weight strategy={self.strategy}, "
                f"supported strategies are {SUPPORTED_STRATEGIES}")

        weight_scale[:] = torch.finfo(torch.float32).min
        layer.register_parameter("weight_scale", weight_scale)

        # INPUT SCALE (to deal with converted checkpoints)
        if self.is_static_input_scheme:
            input_scale = PerTensorScaleParameter(data=torch.empty(
                len(output_partition_sizes), dtype=torch.float32),
                                                  weight_loader=weight_loader)
            layer.register_parameter("input_scale", input_scale)

    def apply_weights(self,
                      layer: torch.nn.Module,
                      x: torch.Tensor,
                      bias: Optional[torch.Tensor] = None) -> torch.Tensor:

        return apply_fp8_marlin_linear(input=x,
                                       weight=layer.weight,
                                       weight_scale=layer.weight_scale,
                                       workspace=layer.workspace,
                                       size_n=layer.output_size_per_partition,
                                       size_k=layer.input_size_per_partition,
                                       bias=bias)
