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

from typing import Any, Optional

import torch
from torch.nn.parameter import Parameter

from vllm import _custom_ops as ops
from vllm.logger import init_logger
from vllm.model_executor.layers.linear import LinearBase, LinearMethodBase
from vllm.model_executor.layers.quantization import (
    QuantizationConfig,
    QuantizationMethods,
)
from vllm.model_executor.parameter import (
    BasevLLMParameter,
    ChannelQuantScaleParameter,
    GroupQuantScaleParameter,
    PackedvLLMParameter,
)
from vllm.scalar_type import scalar_types

logger = init_logger(__name__)

GPTQ_MARLIN_24_TILE = 16
GPTQ_MARLIN_24_MIN_THREAD_N = 128
GPTQ_MARLIN_24_MIN_THREAD_K = 128
GPTQ_MARLIN_24_MAX_PARALLEL = 64

GPTQ_MARLIN_24_SUPPORTED_QUANT_TYPES = [scalar_types.uint4b8, scalar_types.uint8b128]
GPTQ_MARLIN_24_SUPPORTED_GROUP_SIZES = [-1, 128]


class GPTQMarlin24Config(QuantizationConfig):
    """Config class for Marlin24."""

    def __init__(
        self,
        weight_bits: int,
        group_size: int,
    ) -> None:
        super().__init__()
        quant_type = {
            4: scalar_types.uint4b8,
            8: scalar_types.uint8b128,
        }.get(weight_bits)

        self.group_size = group_size

        # Verify
        if quant_type is None or quant_type not in GPTQ_MARLIN_24_SUPPORTED_QUANT_TYPES:
            raise ValueError(
                f"Marlin_24 does not support quant_type = {quant_type}. "
                f"Only weight_bits = {GPTQ_MARLIN_24_SUPPORTED_QUANT_TYPES} "
                "are supported."
            )
        if self.group_size not in GPTQ_MARLIN_24_SUPPORTED_GROUP_SIZES:
            raise ValueError(
                f"Marlin_24 does not support group_size = {self.group_size}. "
                f"Only group_sizes = {GPTQ_MARLIN_24_SUPPORTED_GROUP_SIZES} "
                "are supported."
            )

        self.quant_type = quant_type

        # 4 Bits packed into 32 bit datatype.
        self.pack_factor = 32 // self.quant_type.size_bits

        # Tile size used by marlin kernels.
        self.tile_size = 16

        # Min out_features dim
        self.min_n_threads = GPTQ_MARLIN_24_MIN_THREAD_N

        # Min in_features dim
        self.min_k_threads = GPTQ_MARLIN_24_MIN_THREAD_K

        # Max parallel problems to solve at once (improves large
        # batch performance)
        self.max_parallel = GPTQ_MARLIN_24_MAX_PARALLEL

        # Permutation length used by the marlin kernels.
        self.perm_len = 1024

    def __repr__(self) -> str:
        return "Marlin24Config(quant_type={}, group_size={})".format(
            self.quant_type, self.group_size
        )

    @classmethod
    def get_name(cls) -> QuantizationMethods:
        return "gptq_marlin_24"

    @classmethod
    def get_supported_act_dtypes(cls) -> list[torch.dtype]:
        return [torch.half]

    @classmethod
    # Need to figure it out
    def get_min_capability(cls) -> int:
        return 80

    @classmethod
    def get_config_filenames(cls) -> list[str]:
        return ["quantize_config.json"]

    @classmethod
    def from_config(cls, config: dict[str, Any]) -> "GPTQMarlin24Config":
        weight_bits = cls.get_from_keys(config, ["bits"])
        group_size = cls.get_from_keys(config, ["group_size"])
        return cls(weight_bits, group_size)

    @classmethod
    def override_quantization_method(
        cls, hf_quant_cfg, user_quant
    ) -> QuantizationMethods | None:
        is_marlin_24_format = hf_quant_cfg.get("checkpoint_format") == "marlin_24"

        is_valid_user_quant = (
            user_quant is None or user_quant == "gptq" or user_quant == "gptq_marlin_24"
        )

        if is_marlin_24_format and is_valid_user_quant:
            msg = "The model is serialized in {} format. Using {} kernel.".format(
                cls.get_name(), cls.get_name()
            )
            logger.info(msg)
            return cls.get_name()

        return None

    def get_quant_method(
        self, layer: torch.nn.Module, prefix: str
    ) -> Optional["GPTQMarlin24LinearMethod"]:
        if isinstance(layer, LinearBase):
            return GPTQMarlin24LinearMethod(self)
        return None


class GPTQMarlin24LinearMethod(LinearMethodBase):
    """Linear method for Marlin24.

    Args:
        quant_config: The Marlin24 quantization config.
    """

    def __init__(self, quant_config: GPTQMarlin24Config):
        self.quant_config = quant_config

    def create_weights(
        self,
        layer: torch.nn.Module,
        input_size_per_partition: int,
        output_partition_sizes: list[int],
        input_size: int,
        output_size: int,
        params_dtype: torch.dtype,
        **extra_weight_attrs,
    ):
        del output_size  # Unused.
        weight_loader = extra_weight_attrs["weight_loader"]
        if params_dtype != torch.float16:
            raise ValueError(
                f"The params dtype must be float16, but got {params_dtype}"
            )

        # Validate output_size_per_partition
        output_size_per_partition = sum(output_partition_sizes)
        if output_size_per_partition % self.quant_config.min_n_threads != 0:
            raise ValueError(
                f"Weight output_size_per_partition = "
                f"{output_size_per_partition} is not divisible by "
                f"min_n_threads = {self.quant_config.min_n_threads}."
            )
        if output_size_per_partition % self.quant_config.pack_factor != 0:
            raise ValueError(
                f"Weight output_size_per_partition = "
                f"{output_size_per_partition} is not divisible by "
                f"pack_factor = {self.quant_config.pack_factor}."
            )

        # Validate input_size_per_partition
        if input_size_per_partition % self.quant_config.min_k_threads != 0:
            raise ValueError(
                f"Weight input_size_per_partition = "
                f"{input_size_per_partition} is not divisible by "
                f"min_k_threads = {self.quant_config.min_k_threads}."
            )
        if (
            self.quant_config.group_size != -1
            and input_size_per_partition % self.quant_config.group_size != 0
        ):
            raise ValueError(
                f"Weight input_size_per_partition = "
                f"{input_size_per_partition} is not divisible by "
                f"group_size = {self.quant_config.group_size}."
            )

        # Check that we have at least 4 tiles horizontally in the shard
        num_tiles_per_perm = self.quant_config.perm_len // (
            self.quant_config.tile_size**2
        )
        if output_size_per_partition % num_tiles_per_perm != 0:
            raise ValueError("Each permutation group must reside on the same gpu")

        # Quantized 4Bit weights packed into Int32.
        qweight = PackedvLLMParameter(
            data=torch.empty(
                input_size_per_partition // self.quant_config.tile_size // 2,
                output_size_per_partition
                * self.quant_config.tile_size
                // self.quant_config.pack_factor,
                device="cuda",
                dtype=torch.int32,
            ),
            input_dim=0,
            output_dim=1,
            packed_dim=1,
            packed_factor=self.quant_config.pack_factor,
            marlin_tile_size=self.quant_config.tile_size,
            weight_loader=weight_loader,
        )

        # Meta
        meta = PackedvLLMParameter(
            data=torch.empty(
                input_size_per_partition // 8 // 2 // 2,
                output_size_per_partition * 2,
                device="cuda",
                dtype=torch.int16,
            ),
            input_dim=0,
            output_dim=1,
            packed_dim=1,
            packed_factor=1,
            marlin_tile_size=2,
            weight_loader=weight_loader,
        )

        # Determine if channelwise or not
        input_groups = (
            1
            if self.quant_config.group_size == -1
            else input_size_per_partition // self.quant_config.group_size
        )

        weight_scale_args = {
            "data": torch.empty(
                input_groups,
                output_size_per_partition,
                device="cuda",
                dtype=params_dtype,
            ),
            "weight_loader": weight_loader,
        }
        if input_groups == 1:
            scales = ChannelQuantScaleParameter(output_dim=1, **weight_scale_args)
        else:
            scales = GroupQuantScaleParameter(
                output_dim=1, input_dim=0, **weight_scale_args
            )

        # Allocate workspace (Used for internal locking mechanism)
        max_workspace_size = (
            output_size_per_partition // self.quant_config.min_n_threads
        ) * self.quant_config.max_parallel

        workspace = BasevLLMParameter(
            data=torch.zeros(max_workspace_size, device="cuda", dtype=torch.int),
            weight_loader=weight_loader,
        )

        layer.register_parameter("B_24", qweight)
        layer.register_parameter("B_meta", meta)
        layer.register_parameter("s", scales)
        layer.register_parameter("workspace", workspace)

    def process_weights_after_loading(self, layer: torch.nn.Module) -> None:
        # required by torch.compile
        layer.B_24 = Parameter(layer.B_24.data, requires_grad=False)
        layer.s = Parameter(layer.s.data, requires_grad=False)
        layer.B_meta = Parameter(layer.B_meta.data, requires_grad=False)
        layer.workspace = Parameter(layer.workspace.data, requires_grad=False)

    def apply(
        self,
        layer: torch.nn.Module,
        x: torch.Tensor,
        bias: torch.Tensor | None = None,
    ) -> torch.Tensor:
        qweight = layer.B_24
        meta = layer.B_meta
        scales = layer.s
        workspace = layer.workspace

        x_2d = x.view(-1, x.shape[-1])

        size_m = x_2d.shape[0]
        size_k = x_2d.shape[1]
        size_n = scales.shape[1]

        output_2d = ops.gptq_marlin_24_gemm(
            x_2d,
            qweight,
            meta,
            scales,
            workspace,
            self.quant_config.quant_type,
            size_m,
            size_n,
            size_k,
        )

        output = output_2d.view(x.shape[:-1] + (output_2d.shape[1],))

        if bias is not None:
            output.add_(bias)  # In-place add

        return output
