from typing import Any, Callable, Dict, List, Optional

import torch
from torch.nn.parameter import Parameter

from sglang.srt.distributed import get_tensor_model_parallel_world_size
from sglang.srt.layers.linear import LinearMethodBase
from sglang.srt.layers.parameter import ChannelQuantScaleParameter, ModelWeightParameter
from sglang.srt.layers.quantization.base_config import (
    QuantizationConfig,
    QuantizeMethodBase,
)
from sglang.srt.layers.quantization.int8_kernel import per_token_quant_int8
from sglang.srt.utils import is_cuda, set_weight_attrs

_is_cuda = is_cuda()
if _is_cuda:
    from sgl_kernel import int8_scaled_mm


class W8A8Int8Config(QuantizationConfig):
    """Config class for W8A8 Int8 Quantization.

    - Weight: static, per-channel, symmetric
    - Activation: dynamic, per-token, symmetric
    """

    def __init__(self):
        pass

    @classmethod
    def get_supported_act_dtypes(cls) -> List[torch.dtype]:
        return [torch.float16, torch.bfloat16]

    @classmethod
    def get_min_capability(cls) -> int:
        return 75

    @classmethod
    def get_name(self) -> str:
        return "w8a8_int8"

    @classmethod
    def get_config_filenames(cls) -> List[str]:
        return []

    @classmethod
    def from_config(cls, config: Dict[str, Any]) -> "W8A8Int8Config":
        return cls()

    def get_quant_method(
        self,
        layer: torch.nn.Module,
        prefix: str,
    ) -> Optional["QuantizeMethodBase"]:
        from sglang.srt.layers.linear import LinearBase
        from sglang.srt.layers.moe.fused_moe_triton import FusedMoE

        if isinstance(layer, LinearBase):
            return W8A8Int8LinearMethod(self)
        elif isinstance(layer, FusedMoE):
            return W8A8Int8MoEMethod(self)
        return None

    def get_scaled_act_names(self) -> List[str]:
        return []


class W8A8Int8LinearMethod(LinearMethodBase):

    def __init__(self, quantization_config: W8A8Int8Config):
        self.quantization_config = quantization_config

    def process_weights_after_loading(self, layer: torch.nn.Module) -> None:
        layer.weight = Parameter(layer.weight.t(), requires_grad=False)
        layer.weight_scale = Parameter(layer.weight_scale.data, requires_grad=False)

    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,
    ):

        weight_loader = extra_weight_attrs.get("weight_loader")
        self.logical_widths = output_partition_sizes

        weight = ModelWeightParameter(
            data=torch.empty(
                sum(output_partition_sizes), input_size_per_partition, dtype=torch.int8
            ),
            input_dim=1,
            output_dim=0,
            weight_loader=weight_loader,
        )
        layer.register_parameter("weight", weight)

        weight_scale = ChannelQuantScaleParameter(
            data=torch.empty((sum(output_partition_sizes), 1), dtype=torch.float32),
            output_dim=0,
            weight_loader=weight_loader,
        )
        layer.register_parameter("weight_scale", weight_scale)

    def apply(
        self,
        layer: torch.nn.Module,
        x: torch.Tensor,
        bias: Optional[torch.Tensor] = None,
    ):
        x_q, x_scale = per_token_quant_int8(x)

        return int8_scaled_mm(
            x_q, layer.weight, x_scale, layer.weight_scale, out_dtype=x.dtype, bias=bias
        )


class W8A8Int8MoEMethod:
    """MoE method for INT8.
    Supports loading INT8 checkpoints with static weight scale and
    dynamic/static activation scale.
    Also supports loading quantized FP16/BF16 model checkpoints with dynamic
    activation scaling. The weight scaling factor will be initialized after
    the model weights are loaded.
    Args:
        quant_config: The quantization config.
    """

    def __new__(cls, *args, **kwargs):
        from sglang.srt.layers.moe.fused_moe_triton import FusedMoEMethodBase

        if not hasattr(cls, "_initialized"):
            original_init = cls.__init__
            new_cls = type(
                cls.__name__,
                (FusedMoEMethodBase,),
                {
                    "__init__": original_init,
                    **{k: v for k, v in cls.__dict__.items() if k != "__dict__"},
                },
            )
            obj = super(new_cls, new_cls).__new__(new_cls)
            obj.__init__(*args, **kwargs)
            return obj
        return super().__new__(cls)

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

    def create_weights(
        self,
        layer: torch.nn.Module,
        num_experts: int,
        hidden_size: int,
        intermediate_size: int,
        params_dtype: torch.dtype,
        **extra_weight_attrs,
    ):
        from sglang.srt.layers.moe.fused_moe_triton import FusedMoeWeightScaleSupported

        tp_size = get_tensor_model_parallel_world_size()

        # WEIGHTS
        w13_weight = torch.nn.Parameter(
            torch.empty(
                num_experts, 2 * intermediate_size, hidden_size, dtype=torch.int8
            ),
            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, dtype=torch.int8),
            requires_grad=False,
        )
        layer.register_parameter("w2_weight", w2_weight)
        set_weight_attrs(w2_weight, extra_weight_attrs)

        w13_weight_scale = torch.nn.Parameter(
            torch.ones(num_experts, 2 * intermediate_size, 1, dtype=torch.float32),
            requires_grad=False,
        )
        w2_weight_scale = torch.nn.Parameter(
            torch.ones(num_experts, hidden_size, 1, dtype=torch.float32),
            requires_grad=False,
        )
        layer.register_parameter("w13_weight_scale", w13_weight_scale)
        layer.register_parameter("w2_weight_scale", w2_weight_scale)

        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)

        w13_input_scale = None
        layer.register_parameter("w13_input_scale", w13_input_scale)

        w2_input_scale = None
        layer.register_parameter("w2_input_scale", w2_input_scale)

    def process_weights_after_loading(self, layer: torch.nn.Module) -> None:
        layer.w13_weight = Parameter(layer.w13_weight, requires_grad=False)
        layer.w2_weight = Parameter(layer.w2_weight, requires_grad=False)
        layer.w13_weight_scale = Parameter(
            layer.w13_weight_scale.data, requires_grad=False
        )
        layer.w2_weight_scale = Parameter(
            layer.w2_weight_scale.data, requires_grad=False
        )

    def apply(
        self,
        layer: torch.nn.Module,
        x: torch.Tensor,
        router_logits: torch.Tensor,
        top_k: int,
        renormalize: bool,
        use_grouped_topk: bool,
        topk_group: Optional[int] = None,
        num_expert_group: Optional[int] = None,
        num_fused_shared_experts: int = 0,
        custom_routing_function: Optional[Callable] = None,
        correction_bias: Optional[torch.Tensor] = None,
        activation: str = "silu",
        apply_router_weight_on_input: bool = False,
        inplace: bool = True,
        no_combine: bool = False,
        routed_scaling_factor: Optional[float] = None,
    ) -> torch.Tensor:
        from sglang.srt.layers.moe.fused_moe_triton.fused_moe import fused_experts
        from sglang.srt.layers.moe.topk import select_experts

        # Expert selection
        topk_weights, topk_ids = select_experts(
            hidden_states=x,
            router_logits=router_logits,
            use_grouped_topk=use_grouped_topk,
            top_k=top_k,
            renormalize=renormalize,
            topk_group=topk_group,
            num_expert_group=num_expert_group,
            num_fused_shared_experts=num_fused_shared_experts,
            custom_routing_function=custom_routing_function,
            correction_bias=correction_bias,
            routed_scaling_factor=routed_scaling_factor,
        )

        return fused_experts(
            x,
            layer.w13_weight,
            layer.w2_weight,
            topk_weights=topk_weights,
            topk_ids=topk_ids,
            inplace=inplace,
            activation=activation,
            apply_router_weight_on_input=apply_router_weight_on_input,
            use_int8_w8a8=True,
            per_channel_quant=True,
            w1_scale=(layer.w13_weight_scale),
            w2_scale=(layer.w2_weight_scale),
            a1_scale=layer.w13_input_scale,
            a2_scale=layer.w2_input_scale,
            no_combine=no_combine,
        )
