"""
Copyright 2023-2024 SGLang Team
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at
    http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
"""

"""Fused operators for activation layers."""

from typing import Optional

import torch
import torch.nn as nn
import torch.nn.functional as F
from flashinfer.activation import gelu_tanh_and_mul, silu_and_mul
from vllm.distributed import (
    divide,
    get_tensor_model_parallel_rank,
    get_tensor_model_parallel_world_size,
)
from vllm.model_executor.custom_op import CustomOp
from vllm.model_executor.layers.quantization import QuantizationConfig
from vllm.model_executor.utils import set_weight_attrs


class SiluAndMul(CustomOp):
    def __init__(self, **kwargs):
        super().__init__()
        self.is_lower_sm80 = torch.cuda.get_device_capability()[0] < 8

    def forward_native(self, x: torch.Tensor) -> torch.Tensor:
        d = x.shape[-1] // 2
        return F.silu(x[..., :d]) * x[..., d:]

    def forward_cuda(self, x: torch.Tensor) -> torch.Tensor:
        if self.is_lower_sm80:
            return self.forward_native(x)

        d = x.shape[-1] // 2
        output_shape = x.shape[:-1] + (d,)
        out = torch.empty(output_shape, dtype=x.dtype, device=x.device)
        silu_and_mul(x, out)
        return out


class GeluAndMul(CustomOp):
    def __init__(self, **kwargs):
        super().__init__()

    def forward_native(self, x: torch.Tensor) -> torch.Tensor:
        d = x.shape[-1] // 2
        return F.gelu(x[..., :d], approximate="tanh") * x[..., d:]

    def forward_cuda(self, x: torch.Tensor) -> torch.Tensor:
        d = x.shape[-1] // 2
        output_shape = x.shape[:-1] + (d,)
        out = torch.empty(output_shape, dtype=x.dtype, device=x.device)
        gelu_tanh_and_mul(x, out)
        return out


class ScaledActivation(nn.Module):
    """An activation function with post-scale parameters.

    This is used for some quantization methods like AWQ.
    """

    def __init__(
        self,
        act_module: nn.Module,
        intermediate_size: int,
        input_is_parallel: bool = True,
        params_dtype: Optional[torch.dtype] = None,
    ):
        super().__init__()
        self.act = act_module
        self.input_is_parallel = input_is_parallel
        if input_is_parallel:
            tp_size = get_tensor_model_parallel_world_size()
            intermediate_size_per_partition = divide(intermediate_size, tp_size)
        else:
            intermediate_size_per_partition = intermediate_size
        if params_dtype is None:
            params_dtype = torch.get_default_dtype()
        self.scales = nn.Parameter(
            torch.empty(intermediate_size_per_partition, dtype=params_dtype)
        )
        set_weight_attrs(self.scales, {"weight_loader": self.weight_loader})

    def forward(self, x: torch.Tensor) -> torch.Tensor:
        return self.act(x) / self.scales

    def weight_loader(self, param: nn.Parameter, loaded_weight: torch.Tensor):
        param_data = param.data
        if self.input_is_parallel:
            tp_rank = get_tensor_model_parallel_rank()
            shard_size = param_data.shape[0]
            start_idx = tp_rank * shard_size
            loaded_weight = loaded_weight.narrow(0, start_idx, shard_size)
        assert param_data.shape == loaded_weight.shape
        param_data.copy_(loaded_weight)


_ACTIVATION_REGISTRY = {
    "gelu": nn.GELU(),
    "gelu_pytorch_tanh": nn.GELU(approximate="tanh"),
}


def get_act_fn(
    act_fn_name: str,
    quant_config: Optional[QuantizationConfig] = None,
    intermediate_size: Optional[int] = None,
    input_is_parallel: bool = True,
    params_dtype: Optional[torch.dtype] = None,
) -> nn.Module:
    """Get an activation function by name."""
    act_fn_name = act_fn_name.lower()
    if act_fn_name not in _ACTIVATION_REGISTRY:
        raise ValueError(f"Activation function {act_fn_name!r} is not supported.")

    act_fn = _ACTIVATION_REGISTRY[act_fn_name]
    if quant_config is not None and act_fn_name in quant_config.get_scaled_act_names():
        if intermediate_size is None:
            raise ValueError(
                "intermediate_size must be specified for scaled "
                "activation functions."
            )
        return ScaledActivation(
            act_fn, intermediate_size, input_is_parallel, params_dtype
        )
    return act_fn
