# SPDX-License-Identifier: Apache-2.0
# SPDX-FileCopyrightText: Copyright contributors to the vLLM project
from typing import Any

import torch

from vllm.logger import init_logger
from vllm.platforms import current_platform
from vllm.utils.import_utils import has_triton_kernels
from vllm.utils.torch_utils import direct_register_custom_op, is_torch_equal_or_newer

logger = init_logger(__name__)

# CK's pre-compiled MXFP4 MoE GEMM kernel instances require the
# intermediate_size (after TP split) to be a multiple of this value.
# This arises from FP4 packing (2 values per byte) combined with CK
# tile size constraints. When violated, AITER raises:
# "device_gemm ... does not support this GEMM problem".
CK_MXFP4_MOE_DIM_ALIGNMENT = 256


def should_use_cdna4_mx_scale_swizzle() -> bool:
    """Whether to use the CDNA4 swizzled scale layout for mxfp4 on gfx950.

    CDNA4 swizzle requires BLOCK_K%256==0; at TP>=4 the A8W4 dispatch
    picks BK<256 tiles for the smaller per-rank shapes, so swizzle must
    be off. Used by both the weight-load swizzle in `_swizzle_mxfp4` and
    the kernel-argument gate in `aiter_mxfp4_w4a8_moe`; they must agree.
    """
    from vllm.distributed import get_tensor_model_parallel_world_size
    from vllm.platforms.rocm import on_gfx950

    return on_gfx950() and get_tensor_model_parallel_world_size() <= 2


def _swizzle_mxfp4(quant_tensor, scale, num_warps=8):
    """weight swizzle for mxfp4 moe, used for OAI mxfp4 kernel"""
    assert has_triton_kernels()
    import triton_kernels.matmul_ogs_details.opt_flags as opt_flags
    from triton_kernels.numerics import InFlexData
    from triton_kernels.tensor import FP4, convert_layout, wrap_torch_tensor
    from triton_kernels.tensor_details import layout
    from triton_kernels.tensor_details.layout import StridedLayout

    value_layout_opts: dict[str, Any] = {}
    scale_layout_opts: dict[str, Any] = {}

    if (
        current_platform.is_cuda()
        and current_platform.is_device_capability(90)
        and not is_torch_equal_or_newer("2.8.1")
    ):
        logger.warning_once(
            "Mxfp4 on hopper is running on torch < 2.8.1, "
            "this cause swizling to be disabled, which may "
            "cause performance degradation. Please upgrade to torch nightly"
        )
        value_layout = StridedLayout
        scale_layout = StridedLayout
    elif current_platform.is_rocm():
        value_layout = StridedLayout
        if should_use_cdna4_mx_scale_swizzle():
            try:
                # triton < 3.6
                from triton_kernels.tensor_details.layout import GFX950MXScaleLayout

                scale_layout = GFX950MXScaleLayout
            except ImportError:
                # triton >= 3.6
                from triton_kernels.tensor_details.layout import CDNA4MXScaleLayout

                scale_layout = CDNA4MXScaleLayout
        else:
            scale_layout = StridedLayout
    else:
        value_layout, value_layout_opts = layout.make_default_matmul_mxfp4_w_layout(
            mx_axis=1
        )
        scale_layout, scale_layout_opts = (
            layout.make_default_matmul_mxfp4_w_scale_layout(
                mx_axis=1, num_warps=num_warps
            )
        )
    if current_platform.is_cuda():
        if current_platform.is_device_capability(90):
            constraints = {
                "split_k": 1,
            }
            opt_flags.update_opt_flags_constraints(constraints)
            # Patches #47303: pad K (num scale groups) to 0 mod 4
            # TODO: Remove once we upgrade to Triton 3.8.0+ kernels
            if scale.numel() > 0:
                K = scale.shape[-1]
                pad_k = -K % 4
                scale = torch.nn.functional.pad(scale, (0, pad_k))
        elif current_platform.is_device_capability_family(100):
            constraints = {
                "is_persistent": True,
                "epilogue_subtile": 1,
            }
            opt_flags.update_opt_flags_constraints(constraints)
    # transpose the tensor so that the quantization axis is on dim1
    quant_tensor = quant_tensor.transpose(-2, -1)
    scale = scale.transpose(-2, -1)
    quant_tensor = convert_layout(
        wrap_torch_tensor(quant_tensor, dtype=FP4), value_layout, **value_layout_opts
    )
    scale = convert_layout(wrap_torch_tensor(scale), scale_layout, **scale_layout_opts)
    return quant_tensor, InFlexData(), scale


def _dequant_mxfp4(
    x: torch.Tensor, scale: torch.Tensor, float_dtype: torch.dtype
) -> torch.Tensor:
    try:
        from quark.torch.kernel import mx
    except ImportError as err:
        raise ImportError(
            "The package `amd-quark` is required to use "
            "MX-FP4 models. Please install it with `pip install "
            "amd-quark`."
        ) from err

    return mx.dq_mxfp4(x, scale, float_dtype)


def _dequant_mxfp4_fake(
    x: torch.Tensor, scale: torch.Tensor, float_dtype: torch.dtype
) -> torch.Tensor:
    return torch.empty(
        (*x.shape[:-1], x.shape[-1] * 2), dtype=float_dtype, device=x.device
    )


def _quant_dequant_mxfp4(
    x: torch.Tensor, scale_calculation_mode: str = "even"
) -> torch.Tensor:
    try:
        from quark.torch.kernel import mx
    except ImportError as err:
        raise ImportError(
            "The package `amd-quark` is required to use "
            "MX-FP4 models. Please install it with `pip install "
            "amd-quark`."
        ) from err

    return mx.qdq_mxfp4(x, scale_calculation_mode)


def _quant_dequant_mxfp4_fake(
    x: torch.Tensor, scale_calculation_mode: str = "even"
) -> torch.Tensor:
    return torch.empty_like(x)


# Protect these operations into a torch custom op to avoid errors as
# torch._dynamo.exc.Unsupported: Attempted to call function marked as skipped
# Explanation: Dynamo does not know how to trace the builtin
# `kernel_ext.PyCapsule.dq_uint8_mxfp4_to_half.` This function is either a
# Python builtin (e.g. _warnings.warn) or a third-party C/C++ Python
# extension (perhaps created with pybind).
# TODO: Make sure there is no way to avoid having these functions
# marked as skipped by dynamo.
try:
    direct_register_custom_op(
        op_name="dequant_mxfp4",
        op_func=_dequant_mxfp4,
        fake_impl=_dequant_mxfp4_fake,
    )
    dequant_mxfp4 = torch.ops.vllm.dequant_mxfp4
except AttributeError as error:
    raise error

try:
    direct_register_custom_op(
        op_name="quant_dequant_mxfp4",
        op_func=_quant_dequant_mxfp4,
        fake_impl=_quant_dequant_mxfp4_fake,
    )
    quant_dequant_mxfp4 = torch.ops.vllm.quant_dequant_mxfp4
except AttributeError as error:
    raise error


def xpu_mxfp4_quantize(x: torch.Tensor) -> tuple[torch.Tensor, torch.Tensor]:
    return torch.ops.vllm.xpu_mxfp4_quantize(x)