# BSD 3-Clause License; see https://github.com/scikit-hep/awkward/blob/main/LICENSE

from __future__ import annotations

from awkward._backends.backend import Backend, KernelKeyType
from awkward._backends.dispatch import register_backend
from awkward._kernels import CupyKernel, NumpyKernel
from awkward._nplikes.cupy import Cupy
from awkward._nplikes.numpy import Numpy
from awkward._nplikes.numpy_like import NumpyMetadata
from awkward._typing import Final

np = NumpyMetadata.instance()
numpy = Numpy.instance()


@register_backend(Cupy)  # type: ignore[type-abstract]
class CupyBackend(Backend):
    name: Final[str] = "cuda"

    _cupy: Cupy

    @property
    def nplike(self) -> Cupy:
        return self._cupy

    def __init__(self):
        self._cupy = Cupy.instance()

    def __getitem__(self, index: KernelKeyType) -> CupyKernel | NumpyKernel:
        from awkward._connect import cuda

        cupy = cuda.import_cupy("Awkward Arrays with CUDA")
        _cuda_kernels = cuda.initialize_cuda_kernels(cupy)
        func = _cuda_kernels[index]
        if func is not None:
            return CupyKernel(func, index)
        else:
            raise AssertionError(f"CuPyKernel not found: {index!r}")
