"""TODO: Add docstring."""

import pyarrow as pa

# Make sure to install torch with cuda
import torch
from numba.cuda import to_device

# Make sure to install numba with cuda
from numba.cuda.cudadrv.devicearray import DeviceNDArray

# To install pyarrow.cuda, run `conda install pyarrow "arrow-cpp-proc=*=cuda" -c conda-forge`
from pyarrow import cuda


def torch_to_ipc_buffer(tensor: torch.TensorType) -> tuple[pa.array, dict]:
    """Convert a Pytorch tensor into a pyarrow buffer containing the IPC handle and its metadata.

    Example Use:
    ```python
    torch_tensor = torch.tensor(random_data, dtype=torch.int64, device="cuda")
    ipc_buffer, metadata = torch_to_ipc_buffer(torch_tensor)
    node.send_output("latency", ipc_buffer, metadata)
    ```
    """
    device_arr = to_device(tensor)
    cuda_buf = pa.cuda.CudaBuffer.from_numba(device_arr.gpu_data)
    handle_buffer = cuda_buf.export_for_ipc().serialize()
    metadata = {
        "shape": device_arr.shape,
        "strides": device_arr.strides,
        "dtype": device_arr.dtype.str,
    }
    return pa.array(handle_buffer, type=pa.uint8()), metadata


def ipc_buffer_to_ipc_handle(handle_buffer: pa.array) -> cuda.IpcMemHandle:
    """Convert a buffer containing a serialized handler into cuda IPC MemHandle.

    example use:
    ```python

    import pyarrow as pa
    from dora.cuda import ipc_buffer_to_ipc_handle, cudabuffer_to_torch

    ctx = pa.cuda.context()
    event = node.next()

    ipc_handle = ipc_buffer_to_ipc_handle(event["value"])
    cudabuffer = ctx.open_ipc_buffer(ipc_handle)
    torch_tensor = cudabuffer_to_torch(cudabuffer, event["metadata"])  # on cuda
    ```
    """
    handle_buffer = handle_buffer.buffers()[1]
    return pa.cuda.IpcMemHandle.from_buffer(handle_buffer)


def cudabuffer_to_numba(buffer: cuda.CudaBuffer, metadata: dict) -> DeviceNDArray:
    """Convert a pyarrow CUDA buffer to numba.

    example use:
    ```python

    import pyarrow as pa
    from dora.cuda import ipc_buffer_to_ipc_handle, cudabuffer_to_torch

    ctx = pa.cuda.context()
    event = node.next()

    ipc_handle = ipc_buffer_to_ipc_handle(event["value"])
    cudabuffer = ctx.open_ipc_buffer(ipc_handle)
    numba_tensor = cudabuffer_to_numbda(cudabuffer, event["metadata"])
    ```
    """
    shape = metadata["shape"]
    strides = metadata["strides"]
    dtype = metadata["dtype"]
    return DeviceNDArray(shape, strides, dtype, gpu_data=buffer.to_numba())


def cudabuffer_to_torch(buffer: cuda.CudaBuffer, metadata: dict) -> torch.Tensor:
    """Convert a pyarrow CUDA buffer to a torch tensor.

    example use:
    ```python

    import pyarrow as pa
    from dora.cuda import ipc_buffer_to_ipc_handle, cudabuffer_to_torch

    ctx = pa.cuda.context()
    event = node.next()

    ipc_handle = ipc_buffer_to_ipc_handle(event["value"])
    cudabuffer = ctx.open_ipc_buffer(ipc_handle)
    torch_tensor = cudabuffer_to_torch(cudabuffer, event["metadata"])  # on cuda
    ```
    """
    return torch.as_tensor(cudabuffer_to_numba(buffer, metadata), device="cuda")
