from __future__ import annotations

from collections.abc import AsyncIterable, Mapping, Sequence
from io import BytesIO
from os import PathLike
from subprocess import DEVNULL, PIPE, CalledProcessError, CompletedProcess
from typing import IO, Any, cast

from ..abc import Process
from ._eventloop import get_async_backend
from ._tasks import create_task_group


async def run_process(
    command: str | bytes | Sequence[str | bytes],
    *,
    input: bytes | None = None,
    stdout: int | IO[Any] | None = PIPE,
    stderr: int | IO[Any] | None = PIPE,
    check: bool = True,
    cwd: str | bytes | PathLike[str] | None = None,
    env: Mapping[str, str] | None = None,
    start_new_session: bool = False,
) -> CompletedProcess[bytes]:
    """
    Run an external command in a subprocess and wait until it completes.

    .. seealso:: :func:`subprocess.run`

    :param command: either a string to pass to the shell, or an iterable of strings
        containing the executable name or path and its arguments
    :param input: bytes passed to the standard input of the subprocess
    :param stdout: one of :data:`subprocess.PIPE`, :data:`subprocess.DEVNULL`,
        a file-like object, or `None`
    :param stderr: one of :data:`subprocess.PIPE`, :data:`subprocess.DEVNULL`,
        :data:`subprocess.STDOUT`, a file-like object, or `None`
    :param check: if ``True``, raise :exc:`~subprocess.CalledProcessError` if the
        process terminates with a return code other than 0
    :param cwd: If not ``None``, change the working directory to this before running the
        command
    :param env: if not ``None``, this mapping replaces the inherited environment
        variables from the parent process
    :param start_new_session: if ``true`` the setsid() system call will be made in the
        child process prior to the execution of the subprocess. (POSIX only)
    :return: an object representing the completed process
    :raises ~subprocess.CalledProcessError: if ``check`` is ``True`` and the process
        exits with a nonzero return code

    """

    async def drain_stream(stream: AsyncIterable[bytes], index: int) -> None:
        buffer = BytesIO()
        async for chunk in stream:
            buffer.write(chunk)

        stream_contents[index] = buffer.getvalue()

    async with await open_process(
        command,
        stdin=PIPE if input else DEVNULL,
        stdout=stdout,
        stderr=stderr,
        cwd=cwd,
        env=env,
        start_new_session=start_new_session,
    ) as process:
        stream_contents: list[bytes | None] = [None, None]
        async with create_task_group() as tg:
            if process.stdout:
                tg.start_soon(drain_stream, process.stdout, 0)

            if process.stderr:
                tg.start_soon(drain_stream, process.stderr, 1)

            if process.stdin and input:
                await process.stdin.send(input)
                await process.stdin.aclose()

            await process.wait()

    output, errors = stream_contents
    if check and process.returncode != 0:
        raise CalledProcessError(cast(int, process.returncode), command, output, errors)

    return CompletedProcess(command, cast(int, process.returncode), output, errors)


async def open_process(
    command: str | bytes | Sequence[str | bytes],
    *,
    stdin: int | IO[Any] | None = PIPE,
    stdout: int | IO[Any] | None = PIPE,
    stderr: int | IO[Any] | None = PIPE,
    cwd: str | bytes | PathLike[str] | None = None,
    env: Mapping[str, str] | None = None,
    start_new_session: bool = False,
) -> Process:
    """
    Start an external command in a subprocess.

    .. seealso:: :class:`subprocess.Popen`

    :param command: either a string to pass to the shell, or an iterable of strings
        containing the executable name or path and its arguments
    :param stdin: one of :data:`subprocess.PIPE`, :data:`subprocess.DEVNULL`, a
        file-like object, or ``None``
    :param stdout: one of :data:`subprocess.PIPE`, :data:`subprocess.DEVNULL`,
        a file-like object, or ``None``
    :param stderr: one of :data:`subprocess.PIPE`, :data:`subprocess.DEVNULL`,
        :data:`subprocess.STDOUT`, a file-like object, or ``None``
    :param cwd: If not ``None``, the working directory is changed before executing
    :param env: If env is not ``None``, it must be a mapping that defines the
        environment variables for the new process
    :param start_new_session: if ``true`` the setsid() system call will be made in the
        child process prior to the execution of the subprocess. (POSIX only)
    :return: an asynchronous process object

    """
    if isinstance(command, (str, bytes)):
        return await get_async_backend().open_process(
            command,
            shell=True,
            stdin=stdin,
            stdout=stdout,
            stderr=stderr,
            cwd=cwd,
            env=env,
            start_new_session=start_new_session,
        )
    else:
        return await get_async_backend().open_process(
            command,
            shell=False,
            stdin=stdin,
            stdout=stdout,
            stderr=stderr,
            cwd=cwd,
            env=env,
            start_new_session=start_new_session,
        )
