from __future__ import annotations

import contextlib
import multiprocessing
import os
import random
import re
import shlex
from typing import Any
from typing import Generator
from typing import NoReturn
from typing import Sequence

import pre_commit.constants as C
from pre_commit import parse_shebang
from pre_commit.prefix import Prefix
from pre_commit.util import cmd_output_b
from pre_commit.xargs import xargs

FIXED_RANDOM_SEED = 1542676187

SHIMS_RE = re.compile(r'[/\\]shims[/\\]')


def exe_exists(exe: str) -> bool:
    found = parse_shebang.find_executable(exe)
    if found is None:  # exe exists
        return False

    homedir = os.path.expanduser('~')
    try:
        common: str | None = os.path.commonpath((found, homedir))
    except ValueError:  # on windows, different drives raises ValueError
        common = None

    return (
        # it is not in a /shims/ directory
        not SHIMS_RE.search(found) and
        (
            # the homedir is / (docker, service user, etc.)
            os.path.dirname(homedir) == homedir or
            # the exe is not contained in the home directory
            common != homedir
        )
    )


def run_setup_cmd(prefix: Prefix, cmd: tuple[str, ...], **kwargs: Any) -> None:
    cmd_output_b(*cmd, cwd=prefix.prefix_dir, **kwargs)


def environment_dir(prefix: Prefix, d: str, language_version: str) -> str:
    return prefix.path(f'{d}-{language_version}')


def assert_version_default(binary: str, version: str) -> None:
    if version != C.DEFAULT:
        raise AssertionError(
            f'for now, pre-commit requires system-installed {binary} -- '
            f'you selected `language_version: {version}`',
        )


def assert_no_additional_deps(
        lang: str,
        additional_deps: Sequence[str],
) -> None:
    if additional_deps:
        raise AssertionError(
            f'for now, pre-commit does not support '
            f'additional_dependencies for {lang} -- '
            f'you selected `additional_dependencies: {additional_deps}`',
        )


def basic_get_default_version() -> str:
    return C.DEFAULT


def basic_health_check(prefix: Prefix, language_version: str) -> str | None:
    return None


def no_install(
        prefix: Prefix,
        version: str,
        additional_dependencies: Sequence[str],
) -> NoReturn:
    raise AssertionError('This language is not installable')


@contextlib.contextmanager
def no_env(prefix: Prefix, version: str) -> Generator[None, None, None]:
    yield


def target_concurrency() -> int:
    if 'PRE_COMMIT_NO_CONCURRENCY' in os.environ:
        return 1
    else:
        # Travis appears to have a bunch of CPUs, but we can't use them all.
        if 'TRAVIS' in os.environ:
            return 2
        else:
            try:
                return multiprocessing.cpu_count()
            except NotImplementedError:
                return 1


def _shuffled(seq: Sequence[str]) -> list[str]:
    """Deterministically shuffle"""
    fixed_random = random.Random()
    fixed_random.seed(FIXED_RANDOM_SEED, version=1)

    seq = list(seq)
    fixed_random.shuffle(seq)
    return seq


def run_xargs(
        cmd: tuple[str, ...],
        file_args: Sequence[str],
        *,
        require_serial: bool,
        color: bool,
) -> tuple[int, bytes]:
    if require_serial:
        jobs = 1
    else:
        # Shuffle the files so that they more evenly fill out the xargs
        # partitions, but do it deterministically in case a hook cares about
        # ordering.
        file_args = _shuffled(file_args)
        jobs = target_concurrency()
    return xargs(cmd, file_args, target_concurrency=jobs, color=color)


def hook_cmd(entry: str, args: Sequence[str]) -> tuple[str, ...]:
    return (*shlex.split(entry), *args)


def basic_run_hook(
        prefix: Prefix,
        entry: str,
        args: Sequence[str],
        file_args: Sequence[str],
        *,
        is_local: bool,
        require_serial: bool,
        color: bool,
) -> tuple[int, bytes]:
    return run_xargs(
        hook_cmd(entry, args),
        file_args,
        require_serial=require_serial,
        color=color,
    )