# Copyright (c) OpenMMLab. All rights reserved.
import os
import subprocess
import warnings

from packaging.version import parse


def digit_version(version_str: str, length: int = 4):
    """Convert a version string into a tuple of integers.

    This method is usually used for comparing two versions. For pre-release
    versions: alpha < beta < rc.

    Args:
        version_str (str): The version string.
        length (int): The maximum number of version levels. Default: 4.

    Returns:
        tuple[int]: The version info in digits (integers).
    """
    assert 'parrots' not in version_str
    version = parse(version_str)
    assert version.release, f'failed to parse version {version_str}'
    release = list(version.release)
    release = release[:length]
    if len(release) < length:
        release = release + [0] * (length - len(release))
    if version.is_prerelease:
        mapping = {'a': -3, 'b': -2, 'rc': -1}
        val = -4
        # version.pre can be None
        if version.pre:
            if version.pre[0] not in mapping:
                warnings.warn(f'unknown prerelease version {version.pre[0]}, '
                              'version checking may go wrong')
            else:
                val = mapping[version.pre[0]]
            release.extend([val, version.pre[-1]])
        else:
            release.extend([val, 0])

    elif version.is_postrelease:
        release.extend([1, version.post])  # type: ignore
    else:
        release.extend([0, 0])
    return tuple(release)


def _minimal_ext_cmd(cmd):
    # construct minimal environment
    env = {}
    for k in ['SYSTEMROOT', 'PATH', 'HOME']:
        v = os.environ.get(k)
        if v is not None:
            env[k] = v
    # LANGUAGE is used on win32
    env['LANGUAGE'] = 'C'
    env['LANG'] = 'C'
    env['LC_ALL'] = 'C'
    out = subprocess.Popen(
        cmd, stdout=subprocess.PIPE, env=env).communicate()[0]
    return out


def get_git_hash(fallback='unknown', digits=None):
    """Get the git hash of the current repo.

    Args:
        fallback (str, optional): The fallback string when git hash is
            unavailable. Defaults to 'unknown'.
        digits (int, optional): kept digits of the hash. Defaults to None,
            meaning all digits are kept.

    Returns:
        str: Git commit hash.
    """

    if digits is not None and not isinstance(digits, int):
        raise TypeError('digits must be None or an integer')

    try:
        out = _minimal_ext_cmd(['git', 'rev-parse', 'HEAD'])
        sha = out.strip().decode('ascii')
        if digits is not None:
            sha = sha[:digits]
    except OSError:
        sha = fallback

    return sha
