# -*- coding: utf-8 -*-

"""Calculates the current version number.

If possible, uses output of “git describe” modified to conform to the
visioning scheme that setuptools uses (see PEP 386).  Releases must be
labelled with annotated tags (signed tags are annotated) of the following
format:

   v<num>(.<num>)+ [ {a|b|c|rc} <num> (.<num>)* ]

If “git describe” returns an error (likely because we're in an unpacked copy
of a release tarball, rather than a git working copy), or returns a tag that
does not match the above format, version is read from .version file.

To use this script, simply import it in your setup.py file, and use the results
of get_version() as your package version:

    import version
    setup(
        version=version.get_version(),
        .
        .
        .
    )

This will automatically update the .version file.  The .version file should
*not* be checked into git but it *should* be included in sdist tarballs (as
should version.py file).  To do this, run:

    echo include .version version.py >>MANIFEST.in
    echo .version >>.gitignore

With that setup, a new release can be labelled by simply invoking:

    git tag -s v1.0
"""

__author__ = ('Douglas Creager <dcreager@dcreager.net>',
              'Michal Nazarewicz <mina86@mina86.com>')
__license__ = 'This file is placed into the public domain.'
__maintainer__ = 'Michal Nazarewicz'
__email__ = 'mina86@mina86.com'

__all__ = ('get_version',)


import re
import subprocess
import sys


RELEASE_VERSION_FILE = '.version'

# http://www.python.org/dev/peps/pep-0386/
_PEP386_SHORT_VERSION_RE = r'\d+(?:\.\d+)+(?:(?:[abc]|rc)\d+(?:\.\d+)*)?'
_PEP386_VERSION_RE = r'^%s(?:\.post\d+)?(?:\.dev\d+)?$' % (
    _PEP386_SHORT_VERSION_RE)
_GIT_DESCRIPTION_RE = r'^v(?P<ver>%s)-(?P<commits>\d+)-g(?P<sha>[\da-f]+)$' % (
    _PEP386_SHORT_VERSION_RE)


def read_git_version():
    """Reads version from "git describe" command."""
    try:
        proc = subprocess.Popen(('git', 'describe', '--long',
                                 '--match', 'v[0-9]*.*'),
                                stdout=subprocess.PIPE, stderr=subprocess.PIPE)
        data, _ = proc.communicate()
        if proc.returncode:
            return None
        data = data.decode(getattr(sys.stdin, 'encoding', 'ascii'))
        ver = data.splitlines()[0].strip()
    except:  # pylint: disable=bare-except
        return None

    if not ver:
        return None
    m = re.search(_GIT_DESCRIPTION_RE, ver)
    if not m:
        sys.stderr.write('version: git description (%s) is invalid, '
                         'ignoring\n' % ver)
        return None

    commits = int(m.group('commits'))
    if not commits:
        return m.group('ver')
    else:
        return '%s.post%d.dev%d' % (
            m.group('ver'), commits, int(m.group('sha'), 16))


def read_release_version(warn):
    """Reads release version from a .version file."""
    try:
        fd = open(RELEASE_VERSION_FILE)
        try:
            ver = fd.readline().strip()
        finally:
            fd.close()
        if warn and not re.search(_PEP386_VERSION_RE, ver):
            sys.stderr.write('version: release version (%s) is invalid, '
                             'will use it anyway\n' % ver)
        return ver
    except:  # pylint: disable=bare-except
        return None


def write_release_version(version):
    """Writes release version to a .version file."""
    fd = open(RELEASE_VERSION_FILE, 'w')
    fd.write('%s\n' % version)
    fd.close()


def get_version():
    """Figures out package's version; also stores it in a file."""
    version = read_git_version()
    release_version = read_release_version(not version)
    version = version or release_version
    if not version:
        raise ValueError('Cannot find the version number')
    if version != release_version:
        write_release_version(version)
    return version


if __name__ == '__main__':
    print(get_version())