# -*- coding: utf-8 -*-
# https://www.python.org/dev/peps/pep-0386/
VERSION = (1, 1, 9, 'final', 0)


def get_version(version=None):
    """
    Returns a PEP 386-compliant version number from VERSION.
    """
    if version is None:
        from djmessenger import VERSION as version
    else:
        assert len(version) == 5
        assert version[3] in ('alpha', 'beta', 'rc', 'final')

    # Now build the two parts of the version number:
    # main = X.Y[.Z]
    # sub = .devN - for pre-alpha releases
    #     | {a|b|c}N - for alpha, beta and rc releases

    parts = 2 if version[2] == 0 else 3
    main = '.'.join(str(x) for x in version[:parts])

    sub = ''
    if version[3] == 'alpha' and version[4] == 0:
        git_changeset = get_git_changeset()
        if git_changeset:
            sub = '.dev%s' % git_changeset

    elif version[3] != 'final':
        mapping = {'alpha': 'a', 'beta': 'b', 'rc': 'rc'}
        sub = mapping[version[3]] + str(version[4])

    return str(main + sub)


def get_git_changeset():
    """
    Returns a numeric identifier of the latest git changeset.
    The result is the UTC timestamp of the changeset in YYYYMMDDHHMMSS format.
    This value isn't guaranteed to be unique, but collisions are very unlikely,
    so it's sufficient for generating the development version numbers.
    TODO: Check if we can rely on services like read-the-docs to pick this up.
    """
    import datetime
    import os
    import subprocess

    repo_dir = os.path.dirname(os.path.dirname(os.path.abspath(__file__)))
    git_log = subprocess.Popen(
        'git log --pretty=format:%ct --quiet -1 HEAD', stdout=subprocess.PIPE,
        stderr=subprocess.PIPE, shell=True, cwd=repo_dir,
        universal_newlines=True)
    timestamp = git_log.communicate()[0]
    try:
        timestamp = datetime.datetime.utcfromtimestamp(int(timestamp))
    except ValueError:
        return None
    return timestamp.strftime('%Y%m%d%H%M%S')
