"""
This file is from the Django Project:
http://djangoproject.com/

Copyright (c) Django Software Foundation and individual contributors.
All rights reserved.

Redistribution and use in source and binary forms, with or without modification,
are permitted provided that the following conditions are met:

    1. Redistributions of source code must retain the above copyright notice,
       this list of conditions and the following disclaimer.

    2. Redistributions in binary form must reproduce the above copyright
       notice, this list of conditions and the following disclaimer in the
       documentation and/or other materials provided with the distribution.

    3. Neither the name of Django nor the names of its contributors may be used
       to endorse or promote products derived from this software without
       specific prior written permission.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR
ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
(INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
"""
import datetime
import os
import subprocess


def get_version(version=None):
    "Returns a PEP 386-compliant version number from VERSION."
    version = get_complete_version(version)

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

    major = get_major_version(version)

    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': 'c'}
        sub = mapping[version[3]] + str(version[4])

    return str(major + sub)


def get_major_version(version=None):
    "Returns major version from VERSION."
    version = get_complete_version(version)
    parts = 2 if version[2] == 0 else 3
    major = '.'.join(str(x) for x in version[:parts])
    return major


def get_complete_version(version=None):
    """Returns a tuple of the version. If version argument is non-empty,
    then checks for correctness of the tuple provided.
    """
    if version is None:
        from wiki import VERSION as version
    else:
        assert len(version) == 5
        assert version[3] in ('alpha', 'beta', 'rc', 'final')

    return version


def get_docs_version(version=None):
    version = get_complete_version(version)
    if version[3] != 'final':
        return 'dev'
    else:
        return '%d.%d' % version[:2]


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.
    """
    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')
