#!/usr/bin/env python3
"""
# Make program executable
chmod u+x code.py

# Make it known under various names
ln -s code.py get-version
ln -s code.py get-tag
ln -s code.py new-release-major
ln -s code.py new-release-minor
ln -s code.py new-release-build
ln -s code.py new-dev

get-version:       Get the newest version at or below the current revision.
get-number:        Get the number related to a version.
new-release-major: Invent a new major release version
new-release-minor: Invent a new minor release version
new-release-build: Invent a new build release version
new-dev:           Invent a new development version
"""
import sys, os, subprocess, re

def exe_cmd(cmd, env=None):
    """
    Execute a shell command.

    @param cmd: List of command-line arguments.
    @param env: Environment variables to set (dict of key/value pairs)
    @return: Lines of output.
    @note: If command fails, program is aborted.
    """
    if dump_commands:
        print("CMD: {}".format(" ".join(escape_name(arg) for arg in cmd)))

    if env is not None:
        new_env = os.environ.copy()
        new_env.update(env)
    else:
        new_env = None


    lines = output.splitlines()
    return lines

def get_git_tag(match=None):
    """
    Query git for the current-label, return prefix + label if possible.
    """
    cmd = ['git', 'describe']
    if match is not None:
        cmd.append('--match=' + match)

    if sys.version_info.minor < 5:
        # Pre 3.5 has no subprocess.run
        output = subprocess.check_output(cmd, universal_newlines=True)
    else:
        output = subprocess.run(cmd, check=True, stdout=subprocess.PIPE,
                                universal_newlines=True).stdout

    lines = [line for line in output.splitlines() if line]
    if len(lines) != 1:
        return None
    line = lines[0]
    # Either the current commit is a tag, or it is a commit above a tag.
    parts = line.split('-')
    label = parse_tag(parts[-1])
    if label:
        return "-".join(parts[:-1]), label

    if len(parts) > 1:
        label = parse_tag(parts[-2])
        if label:
            return "-".join(parts[:-2]), label

    if len(parts) > 2:
        label = parse_tag(parts[-3])
        if label:
            return "-".join(parts[:-3]), label

    return None, None

def get_git_label(match=None):
    prefix, label = get_git_tag(match)
    return label


NUMBITS_MAJOR = 4
NUMBITS_MINOR = 8
NUMBITS_RELEASE = 1
NUMBITS_BUILD = 31 - NUMBITS_RELEASE - NUMBITS_MINOR - NUMBITS_MAJOR

MAX_MAJOR = 2 ** NUMBITS_MAJOR - 1
MAX_MINOR = 2 ** NUMBITS_MINOR - 1
MAX_RELEASE = 2 ** NUMBITS_RELEASE - 1
MAX_BUILD = 2 ** NUMBITS_BUILD - 1

assert NUMBITS_BUILD > 0

def good_version(major, minor, release, build):
    """
    Verify whether the 4 provided numbers are within boundaries of a version number.
    """
    if major < 0 or major > MAX_MAJOR: return False
    if minor < 0 or minor > MAX_MINOR: return False
    if release < 0 or release > MAX_RELEASE: return False
    if build < 0 or build > MAX_BUILD: return False
    return True

class VersionLabel:
    """
    Object holding a version. Constructor crashes if an incorret number
    is supplied, check against 'good_version' first.
    """
    def __init__(self, major, minor, release, build):
        assert good_version(major, minor, release, build)
        self.major = major
        self.minor = minor
        self.release = release
        self.build = build

    def to_tag(self, all_numbers=False):
        """
        Convert version label instance to tag text.
        """
        parts = []
        if self.release == 0:
            parts.append('dev')
        else:
            parts.append('rel')
        parts.append(str(self.major))

        if not all_numbers and self.minor == 0 and self.build == 0:
            return "".join(parts)

        parts.extend(['.', str(self.minor)])
        if not all_numbers and self.build == 0:
            return "".join(parts)

        parts.extend(['.', str(self.build)])
        return "".join(parts)

    def to_id(self):
        """
        Convert version label instance to numeric id.
        """
        value = self.build
        shift = NUMBITS_BUILD

        value = value + (self.release << shift)
        shift = shift + NUMBITS_RELEASE

        value = value + (self.minor << shift)
        shift = shift + NUMBITS_MINOR

        value = value + (self.major << shift)
        # 'value' is at most 31 bits, so always fits in a DWORD.
        return value

    def next_major(self):
        assert self.release == 1
        if self.major >= MAX_MAJOR:
            return None
        return VersionLabel(self.major + 1, 0, 1, 0)

    def next_minor(self):
        assert self.release == 1
        if self.minor >= MAX_MINOR:
            return None
        return VersionLabel(self.major, self.minor + 1, 1, 0)

    def next_build(self):
        if self.build >= MAX_BUILD:
            return None
        return VersionLabel(self.major, self.minor, self.release, self.build + 1)

    def next_dev(self):
        if self.release == 0:
            return self.next_build()
        else:
            label = self.next_minor()
            label.release = 0
            return label

TAG_PATTERN = re.compile("(rel|dev)([0-9]+)(?:\\.([0-9]+)(?:\\.([0-9]+))?)?$")

def parse_tag(text):
    """
    Convert a tag text like "rel1.3.25" to a VersionLabel if allowed.
    """
    m = TAG_PATTERN.search(text)
    if m:
        if m.group(1) == 'rel':
            release = 1
        else:
            release = 0

        major = int(m.group(2))

        if m.group(3) is not None:
            minor = int(m.group(3))
        else:
            minor = 0

        if m.group(4) is not None:
            build = int(m.group(4))
        else:
            build = 0

        if good_version(major, minor, release, build):
            return VersionLabel(major, minor, release, build)
    return None

def parse_id(value):
    """
    Convert a numeric id to a VersionLabel, if allowed.
    """
    build = value & MAX_BUILD
    value = value >> NUMBITS_BUILD

    release = value & MAX_RELEASE
    value = value >> NUMBITS_RELEASE

    minor = value & MAX_MINOR
    value = value >> NUMBITS_MINOR

    major = value & MAX_MAJOR
    if good_version(major, minor, release, build):
        return VersionLabel(major, minor, release, build)
    return None

#
# get-version: Get the newest version at or below the current revision.
# get-tag: Get the current tag (so it can be checked out)
# get-number: Get the number related to a version.
# new-release-major: Invent a new major release version
# new-release-minor: Invent a new minor release version
# new-release-build: Invent a new build release version
# new-dev: Invent a new development version

# Dirty hacky way to get several 'binaries' in the same program
if sys.argv[0].endswith('get-version'):
    label = get_git_label()
    if label is None:
        print("Cannot find a git tag with a proper name")
        sys.exit(1)
    print(label.to_id())
    sys.exit(0)

elif sys.argv[0].endswith('get-tag'):
    prefix, label = get_git_tag()
    if prefix is None:
        print("Cannot find a git tag with a proper name")
        sys.exit(1)
    print(prefix + "-" + label.to_tag())
    sys.exit(0)

elif sys.argv[0].endswith('get-label'):
    label = get_git_label()
    if label is None:
        print("Cannot find a git tag with a proper name")
        sys.exit(1)
    print(label.to_tag())
    sys.exit(0)

elif sys.argv[0].endswith('new-release-major'):
    prefix, label = get_git_tag("*-rel[0-9]*")
    if label is None:
        print("Cannot find a git tag with a proper name")
        sys.exit(1)
    label = label.next_major()
    if label is None:
        print("Cannot create a new major release version, maximum major number reached")
        sys.exit(1)
    print(prefix + "-" + label.to_tag())
    sys.exit(0)

elif sys.argv[0].endswith('new-release-minor'):
    prefix, label = get_git_tag("*-rel[0-9]*")
    if label is None:
        print("Cannot find a git tag with a proper name")
        sys.exit(1)
    label = label.next_minor()
    if label is None:
        print("Cannot create a new major release version, maximum minor number reached")
        sys.exit(1)
    print(prefix + "-" + label.to_tag())
    sys.exit(0)

elif sys.argv[0].endswith('new-release-build'):
    prefix, label = get_git_tag("*-rel[0-9]*")
    if label is None:
        print("Cannot find a git tag with a proper name")
        sys.exit(1)
    label = label.next_build()
    if label is None:
        print("Cannot create a new major release version, maximum build number reached")
        sys.exit(1)
    print(prefix + "-" + label.to_tag())
    sys.exit(0)

elif sys.argv[0].endswith('new-dev'):
    prefix, label = get_git_tag()
    if label is None:
        print("Cannot find a git tag with a proper name")
        sys.exit(1)
    label = label.next_dev()
    if label is None:
        print("Cannot create a new development version, maximum minor number reached")
        sys.exit(1)
    print(prefix + "-" + label.to_tag())
    sys.exit(0)

elif sys.argv[0].endswith('get-info'):
    print("Version: \"[rel|dev][major].[minor].[build]\"")
    print("Min/max value of major: 0..{}".format(MAX_MAJOR))
    print("Min/max value of minor: 0..{}".format(MAX_MINOR))
    print("Min/max value of build: 0..{}".format(MAX_BUILD))
    sys.exit(0)

else:
    print("Unknown executable name, bye!")
    sys.exit(1)