"""Provides classes to represent module version numbers (one class for
each style of version numbering).  There are currently two such classes
implemented: StrictVersion and LooseVersion.

Every version number class implements the following interface:
  * the 'parse' method takes a string and parses it to some internal
    representation; if the string is an invalid version number,
    'parse' raises a ValueError exception
  * the class constructor takes an optional string argument which,
    if supplied, is passed to 'parse'
  * __str__ reconstructs the string that was passed to 'parse' (or
    an equivalent string -- ie. one that will generate an equivalent
    version number instance)
  * __repr__ generates Python code to recreate the version number instance
  * _cmp compares the current instance with either another instance
    of the same class or a string (which will be parsed to an instance
    of the same class, thus must follow the same rules)
"""

import sys
import re


# The rules according to Greg Stein:
# 1) a version number has 1 or more numbers separated by a period or by
#    sequences of letters. If only periods, then these are compared
#    left-to-right to determine an ordering.
# 2) sequences of letters are part of the tuple for comparison and are
#    compared lexicographically
# 3) recognize the numeric components may have leading zeroes
#
# The LooseVersion class below implements these rules: a version number
# string is split up into a tuple of integer and string components, and
# comparison is a simple tuple comparison.  This means that version
# numbers behave in a predictable and obvious way, but a way that might
# not necessarily be how people *want* version numbers to behave.  There
# wouldn't be a problem if people could stick to purely numeric version
# numbers: just split on period and compare the numbers as tuples.
# However, people insist on putting letters into their version numbers;
# the most common purpose seems to be:
#   - indicating a "pre-release" version
#     ('alpha', 'beta', 'a', 'b', 'pre', 'p')
#   - indicating a post-release patch ('p', 'pl', 'patch')
# but of course this can't cover all version number schemes, and there's
# no way to know what a programmer means without asking him.
#
# The problem is what to do with letters (and other non-numeric
# characters) in a version number.  The current implementation does the
# obvious and predictable thing: keep them as strings and compare
# lexically within a tuple comparison.  This has the desired effect if
# an appended letter sequence implies something "post-release":
# eg. "0.99" < "0.99pl14" < "1.0", and "5.001" < "5.001m" < "5.002".
#
# However, if letters in a version number imply a pre-release version,
# the "obvious" thing isn't correct.  Eg. you would expect that
# "1.5.1" < "1.5.2a2" < "1.5.2", but under the tuple/lexical comparison
# implemented here, this just isn't so.
#
# Two possible solutions come to mind.  The first is to tie the
# comparison algorithm to a particular set of semantic rules, as has
# been done in the StrictVersion class above.  This works great as long
# as everyone can go along with bondage and discipline.  Hopefully a
# (large) subset of Python module programmers will agree that the
# particular flavour of bondage and discipline provided by StrictVersion
# provides enough benefit to be worth using, and will submit their
# version numbering scheme to its domination.  The free-thinking
# anarchists in the lot will never give in, though, and something needs
# to be done to accommodate them.
#
# Perhaps a "moderately strict" version class could be implemented that
# lets almost anything slide (syntactically), and makes some heuristic
# assumptions about non-digits in version number strings.  This could
# sink into special-case-hell, though; if I was as talented and
# idiosyncratic as Larry Wall, I'd go ahead and implement a class that
# somehow knows that "1.2.1" < "1.2.2a2" < "1.2.2" < "1.2.2pl3", and is
# just as happy dealing with things like "2g6" and "1.13++".  I don't
# think I'm smart enough to do it right though.
#
# In any case, I've coded the test suite for this module (see
# ../test/test_version.py) specifically to fail on things like comparing
# "1.2a2" and "1.2".  That's not because the *code* is doing anything
# wrong, it's because the simple, obvious design doesn't match my
# complicated, hairy expectations for real-world version numbers.  It
# would be a snap to fix the test suite to say, "Yep, LooseVersion does
# the Right Thing" (ie. the code matches the conception).  But I'd rather
# have a conception that matches common notions about version numbers.


class LooseVersion:

    """Version numbering for anarchists and software realists.
    Implements the standard interface for version number classes as
    described above.  A version number consists of a series of numbers,
    separated by either periods or strings of letters.  When comparing
    version numbers, the numeric components will be compared
    numerically, and the alphabetic components lexically.  The following
    are all valid version numbers, in no particular order:

        1.5.1
        1.5.2b2
        161
        3.10a
        8.02
        3.4j
        1996.07.12
        3.2.pl0
        3.1.1.6
        2g6
        11g
        0.960923
        2.2beta29
        1.13++
        5.5.kw
        2.0b1pl0

    In fact, there is no such thing as an invalid version number under
    this scheme; the rules for comparison are simple and predictable,
    but may not always give the results you want (for some definition
    of "want").
    """

    component_re = re.compile(r"(\d+ | [a-z]+ | \.)", re.VERBOSE)

    def __init__(self, vstring=None):
        if vstring:
            self.parse(vstring)

    def __eq__(self, other):
        c = self._cmp(other)
        if c is NotImplemented:
            return c
        return c == 0

    def __lt__(self, other):
        c = self._cmp(other)
        if c is NotImplemented:
            return c
        return c < 0

    def __le__(self, other):
        c = self._cmp(other)
        if c is NotImplemented:
            return c
        return c <= 0

    def __gt__(self, other):
        c = self._cmp(other)
        if c is NotImplemented:
            return c
        return c > 0

    def __ge__(self, other):
        c = self._cmp(other)
        if c is NotImplemented:
            return c
        return c >= 0

    def parse(self, vstring):
        # I've given up on thinking I can reconstruct the version string
        # from the parsed tuple -- so I just store the string here for
        # use by __str__
        self.vstring = vstring
        components = [x for x in self.component_re.split(vstring) if x and x != "."]
        for i, obj in enumerate(components):
            try:
                components[i] = int(obj)
            except ValueError:
                pass

        self.version = components

    def __str__(self):
        return self.vstring

    def __repr__(self):
        return "LooseVersion ('%s')" % str(self)

    def _cmp(self, other):
        other = self._coerce(other)
        if other is NotImplemented:
            return NotImplemented

        if self.version == other.version:
            return 0
        if self.version < other.version:
            return -1
        if self.version > other.version:
            return 1

    @staticmethod
    def _coerce(other):
        if isinstance(other, LooseVersion):
            return other
        elif isinstance(other, str):
            return LooseVersion(other)
        elif "distutils" in sys.modules:
            # Using this check to avoid importing distutils and suppressing the warning
            try:
                from distutils.version import LooseVersion as deprecated
            except ImportError:
                return NotImplemented
            if isinstance(other, deprecated):
                return LooseVersion(str(other))
        return NotImplemented
