#! /usr/bin/python -t

import rpm
from yum import Errors
import rpmUtils.transaction

import sys
import os

def _getsysver(installroot, distroverpkg, old=True):
    ts = rpmUtils.transaction.initReadOnlyTransaction(root=installroot)
    ts.pushVSFlags(~(rpm._RPMVSF_NOSIGNATURES|rpm._RPMVSF_NODIGESTS))
    try:
        idx = ts.dbMatch('provides', distroverpkg)
    except TypeError, e:
        # This is code for "cannot open rpmdb"
        # this is for pep 352 compliance on python 2.6 and above :(
        if sys.hexversion < 0x02050000:
            if hasattr(e,'message'):
                raise Errors.YumBaseError("Error: " + str(e.message))
            else:
                raise Errors.YumBaseError("Error: " + str(e))
        raise Errors.YumBaseError("Error: " + str(e))
    except rpm.error, e:
        # This is the "new" code for "cannot open rpmdb", 4.8.0 ish
        raise Errors.YumBaseError("Error: " + str(e))

    # we're going to take the first one - if there is more than one of these
    # then the user needs a beating
    if idx.count() == 0:
        releasever = '$releasever'
    else:
        try:
            hdr = idx.next()
        except StopIteration:
            raise Errors.YumBaseError("Error: rpmdb failed release provides. Try: rpm --rebuilddb")
        if not old:
            off = hdr[getattr(rpm, 'RPMTAG_PROVIDENAME')].index(distroverpkg)
            flag = hdr[getattr(rpm, 'RPMTAG_PROVIDEFLAGS')][off]
            flag = rpmUtils.miscutils.flagToString(flag)
            if flag != 'EQ':
                old = True
            else:
                releasever = hdr[getattr(rpm, 'RPMTAG_PROVIDEVERSION')][off]
                releasever = rpmUtils.miscutils.stringToVersion(releasever)
                releasever = releasever[1] # Just version
        if old:
            releasever = hdr['version']
        del hdr
    del idx
    del ts
    return releasever

distropkg = "redhat-release"

if len(sys.argv) > 1:
    distropkg = sys.argv[1]

if os.path.exists("/etc/yum/vars/releasever"):
    print "file:", open("/etc/yum/vars/releasever").read(),

print
print 'looking for provide:', distropkg
print

print 'prov:', _getsysver("/", distropkg, old=False)
print ' pkg:', _getsysver("/", distropkg)