simplified CPacMan Yum plugin

import os, sys, re
import os.path
try:
    from hashlib import md5
except ImportError:
    from md5 import md5

import ConfigParser

import rpm

from yum.plugins import PluginYumExit, TYPE_CORE
from yum.repos import Repository
from yum.yumRepo import YumRepository # , YumPackageSack
from yum.packageSack import PackageSack
from yum.packages import YumLocalPackage, YumHeaderPackage, YumAvailablePackage
from yum.repoMDObject import RepoMD
import rpmUtils, yum.Errors


requires_api_version = '2.3'
plugin_type = (TYPE_CORE,)
cpacman_on=True

# really weird location for libraries. Oh well...
sys.path.append('/usr/share/yum-cli')
from yumcommands import YumCommand

# class CPacManPackage(YumHeaderPackage):
class CPacManPackage(YumLocalPackage):
    def __init__(self,repo,hdr,localpath):
        self.localpath=localpath
        YumHeaderPackage.__init__(self,repo,hdr)
        self.pkgid = self.hdr[rpm.RPMTAG_SHA1HEADER]
        if not self.pkgid:
            self.pkgid = "%s.%s" %(self.hdr['name'], self.hdr['buildtime'])
        self.id=self.pkgid
        self.pkgKey = self.__hash__()

    def __getattr__(self, thing):
        #FIXME - if an error - return AttributeError, not KeyError
        # ONLY FIX THIS AFTER THE API BREAK
        if thing.startswith('__') and thing.endswith('__'):
            # If these existed, then we wouldn't get here ...
            # So these are missing.
            raise AttributeError, "%s has no attribute %s" % (self, thing)
        try:
            return self.hdr[thing]
        except KeyError:
            #  Note above, API break to fix this ... this at least is a nicer
            # msg. so we know what we accessed that is bad.
            # print "%s has no attribute %s" % (self, thing)
            # return None
            raise KeyError, "%s (%s) has no attribute %s" % (self, self.repoid, thing)
        except ValueError:
            #  Note above, API break to fix this ... this at least is a nicer
            # msg. so we know what we accessed that is bad.
            raise ValueError, "%s (%s) has no attribute %s" % (self, self.repoid, thing)

    def returnChecksums(self):
        return YumAvailablePackage.returnChecksums(self)

class CPacManSack(PackageSack):
    def __init__(self):
        PackageSack.__init__(self)
        # looks like this is required property in some cases...
        self._pkgtup2pkgs=[]
        self.added={}

    def populate(self, repo, mdtype='metadata', callback=None, cacheonly=0):
        # print "In CPacMan Populate"
        self.added[repo]=[]
        return

    def get_added(self):
        return {}

    # added=property(get_added)

    def searchPrimaryFieldsMultipleStrings(self,fields,searchstrings):
        ##FIXME
        print "-=search=--=search=-"
        return []

class CPacManYumRepo(YumRepository):
    """CPacMan repo that translates from collects all of the available packages into
    a neat Yum-like Repo object"""
    def __init__(self,server_name,repo_path,repoid):
        # global server_db, server
        YumRepository.__init__(self,repoid)
        self.cpacman_sack=CPacManSack()
        # we need private copies of ServerDB and Server here as we're going
        # to manipulate them
        self.repo_path=repo_path
        self.pkgdir=repo_path
        self.cost=1500
        self.__init_sack()
        ##FIXME Hacking around EL5 deficiencies
        try:
            self.repoXML=RepoMD(self.id)
        except TypeError:
            # looks like older version of Yum... we should be OK
            pass
    def __init_sack(self):
        # simplifying original call:
        #  pl=self.server.listAvailablePackages(all_versions=0, ignore_policy=0, filter_path=self.repo_filter)
        # to a bare dictionary:
        pl={'a-1.1-1.i386':{'path':self.repo_path, 'package_name':'a-1.1-1.i386.rpm'}}

        ts=rpm.TransactionSet()
        # hack to disable DIGEST and SIGNATURE checks
        ts.setVSFlags((rpm._RPMVSF_NOSIGNATURES|rpm._RPMVSF_NODIGESTS))
        for pk in pl.keys():
            pkg=pl[pk]

            localpath=os.path.join(pkg['path'],pkg['package_name'])

            try:
                hdr = rpmUtils.miscutils.hdrFromPackage(ts, localpath)
            except rpmUtils.RpmUtilsError:
                raise yum.Errors.MiscError, \
                    'Could not open local rpm file: %s' % localpath
            ypkg=CPacManPackage(self, hdr, localpath)
            ypkg._populatePrco()
            ypkg.basepath='file://'+pkg['path']
            ypkg.relativepath=pkg['package_name']
            self.cpacman_sack.addPackage(ypkg)

    def getPackageSack(self):
        return self.cpacman_sack

CPacManRepo=CPacManYumRepo


def prereposetup_hook(conduit):
    ## Most of action happens here since this is the first stage where command-line arguments are being
    ## processed. Everything prior to this hook has no access to CLI args which we need to identify
    ## the server we're working on, or whether we need to kick-in at all...

    global cpacman_on
    # simplifying process here... we actually get
    # sc_path_str via different means...
    sc_path_str="/foo/bar:/baz/moo"
    # ... we have set cpacman_on based on previous conditions by now...
    if cpacman_on:
        repos=conduit.getRepos()
        ## filter out the paths of repos that are already enabled
        ## to avoid double-repo added via cpacman...
        path_filter=[]
        for r in repos.listEnabled():
            try:
                path_filter.append(r.pkgdir)
                conduit.info(2, "Adding repo.pkgdir: "+r.pkgdir)
            except AttributeError:
                # repo doesn't have pkgrid attribute
                # which is fine (?)...
                pass
        sc_path=sc_path_str.split(':')
        for p in sc_path:
            if not (p in path_filter):
                conduit.info(2, "Adding path: "+p)
                repoid=p.replace('/','_')
                cpm_repo=CPacManRepo(server_name=conf.servername,repo_path=p,repoid=repoid)
                cpacman_repos.append(repoid)
                try:
                    repos.add(cpm_repo)
                except yum.Errors.DuplicateRepoError:
                    pass
                repos.enableRepo(repoid)