#!/usr/bin/python2.2
#
# useupdate - list packages that would be affected by USE changes that have
#             happened since they were built
#
# Copyright (c) Chris Willis-Ford <porridj@hotmail.com>
# This program is distributed under the terms of the GPL version 2.
#
# Note: This is my first Python program, so don't trust it to be 100% perfect
#       or optimal. It *was* written in one night, after all... :P

from os.path import walk, normpath, split
from portage import pkgsplit, settings
from string  import join

installRoot = "/var/db/pkg"
maxRead = 1024*1024 # Read no more than 1MB for safety

def undupe(list):
   unique = []
   for word in list:
      if not ( word in unique ):
         unique.append(word)
   return unique

# Normalize the global USE settings first
use = join(undupe(settings["USE"].strip().split()))

# Compare two USE strings, ignoring order and duplicates.
# Return None if there are no differences that would affect a recompile
# Return differences if there are any
def whatchanged(old,new):
   if (old == new):
      return None
   newsplit=undupe(new.split())
   oldsplit=undupe(old.split())
   for word in oldsplit[:]:
      if ( word in newsplit ): # Setting has not changed
         oldsplit.remove(word)
         newsplit.remove(word)
      else:
         if ( word[0] == '-' ): # Don't care if it was off before
            oldsplit.remove(word)
         else:
            newsplit.append('-'+word) # It was on, now it's not. Notice this.
   diffs=join(newsplit)
   if ( diffs ):
      return diffs
   return None

def affects(usechanges, rdepfile):
   changes=usechanges.split()
   rdep=rdepfile.split()
   important=[]
   for word in rdep:
      if ( word[-1] == '?' ):
         if ( word[:-1] in changes ):
            important.append(word[:-1])
         if ( '-'+word[:-1] in changes ):
            important.append('-'+word[:-1])
   return join(important)

def visit(dummy, dirname, files):
   for file in files:
      if (file == 'USE'):
         f=open(dirname+'/USE')
         thisuse=f.readline(maxRead).strip()
         f.close()
         f=open(dirname+'/RDEPEND')
         thisrdep=f.read(maxRead)
         f.close()
         (cat, fullname)=split(normpath(dirname))
         cat=split(cat)[1]
         (name,ver,rev)=pkgsplit(fullname)
         changes=whatchanged(thisuse,use)
         if ( changes ):
            important=affects(changes, thisrdep)
            if ( important ):
               print cat + '/' + name + ' : ' + important

if __name__ == '__main__':
   import sys
   if (len(sys.argv) != 1):
      print 'Usage: useupdate'
      sys.exit(1)
   walk(installRoot, visit, "")