#!/usr/bin/python
#
# find a linux kernel commit message (including its associated diff)
# given a search text provided by the user
#
# Copyright (C) 2009 Michael S Gilbert 
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.

import os
import re
import sys
import urllib
import tempfile

if ( len( sys.argv ) < 2 ):
    sys.stderr.write( 'usage: %s <search text> {only-rc|oldest-version=2.6.#}\n' % sys.argv[0] )
    sys.exit( 1 )

if ( len( sys.argv ) > 2 ):
    onlyrc = sys.argv[2] == 'only-rc'
    if sys.argv[2].startswith( 'oldest-version=' ):
	oldest_version = int( sys.argv[2].split( '=' )[1].split( '.' )[2] )
    else:
	oldest_version = 12
else:
    onlyrc = False
    oldest_version = 12

if not os.path.exists( '/usr/bin/git' ):
    sys.stderr.write( 'error: this script uses git; please install the package\n' )
    sys.exit( 1 )

# if not already downloadeded, clone stable kernel.org git repo
giturl = 'git://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-2.6-stable.git/'
gitdir = './linux-2.6-stable'
if not os.path.exists( os.path.join( gitdir , '.git/HEAD' ) ):
    sys.stdout.write( 'Existing git repository not found; will now clone from kernel.org.\n\n' )
    sys.stdout.write( 'This may take a while, so if you already have a working stable repository,\n' )
    sys.stdout.write( 'please copy it to the current directory with the name \'%s\'.\n' % gitdir.lstrip( './' ) )
    sys.stdout.write( 'Note that this *is not* Linus Torvald\'s repository, it is the stable repo:\n' )
    sys.stdout.write( '%s\n\n' % giturl)
    if ( os.system( 'git clone %s %s' % ( giturl , gitdir ) ) != 0 ):
	sys.exit( 1 )

# if kernel.org repository has updates, pull them
os.chdir( gitdir )
fread = open( './.git/refs/heads/master' , 'r' )
local_hash = fread.readline().strip( '\n' )
fread.close()
fread = urllib.urlopen( 'http://ftp%s/packed-refs' % giturl[9::] , 'r' )
split = [ '' , '' ]
while ( split[1] != 'refs/heads/master' ):
    split = fread.readline().strip( ' \n' ).split()
    if len( split ) < 2:
        split = [ '' , '' ]
remote_hash = split[0]
fread.close()
if ( local_hash != remote_hash ):
    if ( os.system( 'git pull' ) != 0 ):
	sys.exit( 1 )

# retrieve set of release tags
pipe = os.popen( 'git tag -l' )
tags = pipe.readlines()
tags.reverse()
pipe.close()

# generate changelog+diff files
lastversion = ''
ismainline = True
rootname = 'changelog+diff'
for tag in tags:
    version = tag.strip( '\n' )
    isnotrc = tag.find( '-rc' ) < 0
    if isnotrc:
	ismainline = False
    if isnotrc or ismainline:
	if ( lastversion != '' ):
	    fname = '%s-%s' % ( rootname , lastversion.lstrip( 'v' ) )
	    if onlyrc and ( lastversion.find( '-rc' ) < 0 ):
                break
	    elif ( int( version.split( '.' )[2].split( '-' )[0] ) >= oldest_version ):
	        if not os.path.exists( fname ):
	            tmpname = tempfile.mkstemp()[1]
	            sys.stdout.write( 'generating: %s\n' % fname )
	            if ( os.system( 'git log -p %s..%s > %s' % ( version , lastversion , tmpname ) ) != 0 ):
		        os.system( 'rm %s' % tmpname )
		        sys.exit( 1 )
	            if ( os.system( 'cp %s %s' % ( tmpname , fname ) ) != 0 ):
		        os.system( 'rm %s' % tmpname )
	                sys.exit( 1 )
	            os.system( 'rm %s' % tmpname )
	lastversion = version

# search thru the generated files for text of interest
lastfname = ''
foundtext = False
pipe = os.popen( 'grep \'%s\' $(ls -r %s*)' % ( sys.argv[1] , rootname ) )
pline = pipe.readline()
while pline:
    fname = pline.split( ':' )[0]
    if fname != lastfname:
        fread = open( fname , 'r' )
        line = fread.readline()
        while line:
            if line.startswith( 'commit' ):
	        if foundtext:
		    sys.stdout.write( 'found search text \'%s\' in release %s:\n' % ( sys.argv[1] , fname[len( rootname )+1::] ) )
                    sys.stdout.write( commit )
		    foundtext = False
	        commit = '| %s' % line
            else:
	        commit += '| %s' % line
            if re.search( sys.argv[1] , line ):
                foundtext = True
	    line = fread.readline()
        fread.close()
    lastfname = fname
    pline = pipe.readline()
pipe.close()