#!/usr/bin/env python
# vim: set fileencoding=UTF-8:
# Copyright 2013 Red Hat, Inc.
# Author: Jan Pokorný <jpokorny at redhat dot com>
# Licensed under MIT license

import sys
import re
import getopt
from os import environ
from subprocess import Popen, PIPE

# svn checkout http://python-patch.googlecode.com/svn/trunk/ python-patch
# pushd python-patch
# patch <../python-patch-allow-for-externalizing-hunk-again.patch
# popd
# ln -s python-patch/patch .

import patch

re_h = re.compile(
    r'^Hunk \#(\d+) succeeded at (\d+)(?: with fuzz (\d+))? \(offset (-?\d+) lines?\)\.$',
    re.MULTILINE
)


def adjustment(ret, stderrdata):
    #print >>sys.stderr, "ret = {0}\nstderrdata = {1}".format(ret, stderrdata)
    for match in re_h.finditer(stderrdata):
        #print >>sys.stderr, match.groups()
        ret = int(match.groups()[3])
        break
    else:
        ret = 0
    return ret


def proceed(opts, args):
    null = open('/dev/null', 'a')
    if not args:
        args.append('-')
    cmd_args = reduce(lambda a, x: a + list(x), opts, [])
    #print >>sys.stderr, "cmdargs: {0}, opts: {1}".format(cmd_args, opts)
    for arg in args:
        arg = arg if arg != '-' else '/dev/stdin'
        ps = patch.fromfile(arg)
        if not ps:
            print >>sys.stderr, "Bad patch file: {0}".format(arg)
            continue
        for p in ps.items:
            header = '{0}--- {1}\n+++ {2}'.format('\n'.join(p.header),
                                                    p.source, p.target)
            print header
            for hunk in p.hunks:
                cmd = (lambda *a: a)('/usr/bin/patch', '-o-', *cmd_args)
                e = dict(LC='C')
                for name, value in environ.iteritems():
                    if name in ('TMPDIR', 'TMP', 'TEMP'):
                        e[name] = value
                proc = Popen(cmd, stdin=PIPE, stdout=null, stderr=PIPE, env=e)
                str_hunk = str(hunk)
                partial_patch = header + '\n' + str_hunk
                _, stderrdata = proc.communicate(partial_patch)
                delta = adjustment(proc.wait(), stderrdata)
                if delta:
                    hunk.startsrc += delta
                    hunk.starttgt += delta
                    str_hunk = str(hunk)
                print str_hunk,
    null.close()


if __name__ == '__main__':
    # see PATCH(1)
    opts, args = getopt.getopt(sys.argv[1:], 'p:f:h', ['strip=', 'fuzz='])
    if ('-h', '') in opts:
        print >>sys.stderr, "Usage: {0} {{[-p|-f]}} [patch-or-stdin]" \
                            .format(sys.argv[0])
        sys.exit(0)
    sys.exit(proceed(opts, args))