#!/usr/bin/python3

# rediff-patches.py name.spec

# TODO:
# - handle rediff of last patch (need some way to terminate build just after that patch is applied)
# - or maybe apply patches on our own instead of using rpmbuild for that
# - cleanup

import argparse
import collections
import logging
import os
import re
import rpm
import shutil
import subprocess
import sys
import tempfile

RPMBUILD_ISPATCH = (1<<1)

def unpack(spec, builddir, until_patch=None):
    cmd = [ 'rpmbuild', '-bp', '--define',  '_builddir %s' % builddir, '--define', '_default_patch_fuzz 2' ]
    if until_patch is not None:
        cmd += [ '--define', '%%patch%d exit; #' % until_patch ]
    cmd += [ spec ]
    logging.debug("running %s" % repr(cmd))
    subprocess.check_call(cmd, stdout=sys.stderr, stderr=sys.stderr,
                          env={'LC_ALL': 'C.UTF-8'}, timeout=600)

def diff(diffdir_org, diffdir, builddir, output):
    diffdir_org = os.path.basename(diffdir_org)
    diffdir = os.path.basename(diffdir)

    with open(output, 'wt') as f:
        cmd = [ 'diff', '-urNp', '-x', '*.orig', diffdir_org, diffdir ]
        logging.debug("running %s" % repr(cmd))
        try:
            subprocess.check_call(cmd, cwd=builddir, stdout=f, stderr=sys.stderr,
                                  env={'LC_ALL': 'C.UTF-8'}, timeout=600)
        except subprocess.CalledProcessError as err:
            if err.returncode != 1:
                raise
    logging.info("rediff generated as %s" % output)


def main():
    parser = parser = argparse.ArgumentParser(description='rediff patches to avoid fuzzy hunks')
    parser.add_argument('spec', type=str, help='spec file name')
    parser.add_argument('-p', '--patches', type=str, help='comma separated list of patch numbers to rediff')
    parser.add_argument('-v', '--verbose', help='increase output verbosity', action='store_true')
    args = parser.parse_args()

    logging.basicConfig(level=logging.INFO)
    rpm.setVerbosity(rpm.RPMLOG_ERR)

    if args.verbose:
            logging.basicConfig(level=logging.DEBUG)
            rpm.setVerbosity(rpm.RPMLOG_DEBUG)

    if args.patches:
        args.patches = [int(x) for x in args.patches.split(',')]

    specfile = args.spec

    tempdir = tempfile.TemporaryDirectory(dir="/dev/shm")
    topdir = tempdir.name
    builddir = os.path.join(topdir, 'BUILD')

    rpm.addMacro("_builddir", builddir)

    r = rpm.spec(specfile)

    patches = {}

    for (name, nr, flags) in r.sources:
        if flags & RPMBUILD_ISPATCH:
            patches[nr] = name

    applied_patches = collections.OrderedDict()
    re_patch = re.compile(r'^%patch(?P<patch_number>\d+)\w*(?P<patch_args>.*)')
    for line in r.parsed.split('\n'):
        m = re_patch.match(line)
        if not m:
            continue
        patch_nr = int(m.group('patch_number'))
        patch_args = m.group('patch_args')
        applied_patches[patch_nr] = patch_args

    appsourcedir = rpm.expandMacro("%{_sourcedir}")
    appbuilddir = rpm.expandMacro("%{_builddir}/%{?buildsubdir}")

    for patch_nr, patch_nr_next in zip(applied_patches.keys(), list(applied_patches.keys())[1:] + [None]):
        if args.patches and patch_nr not in args.patches:
            continue
        if patch_nr_next is None:
            logging.warning("can't rediff last patch, see TODO")
            break
        patch_name = patches[patch_nr]
        logging.info("*** patch %d: %s" % (patch_nr, patch_name))
        unpack(specfile, builddir, patch_nr)
        os.rename(appbuilddir, appbuilddir + ".org")
        unpack(specfile, builddir, patch_nr_next)
        diff(appbuilddir + ".org", appbuilddir, builddir, os.path.join(topdir, os.path.join(appsourcedir, patch_name + ".rediff")))
        shutil.rmtree(builddir)
    tempdir.cleanup()

if __name__ == '__main__':
    main()