#!/usr/bin/env python
# vim: tabstop=4 shiftwidth=4 softtabstop=4

# Copyright (c) 2013 OpenStack Foundation
# All Rights Reserved.
#
#    Licensed under the Apache License, Version 2.0 (the "License"); you may
#    not use this file except in compliance with the License. You may obtain
#    a copy of the License at
#
#         http://www.apache.org/licenses/LICENSE-2.0
#
#    Unless required by applicable law or agreed to in writing, software
#    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
#    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
#    License for the specific language governing permissions and limitations
#    under the License.


"""Tool for checking if patch contains a regression test.

By default runs against current patch but can be set to use any gerrit review
as specified by change number (uses 'git review -d').

Idea: take tests from patch to check, and run against code from previous patch.
If new tests pass, then no regression test, if new tests fails against old code
then either
* new tests depend on new code and cannot confirm regression test is valid
  (false positive)
* new tests detects the bug being fixed (detect valid regression test)
Due to the risk of false positives, the results from this need some human
interpretation.
"""

import optparse
import string
import subprocess
import sys


def run(cmd, fail_ok=False):
    print "running: %s" % cmd
    obj = subprocess.Popen(cmd, stdout=subprocess.PIPE, stderr=subprocess.PIPE,
                           shell=True)
    obj.wait()
    if obj.returncode != 0 and not fail_ok:
        print "The above command terminated with an error."
        sys.exit(obj.returncode)
    return obj.stdout.read()


def main():
    usage = """
    Tool for checking if a patch includes a regression test.

    Usage: %prog [options]"""
    parser = optparse.OptionParser(usage)
    parser.add_option("-r", "--review", dest="review",
                      help="gerrit review number to test")
    (options, args) = parser.parse_args()
    if options.review:
        original_branch = run("git rev-parse --abbrev-ref HEAD")
        run("git review -d %s" % options.review)
    else:
        print ("no gerrit review number specified, running on latest commit"
               "on current branch.")

    test_works = False

    # run new tests with old code
    run("git checkout HEAD^ nova")
    run("git checkout HEAD nova/tests")

    # identify which tests have changed
    tests = run("git whatchanged --format=oneline -1 | grep \"nova/tests\" "
                "| cut -f2").split()
    test_list = []
    for test in tests:
        test_list.append(string.replace(test[0:-3], '/', '.'))

    if test_list == []:
        test_works = False
        expect_failure = ""
    else:
        # run new tests, expect them to fail
        expect_failure = run(("tox -epy27 %s 2>&1" % string.join(test_list)),
                             fail_ok=True)
        if "FAILED (id=" in expect_failure:
            test_works = True

    # cleanup
    run("git checkout HEAD nova")
    if options.review:
        new_branch = run("git status | head -1 | cut -d ' ' -f 4")
        run("git checkout %s" % original_branch)
        run("git branch -D %s" % new_branch)

    print expect_failure
    print ""
    print "*******************************"
    if test_works:
        print "FOUND a regression test"
    else:
        print "NO regression test"
        sys.exit(1)


if __name__ == "__main__":
    main()
