"""
Diff based code style checker with flake8

This code come from:
https://github.com/scipy/scipy/blob/main/tools/lint_diff.py

Scipy's licence: https://github.com/scipy/scipy/blob/main/LICENSE.txt
Copyright (c) 2001-2002 Enthought, Inc. 2003-2022, SciPy Developers.
All rights reserved.

Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions
are met:

1. Redistributions of source code must retain the above copyright
 notice, this list of conditions and the following disclaimer.

2. Redistributions in binary form must reproduce the above
 copyright notice, this list of conditions and the following
 disclaimer in the documentation and/or other materials provided
 with the distribution.

3. Neither the name of the copyright holder nor the names of its
 contributors may be used to endorse or promote products derived
 from this software without specific prior written permission.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
"""
import conftest
import subprocess


def rev_list(branch, num_commits):
 """List commits in reverse chronological order.
 Only the first `num_commits` are shown.
 """
 res = subprocess.run(
 [
 'git',
 'rev-list',
 '--max-count',
 f'{num_commits}',
 '--first-parent',
 branch
 ],
 stdout=subprocess.PIPE,
 encoding='utf-8',
 )
 res.check_returncode()
 return res.stdout.rstrip('\n').split('\n')


def find_branch_point(branch):
 """Find when the current branch split off from the given branch.
 It is based off of this Stackoverflow post:
 https://stackoverflow.com/questions/1527234/finding-a-branch-point-with-git#4991675
 """
 branch_commits = rev_list('HEAD', 1000)
 main_commits = set(rev_list(branch, 1000))
 for branch_commit in branch_commits:
 if branch_commit in main_commits:
 return branch_commit

 # If a branch split off over 1000 commits ago we will fail to find
 # the ancestor.
 raise RuntimeError(
 'Failed to find a common ancestor in the last 1000 commits')


def find_diff(sha):
 """Find the diff since the given sha."""
 files = ['*.py']
 res = subprocess.run(
 ['git', 'diff', '--unified=0', sha, '--'] + files,
 stdout=subprocess.PIPE,
 encoding='utf-8'
 )
 res.check_returncode()
 return res.stdout


def run_flake8(diff):
 """Run flake8 on the given diff."""
 res = subprocess.run(
 ['flake8', '--diff'],
 input=diff,
 stdout=subprocess.PIPE,
 encoding='utf-8',
 )
 return res.returncode, res.stdout


def test():
 branch_commit = find_branch_point("origin/master")
 diff = find_diff(branch_commit)
 rc, errors = run_flake8(diff)
 if errors:
 print(errors)
 else:
 print("No lint errors found.")
 assert rc == 0


if __name__ == '__main__':
 conftest.run_this_test(__file__)