#!/usr/bin/env python3

import shlex
import subprocess
import sys
from typing import List

def exit(message: str) -> None:
    print('PROBLEM!')
    print(message)
    sys.exit(1)

def run(command: List[str]) -> None:
    print('\n>>> ' + ' '.join(map(shlex.quote, command)))
    subprocess.check_call(command)

def check_output(command: List[str]) -> str:
    return subprocess.check_output(command).decode('ascii')

def get_git_branch() -> str:
    command = ['git', 'rev-parse', '--abbrev-ref', 'HEAD']
    output = check_output(command)
    return output.strip()

def check_git_pristine() -> None:
    command = ['git', 'status', '--porcelain']
    output = check_output(command)
    if output.strip():
        exit('Git is not pristine:\n' + output)

def ensure_on_clean_master() -> None:
    branch = get_git_branch()
    if branch != 'master':
        exit('You are still on a feature branch: %s' % (branch,))
    check_git_pristine()
    run(['git', 'fetch', 'upstream', 'master'])
    run(['git', 'rebase', 'upstream/master'])

def create_pull_branch(pull_id: int) -> None:
    run(['git', 'fetch', 'upstream', 'pull/%d/head' % (pull_id,)])
    run(['git', 'checkout', '-B', 'review-%s' % (pull_id,), 'FETCH_HEAD'])
    run(['git', 'rebase', 'upstream/master'])
    run(['git', 'log', 'upstream/master..', '--oneline'])
    run(['git', 'diff', 'upstream/master..', '--name-status'])

    print()
    print('PR: %d' % (pull_id,))
    print(subprocess.check_output(['git', 'log', 'HEAD~..',
                                   '--pretty=format:Author: %an']))

def review_pr() -> None:
    try:
        pull_id = int(sys.argv[1])
    except Exception:
        exit('please provide an integer pull request id')

    ensure_on_clean_master()
    create_pull_branch(pull_id)

if __name__ == '__main__':
    review_pr()
