#!/usr/bin/env python3
#
# (C) 2018 by Neels Hofmeyr <neels@hofmeyr.de>
# All rights reserved.
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.

import sys
import subprocess
import argparse
import os
import shlex

doc = '''gits: conveniently manage several git subdirectories.
Instead of doing the 'cd foo; git status; cd ../bar; git status' dance, this
helps to save your time with: status, fetch, rebase, ...
'''


def error(*msgs):
    sys.stderr.write(''.join(msgs))
    sys.stderr.write('\n')
    exit(1)


def cmd_to_str(cmd):
    return ' '.join(shlex.quote(c) for c in cmd)


def git(git_dir, *args, may_fail=False, section_marker=False, show_cmd=True):
    sys.stdout.flush()
    sys.stderr.flush()

    if section_marker:
        print('\n===== %s =====' % git_dir)
        sys.stdout.flush()

    cmd = ['git', '-C', git_dir] + list(args)
    if show_cmd:
        print('+ %s' % cmd_to_str(cmd))
        sys.stdout.flush()

    rc = subprocess.call(cmd)
    if rc and not may_fail:
        error('git returned error! command: git -C %r %s' %
              (git_dir, ' '.join(repr(arg) for arg in args)))


def git_output(git_dir, *args):
    return subprocess.check_output(['git', '-C', git_dir, ] + list(args), stderr=subprocess.STDOUT).decode('utf-8')


def git_bool(git_dir, *args):
    try:
        subprocess.check_output(['git', '-C', git_dir, ] + list(args))
        return True
    except subprocess.CalledProcessError as e:
        return False


def git_ahead_behind(git_dir, branch, branch_upstream):
    ''' Count revisions ahead/behind of the remote branch.
        returns: (ahead, behind) (e.g. (0, 5)) '''

    # Missing remote branch
    if not branch_upstream:
        return (0, 0)

    behind = git_output(git_dir, 'rev-list', '--count', '%s..%s' % (branch, branch_upstream))
    ahead = git_output(git_dir, 'rev-list', '--count', '%s..%s' % (branch_upstream, branch))
    return (int(ahead.rstrip()), int(behind.rstrip()))


def git_branches(git_dir, obj='refs/heads'):
    ret = git_output(git_dir, 'for-each-ref', obj, '--format', '%(refname:short)')
    return ret.splitlines()


def git_branch_current(git_dir):
    ret = git_output(git_dir, 'rev-parse', '--abbrev-ref', 'HEAD').rstrip()
    if ret == 'HEAD':
        return None
    return ret


def git_branch_upstream(git_dir, branch_name='HEAD'):
    '''Return an upstream branch name, or an None if there is none.'''
    try:
        return git_output(git_dir, 'rev-parse', '--abbrev-ref', '%s@{u}' % branch_name).rstrip()
    except subprocess.CalledProcessError:
        return None


def git_has_modifications(git_dir):
    return not git_bool(git_dir, 'diff', '--quiet', 'HEAD')


def git_can_fast_forward(git_dir, branch, branch_upstream):
    return git_bool(git_dir, 'merge-base', '--is-ancestor', branch, branch_upstream)


def format_branch_ahead_behind(branch, ahead, behind):
    ''' branch: string like "master"
        ahead, behind: integers like 5, 3
        returns: string like "master", "master[+5]", "master[-3]", "master[+5|-3]" '''
    # Just the branch
    if not ahead and not behind:
        return branch

    # Suffix with ahead/behind
    ret = branch + '['
    if ahead:
        ret += '+' + str(ahead)
        if behind:
            ret += '|'
    if behind:
        ret += '-' + str(behind)
    ret += ']'
    return ret


def git_branch_summary(git_dir):
    '''return a list of strings: [git_dir, branch-info0, branch-info1,...]
    infos are are arbitrary strings like "master[-1]"'''

    interesting_branch_names = ('master',)

    strs = [git_dir, ]
    if git_has_modifications(git_dir):
        strs.append('MODS')

    branch_current = git_branch_current(git_dir)
    for branch in git_branches(git_dir):
        is_current = (branch == branch_current)
        if not is_current and branch not in interesting_branch_names:
            continue

        ahead, behind = git_ahead_behind(git_dir, branch,
                                         git_branch_upstream(git_dir, branch))

        if not ahead and not behind and not is_current:
            # skip branches that are "not interesting"
            continue

        # Branch with ahead/behind upstream info ("master[+1|-5]")
        strs.append(format_branch_ahead_behind(branch, ahead, behind))
    return strs


def format_summaries(summaries, sep0=' ', sep1=' '):
    first_col = max([len(row[0]) for row in summaries])
    first_col_fmt = '%' + str(first_col) + 's'

    lines = []
    for row in summaries:
        lines.append('%s%s%s' % (first_col_fmt %
                                 row[0], sep0, sep1.join(row[1:])))

    return '\n'.join(lines)


def git_dirs():
    dirs = []
    for sub in os.listdir():
        git_path = os.path.join(sub, '.git')
        if not os.path.isdir(git_path):
            continue
        dirs.append(sub)

    if not dirs:
        error('No subdirectories found that are git clones')

    return list(sorted(dirs))


def print_status():
    infos = [git_branch_summary(git_dir) for git_dir in git_dirs()]
    print(format_summaries(infos))


def cmd_do(argv):
    for git_dir in git_dirs():
        git(git_dir, *argv, may_fail=True, section_marker=True)


def cmd_sh(cmd):
    if not cmd:
        error('which command do you want to run?')
    for git_dir in git_dirs():
        print('\n===== %s =====' % git_dir)
        print('+ %s' % cmd_to_str(cmd))
        sys.stdout.flush()
        subprocess.call(cmd, cwd=git_dir)
        sys.stdout.flush()
        sys.stderr.flush()


class SkipThisRepo(Exception):
    pass


def ask(git_dir, *question, valid_answers=('*',)):
    while True:
        print('\n' + '\n  '.join(question))
        print('  ' + '\n  '.join((
            's  skip this repo',
            't  show in tig',
            'g  show in gitk',
        )))

        answer = sys.stdin.readline().strip()
        if answer == 's':
            raise SkipThisRepo()
        if answer == 't':
            subprocess.call(('tig', '--all'), cwd=git_dir)
            continue
        if answer == 'g':
            subprocess.call(('gitk', '--all'), cwd=git_dir)
            continue

        for v in valid_answers:
            if v == answer:
                return answer
            if v == '*':
                return answer
            if v == '+' and len(answer):
                return answer


def ask_reset_hard_or_push_f(git_dir, orig_branch, upstream_branch):
    do_reset = ask(git_dir, 'Diverged.',
                   '%s: git reset --hard %s?' % (
                       orig_branch, upstream_branch),
                   '<empty>  no',
                   'OK  yes, reset to upstream (write OK in caps!)',
                   'P   `push -f` to overwrite upstream (P in caps!)',
                   valid_answers=('', 'OK', 'P'))

    if do_reset == 'OK':
        git(git_dir, 'reset', '--hard', upstream_branch)
    elif do_reset == 'P':
        git(git_dir, 'push', '-f')


def rebase(git_dir):
    orig_branch = git_branch_current(git_dir)
    if orig_branch is None:
        print('Not on a branch: %s' % git_dir)
        raise SkipThisRepo()

    upstream_branch = git_branch_upstream(git_dir, orig_branch)

    print('Checking for rebase of %r onto %r' % (orig_branch, upstream_branch))
    ahead, behind = git_ahead_behind(git_dir, orig_branch, upstream_branch)

    if git_has_modifications(git_dir):
        do_commit = ask(git_dir, 'Local mods.',
                        'c  commit to this branch',
                        '<name>  commit to new branch',
                        '<empty> skip')

        if not do_commit:
            raise SkipThisRepo()

        if do_commit == 'c':
            git(git_dir, 'commit', '-am', 'wip', may_fail=True)
        else:
            git(git_dir, 'checkout', '-b', do_commit)
            git(git_dir, 'commit', '-am', 'wip', may_fail=True)
            git(git_dir, 'checkout', orig_branch)

        if git_has_modifications(git_dir):
            print('There still are local modifications')
            raise SkipThisRepo()

    # Missing upstream branch
    if not upstream_branch:
        print('there is no upstream branch for %r' % orig_branch)

    # Diverged
    elif ahead and behind:
        ask_reset_hard_or_push_f(git_dir, orig_branch, upstream_branch)

    # Behind
    elif behind:
        if git_can_fast_forward(git_dir, orig_branch, upstream_branch):
            print('fast-forwarding...')
            git(git_dir, 'merge')
        else:
            do_merge = ask(git_dir, 'Behind. git merge?',
                           "<empty>  don't merge",
                           'ok  git merge',
                           valid_answers=('', 'ok')
                           )

            if do_merge == 'ok':
                git(git_dir, 'merge')

    # Ahead
    elif ahead:
        do_commit = ask(git_dir, 'Ahead. commit to new branch?',
                        '<empty>  no',
                        '<name>   create new branch',
                        )
        if do_commit:
            git(git_dir, 'checkout', '-b', do_commit)
            git(git_dir, 'commit', '-am', 'wip', may_fail=True)
            git(git_dir, 'checkout', orig_branch)

        ask_reset_hard_or_push_f(git_dir, orig_branch, upstream_branch)

    if git_has_modifications(git_dir):
        raise SkipThisRepo()

    # Rebase onto origin/master? Only when this isn't already the master branch
    if upstream_branch != 'origin/master':
        ahead, behind = git_ahead_behind(git_dir, orig_branch, 'origin/master')

        if ahead and behind:
            do_rebase = ask(git_dir, '%r diverged from master. git rebase -i origin/master?' % orig_branch,
                            "<empty>  don't rebase",
                            'ok  rebase onto origin/master',
                            valid_answers=('', 'ok'))

            if do_rebase == 'ok':
                git(git_dir, 'rebase', '-i', 'origin/master')
                # On conflicts, we'll exit with error implicitly

                do_push = ask(git_dir, 'git push -f to overwrite %r?' % upstream_branch,
                              "<empty>  don't overwrite upstream",
                              'P   `push -f` to overwrite upstream (P in caps!)',
                              valid_answers=('', 'P'))
                if do_push == 'P':
                    git(git_dir, 'push', '-f')

    return orig_branch


def cmd_rebase():
    skipped = []
    for git_dir in git_dirs():
        try:
            print('\n\n===== %s =====' % git_dir)
            sys.stdout.flush()

            branch = rebase(git_dir)
            if branch != 'master':
                git(git_dir, 'checkout', 'master')
                rebase(git_dir)
                git(git_dir, 'checkout', branch)

        except SkipThisRepo:
            print('\nSkipping %r' % git_dir)
            skipped.append(git_dir)

    print('\n\n==========\nrebase done.\n')
    print_status()
    if skipped:
        print('\nskipped: %s' % ' '.join(skipped))


def parse_args():
    parser = argparse.ArgumentParser(description=doc)
    sub = parser.add_subparsers(title='action', dest='action')
    sub.required = True

    # status
    sub.add_parser('status', aliases=['st', 's'],
                   help='show a branch summary and indicate modifications')

    # fetch
    fetch = sub.add_parser('fetch', aliases=['f'],
                           help="run 'git fetch' in each clone (use before rebase)")
    fetch.add_argument('remainder', nargs=argparse.REMAINDER,
                       help='additional arguments to be passed to git fetch')

    # rebase
    sub.add_parser('rebase', aliases=['r', 're'],
                   help='interactively ff-merge master, rebase current branches')

    # sh
    sh = sub.add_parser('sh',
                        help='run shell command in each clone (`gits sh echo hi`)')
    sh.add_argument('remainder', nargs=argparse.REMAINDER,
                    help='command to run in each clone')

    # do
    do = sub.add_parser('do',
                        help='run git command in each clone (`gits do clean -dxf`)')
    do.add_argument('remainder', nargs=argparse.REMAINDER,
                    help='git command to run in each clone')
    return parser.parse_args()


if __name__ == '__main__':
    args = parse_args()
    if args.action in ['status', 's', 'st']:
        print_status()
    elif args.action in ['fetch', 'f']:
        cmd_do(['fetch'] + args.remainder)
    elif args.action in ['rebase', 'r']:
        cmd_rebase()
    elif args.action == 'sh':
        cmd_sh(args.remainder)
    elif args.action == 'do':
        cmd_do(args.remainder)

# vim: shiftwidth=4 expandtab tabstop=4