#!/usr/bin/env python3
"""Commit everything, tag the version of the newest changelog entry and push main with the tags.

The tag is the version of the first entry of debian-package/debian/changelog, without the
Debian revision 1: vpn-router (0.5.1-1) is tagged 0.5.1 and (0.5.1-2) 0.5.1-2. The tag
starts the release workflow.
"""

import argparse
import pathlib
import shlex
import subprocess
import sys

ROOT = pathlib.Path(__file__).resolve().parent
CHANGELOG = ROOT / 'debian-package' / 'debian' / 'changelog'


#: Print the git commands instead of running them; set by -n/--dry-run.
DRY_RUN = False


def git(*args):
    """Run git in the repository, or print the command on a dry run; stop with git's exit status when it fails."""
    command = ['git', *args]
    if DRY_RUN:
        print(shlex.join(command))
        return
    result = subprocess.run(command, cwd=ROOT)
    if result.returncode != 0:
        sys.exit(result.returncode)


def summary():
    """The summary line of the first changelog entry, or None when it has none.

    The summary is the entry's first text line: indented by two spaces, not a "*" item,
    with a blank line between it and the header and a blank line after it.
    """
    lines = CHANGELOG.read_text(encoding='utf-8').splitlines()
    if len(lines) < 4 or lines[1].strip() or lines[3].strip():
        return None
    line = lines[2]
    text = line.strip()
    if not line.startswith('  ') or line.startswith('   ') or not text or text.startswith('*') or line.startswith(' -- '):
        return None
    return text


def version():
    """The tag of the first changelog entry: its version, without the Debian revision when that is 1."""
    first = CHANGELOG.read_text(encoding='utf-8').splitlines()[0]
    start, end = first.find('('), first.find(')')
    if start == -1 or end < start:
        sys.exit(f'{CHANGELOG}: the first line has no version: {first}')
    full = first[start + 1:end]
    upstream, _, revision = full.rpartition('-')
    return upstream if upstream and revision == '1' else full


def main():
    global DRY_RUN
    parser = argparse.ArgumentParser(description=__doc__.splitlines()[0])
    parser.add_argument('-m', '--message', help='commit message; default: the summary line of the newest changelog entry, a line without "*" between blank lines right after its header')
    parser.add_argument('-n', '--dry-run', action='store_true', help='print the git commands instead of running them')
    parser.add_argument('--no-push', action='store_true', help='commit and tag, but do not push')
    args = parser.parse_args()
    DRY_RUN = args.dry_run

    message = args.message or summary()
    if not message:
        sys.exit(f'no commit message: pass -m, or start the newest entry of {CHANGELOG} with a summary line '
                 'without "*", indented by two spaces, with a blank line above and below it')
    tag = version()
    if subprocess.run(['git', 'rev-parse', '-q', '--verify', f'refs/tags/{tag}'], cwd=ROOT,
                      capture_output=True).returncode == 0:
        sys.exit(f'tag {tag} exists; add a new changelog entry first')

    git('add', '-A')
    git('commit', '-m', message)
    git('tag', tag)
    if not args.no_push:
        git('push', 'origin', 'main', '--tags')
    return 0


if __name__ == '__main__':
    sys.exit(main())