#!/usr/bin/env python3
"""Validate commit messages for GRM.

Rules:
- On master branch: allow anything (merge commits already have task ID).
- On feature branches: must use conventional commit format, must NOT include GRM-N prefix.
"""
import re
import subprocess
import sys

CONVENTIONAL_RE = re.compile(
    r"^(feat|fix|chore|docs|style|refactor|perf|test|ci|build|revert|BREAKING CHANGE)(\(.+\))?: .+"
)
TASK_ID_RE = re.compile(r"^GRM-\d+:")


def first_line(text: str) -> str:
    return text.split("\n")[0]


def get_branch() -> str:
    try:
        result = subprocess.run(
            ["git", "symbolic-ref", "--short", "HEAD"],
            capture_output=True, text=True, check=True,
        )
        return result.stdout.strip()
    except subprocess.CalledProcessError:
        return ""


def main(args=None) -> None:
    argv = args if args is not None else sys.argv
    if len(argv) < 2:
        print("Usage: validate_commit_msg.py <commit-msg-file>")
        sys.exit(1)

    with open(argv[1]) as f:
        msg = f.read().strip()

    branch = get_branch()

    if branch == "master":
        return

    subject = first_line(msg)

    if TASK_ID_RE.match(subject):
        print("ERROR: Do not include task ID (GRM-N) in feature branch commits.")
        print("  Task ID will be added automatically on merge via CI.")
        sys.exit(1)

    if not CONVENTIONAL_RE.match(subject):
        print("ERROR: Commit message must follow conventional commit format.")
        print("  Expected: <type>: <description>")
        print(f"  Got:      {subject}")
        print("  Allowed types: feat, fix, chore, docs, style, refactor,")
        print("                 perf, test, ci, build, revert, BREAKING CHANGE")
        sys.exit(1)


if __name__ == "__main__":  # pragma: no cover
    main()