commit-msg

#!/usr/bin/env python3
import re
import sys
import string

TYPES = [
    "feat", "fix", "chore", "docs", "style",
    "refactor", "test", "perf", "ci", "build", "revert"
]

PATTERN = re.compile(
    r'^(?P<type>[a-zA-Z]+)'       # type (letters only)
    r'(?:\([^)]+\))?'             # optional scope
    r'!?'                         # optional "!" after type/scope
    r':\s+'                       # colon and spaces
    r'(?P<desc>.+)$'              # description
)

def check_line(first_line: str) -> bool:
    match = PATTERN.match(first_line)
    if not match:
        return fail(first_line, "Message must match format: type(optional_scope): description")

    ctype = match.group("type").lower()
    desc = match.group("desc")

    if ctype not in TYPES:
        return fail(first_line, f"Invalid type '{ctype}'. Allowed: {', '.join(TYPES)}")

    if not desc or desc[0] in string.punctuation:
        return fail(first_line, "Description can not be empty or start with punctuation")

    # passed all checks
    return True

def fail(msg, reason):
    print("------------------------------")
    print("ERROR:  Invalid commit message")
    print(f"REASON: {reason}")
    print("------------------------------")
    print("Valid examples:")
    print("   fix: fixed some bug")
    print("   feat!: added feature with breaking changes")
    print("   fix(parser): fixed problem with parser")
    return False

def main():
    commit_msg_file = sys.argv[1]
    with open(commit_msg_file, encoding="utf-8") as f:
        first_line = f.readline().strip()
    ok = check_line(first_line)
    sys.exit(0 if ok else 1)

if __name__ == "__main__":
    main()