#!/bin/sh
# commit-msg hook to enforce Conventional Commits (https://www.conventionalcommits.org/)
# This script checks the commit message subject (first line) for a conventional commit format.
# If the message does not conform, the hook exits non-zero to block the commit.

# Read the commit message (first line)
if [ -z "$1" ]; then
  echo "commit-msg hook: no message file provided" >&2
  exit 0
fi

MSG_FILE="$1"
read -r FIRST_LINE < "$MSG_FILE" || FIRST_LINE=""

# Trim leading/trailing whitespace
FIRST_LINE="$(echo "$FIRST_LINE" | sed -e 's/^[ \t]*//' -e 's/[ \t]*$//')"

# Allow empty message (let git handle it), or allow merges/reverts
case "$FIRST_LINE" in
  Merge:*|merge:*|Revert:*|revert:*)
    exit 0
    ;;
esac

# Conventional Commit regex (POSIX ERE)
# [type](scope)!?: subject
# types: feat|fix|docs|style|refactor|perf|test|build|ci|chore|revert|wip
# scope: any chars except )

regex='^\[(feat|fix|docs|style|refactor|perf|test|build|ci|chore|revert|wip)\](\([^\)]+\))?(!)?: .+'

printf "%s" "$FIRST_LINE" | grep -E "$regex" >/dev/null 2>&1
if [ $? -eq 0 ]; then
  exit 0
fi

cat <<'EOF' >&2
ERROR: Commit message does not follow Conventional Commits.

Expected format:
  [type](scope)?: subject

Examples:
  [feat]: add new feature
  [fix(parser)]: handle edge case
  [docs]!: update API docs (breaking change)

Allowed types: feat, fix, docs, style, refactor, perf, test, build, ci, chore, revert, wip

You can bypass this hook locally by running:
  git commit --no-verify
EOF

exit 1