#!/usr/bin/env bash
# Husky prepare-commit-msg hook — detects AI agent changes mid-branch.
#
# When the Co-Authored-By trailer in the new commit message differs from
# the AI tool signature in the previous commit on the same branch, warns
# the operator to create an ai-agent-handoff.md entry (devaudit-installer#197).
#
# This is a WARNING-only hook — it never blocks the commit. The operator
# decides whether a handoff entry is warranted (e.g. same tool, different
# session → no handoff needed; different tool → handoff recommended).
#
# Install: cp this file to .husky/prepare-commit-msg && chmod +x .husky/prepare-commit-msg
#
# To disable: delete .husky/prepare-commit-msg or set DEVAUDIT_NO_AI_HOOK=1

# Allow opt-out
if [ -n "${DEVAUDIT_NO_AI_HOOK:-}" ]; then
  exit 0
fi

COMMIT_MSG_FILE="$1"
COMMIT_SOURCE="$2"

# Skip merge commits, squash, etc. — only check normal commits
if [ -n "$COMMIT_SOURCE" ] && [ "$COMMIT_SOURCE" != "message" ]; then
  exit 0
fi

# Extract Co-Authored-By from the incoming commit message (if present)
CURRENT_AI=$(grep -i 'Co-Authored-By:' "$COMMIT_MSG_FILE" 2>/dev/null | head -1 | sed 's/.*Co-Authored-By:[[:space:]]*//' | tr -d '\r')

# Extract Co-Authored-By from the previous commit on this branch
LAST_AI=$(git log -1 --format='%b' 2>/dev/null | grep -i 'Co-Authored-By:' | head -1 | sed 's/.*Co-Authored-By:[[:space:]]*//' | tr -d '\r')

# Only warn if both exist and differ — a missing trailer on either side
# is not an agent change (the commitlint hook handles missing trailers)
if [ -z "$CURRENT_AI" ] || [ -z "$LAST_AI" ]; then
  exit 0
fi

if [ "$CURRENT_AI" != "$LAST_AI" ]; then
  echo ""
  echo "⚠️  AI agent change detected (devaudit-installer#197):"
  echo "    Previous: $LAST_AI"
  echo "    Current:  $CURRENT_AI"
  echo ""
  echo "    Consider creating an ai-agent-handoff.md entry in"
  echo "    compliance/evidence/REQ-XXX/ to document the handoff."
  echo "    See SDLC/3-compile-evidence.md Step 5b for the template."
  echo ""
  echo "    To suppress this warning: DEVAUDIT_NO_AI_HOOK=1"
  echo ""
fi

exit 0