#!/usr/bin/env bash
set -euo pipefail

ROOT_DIR="$(cd "$(dirname "$0")/.." && pwd)"
cd "$ROOT_DIR"

BASE_REF="${1:-}"
HEAD_REF="${2:-HEAD}"

if [[ -z "$BASE_REF" ]]; then
  if git rev-parse --verify origin/master >/dev/null 2>&1; then
    BASE_REF="origin/master"
  elif git rev-parse --verify origin/main >/dev/null 2>&1; then
    BASE_REF="origin/main"
  else
    BASE_REF="HEAD~1"
  fi
fi

TS="$(date '+%Y%m%d_%H%M%S')"
OUT_DIR="docs/task_briefs"
OUT_FILE="$OUT_DIR/task_brief_${TS}.md"
mkdir -p "$OUT_DIR"

CHANGED_FILES_RAW="$(git diff --name-only "$BASE_REF"..."$HEAD_REF" || true)"
if [[ -z "$CHANGED_FILES_RAW" ]]; then
  CHANGED_FILES="- (no file changes detected)"
else
  CHANGED_FILES="$(printf '%s\n' "$CHANGED_FILES_RAW" | sed 's#^#- #')"
fi

SCOPE_SUMMARY="- Backend/API: $(printf '%s\n' "$CHANGED_FILES_RAW" | grep -c '^backend/' || true) files\n- Frontend: $(printf '%s\n' "$CHANGED_FILES_RAW" | grep -c '^frontend/' || true) files\n- Docs/Scripts/CI: $(printf '%s\n' "$CHANGED_FILES_RAW" | grep -E -c '^(docs/|scripts/|\.github/)' || true) files"

RISKS="- Contract drift risk when backend API changes without TS sync.\n- Routing regression risk when function_name or route tier changes.\n- Async planner failure should not block signal main flow."

{
  echo "# Task Brief"
  echo
  echo "## Meta"
  echo "- Generated At: $(date '+%Y-%m-%d %H:%M:%S %z')"
  echo "- Base Ref: $BASE_REF"
  echo "- Head Ref: $HEAD_REF"
  echo
  echo "## Changed Files"
  printf '%b\n' "$CHANGED_FILES"
  echo
  echo "## Scope"
  printf '%b\n' "$SCOPE_SUMMARY"
  echo
  echo "## Risks"
  printf '%b\n' "$RISKS"
  echo
  echo "## Verification"
  echo "- Backend: \`python3 -m py_compile backend/app\`"
  echo "- Frontend: \`npm run build\` + \`npx tsc --noEmit\`"
  echo
  echo "## Delivery Checklist"
  echo "- [ ] Code completed"
  echo "- [ ] Contracts synchronized"
  echo "- [ ] Docs synchronized"
  echo "- [ ] Build/lint/tests passed"
} > "$OUT_FILE"

echo "$OUT_FILE"