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

usage() {
  echo "Usage: $0 --uri <uri> --db <dbname> --output <file>"
  echo ""
  echo "  --uri     MongoDB connection URI (e.g. mongodb://user:pass@host:27017/admin)"
  echo "  --db      Database name"
  echo "  --output  Path to output JSON file"
  exit 1
}

URI=""
DB=""
OUTPUT=""

while [[ $# -gt 0 ]]; do
  case "$1" in
    --uri)    URI="$2";    shift 2 ;;
    --db)     DB="$2";     shift 2 ;;
    --output) OUTPUT="$2"; shift 2 ;;
    *) echo "Unknown argument: $1"; usage ;;
  esac
done

[[ -z "$URI" ]]    && echo "Error: --uri is required"    && usage
[[ -z "$DB" ]]     && echo "Error: --db is required"     && usage
[[ -z "$OUTPUT" ]] && echo "Error: --output is required" && usage

TMP_JS=$(mktemp /tmp/mongo-export-XXXXXX.js)
trap 'rm -f "$TMP_JS"' EXIT

cat > "$TMP_JS" <<'EOF'
const dbName = process.env.MONGO_DB;
const targetDb = db.getSiblingDB(dbName);

const result = {};
const collections = targetDb.getCollectionNames();

for (const collName of collections) {
  const indexes = targetDb.getCollection(collName).getIndexes();
  const filtered = indexes.filter(idx => idx.name !== "_id_");

  if (filtered.length > 0) {
    result[collName] = filtered.map(idx => {
      const { v, ns, ...rest } = idx;
      return rest;
    });
  }
}

print(JSON.stringify(result, null, 2));
EOF

MONGO_DB="$DB" mongosh --quiet "$URI" --file "$TMP_JS" > "$OUTPUT"

echo "Exported indexes to: $OUTPUT"