const { MongoClient } = require('mongodb');

const DEFAULT_EXTERNAL_DB_NAME = 'reallives_serverless_eb';
const DEFAULT_EXTERNAL_COLLECTION = 'Food';

function getExternalMongoUri() {
  return process.env.MONGODB_URI || '';
}

function getCollection() {
  return process.env.FOOD_EXTERNAL_COLLECTION || DEFAULT_EXTERNAL_COLLECTION;
}

function getDbName() {
  return process.env.FOOD_EXTERNAL_DB || DEFAULT_EXTERNAL_DB_NAME;
}

/**
 * Fetch existing food record for an event from external DB.
 *
 * @param {string} eventId
 * @returns {Promise<{ location?: string, recommendations?: string, restaurants?: any[], raw?: any } | null>}
 */
async function fetchFoodRecordForEvent(eventId) {
  const eventIdStr = eventId != null ? String(eventId) : '';
  if (!eventIdStr) return null;

  const mongoUri = getExternalMongoUri();
  if (!mongoUri) return null;

  const client = new MongoClient(mongoUri, { useNewUrlParser: true, useUnifiedTopology: true });
  await client.connect();
  try {
    const db = client.db(getDbName());
    const coll = db.collection(getCollection());

    // The external doc created in foodRecommendationService uses { eventId: <string> }
    const doc = await coll.findOne({ eventId: eventIdStr });
    if (!doc) return null;

    return {
      location: doc.location,
      recommendations: doc.recommendations,
      restaurants: doc.restaurants,
      raw: doc,
    };
  } finally {
    await client.close();
  }
}

module.exports = {
  fetchFoodRecordForEvent,
};