const MongoClient = require('mongodb').MongoClient

function buildUri(urlOrOptions) {
  if (!urlOrOptions || typeof urlOrOptions !== 'object') {
    if (typeof urlOrOptions === 'string') {
      return urlOrOptions;
    }
    throw new Error('buildUri: valid options or URI string required');
  }

  const hosts = Array.isArray(urlOrOptions.hosts)
    ? urlOrOptions.hosts.filter(Boolean).join(',')
    : (urlOrOptions.hosts || 'localhost:27017');
  const auth = urlOrOptions.user
    ? `${encodeURIComponent(urlOrOptions.user)}${urlOrOptions.pass ? `:${encodeURIComponent(urlOrOptions.pass)}` : ''}@`
    : '';
  const dbName = urlOrOptions.db || 'agmission';
  const authSource = urlOrOptions.authSource || dbName;
  
  const params = new URLSearchParams();
  if (urlOrOptions.replicaSet) {
    params.append('replicaSet', urlOrOptions.replicaSet);
  }
  if (authSource && authSource !== dbName) {
    params.append('authSource', authSource);
  }
  const queryString = params.toString() ? `?${params.toString()}` : '';

  return `mongodb://${auth}${hosts}/${dbName}${queryString}`;
}

/**
 * Version-agnostic connectivity check using a ping command.
 * Works with MongoDB driver 3.x, 4.x, 5+ (unlike isConnected() which was removed in v5).
 * @param {MongoClient} client
 * @returns {Promise<boolean>}
 */
async function isConnected(client) {
  if (!client) return false;
  try {
    await client.db().admin().command({ ping: 1 });
    return true;
  } catch {
    return false;
  }
}

async function connect(url) {
  const _url = buildUri(url);

  return await MongoClient.connect(_url, {
    family: 4,
    useNewUrlParser: true,
    useUnifiedTopology: true,
    keepAlive: true
  });
}

module.exports = {
  connect,
  isConnected
}