text: 'use strict';
  
  const Connection = require('../index.js').Connection;
  
  class PoolConnection extends Connection {
    constructor(pool, options) {
      super(options);
      this._pool = pool;
      // When a fatal error occurs the connection's protocol ends, which will cause
      // the connection to end as well, thus we only need to watch for the end event
      // and we will be notified of disconnects.
      // REVIEW: Moved to `once`
      this.once('end', () => {
        this._removeFromPool();
      });
      this.once('error', () => {
        this._removeFromPool();
      });
    }
  
    release() {
      if (!this._pool || this._pool._closed) {
        return;
      }
      this._pool.releaseConnection(this);
    }
  
    promise(promiseImpl) {
      const PromisePoolConnection = require('../promise').PromisePoolConnection;
      return new PromisePoolConnection(this, promiseImpl);
    }
  
    end() {
      const err = new Error(
        'Calling conn.end() to release a pooled connection is ' +
          'deprecated. In next version calling conn.end() will be ' +
          'restored to default conn.end() behavior. Use ' +
          'conn.release() instead.'
      );
      this.emit('warn', err);
      // eslint-disable-next-line no-console
      console.warn(err.message);
      this.release();
    }
  
    destroy() {
      this._removeFromPool();
      super.destroy();
    }
  
    _removeFromPool() {
      if (!this._pool || this._pool._closed) {
        return;
      }
      const pool = this._pool;
      this._pool = null;
      pool._removeConnection(this);
    }
  }
  
  PoolConnection.statementKey = Connection.statementKey;
  module.exports = PoolConnection;
  
  // TODO: Remove this when we are removing PoolConnection#end
  PoolConnection.prototype._realEnd = Connection.prototype.end;
  