text: /**
   * Copyright (c) 2010-2016 Brian Carlson (brian.m.carlson@gmail.com)
   * All rights reserved.
   *
   * This source code is licensed under the MIT license found in the
   * README.md file in the root directory of this source tree.
   */
  
  var url = require('url');
  var dns = require('dns');
  
  var defaults = require('./defaults');
  
  var val = function(key, config, envVar) {
    if (envVar === undefined) {
      envVar = process.env[ 'PG' + key.toUpperCase() ];
    } else if (envVar === false) {
      // do nothing ... use false
    } else {
      envVar = process.env[ envVar ];
    }
  
    return config[key] ||
      envVar ||
      defaults[key];
  };
  
  //parses a connection string
  var parse = require('pg-connection-string').parse;
  
  var useSsl = function() {
    switch(process.env.PGSSLMODE) {
    case "disable":
      return false;
    case "prefer":
    case "require":
    case "verify-ca":
    case "verify-full":
      return true;
    }
    return defaults.ssl;
  };
  
  var ConnectionParameters = function(config) {
    //if a string is passed, it is a raw connection string so we parse it into a config
    config = typeof config == 'string' ? parse(config) : (config || {});
    //if the config has a connectionString defined, parse IT into the config we use
    //this will override other default values with what is stored in connectionString
    if(config.connectionString) {
      config = parse(config.connectionString);
    }
    this.user = val('user', config);
    this.database = val('database', config);
    this.port = parseInt(val('port', config), 10);
    this.host = val('host', config);
    this.password = val('password', config);
    this.binary = val('binary', config);
    this.ssl = typeof config.ssl === 'undefined' ? useSsl() : config.ssl;
    this.client_encoding = val("client_encoding", config);
    //a domain socket begins with '/'
    this.isDomainSocket = (!(this.host||'').indexOf('/'));
  
    this.application_name = val('application_name', config, 'PGAPPNAME');
    this.fallback_application_name = val('fallback_application_name', config, false);
  };
  
  var add = function(params, config, paramName) {
    var value = config[paramName];
    if(value) {
      params.push(paramName+"='"+value+"'");
    }
  };
  
  ConnectionParameters.prototype.getLibpqConnectionString = function(cb) {
    var params = [];
    add(params, this, 'user');
    add(params, this, 'password');
    add(params, this, 'port');
    add(params, this, 'application_name');
    add(params, this, 'fallback_application_name');
  
    if(this.database) {
      params.push("dbname='" + this.database + "'");
    }
    if(this.host) {
      params.push("host=" + this.host);
    }
    if(this.isDomainSocket) {
      return cb(null, params.join(' '));
    }
    if(this.client_encoding) {
      params.push("client_encoding='" + this.client_encoding + "'");
    }
    dns.lookup(this.host, function(err, address) {
      if(err) return cb(err, null);
      params.push("hostaddr=" + address);
      return cb(null, params.join(' '));
    });
  };
  
  module.exports = ConnectionParameters;
  