loopback-datasource-juggler/lib/datasource.js

LoopBack DataSource Juggler

// Copyright IBM Corp. 2013,2020. All Rights Reserved.
// Node module: loopback-datasource-juggler
// This file is licensed under the MIT License.
// License text available at https://opensource.org/licenses/MIT

// Turning on strict for this file breaks lots of test cases;
// disabling strict for this file
/* eslint-disable strict */

/*!
 * Module dependencies
 */
const ModelBuilder = require('./model-builder.js').ModelBuilder;
const ModelDefinition = require('./model-definition.js');
const RelationDefinition = require('./relation-definition.js');
const OberserverMixin = require('./observer');
const jutil = require('./jutil');
const utils = require('./utils');
const ModelBaseClass = require('./model.js');
const DataAccessObject = require('./dao.js');
const defineScope = require('./scope.js').defineScope;
const EventEmitter = require('events').EventEmitter;
const util = require('util');
const assert = require('assert');
const async = require('async');
const traverse = require('neotraverse/legacy');
const g = require('strong-globalize')();
const juggler = require('..');
const deprecated = require('depd')('loopback-datasource-juggler');
const Transaction = require('loopback-connector').Transaction;
const pascalCase = require('change-case').pascalCase;
const camelCase = require('change-case').camelCase;

if (process.env.DEBUG === 'loopback') {
  // For back-compatibility
  process.env.DEBUG = 'loopback:*';
}
const debug = require('debug')('loopback:datasource');

/*!
 * Export public API
 */
exports.DataSource = DataSource;

/*!
 * Helpers
 */
const slice = Array.prototype.slice;

/**
 * LoopBack models can manipulate data via the DataSource object.
 * Attaching a `DataSource` to a `Model` adds instance methods and static methods to the `Model`.
 *
 * Define a data source to persist model data.
 * To create a DataSource programmatically, call `createDataSource()` on the LoopBack object; for example:
 * ```js
 * var oracle = loopback.createDataSource({
 *   connector: 'oracle',
 *   host: '111.22.333.44',
 *   database: 'MYDB',
 *   username: 'username',
 *   password: 'password'
 * });
 * ```
 *
 * All classes in single dataSource share same the connector type and
 * one database connection.
 *
 * For example, the following creates a DataSource, and waits for a connection callback.
 *
 * ```
 * var dataSource = new DataSource('mysql', { database: 'myapp_test' });
 * dataSource.define(...);
 * dataSource.on('connected', function () {
 *     // work with database
 * });
 * ```
 * @class DataSource
 * @param {String} [name] Optional name for datasource.
 * @options {Object} settings Database-specific settings to establish connection (settings depend on specific connector).
 * The table below lists a typical set for a relational database.
 * @property {String} connector Database connector to use.  For any supported connector, can be any of:
 *
 * - The connector module from `require(connectorName)`.
 * - The full name of the connector module, such as 'loopback-connector-oracle'.
 * - The short name of the connector module, such as 'oracle'.
 * - A local module under `./connectors/` folder.
 * @property {String} host Database server host name.
 * @property {String} port Database server port number.
 * @property {String} username Database user name.
 * @property {String} password Database password.
 * @property {String} database Name of the database to use.
 * @property {Boolean} debug Display debugging information. Default is false.
 *
 * The constructor allows the following styles:
 *
 * 1. new DataSource(dataSourceName, settings). For example:
 *   - new DataSource('myDataSource', {connector: 'memory'});
 *   - new DataSource('myDataSource', {name: 'myDataSource', connector: 'memory'});
 *   - new DataSource('myDataSource', {name: 'anotherDataSource', connector: 'memory'});
 *
 * 2. new DataSource(settings). For example:
 *   - new DataSource({name: 'myDataSource', connector: 'memory'});
 *   - new DataSource({connector: 'memory'});
 *
 * 3. new DataSource(connectorModule, settings). For example:
 *   - new DataSource(connectorModule, {name: 'myDataSource})
 *   - new DataSource(connectorModule)
 */
function DataSource(name, settings, modelBuilder) {
  if (!(this instanceof DataSource)) {
    return new DataSource(name, settings);
  }

  // Check if the settings object is passed as the first argument
  if (typeof name === 'object' && settings === undefined) {
    settings = name;
    name = undefined;
  }

  // Check if the first argument is a URL
  if (typeof name === 'string' && name.indexOf('://') !== -1) {
    name = utils.parseSettings(name);
  }

  // Check if the settings is in the form of URL string
  if (typeof settings === 'string' && settings.indexOf('://') !== -1) {
    settings = utils.parseSettings(settings);
  }

  // Shallow-clone the settings so that updates to `ds.settings`
  // do not modify the original object provided via constructor arguments
  if (settings) settings = Object.assign({}, settings);
  // It's possible to provide settings object via the "name" arg too!
  if (typeof name === 'object') name = Object.assign({}, name);

  this.modelBuilder = modelBuilder || new ModelBuilder();
  this.models = this.modelBuilder.models;
  this.definitions = this.modelBuilder.definitions;
  this.juggler = juggler;
  this._queuedInvocations = 0;

  // operation metadata
  // Initialize it before calling setup as the connector might register operations
  this._operations = {};

  this.setup(name, settings);

  this._setupConnector();

  // connector
  const connector = this.connector;

  // DataAccessObject - connector defined or supply the default
  const dao = (connector && connector.DataAccessObject) || this.constructor.DataAccessObject;
  this.DataAccessObject = function() {
  };

  // define DataAccessObject methods
  Object.keys(dao).forEach(function(name) {
    const fn = dao[name];
    this.DataAccessObject[name] = fn;

    if (typeof fn === 'function') {
      this.defineOperation(name, {
        accepts: fn.accepts,
        'returns': fn.returns,
        http: fn.http,
        remoteEnabled: fn.shared ? true : false,
        scope: this.DataAccessObject,
        fnName: name,
      });
    }
  }.bind(this));

  // define DataAccessObject.prototype methods
  Object.keys(dao.prototype || []).forEach(function(name) {
    const fn = dao.prototype[name];
    this.DataAccessObject.prototype[name] = fn;
    if (typeof fn === 'function') {
      this.defineOperation(name, {
        prototype: true,
        accepts: fn.accepts,
        'returns': fn.returns,
        http: fn.http,
        remoteEnabled: fn.shared ? true : false,
        scope: this.DataAccessObject.prototype,
        fnName: name,
      });
    }
  }.bind(this));
}

util.inherits(DataSource, EventEmitter);

// allow child classes to supply a data access object
DataSource.DataAccessObject = DataAccessObject;

/**
 * Global maximum number of event listeners
 */
DataSource.DEFAULT_MAX_OFFLINE_REQUESTS = 16;

/**
 * Set up the connector instance for backward compatibility with JugglingDB schema/adapter
 * @private
 */
DataSource.prototype._setupConnector = function() {
  this.connector = this.connector || this.adapter; // The legacy JugglingDB adapter will set up `adapter` property
  this.adapter = this.connector; // Keep the adapter as an alias to connector
  if (this.connector) {
    if (!this.connector.dataSource) {
      // Set up the dataSource if the connector doesn't do so
      this.connector.dataSource = this;
    }
    const dataSource = this;

    // Set max listeners to a default/configured value
    dataSource.setMaxListeners(dataSource.getMaxOfflineRequests());

    this.connector.log = function(query, start) {
      dataSource.log(query, start);
    };

    this.connector.logger = function(query) {
      const t1 = Date.now();
      const log = this.log;
      return function(q) {
        log(q || query, t1);
      };
    };
    // Configure the connector instance to mix in observer functions
    jutil.mixin(this.connector, OberserverMixin);
  }
};

// List possible connector module names
function connectorModuleNames(name) {
  const names = []; // Check the name as is
  if (!name.match(/^\//)) {
    names.push('./connectors/' + name); // Check built-in connectors
    if (name.indexOf('loopback-connector-') !== 0) {
      names.push('loopback-connector-' + name); // Try loopback-connector-<name>
    }
  }
  // Only try the short name if the connector is not from StrongLoop
  if (['mongodb', 'oracle', 'mysql', 'postgresql', 'mssql', 'rest', 'soap', 'db2', 'cloudant']
    .indexOf(name) === -1) {
    names.push(name);
  }
  return names;
}

// testable with DI
function tryModules(names, loader) {
  let mod;
  loader = loader || require;
  for (let m = 0; m < names.length; m++) {
    try {
      mod = loader(names[m]);
    } catch (e) {
      const notFound = e.code === 'MODULE_NOT_FOUND' &&
        e.message && e.message.indexOf(names[m]) > 0;

      if (notFound) {
        debug('Module %s not found, will try another candidate.', names[m]);
        continue;
      }

      debug('Cannot load connector %s: %s', names[m], e.stack || e);
      throw e;
    }
    if (mod) {
      break;
    }
  }
  return mod;
}

/*!
 * Resolve a connector by name
 * @param name The connector name
 * @returns {*}
 * @private
 */
DataSource._resolveConnector = function(name, loader) {
  const names = connectorModuleNames(name);
  const connector = tryModules(names, loader);
  let error = null;
  if (!connector) {
    error = g.f('\nWARNING: {{LoopBack}} connector "%s" is not installed ' +
      'as any of the following modules:\n\n %s\n\nTo fix, run:\n\n    {{npm install %s --save}}\n',
    name, names.join('\n'), names[names.length - 1]);
  }
  return {
    connector: connector,
    error: error,
  };
};

/**
 * Connect to the data source.
 * If no callback is provided, it will return a Promise.
 * Emits the 'connect' event.
 * @param callback
 * @returns {Promise}
 * @emits connected
 */
DataSource.prototype.connect = function(callback) {
  callback = callback || utils.createPromiseCallback();
  const self = this;
  if (this.connected) {
    // The data source is already connected, return immediately
    process.nextTick(callback);
    return callback.promise;
  }
  if (typeof this.connector.connect !== 'function') {
    // Connector doesn't have the connect function
    // Assume no connect is needed
    self.connected = true;
    self.connecting = false;
    process.nextTick(function() {
      self.emit('connected');
      callback();
    });
    return callback.promise;
  }

  // Queue the callback
  this.pendingConnectCallbacks = this.pendingConnectCallbacks || [];
  this.pendingConnectCallbacks.push(callback);

  // The connect is already in progress
  if (this.connecting) return callback.promise;
  this.connector.connect(function(err, result) {
    self.connecting = false;
    if (!err) self.connected = true;
    const cbs = self.pendingConnectCallbacks;
    self.pendingConnectCallbacks = [];
    if (!err) {
      self.emit('connected');
    } else {
      self.emit('error', err);
    }
    // Invoke all pending callbacks
    async.each(cbs, function(cb, done) {
      try {
        cb(err);
      } catch (e) {
        // Ignore error to make sure all callbacks are invoked
        debug('Uncaught error raised by connect callback function: ', e);
      } finally {
        done();
      }
    }, function(err) {
      if (err) throw err; // It should not happen
    });
  });

  // Set connecting flag to be `true` so that the connector knows there is
  // a connect in progress. The change of `connecting` should happen immediately
  // after the connect request is sent
  this.connecting = true;
  return callback.promise;
};

/**
 * Set up the data source. The following styles are supported:
 * ```js
 * ds.setup('myDataSource', {connector: 'memory'}); // ds.name -> 'myDataSource'
 * ds.setup('myDataSource', {name: 'myDataSource', connector: 'memory'}); // ds.name -> 'myDataSource'
 * ds.setup('myDataSource', {name: 'anotherDataSource', connector: 'memory'}); // ds.name -> 'myDataSource' and a warning will be issued
 * ds.setup({name: 'myDataSource', connector: 'memory'}); // ds.name -> 'myDataSource'
 * ds.setup({connector: 'memory'}); // ds.name -> 'memory'
 * ```
 * @param {String} dsName The name of the datasource. If not set, use
 * `settings.name`
 * @param {Object} settings The settings
 * @returns {*}
 * @private
 */
DataSource.prototype.setup = function(dsName, settings) {
  const dataSource = this;
  let connector;

  // First argument is an `object`
  if (dsName && typeof dsName === 'object') {
    if (settings === undefined) {
      // setup({name: 'myDataSource', connector: 'memory'})
      settings = dsName;
      dsName = undefined;
    } else {
      // setup(connector, {name: 'myDataSource', host: 'localhost'})
      connector = dsName;
      dsName = undefined;
    }
  }

  if (typeof dsName !== 'string') {
    dsName = undefined;
  }

  if (typeof settings === 'object') {
    if (settings.initialize) {
      // Settings is the resolved connector instance
      connector = settings;
      // Set settings to undefined to avoid confusion
      settings = undefined;
    } else if (settings.connector) {
      // Use `connector`
      connector = settings.connector;
    } else if (settings.adapter) {
      // `adapter` as alias for `connector`
      connector = settings.adapter;
    }
  }

  // just save everything we get
  this.settings = settings || {};

  this.settings.debug = this.settings.debug || debug.enabled;

  if (this.settings.debug) {
    debug('Settings: %j', this.settings);
  }

  if (typeof settings === 'object' && typeof settings.name === 'string' &&
      typeof dsName === 'string' && dsName !== settings.name) {
    // setup('myDataSource', {name: 'anotherDataSource', connector: 'memory'});
    // ds.name -> 'myDataSource' and a warning will be issued
    console.warn(
      'A datasource is created with name %j, which is different from the name in settings (%j). ' +
      'Please adjust your configuration to ensure these names match.',
      dsName, settings.name,
    );
  }

  // Disconnected by default
  this.connected = false;
  this.connecting = false;
  this.initialized = false;

  this.name = dsName || (typeof this.settings.name === 'string' && this.settings.name);

  let connectorName;
  if (typeof connector === 'string') {
    // Connector needs to be resolved by name
    connectorName = connector;
    connector = undefined;
  } else if ((typeof connector === 'object') && connector) {
    connectorName = connector.name;
  } else {
    connectorName = dsName;
  }
  if (!this.name) {
    // Fall back to connector name
    this.name = connectorName;
  }

  if ((!connector) && connectorName) {
    // The connector has not been resolved
    const result = DataSource._resolveConnector(connectorName);
    connector = result.connector;
    if (!connector) {
      console.error(result.error);
      this.emit('error', new Error(result.error));
      return;
    }
  }

  if (connector) {
    const postInit = function postInit(err, result) {
      this._setupConnector();
      // we have an connector now?
      if (!this.connector) {
        throw new Error(g.f('Connector is not defined correctly: ' +
          'it should create `{{connector}}` member of dataSource'));
      }
      if (!err) {
        this.initialized = true;
        this.emit('initialized');
      }
      debug('Connector is initialized for dataSource %s', this.name);
      // If `result` is set to `false` explicitly, the connection will be
      // lazily established
      if (!this.settings.lazyConnect) {
        this.connected = (!err) && (result !== false); // Connected now
      }
      if (this.connected) {
        debug('DataSource %s is now connected to %s', this.name, this.connector.name);
        this.emit('connected');
      } else if (err) {
        // The connection fails, let's report it and hope it will be recovered in the next call
        // Reset the connecting to `false`
        this.connecting = false;
        if (this._queuedInvocations) {
          // Another operation is already waiting for connect() result,
          // let them handle the connection error.
          debug('Connection fails: %s\nIt will be retried for the next request.', err);
        } else {
          g.error('Connection fails: %s\nIt will be retried for the next request.', err);
          if (settings.catchFailure) {
            try {
              this.emit('error', err);
            } catch (error) {
              console.log(error);
            }
          } else {
            this.emit('error', err);
          }
        }
      } else {
        // Either lazyConnect or connector initialize() defers the connection
        debug('DataSource %s will be connected to connector %s', this.name,
          this.connector.name);
      }
    }.bind(this);

    try {
      if ('function' === typeof connector.initialize) {
        // Call the async initialize method
        debug('Initializing connector %s', connector.name);
        connector.initialize(this, postInit);
      } else if ('function' === typeof connector) {
        // Use the connector constructor directly
        this.connector = new connector(this.settings);
        postInit();
      }
    } catch (err) {
      if (err.message) {
        err.message = 'Cannot initialize connector ' +
          JSON.stringify(connectorName) + ': ' +
          err.message;
      }
      throw err;
    }
  }
};

function isModelClass(cls) {
  if (!cls) {
    return false;
  }
  return cls.prototype instanceof ModelBaseClass;
}

DataSource.relationTypes = Object.keys(RelationDefinition.RelationTypes);

function isModelDataSourceAttached(model) {
  return model && (!model.settings.unresolved) && (model.dataSource instanceof DataSource);
}

/*!
 * Define scopes for the model class from the scopes object. See
 * [scopes](./Model-definition-JSON-file.html#scopes) for more information on
 * scopes and valid options objects.
 * @param {Object} modelClass - The model class that corresponds to the model
 * definition that will be enhanced by the provided scopes.
 * @param {Object} scopes A key-value collection of names and their object
 * definitions
 * @property options The options defined on the scope object.
 */
DataSource.prototype.defineScopes = function(modelClass, scopes) {
  if (scopes) {
    for (const s in scopes) {
      defineScope(modelClass, modelClass, s, scopes[s], {}, scopes[s].options);
    }
  }
};

/*!
 * Define relations for the model class from the relations object. See
 * [relations](./Model-definition-JSON-file.html#relations) for more information.
 * @param {Object} modelClass - The model class that corresponds to the model
 * definition that will be enhanced by the provided relations.
 * @param {Object} relations A key-value collection of relation names and their
 * object definitions.
 */
DataSource.prototype.defineRelations = function(modelClass, relations) {
  const self = this;

  // Wait for target/through models to be attached before setting up the relation
  const deferRelationSetup = function(relationName, relation, targetModel, throughModel) {
    if (!isModelDataSourceAttached(targetModel)) {
      targetModel.once('dataAccessConfigured', function(targetModel) {
        // Check if the through model doesn't exist or resolved
        if (!throughModel || isModelDataSourceAttached(throughModel)) {
          // The target model is resolved
          const params = traverse(relation).clone();
          params.as = relationName;
          params.model = targetModel;
          if (throughModel) {
            params.through = throughModel;
          }
          modelClass[relation.type].call(modelClass, relationName, params);
        }
      });
    }

    if (throughModel && !isModelDataSourceAttached(throughModel)) {
      // Set up a listener to the through model
      throughModel.once('dataAccessConfigured', function(throughModel) {
        if (isModelDataSourceAttached(targetModel)) {
          // The target model is resolved
          const params = traverse(relation).clone();
          params.as = relationName;
          params.model = targetModel;
          params.through = throughModel;
          modelClass[relation.type].call(modelClass, relationName, params);
        }
      });
    }
  };

  // Set up the relations
  if (relations) {
    Object.keys(relations).forEach(function(relationName) {
      let targetModel;
      const r = relations[relationName];

      validateRelation(relationName, r);

      if (r.model) {
        targetModel = isModelClass(r.model) ? r.model : self.getModel(r.model, true);
      }

      let throughModel = null;
      if (r.through) {
        throughModel = isModelClass(r.through) ? r.through : self.getModel(r.through, true);
      }

      if ((targetModel && !isModelDataSourceAttached(targetModel)) ||
          (throughModel && !isModelDataSourceAttached(throughModel))) {
        // Create a listener to defer the relation set up
        deferRelationSetup(relationName, r, targetModel, throughModel);
      } else {
        // The target model is resolved
        const params = traverse(r).clone();
        params.as = relationName;
        params.model = targetModel;
        if (throughModel) {
          params.through = throughModel;
        }
        modelClass[r.type].call(modelClass, relationName, params);
      }
    });
  }
};

function validateRelation(relationName, relation) {
  const rn = relationName;
  const r = relation;
  let msg, code;

  assert(DataSource.relationTypes.indexOf(r.type) !== -1, 'Invalid relation type: ' + r.type);
  assert(isValidRelationName(rn), 'Invalid relation name: ' + rn);

  // VALIDATION ERRORS

  // non polymorphic belongsTo relations should have `model` defined
  if (!r.polymorphic && r.type === 'belongsTo' && !r.model) {
    msg = g.f('%s relation: %s requires param `model`', r.type, rn);
    code = 'BELONGS_TO_MISSING_MODEL';
  }
  // polymorphic belongsTo relations should not have `model` defined
  if (r.polymorphic && r.type === 'belongsTo' && r.model) {
    msg = g.f('{{polymorphic}} %s relation: %s does not expect param `model`', r.type, rn);
    code = 'POLYMORPHIC_BELONGS_TO_MODEL';
  }
  // polymorphic relations other than belongsTo should have `model` defined
  if (r.polymorphic && r.type !== 'belongsTo' && !r.model) {
    msg = g.f('{{polymorphic}} %s relation: %s requires param `model`', r.type, rn);
    code = 'POLYMORPHIC_NOT_BELONGS_TO_MISSING_MODEL';
  }
  // polymorphic relations should provide both discriminator and foreignKey or none
  if (r.polymorphic && r.polymorphic.foreignKey && !r.polymorphic.discriminator) {
    msg = g.f('{{polymorphic}} %s relation: %s requires param `polymorphic.discriminator` ' +
    'when param `polymorphic.foreignKey` is provided', r.type, rn);
    code = 'POLYMORPHIC_MISSING_DISCRIMINATOR';
  }
  // polymorphic relations should provide both discriminator and foreignKey or none
  if (r.polymorphic && r.polymorphic.discriminator && !r.polymorphic.foreignKey) {
    msg = g.f('{{polymorphic}} %s relation: %s requires param `polymorphic.foreignKey` ' +
    'when param `polymorphic.discriminator` is provided', r.type, rn);
    code = 'POLYMORPHIC_MISSING_FOREIGN_KEY';
  }
  // polymorphic relations should not provide polymorphic.as when using custom foreignKey/discriminator
  if (r.polymorphic && r.polymorphic.as && r.polymorphic.foreignKey) {
    msg = g.f('{{polymorphic}} %s relation: %s does not expect param `polymorphic.as` ' +
    'when defing custom `foreignKey`/`discriminator` ', r.type, rn);
    code = 'POLYMORPHIC_EXTRANEOUS_AS';
  }
  // polymorphic relations should not provide polymorphic.as when using custom foreignKey/discriminator
  if (r.polymorphic && r.polymorphic.selector && r.polymorphic.foreignKey) {
    msg = g.f('{{polymorphic}} %s relation: %s does not expect param `polymorphic.selector` ' +
    'when defing custom `foreignKey`/`discriminator` ', r.type, rn);
    code = 'POLYMORPHIC_EXTRANEOUS_SELECTOR';
  }

  if (msg) {
    const error = new Error(msg);
    error.details = {code: code, rType: r.type, rName: rn};
    throw error;
  }

  // DEPRECATION WARNINGS
  if (r.polymorphic && r.polymorphic.as) {
    deprecated(g.f('WARNING: {{polymorphic}} %s relation: %s uses keyword `polymorphic.as` which will ' +
    'be DEPRECATED in LoopBack.next, refer to this doc for replacement solutions ' +
    '(https://loopback.io/doc/en/lb3/Polymorphic-relations.html#deprecated-polymorphic-as)',
    r.type, rn), r.type);
  }
}

function isValidRelationName(relationName) {
  const invalidRelationNames = ['trigger'];
  return invalidRelationNames.indexOf(relationName) === -1;
}

/*!
 * Set up the data access functions from the data source. Each data source will
 * expose a data access object (DAO), which will be mixed into the modelClass.
 * @param {Model} modelClass The model class that will receive DAO mixins.
 * @param {Object} settings The settings object; typically allows any settings
 * that would be valid for a typical Model object.
 */
DataSource.prototype.setupDataAccess = function(modelClass, settings) {
  if (this.connector) {
    // Check if the id property should be generated
    const idName = modelClass.definition.idName();
    const idProp = modelClass.definition.rawProperties[idName];
    if (idProp && idProp.generated && idProp.useDefaultIdType !== false && this.connector.getDefaultIdType) {
      // Set the default id type from connector's ability
      const idType = this.connector.getDefaultIdType() || String;
      idProp.type = idType;
      modelClass.definition.rawProperties[idName].type = idType;
      modelClass.definition.properties[idName].type = idType;
    }
    if (this.connector.define) {
      // pass control to connector
      this.connector.define({
        model: modelClass,
        properties: modelClass.definition.properties,
        settings: settings,
      });
    }
  }

  // add data access objects
  this.mixin(modelClass);

  // define relations from LDL (options.relations)
  const relations = settings.relationships || settings.relations;
  this.defineRelations(modelClass, relations);

  // Emit the dataAccessConfigured event to indicate all the methods for data
  // access have been mixed into the model class
  modelClass.emit('dataAccessConfigured', modelClass);

  // define scopes from LDL (options.relations)
  const scopes = settings.scopes || {};
  this.defineScopes(modelClass, scopes);
};

/**
 * Define a model class.  Returns newly created model object.
 * The first (String) argument specifying the model name is required.
 * You can provide one or two JSON object arguments, to provide configuration options.
 * See [Model definition reference](http://docs.strongloop.com/display/DOC/Model+definition+reference) for details.
 *
 * Simple example:
 * ```
 * var User = dataSource.createModel('User', {
 *     email: String,
 *     password: String,
 *     birthDate: Date,
 *     activated: Boolean
 * });
 * ```
 * More advanced example
 * ```
 * var User = dataSource.createModel('User', {
 *     email: { type: String, limit: 150, index: true },
 *     password: { type: String, limit: 50 },
 *     birthDate: Date,
 *     registrationDate: {type: Date, default: function () { return new Date }},
 *     activated: { type: Boolean, default: false }
 * });
 * ```
 * You can also define an ACL when you create a new data source with the `DataSource.create()` method. For example:
 *
 * ```js
 * var Customer = ds.createModel('Customer', {
 *       name: {
 *         type: String,
 *         acls: [
 *           {principalType: ACL.USER, principalId: 'u001', accessType: ACL.WRITE, permission: ACL.DENY},
 *           {principalType: ACL.USER, principalId: 'u001', accessType: ACL.ALL, permission: ACL.ALLOW}
 *         ]
 *       }
 *     }, {
 *       acls: [
 *         {principalType: ACL.USER, principalId: 'u001', accessType: ACL.ALL, permission: ACL.ALLOW}
 *       ]
 *     });
 * ```
 *
 * @param {String} className Name of the model to create.
 * @param {Object} properties Hash of model properties in format `{property: Type, property2: Type2, ...}` or `{property: {type: Type}, property2: {type: Type2}, ...}`
 * @options {Object} properties Other configuration options.  This corresponds to the options key in the config object.
 * @param {Object} settings A settings object that would typically be used for Model objects.
 */

DataSource.prototype.createModel =
DataSource.prototype.define = function defineClass(className, properties, settings) {
  const args = slice.call(arguments);

  if (!className) {
    throw new Error(g.f('Class name required'));
  }
  if (args.length === 1) {
    properties = {};
    args.push(properties);
  }
  if (args.length === 2) {
    settings = {};
    args.push(settings);
  }

  properties = properties || {};
  settings = settings || {};

  if (this.isRelational()) {
    // Set the strict mode to be true for relational DBs by default
    if (settings.strict === undefined || settings.strict === null) {
      settings.strict = true;
    }
    if (settings.strict === false) {
      console.warn("WARNING: relational database doesn't support {strict: false} mode." +
      ` {strict: true} mode will be set for model ${className} instead.`);
      settings.strict = true;
    }
  }

  const modelClass = this.modelBuilder.define(className, properties, settings);
  modelClass.dataSource = this;

  if (settings.unresolved) {
    return modelClass;
  }

  this.setupDataAccess(modelClass, settings);
  modelClass.emit('dataSourceAttached', modelClass);

  return modelClass;
};

/**
 * Remove a model from the registry.
 *
 * @param {String} modelName
 */
DataSource.prototype.deleteModelByName = function(modelName) {
  this.modelBuilder.deleteModelByName(modelName);
  delete this.connector._models[modelName];
};

/**
 * Remove all models from the registry, but keep the connector instance
 * (including the pool of database connections).
 */
DataSource.prototype.deleteAllModels = function() {
  for (const m in this.modelBuilder.models) {
    this.deleteModelByName(m);
  }
};

/**
 * Mixin DataAccessObject methods.
 *
 * @param {Function} ModelCtor The model constructor
 * @private
 */

DataSource.prototype.mixin = function(ModelCtor) {
  const ops = this.operations();
  const DAO = this.DataAccessObject;

  // mixin DAO
  jutil.mixin(ModelCtor, DAO, {proxyFunctions: true, override: true});

  // decorate operations as alias functions
  Object.keys(ops).forEach(function(name) {
    const op = ops[name];
    let scope;

    if (op.enabled) {
      scope = op.prototype ? ModelCtor.prototype : ModelCtor;
      // var sfn = scope[name] = function () {
      //   op.scope[op.fnName].apply(self, arguments);
      // }
      Object.keys(op)
        .filter(function(key) {
          // filter out the following keys
          return ~[
            'scope',
            'fnName',
            'prototype',
          ].indexOf(key);
        })
        .forEach(function(key) {
          if (typeof op[key] !== 'undefined') {
            op.scope[op.fnName][key] = op[key];
          }
        });
    }
  });
};

/*! Method will be deprecated in LoopBack.next
*/
/**
 * See [ModelBuilder.getModel](http://apidocs.strongloop.com/loopback-datasource-juggler/#modelbuilder-prototype-getmodel)
 * for details.
 */
DataSource.prototype.getModel = function(name, forceCreate) {
  return this.modelBuilder.getModel(name, forceCreate);
};

/*! Method will be deprecated in LoopBack.next
*/
/**
 * See ModelBuilder.getModelDefinition
 * See [ModelBuilder.getModelDefinition](http://apidocs.strongloop.com/loopback-datasource-juggler/#modelbuilder-prototype-getmodeldefinition)
 * for details.
 */
DataSource.prototype.getModelDefinition = function(name) {
  return this.modelBuilder.getModelDefinition(name);
};

/*! Method will be deprecated in LoopBack.next
*/
/**
 * Get the data source types collection.
 * @returns {String[]} The data source type array.
 * For example, ['db', 'nosql', 'mongodb'] would be represent a datasource of
 * type 'db', with a subtype of 'nosql', and would use the 'mongodb' connector.
 *
 * Alternatively, ['rest'] would be a different type altogether, and would have
 * no subtype.
 */
DataSource.prototype.getTypes = function() {
  const getTypes = this.connector && this.connector.getTypes;
  let types = getTypes && getTypes() || [];
  if (typeof types === 'string') {
    types = types.split(/[\s,\/]+/);
  }
  return types;
};

/**
 * Check the data source supports the specified types.
 * @param {String|String[]} types Type name or an array of type names.
 * @returns {Boolean} true if all types are supported by the data source
 */
DataSource.prototype.supportTypes = function(types) {
  const supportedTypes = this.getTypes();
  if (Array.isArray(types)) {
    // Check each of the types
    for (let i = 0; i < types.length; i++) {
      if (supportedTypes.indexOf(types[i]) === -1) {
        // Not supported
        return false;
      }
    }
    return true;
  } else {
    // The types is a string
    return supportedTypes.indexOf(types) !== -1;
  }
};

/*! In future versions, this will not maintain a strict 1:1 relationship between datasources and model classes
* Moving forward, we will allow a model to be attached to a datasource. The model itself becomes a template.
*/
/**
 * Attach an existing model to a data source.
 * This will mixin all of the data access object functions (DAO) into your
 * modelClass definition.
 * @param {Function} modelClass The model constructor that will be enhanced by
 * DAO mixins.
 */

DataSource.prototype.attach = function(modelClass) {
  if (modelClass.dataSource === this) {
    // Already attached to the data source
    return modelClass;
  }

  if (modelClass.modelBuilder !== this.modelBuilder) {
    this.modelBuilder.definitions[modelClass.modelName] = modelClass.definition;
    this.modelBuilder.models[modelClass.modelName] = modelClass;
    // reset the modelBuilder
    modelClass.modelBuilder = this.modelBuilder;
  }

  // redefine the dataSource
  modelClass.dataSource = this;

  this.setupDataAccess(modelClass, modelClass.settings);
  modelClass.emit('dataSourceAttached', modelClass);
  return modelClass;
};

/*! Method will be deprecated in LoopBack.next
*/
/**
 * Define a property with name `prop` on a target `model`. See
 * [Properties](./Model-definition-JSON-file.html#properties) for more information
 * regarding valid options for `params`.
 * @param {String} model Name of model
 * @param {String} prop Name of property
 * @param {Property} params Property settings
 */
DataSource.prototype.defineProperty = function(model, prop, params) {
  this.modelBuilder.defineProperty(model, prop, params);

  const resolvedProp = this.getModelDefinition(model).properties[prop];
  if (this.connector && this.connector.defineProperty) {
    this.connector.defineProperty(model, prop, resolvedProp);
  }
};

/**
 * Drop schema objects such as tables, indexes, views, triggers, etc that correspond
 * to model definitions attached to this DataSource instance, specified by the `models` parameter.
 *
 * **WARNING**: In many situations, this will destroy data! `autoupdate()` will attempt to preserve
 * data while updating the schema on your target DataSource, but this is not guaranteed to be safe.
 *
 * Please check the documentation for your specific connector(s) for a detailed breakdown of
 * behaviors for automigrate!
 *
 * @param {String|String[]} [models] Model(s) to migrate.  If not present, apply to all models.
 * @param {Function} [callback] Callback function. Optional.
 *
 */
DataSource.prototype.automigrate = function(models, cb) {
  this.freeze();

  if ((!cb) && ('function' === typeof models)) {
    cb = models;
    models = undefined;
  }

  cb = cb || utils.createPromiseCallback();

  if (!this.connector.automigrate) {
    // NOOP
    process.nextTick(cb);
    return cb.promise;
  }

  // First argument is a model name
  if ('string' === typeof models) {
    models = [models];
  }

  const attachedModels = this.connector._models;

  if (attachedModels && typeof attachedModels === 'object') {
    models = models || Object.keys(attachedModels);

    if (models.length === 0) {
      process.nextTick(cb);
      return cb.promise;
    }

    const invalidModels = models.filter(function(m) {
      return !(m in attachedModels);
    });

    if (invalidModels.length) {
      process.nextTick(function() {
        cb(new Error(g.f('Cannot migrate models not attached to this datasource: %s',
          invalidModels.join(' '))));
      });
      return cb.promise;
    }
  }

  const args = [models, cb];
  args.callee = this.automigrate;
  const queued = this.ready(this, args);
  if (queued) {
    // waiting to connect
    return cb.promise;
  }

  this.connector.automigrate(models, cb);
  return cb.promise;
};

/**
 * Update existing database tables.
 * This method applies only to database connectors.
 *
 * **WARNING**: `autoupdate()` will attempt to preserve data while updating the
 * schema on your target DataSource, but this is not guaranteed to be safe.
 *
 * Please check the documentation for your specific connector(s) for a detailed breakdown of
 * behaviors for automigrate!*
 *
 * @param {String|String[]} [models] Model(s) to migrate.  If not present, apply to all models.
 * @param {Function} [cb] The callback function
 */
DataSource.prototype.autoupdate = function(models, cb) {
  this.freeze();

  if ((!cb) && ('function' === typeof models)) {
    cb = models;
    models = undefined;
  }

  cb = cb || utils.createPromiseCallback();

  if (!this.connector.autoupdate) {
    // NOOP
    process.nextTick(cb);
    return cb.promise;
  }

  // First argument is a model name
  if ('string' === typeof models) {
    models = [models];
  }

  const attachedModels = this.connector._models;

  if (attachedModels && typeof attachedModels === 'object') {
    models = models || Object.keys(attachedModels);

    if (models.length === 0) {
      process.nextTick(cb);
      return cb.promise;
    }

    const invalidModels = models.filter(function(m) {
      return !(m in attachedModels);
    });

    if (invalidModels.length) {
      process.nextTick(function() {
        cb(new Error(g.f('Cannot migrate models not attached to this datasource: %s',
          invalidModels.join(' '))));
      });
      return cb.promise;
    }
  }

  const args = [models, cb];
  args.callee = this.autoupdate;
  const queued = this.ready(this, args);
  if (queued) {
    // waiting to connect
    return cb.promise;
  }

  this.connector.autoupdate(models, cb);
  return cb.promise;
};

/**
 * Discover existing database tables.
 * This method returns an array of model objects, including {type, name, onwer}
 *
 * @options {Object} options Discovery options.  See below.
 * @param {Function} Callback function.  Optional.
 * @property {String} owner/schema The owner or schema to discover from.
 * @property {Boolean} all If true, discover all models; if false, discover only models owned by the current user.
 * @property {Boolean} views If true, include views; if false, only tables.
 * @property {Number} limit Page size
 * @property {Number} offset Starting index
 * @returns {ModelDefinition[]}
 */
DataSource.prototype.discoverModelDefinitions = function(options, cb) {
  this.freeze();

  if (cb === undefined && typeof options === 'function') {
    cb = options;
    options = {};
  }
  options = options || {};
  cb = cb || utils.createPromiseCallback();

  if (this.connector.discoverModelDefinitions) {
    this.connector.discoverModelDefinitions(options, cb);
  } else if (cb) {
    process.nextTick(cb);
  }
  return cb.promise;
};

/*! Method will be completely removed in LoopBack.next
*/
/**
 * The synchronous version of discoverModelDefinitions.
 * @options {Object} options The options
 * @property {Boolean} all If true, discover all models; if false, discover only models owned by the current user.
 * @property {Boolean} views If true, nclude views; if false, only tables.
 * @property {Number} limit Page size
 * @property {Number} offset Starting index
 * @returns {ModelDefinition[]}
 */
DataSource.prototype.discoverModelDefinitionsSync = function(options) {
  this.freeze();
  if (this.connector.discoverModelDefinitionsSync) {
    return this.connector.discoverModelDefinitionsSync(options);
  }
  return null;
};

/**
 * Discover properties for a given model.
 *
 * Callback function return value is an object that can have the following properties:
 *
 *| Key | Type | Description |
 *|-----|------|-------------|
 *|owner | String | Database owner or schema|
 *|tableName | String | Table/view name|
 *|columnName | String | Column name|
 *|dataType | String | Data type|
 *|dataLength | Number | Data length|
 *|dataPrecision | Number | Numeric data precision|
 *|dataScale |Number | Numeric data scale|
 *|nullable |Boolean | If true, then the data can be null|
 * See [Properties](./Model-definition-JSON-file.html#properties) for more
 * details on the Property return type.
 * @param {String} modelName The table/view name
 * @options {Object} options The options
 * @property {String} owner|schema The database owner or schema
 * @param {Function} cb Callback function. Optional
 * @callback cb
 * @returns {Promise} A promise that returns an array of Properties (Property[])
 *
 */
DataSource.prototype.discoverModelProperties = function(modelName, options, cb) {
  this.freeze();

  if (cb === undefined && typeof options === 'function') {
    cb = options;
    options = {};
  }
  options = options || {};
  cb = cb || utils.createPromiseCallback();

  if (this.connector.discoverModelProperties) {
    this.connector.discoverModelProperties(modelName, options, cb);
  } else if (cb) {
    process.nextTick(cb);
  }
  return cb.promise;
};

/*! Method will be completely removed in LoopBack.next
*/
/**
 * The synchronous version of discoverModelProperties
 * @param {String} modelName The table/view name
 * @param {Object} options The options
 * @returns {*}
 */
DataSource.prototype.discoverModelPropertiesSync = function(modelName, options) {
  this.freeze();
  if (this.connector.discoverModelPropertiesSync) {
    return this.connector.discoverModelPropertiesSync(modelName, options);
  }
  return null;
};

/**
 * Discover primary keys for a given owner/modelName.
 * Callback function return value is an object that can have the following properties:
 *
 *| Key | Type | Description |
 *|-----|------|-------------|
 *| owner |String | Table schema or owner (may be null). Owner defaults to current user.
 *| tableName |String| Table name
 *| columnName |String| Column name
 *| keySeq |Number| Sequence number within primary key (1 indicates the first column in the primary key; 2 indicates the second column in the primary key).
 *| pkName |String| Primary key name (may be null)
 * See [ID Properties](./Model-definition-JSON-file.html#id-properties) for more
 * information.
 * @param {String} modelName The model name
 * @options {Object} options The options
 * @property {String} owner|schema The database owner or schema
 * @param {Function} [cb] The callback function
 * @returns {Promise} A promise with an array of Primary Keys (Property[])
 */
DataSource.prototype.discoverPrimaryKeys = function(modelName, options, cb) {
  this.freeze();

  if (cb === undefined && typeof options === 'function') {
    cb = options;
    options = {};
  }
  options = options || {};
  cb = cb || utils.createPromiseCallback();

  if (this.connector.discoverPrimaryKeys) {
    this.connector.discoverPrimaryKeys(modelName, options, cb);
  } else if (cb) {
    process.nextTick(cb);
  }
  return cb.promise;
};

/**
 * Discover unique keys for a given modelName.
 * Callback function return value is an object that can have the following properties:
 *
 *| Key | Type | Description |
 *|-----|------|-------------|
 *| owner |String | Table schema or owner (may be null). Owner defaults to current user.
 *| tableName |String| Table name
 *| columnName |String| Column name
 * See [ID Properties](./Model-definition-JSON-file.html#id-properties) for more
 * information.
 * @param {String} modelName The model name
 * @options {Object} options The options
 * @param {Function} [cb] The callback function
 * @returns {Promise} A promise with an array of Primary Keys (Property[])
 */
DataSource.prototype.discoverUniqueKeys = function(modelName, options, cb) {
  this.freeze();

  if (cb === undefined && typeof options === 'function') {
    cb = options;
    options = {};
  }
  options = options || {};
  cb = cb || utils.createPromiseCallback();

  if (this.connector.discoverUniqueKeys) {
    this.connector.discoverUniqueKeys(modelName, options, cb);
  } else if (cb) {
    process.nextTick(cb);
  }
  return cb.promise;
};

/*! Method will be completely removed in LoopBack.next
*/
/**
 * The synchronous version of discoverPrimaryKeys
 * @param {String} modelName The model name
 * @options {Object} options The options
 * @property {String} owner|schema The database owner or schema
 * @returns {*}
 */
DataSource.prototype.discoverPrimaryKeysSync = function(modelName, options) {
  this.freeze();
  if (this.connector.discoverPrimaryKeysSync) {
    return this.connector.discoverPrimaryKeysSync(modelName, options);
  }
  return null;
};

/**
 * Discover foreign keys for a given owner/modelName
 *
 * Callback function return value is an object that can have the following properties:
 *
 *| Key | Type | Description |
 *|-----|------|-------------|
 *|fkOwner |String | Foreign key table schema (may be null)
 *|fkName |String | Foreign key name (may be null)
 *|fkTableName |String | Foreign key table name
 *|fkColumnName |String | Foreign key column name
 *|keySeq |Number | Sequence number within a foreign key( a value of 1 represents the first column of the foreign key, a value of 2 would represent the second column within the foreign key).
 *|pkOwner |String | Primary key table schema being imported (may be null)
 *|pkName |String | Primary key name (may be null)
 *|pkTableName |String | Primary key table name being imported
 *|pkColumnName |String | Primary key column name being imported
 * See [Relations](/Model-definition-JSON-file.html#relations) for more
 * information.
 * @param {String} modelName The model name
 * @options {Object} options The options
 * @property {String} owner|schema The database owner or schema
 * @param {Function} [cb] The callback function
 * @returns {Promise} A Promise with an array of foreign key relations.
 *
 */
DataSource.prototype.discoverForeignKeys = function(modelName, options, cb) {
  this.freeze();

  if (cb === undefined && typeof options === 'function') {
    cb = options;
    options = {};
  }
  options = options || {};
  cb = cb || utils.createPromiseCallback();

  if (this.connector.discoverForeignKeys) {
    this.connector.discoverForeignKeys(modelName, options, cb);
  } else if (cb) {
    process.nextTick(cb);
  }
  return cb.promise;
};

/*! Method will be completely removed in LoopBack.next
*/
/**
 * The synchronous version of discoverForeignKeys
 *
 * @param {String} modelName The model name
 * @param {Object} options The options
 * @returns {*}
 */
DataSource.prototype.discoverForeignKeysSync = function(modelName, options) {
  this.freeze();
  if (this.connector.discoverForeignKeysSync) {
    return this.connector.discoverForeignKeysSync(modelName, options);
  }
  return null;
};

/**
 * Retrieves a description of the foreign key columns that reference the given table's primary key columns
 * (the foreign keys exported by a table), ordered by fkTableOwner, fkTableName, and keySeq.
 *
 * Callback function return value is an object that can have the following properties:
 *
 *| Key | Type | Description |
 *|-----|------|-------------|
 *|fkOwner |String | Foreign key table schema (may be null)
 *|fkName |String | Foreign key name (may be null)
 *|fkTableName |String | Foreign key table name
 *|fkColumnName |String | Foreign key column name
 *|keySeq |Number | Sequence number within a foreign key( a value of 1 represents the first column of the foreign key, a value of 2 would represent the second column within the foreign key).
 *|pkOwner |String | Primary key table schema being imported (may be null)
 *|pkName |String | Primary key name (may be null)
 *|pkTableName |String | Primary key table name being imported
 *|pkColumnName |String | Primary key column name being imported
 * See [Relations](/Model-definition-JSON-file.html#relations) for more
 * information.
 *
 * @param {String} modelName The model name
 * @options {Object} options The options
 * @property {String} owner|schema The database owner or schema
 * @param {Function} [cb] The callback function
 * @returns {Promise} A Promise with an array of exported foreign key relations.
 */
DataSource.prototype.discoverExportedForeignKeys = function(modelName, options, cb) {
  this.freeze();

  if (cb === undefined && typeof options === 'function') {
    cb = options;
    options = {};
  }
  options = options || {};
  cb = cb || utils.createPromiseCallback();

  if (this.connector.discoverExportedForeignKeys) {
    this.connector.discoverExportedForeignKeys(modelName, options, cb);
  } else if (cb) {
    process.nextTick(cb);
  }
  return cb.promise;
};

/*! Method will be completely removed in LoopBack.next
*/
/**
 * The synchronous version of discoverExportedForeignKeys
 * @param {String} modelName The model name
 * @param {Object} options The options
 * @returns {*}
 */
DataSource.prototype.discoverExportedForeignKeysSync = function(modelName, options) {
  this.freeze();
  if (this.connector.discoverExportedForeignKeysSync) {
    return this.connec