Enabling third-party drivers

Added a method and some documentation for plugging in a third-party driver for `orm2`.

Conflicts:
	.gitignore

Author: jpage-godaddy

Drivers.md

@@ -0,0 +1,161 @@
+# Creating drivers for orm2
+
+To add a driver to `orm2`, call its `addDriver` method:
+ 
+```js
+require('orm2').addDriver('cassandra', CassandraDriver);
+```
+
+The first argument is the alias to register for connection URLs. For example, the above will allow you to do this:
+ 
+```js
+var orm = require('orm2');
+orm.connect('cassandra://username:password@localhost/test', function (err, db) { });
+```
+
+The second argument is the constructor for your driver object.
+
+## Defining driver objects
+
+Your driver should provide the following members. 
+
+### Constructor(config, connection, opts)
+
+The driver object constructor should have three parameters:
+ 
+* config - optional configuration for the database connection. It contains the following properties:
+    * timezone - optional timezone
+    * href - URL to use for connecting to the database if the connection argument is null
+    * host - The hostname of `href`
+    * pathname - The `path` of `href`
+    * ssl - Boolean indicating whether the driver should use SSL when connecting to the database
+    * query - Optional configuration for how the driver should perform queries
+        * ssl - Boolean indicating whether queries should be sent using SSL
+        * strdates - Boolean indicating whether strings should be used for dates 
+* connection - optionally passed if reusing an existing connection
+* opts - optional options configuring the driver's behavior. It contains the following properties:
+    * pool - A boolean indicating whether the driver should use connection pooling
+    * debug - If true, whether the driver should operate in debug mode
+    * settings - A key/value object store. Use `get(key)` and `set(key, value)` methods to manipulate the settings. The
+      following settings are defined:
+        * properties.primary_key - The column/field name to use for object primary keys
+        * properties.association_key - A function taking a `name` and `field` parameter that returns the name of the
+          column that establishes the association
+
+### isSql property
+
+This should be set to `true` if your database is a SQL database.
+
+### customTypes property
+
+Your driver should have a `customTypes` object, with the property names being the names of the custom types, and each 
+value being the options relating to the type.
+
+### connect(cb) method (required)
+
+Establishes your database connection.
+
+### reconnect(cb, connection) method (optional)
+
+Establishes/re-establishes a connection. The optional prior connection is passed in the `connection` parameter. 
+
+### ping(cb) method (required)
+
+Tests whether your connection is still alive.
+
+### close(cb) method (required)
+
+Closes your database connection.
+
+### propertyToValue(value, property) method (required)
+
+Maps an object property to the correlated value to use for the database. 
+
+### valueToProperty(value, property) method (required)
+
+Maps a database value to the property value to use for the mapped object. 
+
+### find(fields, table, conditions, opts, cb) method (required)
+
+Implement this to select and return data stored in the database. 
+See the [documentation for Model.find](./README.md#modelfind-conditions---options---limit---order---cb-).
+
+### insert(table, data, id_prop, cb) method (required)
+
+Inserts an object into a database table.
+
+### update(table, changes, conditions, cb) method (required)
+
+Updates an object in the appropriate database row.
+
+### remove(table, conditions, cb) method (required)
+
+Implement this to support the removal of an object from a table.
+
+### count(table, conditions, opts, cb) method (required)
+
+Implement this to support [Model.count](./README.md#modelcount-conditions--cb).
+
+### clear(table, cb) method (required)
+
+Implement this to support `Model.clear`, which deletes all objects from a given table.
+
+### eagerQuery(association, opts, ids, cb) method (required)
+
+Implement this to support eager loading of associated objects.
+
+### query property (optional)
+
+For SQL databases, the `Query` object from the `sql-query` package used to generate ad-hoc queries.
+
+### getQuery() method (optional)
+
+For SQL databases, returns a `Query` object from the `sql-query` package.
+
+### execQuery(query, cb) method (optional)
+
+For SQL databases, this executes a `Query` object from the `sql-query` package.
+
+### aggregate_functions[] property (optional)
+
+If your driver supports SQL aggregate functions, this should be an array of supported function names.
+
+### hasMany(Model, association) method (optional)
+
+If your driver maintains associations in a unique (non-SQL-like) manner, return an object from this method to implement
+a one-to-many association. The return value should have the following methods:
+ 
+* has(Instance, Associations, conditions, cb) - tests if the associations have any objects matching the conditions
+* get(Instance, conditions, options, createInstance, cb) - retrieves associated objects
+* add(Instance, Association, data, cb) - inserts an associated object
+* del(Instance, Associations, cb) - deletes an object from a set of associations
+
+### sync(opts, cb) method (optional)
+
+If your driver supports creating a table from a model, implement this method. The following options are passed:
+
+* extension
+* id
+* table
+* properties
+* allProperties
+* indexes
+* customTypes
+* one_associations
+* many_associations
+* extend_associations
+ 
+### drop(opts, cb) method (optional)
+
+If your driver supports dropping a table, implement this method. The following options are passed to this method:
+
+* table - The name of the table
+* properties
+* one_associations
+* many_associations
+
+### on(event, cb) method (required)
+
+Your driver should be an `EventEmitter`, and should emit the following types of events, when applicable:
+
+* error

Readme.md

@@ -840,3 +840,14 @@ Person.hasMany("pets", Pet, {
 Person(1).getPets(...);
 Pet(2).getOwners(...);
 ```
+
+## Adding external drivers
+
+To add an external driver to `orm2`, call the `addDriver` method, passing in the alias to use for connecting with this
+driver, along with the constructor for the driver object:
+
+```js
+require('orm2').addDriver('cassandra', CassandraDriver);
+```
+
+See [the documentation for creating drivers](./Drivers.md) for more details.

lib/Drivers/drivers.js

@@ -0,0 +1,21 @@
+var aliases = require('./aliases');
+
+module.exports.add = addDriver;
+module.exports.get = getDriver;
+
+
+var drivers = {};
+
+function addDriver(name, constructor) {
+  drivers[name] = constructor;
+}
+
+function getDriver(name) {
+  if (name in aliases) {
+    return getDriver(aliases[name]);
+  } else if (!(name in drivers)) {
+    drivers[name] = require("./DML/" + name).Driver;
+  }
+
+  return drivers[name];
+}

lib/ORM.js

@@ -8,6 +8,7 @@ var _              = require("lodash");
 
 var Model          = require("./Model").Model;
 var DriverAliases  = require("./Drivers/aliases");
+var drivers        = require("./Drivers/drivers");
 var Settings       = require("./Settings");
 var Singleton      = require("./Singleton");
 var ORMError       = require("./Error");
@@ -48,7 +49,7 @@ exports.use = function (connection, proto, opts, cb) {
 	}
 
 	try {
-		var Driver   = require("./Drivers/DML/" + proto).Driver;
+		var Driver   = drivers.get(proto);
 		var settings = new Settings.Container(exports.settings.get('*'));
 		var driver   = new Driver(null, connection, {
 			debug    : (opts.query && opts.query.debug === 'true'),
@@ -109,7 +110,7 @@ exports.connect = function (opts, cb) {
 	}
 
 	try {
-		var Driver   = require("./Drivers/DML/" + proto).Driver;
+		var Driver   = drivers.get(proto);
 		var settings = new Settings.Container(exports.settings.get('*'));
 		var debug    = extractOption(opts, "debug");
 		var pool     = extractOption(opts, "pool");
@@ -142,6 +143,8 @@ exports.connect = function (opts, cb) {
 	return db;
 };
 
+exports.addDriver = drivers.add;
+
 function ORM(driver_name, driver, settings) {
 	this.validators  = exports.validators;
 	this.enforce     = exports.enforce;