Implement ve.NodeFactory and add tests

Change-Id: I34fdf24c0099072fe5f7178400abbc323be975d4

modules/ve2/ve.NodeFactory.js

@@ -1,15 +1,44 @@
 /**
- * Data model node factory.
+ * Generic node factory.
  * 
  * @class
  * @constructor
  */
 ve.NodeFactory = function() {
-	//
+	this.registry = [];
 };
 
 /* Methods */
 
-ve.NodeFactory.prototype.register = function( name, constructor ) {
-	//
+/**
+ * Register a node type with the factory.
+ * 
+ * The constructor will be called as constructor( contents, attributes ), see createNode().
+ * 
+ * @param {String} type Node type
+ * @param {Function} constructor Node constructor subclassing ve.Node
+ */
+ve.NodeFactory.prototype.register = function( type, constructor ) {
+	if ( typeof constructor !== 'function' ) {
+		throw 'Constructor must be a function, cannot be a ' + typeof constructor;
+	}
+	this.registry[type] = constructor;
+};
+
+/**
+ * Create a node based on a type. type is used to look up the constructor to use, contents and
+ * attributes are passed to the constructor.
+ * 
+ * @param {String} type Node type
+ * @param {Array|Number} contents Either an array of child nodes (for non-leaf nodes)
+ *                                or the length (for leaf nodes)
+ * @param {Object} [attributes] Attribute key/value pairs
+ * @returns {ve.Node|null} The node object, or null if type is not a registered node type.
+ */
+ve.NodeFactory.prototype.createNode = function( type, contents, attributes ) {
+	if ( type in this.registry ) {
+		return new this.registry[type]( contents, attributes );
+	} else {
+		return null;
+	}
 };

tests/ve2/index.html

@@ -23,6 +23,7 @@
 		<script src="../../modules/ve2/ve.BranchNode.js"></script>
 		<script src="../../modules/ve2/ve.TwigNode.js"></script>
 		<script src="../../modules/ve2/ve.LeafNode.js"></script>
+		<script src="../../modules/ve2/ve.NodeFactory.js"></script>
 
 		<!-- VisualEditor DataModel -->
 		<script src="../../modules/ve2/dm/ve.dm.js"></script>
@@ -37,6 +38,7 @@
 		<script src="ve.BranchNode.test.js"></script>
 		<script src="ve.TwigNode.test.js"></script>
 		<script src="ve.LeafNode.test.js"></script>
+		<script src="ve.NodeFactory.test.js"></script>
 		<script src="dm/ve.dm.Node.test.js"></script>
 		<script src="dm/ve.dm.BranchNode.test.js"></script>
 		<script src="dm/ve.dm.TwigNode.test.js"></script>

tests/ve2/ve.NodeFactory.test.js

@@ -0,0 +1,40 @@
+module( 've.NodeFactory' );
+
+/* Stubs */
+
+ve.NodeStub1 = function( content, attributes ) {
+	this.content = content;
+	this.attributes = attributes;
+	this.type = 'nodestub1';
+};
+
+ve.NodeStub2 = function( content, attributes ) {
+	this.content = content;
+	this.attributes = attributes;
+	this.type = 'nodestub2';
+};
+
+/* Tests */
+
+test( 've.NodeFactory', function() {
+	var factory = new ve.NodeFactory();
+	
+	factory.register( 'nodestub1', ve.NodeStub1 );
+	var ns1 = factory.createNode( 'nodestub1', 42, { 'foo': 'bar' } );
+	deepEqual( ns1, new ve.NodeStub1( 42, { 'foo': 'bar' } ), 'createNode creates a node ' +
+		'using the registered constructor and passes through arguments' );
+	
+	deepEqual( factory.createNode( 'nodestub2', 23, { 'bar': 'baz' } ), null, 'createNode ' +
+		'returns null for unregistered node types' );
+	factory.register( 'nodestub2', ve.NodeStub2 );
+	var ns2 = factory.createNode( 'nodestub2', 16, { 'baz': 'quux' } );
+	deepEqual( ns2, new ve.NodeStub2( 16, { 'baz': 'quux' } ), 'createNode creates a node ' +
+		'with a previously unregistered type' );
+	
+	raises( function() {
+			factory.register( 'nodestub3', 'nodestub3' );
+		},
+		/^Constructor must be a function, cannot be a string$/,
+		'register throws an exception when trying to register a string as a constructor'
+	);
+} );