feat(forms): add form builder

modules/angular2/src/forms/form_builder.js

@@ -0,0 +1,48 @@
+import {StringMapWrapper, ListWrapper} from 'angular2/src/facade/collection';
+import {isPresent} from 'angular2/src/facade/lang';
+import {ControlGroup, Control, OptionalControl, OptionalControlGroup} from 'angular2/forms';
+
+
+export class FormBuilder {
+  group(controlsConfig, extra = null):ControlGroup {
+    var controls = this._reduceControls(controlsConfig);
+    var optionals = isPresent(extra) ? StringMapWrapper.get(extra, "optionals") : null;
+    var validator = isPresent(extra) ? StringMapWrapper.get(extra, "validator") : null;
+
+    if (isPresent(validator)) {
+      return new ControlGroup(controls, optionals, validator);
+    } else {
+      return new ControlGroup(controls, optionals);
+    }
+  }
+
+  control(value, validator:Function = null):Control {
+    if (isPresent(validator)) {
+      return new Control(value, validator);
+    } else {
+      return new Control(value);
+    }
+  }
+
+  _reduceControls(controlsConfig) {
+    var controls = {};
+    StringMapWrapper.forEach(controlsConfig, (controlConfig, controlName) => {
+      controls[controlName] = this._createControl(controlConfig);
+    });
+    return controls;
+  }
+
+  _createControl(controlConfig) {
+    if (controlConfig instanceof Control || controlConfig instanceof ControlGroup) {
+      return controlConfig;
+
+    } else if (ListWrapper.isList(controlConfig)) {
+      var value = ListWrapper.get(controlConfig, 0);
+      var validator = controlConfig.length > 1 ? controlConfig[1] : null;
+      return this.control(value, validator);
+
+    } else {
+      return this.control(controlConfig);
+    }
+  }
+}