feat(i18n): add ngPlural directive

modules/angular2/src/common/directives.ts

@@ -8,5 +8,6 @@ export {NgFor} from './directives/ng_for';
 export {NgIf} from './directives/ng_if';
 export {NgStyle} from './directives/ng_style';
 export {NgSwitch, NgSwitchWhen, NgSwitchDefault} from './directives/ng_switch';
+export {NgPlural, NgPluralCase, NgLocalization} from './directives/ng_plural';
 export * from './directives/observable_list_diff';
-export {CORE_DIRECTIVES} from './directives/core_directives';
+export {CORE_DIRECTIVES} from './directives/core_directives';

modules/angular2/src/common/directives/core_directives.ts

@@ -4,6 +4,7 @@ import {NgFor} from './ng_for';
 import {NgIf} from './ng_if';
 import {NgStyle} from './ng_style';
 import {NgSwitch, NgSwitchWhen, NgSwitchDefault} from './ng_switch';
+import {NgPlural, NgPluralCase} from './ng_plural';
 
 /**
  * A collection of Angular core directives that are likely to be used in each and every Angular
@@ -45,5 +46,14 @@ import {NgSwitch, NgSwitchWhen, NgSwitchDefault} from './ng_switch';
  * }
  * ```
  */
-export const CORE_DIRECTIVES: Type[] =
-    CONST_EXPR([NgClass, NgFor, NgIf, NgStyle, NgSwitch, NgSwitchWhen, NgSwitchDefault]);
+export const CORE_DIRECTIVES: Type[] = CONST_EXPR([
+  NgClass,
+  NgFor,
+  NgIf,
+  NgStyle,
+  NgSwitch,
+  NgSwitchWhen,
+  NgSwitchDefault,
+  NgPlural,
+  NgPluralCase
+]);

modules/angular2/src/common/directives/ng_plural.ts

@@ -0,0 +1,146 @@
+import {
+  Directive,
+  ViewContainerRef,
+  TemplateRef,
+  ContentChildren,
+  QueryList,
+  Attribute,
+  AfterContentInit,
+  Input
+} from 'angular2/core';
+import {isPresent, NumberWrapper} from 'angular2/src/facade/lang';
+import {Map} from 'angular2/src/facade/collection';
+import {SwitchView} from './ng_switch';
+
+const _CATEGORY_DEFAULT = 'other';
+
+export abstract class NgLocalization { abstract getPluralCategory(value: any): string; }
+
+/**
+ * `ngPlural` is an i18n directive that displays DOM sub-trees that match the switch expression
+ * value, or failing that, DOM sub-trees that match the switch expression's pluralization category.
+ *
+ * To use this directive, you must provide an extension of `NgLocalization` that maps values to
+ * category names. You then define a container element that sets the `[ngPlural]` attribute to a
+ * switch expression.
+ *    - Inner elements defined with an `[ngPluralCase]` attribute will display based on their
+ * expression.
+ *    - If `[ngPluralCase]` is set to a value starting with `=`, it will only display if the value
+ * matches the switch expression exactly.
+ *    - Otherwise, the view will be treated as a "category match", and will only display if exact
+ * value matches aren't found and the value maps to its category using the `getPluralCategory`
+ * function provided.
+ *
+ * If no matching views are found for a switch expression, inner elements marked
+ * `[ngPluralCase]="other"` will be displayed.
+ *
+ * ```typescript
+ * class MyLocalization extends NgLocalization {
+ *    getPluralCategory(value: any) {
+ *       if(value < 5) {
+ *          return 'few';
+ *       }
+ *    }
+ * }
+ *
+ * @Component({
+ *    selector: 'app',
+ *    providers: [provide(NgLocalization, {useClass: MyLocalization})]
+ * })
+ * @View({
+ *   template: `
+ *     <p>Value = {{value}}</p>
+ *     <button (click)="inc()">Increment</button>
+ *
+ *     <div [ngPlural]="value">
+ *       <template ngPluralCase="=0">there is nothing</template>
+ *       <template ngPluralCase="=1">there is one</template>
+ *       <template ngPluralCase="few">there are a few</template>
+ *       <template ngPluralCase="other">there is some number</template>
+ *     </div>
+ *   `,
+ *   directives: [NgPlural, NgPluralCase]
+ * })
+ * export class App {
+ *   value = 'init';
+ *
+ *   inc() {
+ *     this.value = this.value === 'init' ? 0 : this.value + 1;
+ *   }
+ * }
+ *
+ * ```
+ */
+
+@Directive({selector: '[ngPluralCase]'})
+export class NgPluralCase {
+  _view: SwitchView;
+  constructor(@Attribute('ngPluralCase') public value: string, template: TemplateRef,
+              viewContainer: ViewContainerRef) {
+    this._view = new SwitchView(viewContainer, template);
+  }
+}
+
+
+@Directive({selector: '[ngPlural]'})
+export class NgPlural implements AfterContentInit {
+  private _switchValue: number;
+  private _activeView: SwitchView;
+  private _caseViews = new Map<any, SwitchView>();
+  @ContentChildren(NgPluralCase) cases: QueryList<NgPluralCase> = null;
+
+  constructor(private _localization: NgLocalization) {}
+
+  @Input()
+  set ngPlural(value: number) {
+    this._switchValue = value;
+    this._updateView();
+  }
+
+  ngAfterContentInit() {
+    this.cases.forEach((pluralCase: NgPluralCase): void => {
+      this._caseViews.set(this._formatValue(pluralCase), pluralCase._view);
+    });
+    this._updateView();
+  }
+
+  /** @internal */
+  _updateView(): void {
+    this._clearViews();
+
+    var view: SwitchView = this._caseViews.get(this._switchValue);
+    if (!isPresent(view)) view = this._getCategoryView(this._switchValue);
+
+    this._activateView(view);
+  }
+
+  /** @internal */
+  _clearViews() {
+    if (isPresent(this._activeView)) this._activeView.destroy();
+  }
+
+  /** @internal */
+  _activateView(view: SwitchView) {
+    if (!isPresent(view)) return;
+    this._activeView = view;
+    this._activeView.create();
+  }
+
+  /** @internal */
+  _getCategoryView(value: number): SwitchView {
+    var category: string = this._localization.getPluralCategory(value);
+    var categoryView: SwitchView = this._caseViews.get(category);
+    return isPresent(categoryView) ? categoryView : this._caseViews.get(_CATEGORY_DEFAULT);
+  }
+
+  /** @internal */
+  _isValueView(pluralCase: NgPluralCase): boolean { return pluralCase.value[0] === "="; }
+
+  /** @internal */
+  _formatValue(pluralCase: NgPluralCase): any {
+    return this._isValueView(pluralCase) ? this._stripValue(pluralCase.value) : pluralCase.value;
+  }
+
+  /** @internal */
+  _stripValue(value: string): number { return NumberWrapper.parseInt(value.substring(1), 10); }
+}