feat(router): add events tracking activation of individual routes

* Adds `ChildActivationStart` and `ChildActivationEnd`
* Adds test to verify the PreActivation phase of routing

packages/router/src/utils/collection.ts

@@ -41,14 +41,23 @@ export function shallowEqual(a: {[x: string]: any}, b: {[x: string]: any}): bool
   return true;
 }
 
+/**
+ * Flattens single-level nested arrays.
+ */
 export function flatten<T>(arr: T[][]): T[] {
   return Array.prototype.concat.apply([], arr);
 }
 
+/**
+ * Return the last element of an array.
+ */
 export function last<T>(a: T[]): T|null {
   return a.length > 0 ? a[a.length - 1] : null;
 }
 
+/**
+ * Verifys all booleans in an array are `true`.
+ */
 export function and(bools: boolean[]): boolean {
   return !bools.some(v => !v);
 }
@@ -85,6 +94,10 @@ export function waitForMap<A, B>(
   return map.call(last$, () => res);
 }
 
+/**
+ * ANDs Observables by merging all input observables, reducing to an Observable verifying all
+ * input Observables return `true`.
+ */
 export function andObservables(observables: Observable<Observable<any>>): Observable<boolean> {
   const merged$ = mergeAll.call(observables);
   return every.call(merged$, (result: any) => result === true);

packages/router/src/utils/tree.ts

@@ -87,4 +87,15 @@ export class TreeNode<T> {
   constructor(public value: T, public children: TreeNode<T>[]) {}
 
   toString(): string { return `TreeNode(${this.value})`; }
+}
+
+// Return the list of T indexed by outlet name
+export function nodeChildrenAsMap<T extends{outlet: string}>(node: TreeNode<T>| null) {
+  const map: {[outlet: string]: TreeNode<T>} = {};
+
+  if (node) {
+    node.children.forEach(child => map[child.value.outlet] = child);
+  }
+
+  return map;
 }