perf: prevent unnecessary actions (#1580)

* perf: prevent firing price action twice
* perf: prevent firing empty add to cart
* perf: reduce firing product links request
* perf: reduce number of variations actions

src/app/core/facades/shopping.facade.ts

@@ -1,7 +1,7 @@
 import { Inject, Injectable } from '@angular/core';
 import { Store, select } from '@ngrx/store';
 import { Observable, combineLatest, identity } from 'rxjs';
-import { debounce, filter, map, pairwise, startWith, switchMap, tap } from 'rxjs/operators';
+import { debounce, distinctUntilChanged, filter, map, pairwise, startWith, switchMap, tap } from 'rxjs/operators';
 
 import { PRICE_UPDATE } from 'ish-core/configurations/injection-keys';
 import { PriceItemHelper } from 'ish-core/models/price-item/price-item.helper';
@@ -120,6 +120,7 @@ export class ShoppingFacade {
             select(getProductPrice(plainSKU)),
             // reset state when updates are forced
             this.priceUpdate === 'always' || fresh ? startWith(undefined) : identity,
+            distinctUntilChanged(),
             tap(prices => {
               if (!prices) {
                 this.store.dispatch(loadProductPrices({ skus: [plainSKU] }));
@@ -162,10 +163,16 @@ export class ShoppingFacade {
   productLinks$(sku: string | Observable<string>) {
     return toObservable(sku).pipe(
       whenTruthy(),
-      tap(plainSKU => {
-        this.store.dispatch(loadProductLinks({ sku: plainSKU }));
-      }),
-      switchMap(plainSKU => this.store.pipe(select(getProductLinks(plainSKU))))
+      switchMap(plainSKU =>
+        this.store.pipe(
+          select(getProductLinks(plainSKU)),
+          tap(links => {
+            if (!links) {
+              this.store.dispatch(loadProductLinks({ sku: plainSKU }));
+            }
+          })
+        )
+      )
     );
   }
 

src/app/core/store/customer/basket/basket-items.effects.ts

@@ -55,6 +55,7 @@ export class BasketItemsEffects {
       // accumulate all actions
       window(this.actions$.pipe(ofType(addProductToBasket), debounceTime(500))),
       mergeMap(window$ => window$.pipe(toArray())),
+      filter(items => items.length > 0),
       map(items => addItemsToBasket({ items }))
     )
   );

src/app/core/store/shopping/products/products.effects.ts

@@ -314,7 +314,13 @@ export class ProductsEffects {
             : undefined
         ),
         whenTruthy(),
-        map(sku => loadProductVariationsIfNotLoaded({ sku }))
+        groupBy(identity),
+        mergeMap(group$ =>
+          group$.pipe(
+            throttleTime(10),
+            map(sku => loadProductVariationsIfNotLoaded({ sku }))
+          )
+        )
       ),
     { dispatch: true }
   );