Sky.Net/client/src/app/basket/basket.service.ts

import { HttpClient } from '@angular/common/http';
import { Injectable } from '@angular/core';
import { BehaviorSubject, map } from 'rxjs';
import { environment } from 'src/environments/environment';
import { Basket, IBasket, IBasketItem, IBasketTotals } from '../shared/models/baskset';
import { IProduct } from '../shared/models/product';

@Injectable({
  providedIn: 'root'
})
export class BasketService {
  baseUrl = environment.apiUrl;
  private basketSource = new BehaviorSubject<IBasket>(null);
  basket$ = this.basketSource.asObservable();
  private basketTotalSource = new BehaviorSubject<IBasketTotals>(null);
  basketTotal$ = this.basketTotalSource.asObservable();

  constructor(private http: HttpClient) { }

  getBasket(id: string){
    return this.http.get(this.baseUrl + 'basket?id=' + id).pipe(
      map((basket: IBasket) => {
        this.basketSource.next(basket);
        this.calculateTotals();
      })
    );
  }

  setBasket(basket: IBasket){
    return this.http.post(this.baseUrl + 'basket', basket).subscribe({
      next: (response: IBasket) => {
        this.basketSource.next(response);
        this.calculateTotals();
      },
      error: (e: any) => { console.log(e); },
      complete: () => { console.log('complete'); }
    });
  }

  getCurrentBasketValue(){
    return this.basketSource.value;
  }

  addItemToBasket(item: IProduct, quantity = 1){
    const itemToAdd: IBasketItem = this.mapProductItemToBasketItem(item, quantity);
    const basket = this.getCurrentBasketValue() ?? this.createBasket();
    basket.items = this.addOrUpdateItem(basket.items, itemToAdd, quantity);
    this.setBasket(basket);
  }

  private calculateTotals(){
    const basket = this.getCurrentBasketValue();
    const shipping = 0;
    const subtotal = basket.items.reduce((a, b) => (b.price * b.quantity) + a, 0);
    const total = subtotal + shipping;
    this.basketTotalSource.next({
      shipping,
      total,
      subtotal
    });
  }

  private addOrUpdateItem(items: IBasketItem[], itemToAdd: IBasketItem, quantity: number): IBasketItem[] {
    const index = items.findIndex(i => i.id === itemToAdd.id);
    if(index === -1){
      itemToAdd.quantity = quantity;
      items.push(itemToAdd);
    } else {
      items[index].quantity += quantity;
    }

    return items;
  }

  private createBasket(): IBasket {
   const basket = new Basket();
   localStorage.setItem('basket_id', basket.id);
   return basket;
  }

  private mapProductItemToBasketItem(item: IProduct, quantity: number): IBasketItem {
    return {
      id: item.id,
      productName: item.name,
      price: item.price,
      pictureUrl: item.pictureUrl,
      quantity,
      brand: item.productBrand,
      type: item.productType
    }
  }

}