OpenCloseViolates.ts

// Code which violates Oped Close Principles


class Product {
    constructor(public name : string, public price : number){
    }
}

class ShoppingCart {
    public products : Product[] = []

    public addProduct(product : Product){
        this.products.push(product)
    }
    public calculateTotalProduc() : number {
        const total = this.products
        .map(x => x.price)
        .reduce((accumulator, currEle) => {
            return  accumulator + currEle
        }, 0);
        return total
    }
    public printInvoice() : void {
        const total = this.calculateTotalProduc()
        console.log("Invoice Printed :", total);
    } 
    public saveToDB(): void {
        console.log("saving data to DB")
    }
}

class ShoppingCartPrinter {
    constructor(public cart : ShoppingCart){}
    public printer() : void {
        const total = this.cart.calculateTotalProduc();
        console.log("Invoice Printed :", total);
    }

}

class ShoppingDBService{
    constructor(public cart : ShoppingCart){}

    public saveCartToPostgresDb():void{
        console.log("saving items", this.cart.products)
    }

    public saveCartToMongoDB():void {
        console.log("saving items to MongoDB", this.cart.products)
    }

    public saveCardToDynamoDB():void {
        console.log("saving items to DynamoDB", this.cart.products)
    }

}

const product1 = new Product("1", 1)
const product2 = new Product("2", 2)
const product3 = new Product("3", 3)

const shoppingCart1 = new ShoppingCart()
shoppingCart1.addProduct(product1)
shoppingCart1.addProduct(product2)
shoppingCart1.addProduct(product3) 

const shopingcartPrinter = new ShoppingCartPrinter(shoppingCart1)
shopingcartPrinter.printer()

//Here saving db, as, we had to introduce multiple saving option, 
//we introduced multiple function 
// Here we modified an existing class to do this
// this violates Open close principle
const shoppingDBService = new ShoppingDBService(shoppingCart1)
shoppingDBService.saveCartToPostgresDb()
shoppingDBService.saveCartToMongoDB()
shoppingDBService.saveCardToDynamoDB()