LunchNLearn - Mixins

LunchNLearn-Mixins.js

// General library function to apply mixins to classes
function applyMixins(derivedCtor: any, baseCtors: any[]) {
    baseCtors.forEach(baseCtor => {
        Object.getOwnPropertyNames(baseCtor.prototype).forEach(name => {
            derivedCtor.prototype[name] = baseCtor.prototype[name];
        })
    }); 
}

// An Enum to classify items for pricing
enum Fruits {
	Apple,
	Pear,
	Grape,
	Orange
}

// Item Definition
class Item {
	constructor(options?  : { type: Fruits, description : string}) {
		this.type = options.type;
		this.description = options.description;
	}
	
	type : Fruits;
	description : string;
}

// Item + Quantity
class LineItem extends Item {
	quantity : number;
	
	constructor(options?  : { type: Fruits, description : string, quantity : number}) {
		super( { type: options.type, description : options.description});
		this.quantity = options.quantity;
	}
}

// Address + static methods
class Address {
	number : number; 
	street : string;
	suffix : string;
	city   : string;
	state  : string;
	zip    : number;
	zip4   : number
}

// Item Pricer
class ItemPricer {
	getPrice(item : Item) : number {
		if (item.type == Fruits.Apple) return 10;
		if (item.type == Fruits.Pear) return 20;
		if (item.type == Fruits.Grape) return 30;
		if (item.type == Fruits.Orange) return 40;
	}
}

// Line Item Pricer (Item Pricer * quantity)
class LineItemPricer implements ItemPricer {
	
	getPrice : (item : Item) => number;
	
	priceLineItem(item : LineItem) {
		return this.getPrice(item) * item.quantity;
	}
}

// Setup the Pricer mixin
applyMixins(LineItemPricer, [ItemPricer]);

// Class to determine whether to insure the invoce
class Insurable {
	lowLimit : number = 10;
	requiresInsurance(price : number) : Boolean {
		if (price > this.lowLimit) {
			return true;
		}
		return false;
	}
}

// Invoice Builder combining all the other stuff
class InvoiceBuilder implements LineItemPricer, Insurable {
	lineItems : LineItem[];
	lowLimit : number;
	getPrice : (item : Item) => number;
	priceLineItem : (item : LineItem) => number; 
	requiresInsurance : (price : number) => boolean;
	
	constructor(lowLimit : number = 150, lineItems : LineItem[]) {
		this.lowLimit = lowLimit;
		this.lineItems = lineItems;
	}
	
	build() {
		let lineItemNumber = 1;
		let totalInvoicePrice = 0;
		
		// Table creation	
		let table = document.createElement('table');
		let tableHeader = <HTMLTableElement> table.createTHead();
		let headerRow = <HTMLTableRowElement> tableHeader.insertRow(0);
		let tableBody = <HTMLTableElement> table.createTBody();

        // Header creation
		let lineItemNumberHeaderCell = headerRow.insertCell();
		lineItemNumberHeaderCell.innerText = "Item Number";		
		let descriptionHeaderCell = headerRow.insertCell();
		descriptionHeaderCell.innerText = "Description";
		let unitPriceHeaderCell = headerRow.insertCell();
		unitPriceHeaderCell.innerText = "Unit Price";
		let quantityHeaderCell = headerRow.insertCell();
		quantityHeaderCell.innerText = "Quantity";
		let lineItemPriceHeaderCell = headerRow.insertCell();
		lineItemPriceHeaderCell.innerText = "Total Price";
		
		// Table content creation
		for(let lineItem of this.lineItems) {
			let row = <HTMLTableRowElement> tableBody.insertRow();
			let lineItemNumberCell = row.insertCell();
			lineItemNumberCell.innerText = lineItemNumber.toString();		
			let descriptionCell = row.insertCell();
			descriptionCell.innerText = lineItem.description;
			let unitPriceCell = row.insertCell();
			unitPriceCell.innerText = this.getPrice(lineItem).toString();
			let quantityCell = row.insertCell();
			quantityCell.innerText = lineItem.quantity.toString();
			let lineItemPriceCell = row.insertCell();
			let lineItemPrice = this.priceLineItem(lineItem);
			lineItemPriceCell.innerText = lineItemPrice.toString();
			
			totalInvoicePrice += lineItemPrice;
			lineItemNumber++;
			
		}
		
		let footerText = document.createElement('div');
		footerText.innerText = `The total price for the invoice is ${totalInvoicePrice.toString()}, and it ${this.requiresInsurance(totalInvoicePrice) === true ? "requires insurance" : "does not require insurance"}`;
		document.body.appendChild(footerText);		
		
		document.body.appendChild(table);
	} 
}

applyMixins(InvoiceBuilder, [LineItemPricer, Insurable]);

var sampleLineItems = [
	new LineItem ({ type: Fruits.Apple, description : "Best Apples Ever", quantity : 10  }),
	new LineItem ({ type: Fruits.Pear, description: "Best Pears Ever", quantity : 3  }),
	new LineItem ({ type: Fruits.Grape, description: "Best Grapes Ever",  quantity : 5  }),
	new LineItem ({ type: Fruits.Orange, description : "Best Oranges Ever", quantity : 7  })			
];

var sampleInvoice = new InvoiceBuilder(5000, sampleLineItems).build();