package com.skatestown.invoice;

import com.skatestown.ns.invoice.InvoiceType;

import javax.xml.bind.JAXBContext;
import javax.xml.bind.Unmarshaller;
import java.util.Iterator;
import java.util.List;
import java.io.File;

/**
 * Check Skatestown invoice totals using JAXB
 */
 
 public class InvoiceCheckerJAXB
    implements InvoiceChecker 
   {
	   /**
	    * Check invoice totals
		* @param inoviceXML Invoice XML document
		* @exception Exception any exception returned during processing
		*/
		public void checkInvoice(File invoiceXML) throws Exception {
			// Create JAXB context + point it to schema types
			JAXBContext jc = JAXBContext.newInstance(
			    "com.skatestown.ns.po:com.skatestown.ns.invoice");
				
			// Create an unmarshaller
			Unmarshaller u = jc.createUnmarshaller();
			
			// Unmarshall the invoice document
			InvoiceType inv = (InvoiceType) u.unmarshall(invoiceXML);
			
			double runningTotal = 0.0;
			
			// Iterate over items and update running total
			List items = inv.getOrder().getItem(); 
			for (Iterator iter = items.iterator(); iter.hasNext(); ) {
				com.skatestown.ns.invoice.ItemType item =
				  (com.skatestown.ns.invoice.ItemType) iter.next();
				runningTotal += item.getQuantity() * item.getUnitPrice();
			}
			
			// Add tax and shipping and handling
			runningTotal += inv.getShippingAndHandling();
			runningTotal += inv.getTax();
			
			// Get invoice total
			double total = inv.getTotalCost();
			
			// Use delta equality to prevent cumulative binary arithmetic errors. 
			// Choose delta = 1/2 of one cent
			if (Math.abs(runningTotal - total) >= .005) {
				throw new Exception(
				  "Invoice error: total is " + Double.toString(total) + 
				  " while our calculation shows a total of " + 
				  Double.toString(Math.round(runningTotal * 100) / 100.0));
			}

		}		
}