package org.apidesign.apifest08.currency;

 import static org.apidesign.apifest08.currency.Assert.notNull;

 import java.math.BigDecimal;

 import java.math.RoundingMode;

 import java.util.ArrayList;

 import java.util.Currency;

 import java.util.List;

 /**

  * The factory for {@link Convertor}.

  * 

  * @see #newInstance()

  */

 public final class ConvertorFactory {

 	//do not expose constructor

 	private ConvertorFactory(){}

 	/**

 	 * @return a convertor instance. 

 	 *  

 	 * @throws CurrencyException in a convertor cannot be instantiated

 	 */

 	public static Convertor newInstance() throws CurrencyException{

 		return new DefaultConvertor();

 	}

 	private static final class DefaultConvertor extends  Convertor {

 		private List<Bid> bids;

 		private DefaultConvertor() {

 			bids = new ArrayList<Bid>();

 			Bid usdCzk = new Bid(Currencies.USD, Currencies.CZK, new BigDecimal("17"));

 			bids.add(usdCzk);

 			Bid skCzk = new Bid(Currencies.SKK, Currencies.CZK, new BigDecimal("0.8"));

 			bids.add(skCzk);

 		}

 		@Override

 		public Amount convert(Amount from, Currency targetCurrency)

 				throws CurrencyException {

 			return convert(from.getValue(), from.getCurrency(), targetCurrency);

 		}

 		@Override

 		public Amount convert(BigDecimal amount, Currency from,

 				Currency targetCurrency) throws ConversionException,

 				UnsupportedConversionException {

 			notNull(from, "from");

 			notNull(targetCurrency, "targetCurrency");

 			int index = bids.indexOf(new Bid(from, targetCurrency));

 			if(index == -1) {

 				throw new UnsupportedConversionException(from, targetCurrency);

 			}

 			Bid bid = bids.get(index);

 			BigDecimal bidValue = bid.getBidValue(from, targetCurrency);

 			BigDecimal result = bidValue.multiply(amount);			

 			return new Amount(result, targetCurrency);

 		}

    }

 }