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);

		}

   }

}