package org.apidesign.apifest08.test;

import java.math.BigDecimal;

import java.math.RoundingMode;

import junit.framework.TestCase;

import org.apidesign.apifest08.currency.Convertor;

import static org.apidesign.apifest08.test.Currencies.*;

/** The exchange rates are not always the same. They are changing. Day by day,

 * hour by hour, minute by minute. For every bank it is important to always

 * have the actual exchange rate available in the system. That is why let's

 * create a pluggable convertor that will always have up to date value of its

 * exchange rate.

 * <p>

 * The quest for today is to allow 3rd party developer to write a convertor

 * that adjusts its exchange rate everytime it is queried. This convertor is

 * written by independent vendor, the vendor knows only your Convertor API,

 * he does not know how the whole system looks and how the convertor is supposed

 * to be used.

 */

public class Task3Test extends TestCase {

    public Task3Test(String testName) {

        super(testName);

    }

    @Override

    protected void setUp() throws Exception {

    }

    @Override

    protected void tearDown() throws Exception {

    }

    // Backward compatibly enhance your existing API to support following

    // usecases:

    //

    /** Without knowing anything about the surrounding system, write an

     * implementation of convertor that will return different rates everytime

     * it is queried. Convert USD to CZK and vice versa. Start with the rate of

     * 1USD = 16CZK and adjust it in favor of CZK by 0.01 CZK with every query.

     * As soon as you reach 1USD = 15CZK adjust it by 0.01 CZK in favor of USD

     * until you reach 1USD = 16CZK

     *

     * @return new instance of "online" USD and CZK convertor starting with rate 1USD = 16CZK

     */

    public static Convertor createOnlineCZKUSDConvertor() {

    	Convertor.RateProvider rateProvider = new Convertor.RateProvider() {

    		private BigDecimal seed = new BigDecimal("16.01").setScale(2);

			@Override

			public BigDecimal getRate() {

				if(seed.equals(new BigDecimal("15").setScale(2))) {

					seed = seed.add(new BigDecimal("0.01")).setScale(2);

				} else {

					seed = seed.subtract(new BigDecimal("0.01")).setScale(2);

				}	

				return seed;

			}

    	};

        // initial rate: 1USD = 16CZK

        // 2nd query 1USD = 15.99CZK

        // 3rd query 1USD = 15.98CZK

        // until 1USD = 15.00CZK

        // then 1USD = 15.01CZK

        // then 1USD = 15.02CZK

        // and so on and on up to 1USD = 16CZK

        // and then another round to 15, etc.

        return new Convertor(rateProvider, USD, CZK);

    }

    public void testFewQueriesForOnlineConvertor() {

        Convertor c = createOnlineCZKUSDConvertor();

        doFewQueriesForOnlineConvertor(c);

    }

    static void doFewQueriesForOnlineConvertor(Convertor c) {

        // convert $5 to CZK using c:

        assertEquals("Result is 80 CZK",80 ,c.convert(new BigDecimal(5), USD, CZK).getValue().intValue());

        // convert $8 to CZK using c:

        assertEquals("Result is 127.92 CZK", 127.92d , c.convert(new BigDecimal(8), USD, CZK).getValue().doubleValue());

        // convert $1 to CZK using c:

        assertEquals("Result is 15.98 CZK", 15.98d,  c.convert(new BigDecimal(1), USD, CZK).getValue().doubleValue());

        // convert 15.97CZK to USD using c:

        assertEquals("Result is 1$", 1, c.convert(new BigDecimal("15.97").setScale(2), CZK, USD).getValue().intValue());

    }

    /** Join the convertors and show they behave sane.

     */

    public void testOnlineConvertorComposition() throws Exception {

        Convertor c = Task2Test.merge(

            createOnlineCZKUSDConvertor(),

            Task1Test.createSKKtoCZK()

        );

        // convert 16CZK to SKK using c:

        assertEquals("Result is 20 SKK", 20, c.convert(new BigDecimal(16), CZK, SKK).getValue().intValue());

        // convert 500SKK to CZK using c:

        assertEquals("Result is 400 CZK", 400, c.convert(new BigDecimal(500), SKK, CZK).getValue().intValue());

        doFewQueriesForOnlineConvertor(c);

    }

}