package org.apidesign.apifest08.test;

import java.math.BigDecimal;

import java.util.Currency;

import junit.framework.TestCase;

import org.apidesign.apifest08.currency.Convertor;

import org.apidesign.apifest08.currency.InvalidConversionException;

import org.apidesign.apifest08.currency.OnlineConvertor;

/** 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

{

    private final static Currency CZK;

    private final static Currency SKK;

    private final static Currency USD;

    static

    {

        CZK = Currency.getInstance("CZK");

        SKK = Currency.getInstance("SKK");

        USD = Currency.getInstance("USD");

    }

    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

     * @throws InvalidConversionException 

     */

    public static Convertor createOnlineCZKUSDConvertor() 

        throws InvalidConversionException

    {

        final Convertor convertor;

        convertor = new OnlineConvertor(USD,

                                        CZK,

                                        new TestExchangeRateFinder(new BigDecimal("15.00"), 

                                                                   new BigDecimal("16.00"),

                                                                   new BigDecimal("16.00"),

                                                                   new BigDecimal("0.01"),

                                                                   new BigDecimal("-0.01")));

        // 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 convertor;

    }

    public void testFewQueriesForOnlineConvertor() 

        throws InvalidConversionException

    {

        Convertor c = createOnlineCZKUSDConvertor();

        doFewQueriesForOnlineConvertor(c);

    }

    static void doFewQueriesForOnlineConvertor(Convertor c) 

        throws InvalidConversionException            

    {

        BigDecimal amount;

        // convert $5 to CZK using c:

        //assertEquals("Result is 80 CZK");

        amount = c.convert(USD, CZK, new BigDecimal("5.00"));

        assertEquals(new BigDecimal("80.00"), amount);

        // convert $8 to CZK using c:

        //assertEquals("Result is 127.92 CZK");

        amount = c.convert(USD, CZK, new BigDecimal("8.00"));

        assertEquals(new BigDecimal("127.92"), amount);

        // convert $1 to CZK using c:

        //assertEquals("Result is 15.98 CZK");

        amount = c.convert(USD, CZK, new BigDecimal("1.00"));

        assertEquals(new BigDecimal("15.98"), amount);

        // convert 15.97CZK to USD using c:

        //assertEquals("Result is 1$");

        amount = c.convert(CZK, USD, new BigDecimal("15.97"));

        assertEquals(new BigDecimal("1.00"), amount);

    }

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

     */

    public void testOnlineConvertorComposition() throws Exception {

        BigDecimal amount;

        Convertor c = Task2Test.merge(

            createOnlineCZKUSDConvertor(),

            Task1Test.createSKKtoCZK()

        );

        // convert 16CZK to SKK using c:

        // assertEquals("Result is 20 SKK");

        amount = c.convert(CZK, SKK, new BigDecimal("16.00"));

        assertEquals(new BigDecimal("20.00"), amount);

        // convert 500SKK to CZK using c:

        // assertEquals("Result is 400 CZK");

        amount = c.convert(SKK, CZK, new BigDecimal("500.00"));

        assertEquals(new BigDecimal("400.00"), amount);

        doFewQueriesForOnlineConvertor(c);

    }

}