package org.apidesign.apifest08.test;

import java.util.Currency;

import junit.framework.TestCase;

import org.apidesign.apifest08.currency.Convertor;

import org.apidesign.apifest08.currency.exceptions.UnknownConvertorException;

/** 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 static double actualRate;

    private static boolean increasing;

    private static final double EXCHANGE_RATE_MAX = 16.0;

    private static final double EXCHANGE_RATE_MIN = 15.0;

    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() {

      actualRate = 16.01;

      increasing = false;

      // sets actual exchange rates

      setRates();

      // create new instance

      Convertor convertor = null;

      try {

        convertor = Convertor.getConvertorInstance(Currency.getInstance("USD"), Currency.getInstance("CZK"));

      } catch (UnknownConvertorException e) {

        e.printStackTrace();

      }

      return convertor;

    }

    public void testFewQueriesForOnlineConvertor() throws Exception {

        Convertor c = createOnlineCZKUSDConvertor();

        doFewQueriesForOnlineConvertor(c);

    }

    static void doFewQueriesForOnlineConvertor(Convertor c) throws Exception {

        // convert $5 to CZK using c:

        double result = c.convert(5d, Currency.getInstance("USD"), Currency.getInstance("CZK"));

        double expectedResult = actualRate * 5;

        assertEquals("Result is not " + expectedResult + " CZK", expectedResult, result);

        // change exchange rates

        setRates();

        // convert $8 to CZK using c:

        result = c.convert(8d, Currency.getInstance("USD"), Currency.getInstance("CZK"));

        expectedResult = actualRate * 8;

        assertEquals("Result is not " + expectedResult + " CZK", expectedResult, result);

        // change exchange rates

        setRates();

        // convert $1 to CZK using c:

        result = c.convert(1d, Currency.getInstance("USD"), Currency.getInstance("CZK"));

        expectedResult = actualRate * 1;

        assertEquals("Result is not " + expectedResult + " CZK", expectedResult, result);

        // change exchange rates

        setRates();

        // convert 15.97CZK to USD using c:

        result = c.convert(15.97d, Currency.getInstance("CZK"), Currency.getInstance("USD"));

        expectedResult = 15.97 / actualRate ;

        assertEquals("Result is not " + expectedResult + " USD", expectedResult, result);

    }

    /** 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:

        double result = c.convert(16d, Currency.getInstance("CZK"), Currency.getInstance("SKK"));

        assertEquals("Result is not 20 SKK", 20d, result);

        // convert 500SKK to CZK using c:

        result = c.convert(500d, Currency.getInstance("SKK"), Currency.getInstance("CZK"));

        assertEquals("Result is not 400 CZK", 400d, result);

        doFewQueriesForOnlineConvertor(c);

    }

    private static void setRates() {

      // logic for change of actual exchange rate

      if(increasing) {

        actualRate += 0.01;

        if(actualRate == EXCHANGE_RATE_MAX){

          increasing = false;

        }

      } else {

        actualRate -= 0.01;

        if(actualRate == EXCHANGE_RATE_MIN){

          increasing = true;

        }

      }

      // set exchange rates

      Convertor.setConvertorRates(Currency.getInstance("USD"), Currency.getInstance("CZK"), actualRate, 1d);

    }

}