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);

     }

 }