package org.apidesign.apifest08.currency;

 import java.util.Currency;

 import java.util.Hashtable;

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

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

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

 /**

  * This is the skeleton class for your API. You need to make it public, so it is accessible to your client code

  * (currently in Task1Test.java) file.

  * <p>

  * Feel free to create additional classes or rename this one, just keep all the API and its implementation in this

  * package. Do not spread it outside to other packages.

  */

 public class Convertor {

   private static Hashtable<String, ExchangeRate> exchangeRates;

   private ExchangeRate exchangeRate12;

   private ExchangeRate exchangeRate21;

   private Convertor(Currency currency1, Currency currency2) throws UnknownConvertorException {

     String key12 = currency1.getCurrencyCode() + currency2.getCurrencyCode();

     String key21 = currency2.getCurrencyCode() + currency1.getCurrencyCode();

     if (!(exchangeRates.containsKey(key12) && exchangeRates.containsKey(key21))) {

       throw new UnknownConvertorException("Selected convertor (" + currency1.getCurrencyCode() + "->"

           + currency2.getCurrencyCode() + ") has not defined any rates!!!");

     }

     this.exchangeRate12 = exchangeRates.get(key12);

     this.exchangeRate21 = exchangeRates.get(key21);

   }

   /**

    * Sets convertor rate for selected currencies.

    * @param currency1

    *          one of the currencies we want to convert to/from

    * @param currency2

    *          the other currency

    * @param rate

    *          exchange rate from currency1 to currency2

    * @param unit

    *          unit of exchangeRate (USD->CZK - unit=1, you exchange one dollar, SKK->CZK unit=100, exchange rate is for

    *          100SKK)

    */

   public static void setConvertorRates(Currency currency1, Currency currency2, double rate, double unit) {

     if (currency1 == null || currency2 == null) {

       throw new ConvertorException("None of the currencies should be null!!!");

     }

     if (rate <= 0 || unit <= 0) {

       throw new ConvertorException("Rate(" + rate + ") and unit(" + unit + ") has to be grater then zero!!!");

     }

     if (exchangeRates == null) {

       exchangeRates = new Hashtable<String, ExchangeRate>();

     }

     String key12 = currency1.getCurrencyCode() + currency2.getCurrencyCode();

     String key21 = currency2.getCurrencyCode() + currency1.getCurrencyCode();

     double recountedRate = (unit / rate) * unit;

     exchangeRates.put(key12, new ExchangeRate(currency1, currency2, rate, unit));

     exchangeRates.put(key21, new ExchangeRate(currency2, currency1, recountedRate, unit));

   }

   /**

    * Creates new instance of convertor.

    * @param currency1

    *          one of the currencies we want to convert to/from

    * @param currency2

    *          the other currency

    * @return new instance of convertor

    * @throws UnknownConvertorException

    *           thrown if convertor for selected currencies has not been defined

    */

   public static Convertor getConvertorInstance(Currency currency1, Currency currency2) throws UnknownConvertorException {

     if (currency1 == null || currency2 == null) {

       throw new ConvertorException("None of the currencies should be null!!!");

     }

     return new Convertor(currency1, currency2);

   }

   /**

    * Converts selected amout of selected currency to other currency of this convertor instance.

    * @param amount

    *          amount to convert

    * @param originalCurrency

    *          currency of this amount

    * @param newCurrency

    *          currency to which we want convert

    * @return converted amount

    * @throws InvalidCurrencyException

    *           while one or both currencies doesn't fit for this convertor

    */

   public double convert(double amount, Currency originalCurrency, Currency newCurrency) throws InvalidCurrencyException {

     ExchangeRate actualyUsedExchangeRate = null;

     if (originalCurrency == null) {

       throw new ConvertorException("Original currency is null!!!");

     }

     if (newCurrency == null) {

       throw new ConvertorException("Destination currency is null!!!");

     }

     actualyUsedExchangeRate = getExchangeRate(originalCurrency, newCurrency);

     return countResult(actualyUsedExchangeRate, amount);

   }

   private double countResult(ExchangeRate actualyUsedExchangeRate, double amount) {

     return amount * actualyUsedExchangeRate.getRate() / actualyUsedExchangeRate.getUnit();

   }

   /**

    * Decides the direction of conversion and returns instance of actual exchange rate.

    * @param actualCurrency

    *          actual currency we want to convert

    * @return actual exchange rate of this convertor for selected currency

    */

   private ExchangeRate getExchangeRate(Currency originalCurrency, Currency newCurrency) throws InvalidCurrencyException {

     ExchangeRate actualyUsedExchangeRate = null;

     if (originalCurrency.getCurrencyCode().equals(exchangeRate12.getOriginalCurrency().getCurrencyCode())

         && newCurrency.getCurrencyCode().equals(exchangeRate12.getNewCurrency().getCurrencyCode())) {

       actualyUsedExchangeRate = exchangeRate12;

     } else if (originalCurrency.getCurrencyCode().equals(exchangeRate21.getOriginalCurrency().getCurrencyCode())

         && newCurrency.getCurrencyCode().equals(exchangeRate21.getNewCurrency().getCurrencyCode())) {

       actualyUsedExchangeRate = exchangeRate21;

     } else {

       throw new InvalidCurrencyException("This convertor " + this

           + " could not be used for converting selected currencies (" + originalCurrency.getCurrencyCode() + "->"

           + newCurrency.getCurrencyCode() + ") !!!");

     }

     return actualyUsedExchangeRate;

   }

   public String toString() {

     String currency1Code = exchangeRate12.getOriginalCurrency().getCurrencyCode();

     String currency2Code = exchangeRate12.getNewCurrency().getCurrencyCode();

     return "Converter [" + currency1Code + "->" + currency2Code + ", " + currency2Code + "->" + currency1Code + "]";

   }

 }