package org.apidesign.apifest08.currency;

 import java.util.ArrayList;

 import java.util.Currency;

 import java.util.Hashtable;

 import java.util.List;

 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 List<String> currencyConvertors; 

   /**

    * Constructor. Checks if all selected currencies are not null and has defined exchange rates for both

    * directions.

    * @param currencies currencies for new instance of convertor

    * @throws UnknownConvertorException if there are not defined exchange rates for both directions for each

    * pair of currencies

    */

   private Convertor(Currency[] currencies) throws UnknownConvertorException {

     currencyConvertors = new ArrayList<String>();

     for (Currency currency1 : currencies) {

       for (Currency currency2 : currencies) {

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

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

         }

         if(!currency1.getCurrencyCode().equals(currency2.getCurrencyCode())) {

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

           if (!exchangeRates.containsKey(key)) {

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

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

           } 

           currencyConvertors.add(key);            

         }

       }

     }

   }

   /**

    * 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));

   }

   /**

    * Merge exchange rates of actual convertor with exchange rates from selected 

    * convertor. If there are same currencies in both convertors, these from selected

    * convertor rewrites these in actual convertor.

    * @param convertor convertor to merge with actual one

    * @return convertor with merged exchange rates 

    */

   public Convertor merge(Convertor convertor) {

     if(convertor == null) {

       throw new ConvertorException("It's impossible to merge with null convertor!!!");

     }

     currencyConvertors.addAll(convertor.getCurrencyConvertors());

 	  return this;

   }

   /**

    * 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... currencies) throws UnknownConvertorException {

    	if(currencies.length < 2) {

    		throw new ConvertorException("To get convertor instance, you have to select at least two currencies!!!");

    	}

     return new Convertor(currencies);

   }

   /**

    * 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;

     String key = originalCurrency.getCurrencyCode() + newCurrency.getCurrencyCode();

     if(currencyConvertors.contains(key)) {

       actualyUsedExchangeRate = exchangeRates.get(key);

     } else {

       throw new InvalidCurrencyException("This convertor could not be used for converting selected currencies (" + originalCurrency.getCurrencyCode() + "->"

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

     }

     return actualyUsedExchangeRate;

   }

   /**

    * Returns currency convertors for actual instance of convertor.

    * @return currency convertors for actual instance of convertor

    */

   List<String> getCurrencyConvertors() {

 	  return currencyConvertors;

   }

 }