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;

  }

}