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 + "]";

  }

}