package org.apidesign.apifest08.currency;

import java.util.Currency;

/**

 * 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 Currency currency1;

  private Currency currency2;

  private Convertor(Currency currency1, Currency currency2) {

    this.currency1 = currency1;

    this.currency2 = currency2;

  }

  /**

   * 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

   */

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

    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 actualCurrency

   *          currency of this amount

   * @return converted amount

   */

  public double convert(double amount, Currency actualCurrency) {

    ExchangeRate exchangeRate = null;

    if (actualCurrency == null) {

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

    }

    if (currency1.getSymbol().equals(actualCurrency.getSymbol())

        || currency2.getSymbol().equals(actualCurrency.getSymbol())) {

      exchangeRate = getExchangeRate(actualCurrency);

    } else {

      throw new ConvertorException("This convertor could not be used for selected currency("

          + actualCurrency.getCurrencyCode() + ") " + this + "!!!");

    }

    return countResult(exchangeRate, amount);

  }

  private double countResult(ExchangeRate exchangeRate, double amount) {

    return amount * exchangeRate.getRate() / exchangeRate.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 actualCurrency) {

    ExchangeRate exchangeRate = null;

    if (actualCurrency.getCurrencyCode().equals(currency1.getCurrencyCode())) {

      exchangeRate = getExchangeRateInstance(actualCurrency, currency2);

    } else if (actualCurrency.getCurrencyCode().equals(currency2.getCurrencyCode())) {

      exchangeRate = getExchangeRateInstance(actualCurrency, currency1);

    }

    return exchangeRate;

  }

  /**

   * Returns actual exchange rate between original and destination currency.

   * @param originalCurrency

   *          original currency, from which we want to convert

   * @param newCurrency

   *          destination currency, to which we want to convert

   * @return exchange rate between this two currencies

   */

  private ExchangeRate getExchangeRateInstance(Currency originalCurrency, Currency newCurrency) {

    if ("USD".equals(originalCurrency.getCurrencyCode()) && "CZK".equals(newCurrency.getCurrencyCode())) {

      return new ExchangeRate(originalCurrency, newCurrency, 17d, 1d);

    } else if ("CZK".equals(originalCurrency.getCurrencyCode()) && "USD".equals(newCurrency.getCurrencyCode())) {

      return new ExchangeRate(originalCurrency, newCurrency, 1d / 17d, 1d);

    } else if ("SKK".equals(originalCurrency.getCurrencyCode()) && "CZK".equals(newCurrency.getCurrencyCode())) {

      return new ExchangeRate(originalCurrency, newCurrency, 80d, 100d);

    } else if ("CZK".equals(originalCurrency.getCurrencyCode()) && "SKK".equals(newCurrency.getCurrencyCode())) {

      return new ExchangeRate(originalCurrency, newCurrency, 100d / (80d / 100d), 100d);

    } else {

      throw new ConvertorException("Defined currencies don't have secified rates ["

          + originalCurrency.getCurrencyCode() + ", " + newCurrency.getCurrencyCode() + "]!!!");

    }

  }

  public String toString() {

    return "Converter [" + currency1.getCurrencyCode() + ", " + currency2.getCurrencyCode() + "]";

  }

}