package org.apidesign.apifest08.currency;

import java.util.ArrayList;

import java.util.Calendar;

import java.util.Currency;

import java.util.Date;

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, List<ExchangeRate>> exchangeRates;

  private List<ExchangeRateInstance> exchangeRateInstances;

  /**

   * 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 {

    exchangeRateInstances = new ArrayList<ExchangeRateInstance>();

    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!!!");

          }

          exchangeRateInstances.add(new ExchangeRateInstance(key, null, null));            

        }

      }

    }

  }

  /**

   * 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, List<ExchangeRate>>();

    }

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

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

    double recountedRate = (unit / rate) * unit;

    exchangeRates.put(key12, addNewExchangeRate(key12, currency1, currency2, rate, unit, null, null));

    exchangeRates.put(key21, addNewExchangeRate(key21, currency2, currency1, recountedRate, unit, null, null));

  }

  public static Convertor limitExchangeRatesValidity(Convertor convertor, Date validFrom, Date validTo) {

    if(convertor == null || validFrom == null || validTo == null) {

      throw new ConvertorException("None of parameters of method limitExchangeRatesValidity should be null!!!");

    }

    List<ExchangeRateInstance> exchangeRateInstances = convertor.getExchangeRateInstances();

    for (ExchangeRateInstance exchangeRateInstance : exchangeRateInstances) {

      // get actual convertor rates for actual validity

      ExchangeRate actualExchangeRate = getExchangeRate(exchangeRateInstance.getKey(), exchangeRateInstance.getValidFrom(), exchangeRateInstance.getValidTo());

      // set new validity for theese rates

      actualExchangeRate.setValidFrom(validFrom);

      actualExchangeRate.setValidTo(validTo);

      // and for selected currency convertor

      exchangeRateInstance.setValidFrom(validFrom);

      exchangeRateInstance.setValidTo(substractSecond(validTo));

    }

    return convertor;

  }

  /**

   * 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!!!");

    }

    exchangeRateInstances.addAll(convertor.getExchangeRateInstances());

	  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 actual exchange rate

   * for selected currencies and actual moment.

   * @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();

    ExchangeRateInstance exchangeRateInstance = findExchangeRateInstance(key);

    if(exchangeRateInstance != null) {

      actualyUsedExchangeRate = getExchangeRate(exchangeRateInstance.getKey(), exchangeRateInstance.getValidFrom(), exchangeRateInstance.getValidTo());

    } else {

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

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

    }

    return actualyUsedExchangeRate;

  }

  /**

   * Finds instance of exchange rate for actual instance of convertor and actual moment.

   * @param key exchange rate instance key

   * @return exchange rate instance

   */

  private ExchangeRateInstance findExchangeRateInstance(String key) {

    ExchangeRateInstance instance = null;

    Date now = new Date();

    for (ExchangeRateInstance item : exchangeRateInstances) {

      if(item.getKey().equals(key) && item.getValidFrom() == null && item.getValidTo() == null) {

        instance = item;

        break;

      } else if(item.getKey().equals(key) && item.getValidFrom().compareTo(now) <= 0 && item.getValidTo().compareTo(now) >= 0) {

        instance = item;

        break;

      }

    }

    return instance;

  }

  /**

   * Returns currency convertors for actual instance of convertor.

   * @return currency convertors for actual instance of convertor

   */

  private List<ExchangeRateInstance> getExchangeRateInstances() {

    return exchangeRateInstances;

  }

  private static ExchangeRate getExchangeRate(String key, Date validFrom, Date validTo) {

    ExchangeRate exchangeRate = null;

    List<ExchangeRate> currencyExchangeRates = exchangeRates.get(key);

    for (ExchangeRate currencyExchangeRate : currencyExchangeRates) {

      Date actValidFrom = currencyExchangeRate.getValidFrom();

      Date actValidTo = currencyExchangeRate.getValidTo();

      if(actValidFrom == null && validFrom == null && actValidTo == null && validTo == null) {

        exchangeRate = currencyExchangeRate;

        break;

      } else if(actValidFrom != null && validFrom != null && actValidTo != null && validTo != null && actValidFrom.compareTo(validFrom) <= 0 && actValidTo.compareTo(validTo) > 0) {

        exchangeRate = currencyExchangeRate;

        break;

      }

    }

    if(exchangeRate == null) {

      throw new ConvertorException("Exchange rate for actual exchange rate instance not found!!!");

    }

    return exchangeRate;

  }

  private static List<ExchangeRate> addNewExchangeRate(String key, Currency currency1, Currency currency2, double rate, double unit, Date validFrom, Date validTo) {

    List<ExchangeRate> actualExchangeRates = new ArrayList<ExchangeRate>();

    ExchangeRate newExchangeRate = null;

    if(exchangeRates.containsKey(key)) {

      List<ExchangeRate> rates = exchangeRates.get(key);

      for (ExchangeRate exchangeRate : rates) {

        if(exchangeRate.getValidFrom() == null && exchangeRate.getValidTo() == null && validFrom == null && validTo == null) {

          newExchangeRate = exchangeRate;

          break;

        } else if(exchangeRate.getValidFrom() != null && exchangeRate.getValidTo() != null && validFrom != null && validTo != null) {

          if(exchangeRate.getValidFrom().compareTo(validFrom) == 0 && exchangeRate.getValidTo().compareTo(validTo) == 0) {

            newExchangeRate = exchangeRate;

            break;

          }

        }

      }

      actualExchangeRates.addAll(rates);

    }

    if(newExchangeRate == null) {

      actualExchangeRates.add(new ExchangeRate(currency1, currency2, rate, unit, validFrom, validTo));

    } else {

      newExchangeRate.setRate(rate);

      newExchangeRate.setUnit(unit);

      actualExchangeRates.add(newExchangeRate);

    }

    return actualExchangeRates;

  }

  /**

   * Substracts one second from selected date.

   * @param date date

   * @return date -1s

   */

  private static Date substractSecond(Date date) {

    Calendar calendar = Calendar.getInstance();

    calendar.setTime(date);

    calendar.set(Calendar.SECOND, -1);

    return calendar.getTime();

  }

}