package org.apidesign.apifest08.currency;

 import java.math.BigDecimal;

 import java.math.MathContext;

 import java.math.RoundingMode;

 import java.util.Date;

 /** Convertor able to convert amount from one currency to other currency.

  * <p>

  * Conversion method are:

  * <ul>

  * <li>{@link #convert(ConvertorCurrency, ConvertorCurrency, BigDecimal)} - convert

  * using exchange rate specified in exchange rate provide. This method is not try 

  * use reverted excahnage rate. 

  * <li>{@link #convertWithReversibleRates(ConvertorCurrency, ConvertorCurrency, BigDecimal)} - 

  * convert using exchange rate specified in exchange rate provide. This method

  * is not trying to use reverted exchange rate.

  * </ul>

  * 

  * Exchange rate is provided by {@link ExchangeRateProvider}.

  */

 public class Convertor {

     private Convertor[] convertors;

     private IDateProviderEngine dateProvider;

     boolean remainderAllowed = true; //if false, remained is not allowed (should be true ideally, but can't handle it now)

     private ExchangeRateProvider exchangeRateProvider;

     private Date fromDate;

     private Date toDate;

     /** Create new <code>Convertor</code> as merge of provided convertors. Merged convertor will use

      * provided convertors to convert between currencies.

      * <p>

      * Only one should be able to provide conversion between currencies. If more than one convertos

      * are able to convert currency, one of conversions will be used (it is not defined which).

      * 

      * @since version 2

      * @param convertors Convertor used to create merge-convertor.

      * @return Returns new convertor instance.

      */

     public static Convertor createConvertorAsMerge(Convertor[] convertors) {

         for (int i=0;i<convertors.length;i++) {

             if (convertors[i]==null) {

                 throw new NullPointerException("Convertor at index "+i+" can't be null");

             }

         }

         return new Convertor(convertors);

     }

     /** Create simle convertor.

      */

     private Convertor() {

         setDateProvider(DateProvider.createCurrentDateProvider());

         this.convertors=new Convertor[0];

     }

     /** Create merge convertor.

      */            

     private Convertor(Convertor[] convertors) {

         this();

         this.convertors = convertors;       

     }

     /**

      * Create new <code>Convertor</code> using <code>ExchangeRateProvider</code>.

      * 

      * @param exchangeRateProvider {@link ExchangeRateProvider} used to get exchange rate.

      * 

      * @return Returns <code>Convertor</code> which can be used to convert money.

      * @since version1

      */

     public static Convertor createConvertor(ExchangeRateProvider exchangeRateProvider) {

         Convertor c = new Convertor();

         c.exchangeRateProvider = exchangeRateProvider;

         return c;

     }

     /**

      * Convert <code>amount</code> from <code>fromCurrency</code> to <code>toCurrency</code> as specified

      * in <code>ExchangeRateProvider</code>.

      * 

      * @param amount Amount which should be converted. Can't be negative value (can be zero or positive).

      * @return Return <code>ConversionResult</code> which holds conversion result.

      * @since version1

      * @deprecated since version2. Use {@link #convert(ConvertorCurrency, ConvertorCurrency, BigDecimal) } - explicitly specify conversion currencies.

      */

     public ConversionResult convert(BigDecimal amount) {

         return convertValue(exchangeRateProvider.getFromCurrency(), exchangeRateProvider.getToCurrency(),amount, false,false,null);

     }

     /**

      * Convert <code>amount</code> from <code>toCurrency</code> to <code>fromCurrency</code> as specified

      * in <code>ExchangeRateProvider</code>. This is <em>reverted</em> order than suggested by  names of currency fields in <code>ExchangeRate</code>.

      * 

      * @param amount Amount which should be converted. Can't be negative value (can be zero or positive).

      * @return Return <code>ConversionResult</code> which holds conversion result.

      * @since version1

      * @deprecated since version2. Use {@link #convert(ConvertorCurrency, ConvertorCurrency, BigDecimal) } - explicitly specify conversion currencies.

      */

     public ConversionResult convertBack(BigDecimal amount) {

         return convertValue(exchangeRateProvider.getFromCurrency(), exchangeRateProvider.getToCurrency(),amount, true,false,null);

     }

     private ConversionResult convertUsingSimpleConvertor(ConvertorCurrency fromCurrency, ConvertorCurrency toCurrency, boolean reversibleExRate, BigDecimal amount, boolean convertBack,Date date) throws ConversionNotSupportedException, RuntimeException {

         if (date == null) {

             date = dateProvider.getCurrentDate();

         }

         ExchangeRate rate;

         if (reversibleExRate) {

             rate = exchangeRateProvider.getReversibleExchangeRate(fromCurrency, toCurrency, date);

         } else {

             rate = exchangeRateProvider.getExchangeRate(fromCurrency, toCurrency, date);

         }

         if (rate == null) {

             return null;

         }

         ConversionResult result = new ConversionResult();

         int fromFranctionDigits = fromCurrency.getDefaultFractionDigits();

         int toFractionDigits = toCurrency.getDefaultFractionDigits();

         int usedFractionDigits = Math.max(fromFranctionDigits, toFractionDigits);

         //if (toFractionDigits != 2) {

         //    throw new ConvertorException("Can't process currency with defaultFractionDigits!=2, " + toCurrency + " has " + toFractionDigits + " defaultFractionDigits");

         //}

         //if (fromFranctionDigits != 2) {

         //    throw new ConvertorException("Can't process currency with defaultFractionDigits!=2, " + fromCurrency + " has " + fromFranctionDigits + " defaultFractionDigits");

         //}

         if (amount.signum() == -1) {

             throw new RuntimeException("Can convert only non-negative value, current value is " + amount);

         }

         MathContext context = new MathContext(0, RoundingMode.DOWN);

         BigDecimal from;

         BigDecimal to;

         if (convertBack) {

             //converting in reverted way

             to = rate.getFromValue();

             from = rate.getToValue();

         } else {

             //converting in normal way

             from = rate.getFromValue();

             to = rate.getToValue();

         }

         BigDecimal amountCent = amount.movePointRight(usedFractionDigits);

         final BigDecimal multiplied = amountCent.multiply(to, context);

         BigDecimal[] division = multiplied.divideAndRemainder(from, context);

         if (!remainderAllowed && !(BigDecimal.ZERO.equals(division[1]))) {

             throw new RuntimeException("Remained is not allowed - remaining amount is " + division[1] + " cents");

         } else {

             result.setRemainder(BigDecimal.ZERO.setScale(fromFranctionDigits));

         }

         BigDecimal converted = division[0].movePointLeft(usedFractionDigits);

         converted = converted.setScale(toFractionDigits,RoundingMode.DOWN); //XXX ugly

         result.setConverted(converted);

         BigDecimal[] convertedInBase = converted.multiply(from).divideAndRemainder(to);

         BigDecimal x2 = convertedInBase[0].add(convertedInBase[1]);

         BigDecimal remainder = amount.subtract(x2);

         result.setRemainder(remainder);

         //System.out.println("ConvertedInBase="+Arrays.asList(convertedInBase)+":"+x2 +" ("+amount+") ["+converted+"] <"+from+","+to+"> ->"+remainder);

         return result;

     }

     private ConversionResult convertValue(ConvertorCurrency fromCurrency, ConvertorCurrency toCurrency,BigDecimal amount, boolean convertBack,boolean reversibleExRate,Date date) throws RuntimeException {

         //result.setRemainder(...);

         if (!dateIsInLimit(date)) {

             return null;

         }        

         if (convertors.length==0) {

             return convertUsingSimpleConvertor(fromCurrency, toCurrency, reversibleExRate, amount, convertBack,date);

         } else {

             ConversionResult result = null;

             for (int i = 0;i<convertors.length;i++) {

                 Convertor subConvertor = convertors[i];

                 result = subConvertor.convertValue(fromCurrency, toCurrency, amount, convertBack, reversibleExRate,date);

                 if (result!=null) {

                     break;

                 }

             }

             return result;

         }

     }

     /**

      * Convert <code>value</code> from <code>fromCurrency</code> to <code>toCurrency</code>.

      * <p>

      * Exchange rate is provided by exchange rate provider which was specified when Convertor was created.

      * This method is using only exchange rate from->to and not trying to use reverted excange rate to->from.

      * <p>

      * This method is using date from <code>IDateProviderEngine</code> to get exchange rate (see {@link #getDateProvider() }.

      * 

      * @param fromCurrency Source currency to convert from.

      * @param toCurrency Target currency to convert to.

      * @param value Value in source currency which should be converted.

      * @return Return conversion result.

      * @since version2

      * @throws ConversionNotSupportedException If conversion from <code>fromCurrency</code> to <code>toCurrency</code> is not supported.

      */

     public ConversionResult convert(ConvertorCurrency fromCurrency, ConvertorCurrency toCurrency, BigDecimal value) {

         Date defaultDate = dateProvider.getCurrentDate();

         ConversionResult result = convertValue(fromCurrency, toCurrency, value, false,false,defaultDate);

         if (result==null) {

             //throw new ConversionNotSupportedException("Conversion from " + fromCurrency + " to " + toCurrency + " is not supported");

             throw new ConversionNotSupportedException(fromCurrency.getCurrencyCode(),toCurrency.getCurrencyCode(),false);

         }

         return result;

     }

     /**

      * Same as {@link #convert(ConvertorCurrency, ConvertorCurrency, java.math.BigDecimal)} but using provided rate instead of

      * <code>IDateProviderEngine</code>.

      * 

      * @param fromCurrency Source currency to convert from.

      * @param toCurrency Target currency to convert to.

      * @param value Value in source currency which should be converted.

      * @return Return conversion result.

      * @param date Conversion date

      * @return Return conversion result.

      */

     public ConversionResult convert(ConvertorCurrency fromCurrency, ConvertorCurrency toCurrency, BigDecimal value, Date date) {

         ConversionResult result = convertValue(fromCurrency, toCurrency, value, false,false,date);

         if (result==null) {

             throw new ConversionNotSupportedException(fromCurrency.getCurrencyCode(),toCurrency.getCurrencyCode(),false);

         }

         return result;

     }    

     /**

      * Convert <code>value</code> from <code>fromCurrency</code> to <code>toCurrency</code>.

      * Exchange rate is provided by exchange rate provider which was specified when Convertor was created.

      * <p>

      *  This method is using only exchange rate from->to and if not found, it is trying to use reverted excange rate to->from.

      * <p>

      * This method is using date from <code>IDateProviderEngine</code> to get exchange rate (see {@link #getDateProvider() }.

      * 

      * @param fromCurrency Source currency to convert from.

      * @param toCurrency Target currency to convert to.

      * @param value Value in source currency which should be converted.

      * @return Return conversion result.

      * @since version2

      * @throws ConversionNotSupportedException If conversion from <code>fromCurrency</code> to <code>toCurrency</code> 

      *         is not supported and neither conversion from <code>toCurrency</code> to <code>fromCurrency</code> is not supported.

      */

     public ConversionResult convertWithReversibleRates(ConvertorCurrency fromCurrency, ConvertorCurrency toCurrency, BigDecimal value) {

         Date defaultDate = dateProvider.getCurrentDate();

         ConversionResult result = convertValue(fromCurrency, toCurrency, value, false,true,defaultDate);

         if (result==null) {

             //throw new ConversionNotSupportedException("Neither onversion nor reverted conversion from " + fromCurrency + " to " + toCurrency + "  is not supported,");

             throw new ConversionNotSupportedException(fromCurrency.getCurrencyCode(),toCurrency.getCurrencyCode(),true);

         }

         return result;

     }

     /**

      * Same as {@link #convertWithReversibleRates(ConvertorCurrency, ConvertorCurrency, java.math.BigDecimal)} but using provided rate instead of

      * <code>IDateProviderEngine</code>.

      * 

      * @param fromCurrency Source currency to convert from.

      * @param toCurrency Target currency to convert to.

      * @param value Value in source currency which should be converted.

      * @return Return conversion result.

      * @param date Conversion date

      * @return Return conversion result.

      */

     public ConversionResult convertWithReversibleRates(ConvertorCurrency fromCurrency, ConvertorCurrency toCurrency, BigDecimal value, Date date) {

         ConversionResult result = convertValue(fromCurrency, toCurrency, value, false,true,date);

         if (result==null) {

             throw new ConversionNotSupportedException(fromCurrency.getCurrencyCode(),toCurrency.getCurrencyCode(),true);

         }

         return result;

     }

     private boolean dateIsInLimit(Date date) {

         boolean result;

 //        if (date==null) {

 //          result = true;  

 //        } else 

         if (fromDate == null && toDate == null) {

             result = true;

         } else if (fromDate.getTime()<=date.getTime() && date.getTime()<=toDate.getTime()) {

             result = true;

         } else {

             result = false;

         }

         return result;

     }

     public void limitAllowedDates(Date from, Date till) {

         if (from==null) {

             throw new NullPointerException("from Date can't be null");

         }

         if (till==null) {

             throw new NullPointerException("till Date can't be null");

         }

         if (from.getTime()>till.getTime()) {

             throw new IllegalArgumentException("From date "+from+" must be before tii date "+till);

         }

         this.fromDate = from;

         this.toDate = till;

     }

     /** Return current date provider.

      * @return Returns current date provider.

      */

     public IDateProviderEngine getDateProvider() {

         return dateProvider;

     }

     /**

      * Set date provider. Date provider is used to get "current date". Current date 

      * is used by methods {@link #convert(ConvertorCurrency, ConvertorCurrency, java.math.BigDecimal)} and  

      * {@link #convertWithReversibleRates(ConvertorCurrency, ConvertorCurrency, java.math.BigDecimal)}.

      * 

      * @param dateProvider Date provider which should be used by Convertor.

      */

     public void setDateProvider(IDateProviderEngine dateProvider) {

         this.dateProvider = dateProvider;

     }

 }