1.1 --- /dev/null	Thu Jan 01 00:00:00 1970 +0000
     1.2 +++ b/task2/solution13/src/org/apidesign/apifest08/currency/Convertor.java	Wed Oct 01 10:43:05 2008 +0200
     1.3 @@ -0,0 +1,105 @@
     1.4 +package org.apidesign.apifest08.currency;
     1.5 +
     1.6 +import java.math.BigDecimal;
     1.7 +import java.math.MathContext;
     1.8 +import java.math.RoundingMode;
     1.9 +
    1.10 +/** Convertor able to convert amount from one currency to other currency.
    1.11 + * 
    1.12 + * Exchange rate is provided by {@link ExchangeRateProvider}.
    1.13 + */
    1.14 +public class Convertor {
    1.15 +    boolean remainderAllowed = false; //if false, remained is not allowed (should be true ideally, but can't handle it now)
    1.16 +    ExchangeRateProvider exchangeRateProvider; 
    1.17 +    
    1.18 +    private Convertor() {
    1.19 +        
    1.20 +    }
    1.21 +    
    1.22 +    /**
    1.23 +     * Static method used to create convertor.
    1.24 +     * 
    1.25 +     * @param exchangeRateProvider {@link ExchangeRateProvider} used to get exchange rate.
    1.26 +     * 
    1.27 +     * @return Returns <code>Convertor</code> which can be used to convert money.
    1.28 +     */
    1.29 +    public static Convertor createConvertor(ExchangeRateProvider exchangeRateProvider) {
    1.30 +        Convertor c = new Convertor();
    1.31 +
    1.32 +        c.exchangeRateProvider = exchangeRateProvider;
    1.33 +        return c;
    1.34 +    }
    1.35 +    
    1.36 +    /**
    1.37 +     * Convert <code>amount</code> from <code>fromCurrency</code> to <code>toCurrency</code> as specified
    1.38 +     * in <code>ExchangeRateProvider</code>.
    1.39 +     * 
    1.40 +     * @param amount Amount which should be converted. Can't be negative value (can be zero or positive).
    1.41 +     * @return Return <code>ConversionResult</code> which holds conversion result.
    1.42 +     */
    1.43 +    public ConversionResult convert(BigDecimal amount) {
    1.44 +        return convertValue(amount, false);
    1.45 +    }
    1.46 +    
    1.47 +    /**
    1.48 +     * Convert <code>amount</code> from <code>toCurrency</code> to <code>fromCurrency</code> as specified
    1.49 +     * in <code>ExchangeRateProvider</code>. This is <em>reverted</em> order than suggested by  names of currency fields in <code>ExchangeRate</code>.
    1.50 +     * 
    1.51 +     * @param amount Amount which should be converted. Can't be negative value (can be zero or positive).
    1.52 +     * @return Return <code>ConversionResult</code> which holds conversion result.
    1.53 +     */
    1.54 +    public ConversionResult convertBack(BigDecimal amount) {
    1.55 +        return convertValue(amount, true);
    1.56 +    }
    1.57 +
    1.58 +    private ConversionResult convertValue(BigDecimal amount, boolean convertBack) throws RuntimeException {
    1.59 +        ConversionResult result = new ConversionResult();
    1.60 +        
    1.61 +        ExchangeRate rate = exchangeRateProvider.getExchangeRate();
    1.62 +        int fromFranctionDigits = exchangeRateProvider.getFromCurrency().getDefaultFractionDigits();
    1.63 +        int toFractionDigits = exchangeRateProvider.getToCurrency().getDefaultFractionDigits();
    1.64 +         
    1.65 +        if (toFractionDigits!=2) {
    1.66 +            throw new RuntimeException("Can't process currency with defaultFractionDigits!=2, "+exchangeRateProvider.getToCurrency()+" has "+toFractionDigits+" defaultFractionDigits");
    1.67 +        }
    1.68 +        if (fromFranctionDigits!=2) {
    1.69 +            throw new RuntimeException("Can't process currency with defaultFractionDigits!=2, "+exchangeRateProvider.getFromCurrency()+" has "+fromFranctionDigits+" defaultFractionDigits");
    1.70 +        }
    1.71 +        
    1.72 +        if (amount.signum()==-1) {
    1.73 +            throw new RuntimeException("Can convert only non-negative value, current value is "+amount);
    1.74 +        }
    1.75 +        
    1.76 +        
    1.77 +        MathContext context = new MathContext(0, RoundingMode.DOWN);
    1.78 +        
    1.79 +        BigDecimal from;
    1.80 +        BigDecimal to;
    1.81 +        if (convertBack) {
    1.82 +            //converting in reverted way
    1.83 +            to = rate.getFromValue();
    1.84 +            from = rate.getToValue();
    1.85 +        } else {
    1.86 +            //converting in mornak way
    1.87 +            from = rate.getFromValue();
    1.88 +            to = rate.getToValue();
    1.89 +        }
    1.90 +
    1.91 +        BigDecimal amountCent = amount.movePointRight(2);
    1.92 +        
    1.93 +        final BigDecimal multiplied = amountCent.multiply(to,context);
    1.94 +        BigDecimal[] division = multiplied.divideAndRemainder(from,context);
    1.95 +
    1.96 +        if (!remainderAllowed && !(BigDecimal.ZERO.equals(division[1]))) {
    1.97 +            throw new RuntimeException("Remained is not allowed - remaining amount is " + division[1]+ " cents");
    1.98 +        } else {
    1.99 +            result.setRemainder(BigDecimal.ZERO);
   1.100 +        }
   1.101 +        
   1.102 +        final BigDecimal converted = division[0].movePointLeft(2);        
   1.103 +        result.setConverted(converted);
   1.104 +        //result.setRemainder(...);
   1.105 +
   1.106 +        return result;
   1.107 +    }
   1.108 +}