japod@6: package org.apidesign.apifest08.currency;
japod@6: 
japod@6: import java.math.BigDecimal;
japod@6: import java.math.RoundingMode;
japod@6: 
japod@6: /**
japod@6:  * A rate of conversion from one currency to another.
japod@6:  * @author jdvorak
japod@6:  */
japod@6: public class ConversionRate {
japod@6: 
japod@6:     private final MonetaryAmount srcUnitAmount;
japod@6:     private final MonetaryAmount tgtUnitAmount;
japod@6:     private final int tgtScale;
japod@6:     private final RoundingMode roundingMode;
japod@6: 
japod@6:     /**
japod@6:      * A new conversion rate that gives tgtUnitAmount per every srcUnitAmount.
japod@6:      * @param srcUnitAmount the amount of source currency
japod@6:      * @param tgtUnitAmount the corresponding amount of target currency
japod@6:      * @param tgtScale the scale of the target amounts
japod@6:      * @param roundingMode the rounding mode to use when producing the target amounts
japod@6:      */
japod@6:     public ConversionRate( final MonetaryAmount srcUnitAmount, final MonetaryAmount tgtUnitAmount, final int targetScale, final RoundingMode roundingMode ) {
japod@6:         this.srcUnitAmount = srcUnitAmount;
japod@6:         this.tgtUnitAmount = tgtUnitAmount;
japod@6:         this.tgtScale = targetScale;
japod@6:         this.roundingMode = roundingMode;
japod@6:     }
japod@6: 
japod@6:     /**
japod@6:      * A new conversion rate that gives tgtUnitAmount per every srcUnitAmount, default number of fraction digits and the given rounding mode.
japod@6:      * @param srcUnitAmount the amount of source currency
japod@6:      * @param tgtUnitAmount the corresponding amount of target currency
japod@6:      * @param roundingMode the rounding mode to use
japod@6:      */
japod@6:     public ConversionRate( final MonetaryAmount srcUnitAmount, final MonetaryAmount tgtUnitAmount, final RoundingMode roundingMode ) {
japod@6:         this( srcUnitAmount, tgtUnitAmount, tgtUnitAmount.getCurrency().getDefaultFractionDigits(), roundingMode );
japod@6:     }
japod@6: 
japod@6:     /**
japod@6:      * A new conversion rate that gives tgtUnitAmount per every srcUnitAmount, default number of fraction digits and {@link RoundingMode#HALF_EVEN}.
japod@6:      * @param srcUnitAmount the amount of source currency
japod@6:      * @param tgtUnitAmount the corresponding amount of target currency
japod@6:      */
japod@6:     public ConversionRate( final MonetaryAmount srcUnitAmount, final MonetaryAmount tgtUnitAmount ) {
japod@6:         this( srcUnitAmount, tgtUnitAmount, RoundingMode.HALF_EVEN );
japod@6:     }
japod@6: 
japod@6:     public RoundingMode getRoundingMode() {
japod@6:         return roundingMode;
japod@6:     }
japod@6: 
japod@6:     public MonetaryAmount getSrcUnitAmount() {
japod@6:         return srcUnitAmount;
japod@6:     }
japod@6: 
japod@6:     public int getTgtScale() {
japod@6:         return tgtScale;
japod@6:     }
japod@6: 
japod@6:     public MonetaryAmount getTgtUnitAmount() {
japod@6:         return tgtUnitAmount;
japod@6:     }
japod@6:     
japod@6:     /**
japod@6:      * Multiplies the given amount with the given rate.
japod@6:      * @param srcAmount
japod@6:      * @return
japod@6:      */
japod@6:     public BigDecimal convert( final BigDecimal srcAmount ) {
japod@6:         return srcAmount
japod@6:             .multiply( tgtUnitAmount.getAmount() )
japod@6:             .divide( srcUnitAmount.getAmount(), tgtScale, roundingMode );
japod@6:     }
japod@6:     
japod@6:     /**
japod@6:      * Creates a monetary amount that corresponds to the given source amount multiplied by the rate.
japod@6:      * @param srcAmount the source amount
japod@6:      * @return the monetary amount in the target currency
japod@6:      * @throws IllegalArgumentException if the currency of srcAmount is not equal to the source currency of this rate
japod@6:      */
japod@6:     public MonetaryAmount convert( final MonetaryAmount srcAmount ) {
japod@6:         if ( srcUnitAmount.getCurrency().equals( srcAmount.getCurrency() ) ) {
japod@6:             return new MonetaryAmount( convert( srcAmount.getAmount() ), tgtUnitAmount.getCurrency() );
japod@6:         } else {
japod@6:             throw new IllegalArgumentException( "This rate converts from " + srcUnitAmount.getCurrency() + ", but a conversion from " + srcAmount.getCurrency() + " is attempted" );
japod@6:         }
japod@6:     }
japod@6:     
japod@6: }