japod@57: /*
japod@57:  * To change this template, choose Tools | Templates
japod@57:  * and open the template in the editor.
japod@57:  */
japod@57: 
japod@57: package org.apidesign.apifest08.currency.anothervendor;
japod@57: 
japod@57: import java.math.BigDecimal;
japod@57: import java.util.Currency;
japod@57: import java.util.Iterator;
japod@57: import org.apidesign.apifest08.currency.Convertor;
japod@57: import org.apidesign.apifest08.currency.IllegalRequestSubtypeException;
japod@57: import org.apidesign.apifest08.currency.MonetaryAmount;
japod@57: 
japod@57: 
japod@57: /**
japod@57:  * A convertor that changes the rate by a step amount on every conversion it performs.
japod@57:  * @author jdvorak
japod@57:  */
japod@57: public class ZigZaggingBidirectionalConvertor implements Convertor {
japod@57: 
japod@57:     private final MonetaryAmount srcRateAmount;
japod@57:     
japod@57:     private final Currency tgtCurrency;
japod@57:     
japod@57:     private final Iterator<BigDecimal> rateIterator;
japod@57: 
japod@57:     /**
japod@57:      * Costructor with the precise amounts.
japod@57:      * @param srcRateAmount
japod@57:      * @param tgtCurrency
japod@57:      * @param startAmount
japod@57:      * @param endAmount
japod@57:      * @param stepAmount
japod@57:      */
japod@57:     public ZigZaggingBidirectionalConvertor( final MonetaryAmount srcRateAmount, final Currency tgtCurrency, final BigDecimal startAmount, final BigDecimal endAmount, final BigDecimal stepAmount ) {
japod@57:         this.srcRateAmount = srcRateAmount;
japod@57:         this.tgtCurrency = tgtCurrency;
japod@57:         this.rateIterator = new ZigZaggingBigDecimalIterator( startAmount, endAmount, stepAmount );
japod@57:     }
japod@57: 
japod@57:     /**
japod@57:      * Do the conversion; updates the rate.
japod@57:      * @param req
japod@57:      * @return
japod@57:      * @throws org.apidesign.apifest08.currency.IllegalRequestSubtypeException
japod@57:      */
japod@57:     public synchronized ConversionResult convert( ConversionRequest req ) throws IllegalRequestSubtypeException {
japod@57:         if ( tgtCurrency.equals( req.getTgtCurrency() ) ) {
japod@57:             if ( srcRateAmount.getCurrency().equals( req.getSrcAmount().getCurrency() ) ) {
japod@57:                 final BigDecimal tgtRateAmount = rateIterator.next();
japod@57:                 final BigDecimal tgtAmount = req.getSrcAmount().getAmount().multiply( tgtRateAmount ).divide( srcRateAmount.getAmount() );
japod@57:                 return new ConversionResult( new MonetaryAmount( tgtAmount, tgtCurrency ) );
japod@57:             }
japod@57:         }
japod@57:         if ( srcRateAmount.getCurrency().equals( req.getTgtCurrency() ) ) {
japod@57:             if ( tgtCurrency.equals( req.getSrcAmount().getCurrency() ) ) {
japod@57:                 final BigDecimal tgtRateAmount = rateIterator.next();
japod@57:                 final BigDecimal tgtAmount = req.getSrcAmount().getAmount().multiply( srcRateAmount.getAmount() ).divide( tgtRateAmount );
japod@57:                 return new ConversionResult( new MonetaryAmount( tgtAmount, srcRateAmount.getCurrency() ) );
japod@57:             }
japod@57:         }
japod@57:         return new ConversionResult( null );
japod@57:     }
japod@57: 
japod@57: }
japod@57: 
japod@57: /**
japod@57:  * An iterator that goes zig first, then zag, then zig again, then zag again, ad libitum.
japod@57:  * @author jdvorak
japod@57:  */
japod@57: class ZigZaggingBigDecimalIterator implements Iterator<BigDecimal> {
japod@57: 
japod@57:     private BigDecimal zigBounce;
japod@57:     
japod@57:     private BigDecimal zagBounce;
japod@57:     
japod@57:     private BigDecimal step;
japod@57:     
japod@57:     private BigDecimal currentValue;
japod@57:     
japod@57:     protected ZigZaggingBigDecimalIterator( final BigDecimal zagBounce, final BigDecimal zigBounce, final BigDecimal step ) {
japod@57:         this. zigBounce = zigBounce;
japod@57:         this.zagBounce = zagBounce;
japod@57:         this.currentValue = zagBounce;
japod@57:         this.step = step;
japod@57:         
japod@57:         if (  zigBounce == null ) {
japod@57:             throw new NullPointerException( "zigAmount" );
japod@57:         }
japod@57:         if ( zagBounce == null ) {
japod@57:             throw new NullPointerException( "zagAmount" );
japod@57:         }
japod@57:         if ( step == null ) {
japod@57:             throw new NullPointerException( "stepAmount" );
japod@57:         }
japod@57:         final int stepSign = step.signum();
japod@57:         if ( stepSign == 0 ) {
japod@57:             throw new IllegalArgumentException( "stepAmount can't be zero" );
japod@57:         }
japod@57:         if ( stepSign * zigBounce.compareTo( zagBounce ) < 0 ) {
japod@57:             throw new IllegalArgumentException( "stepAmount shall have the same sign as endAmount - startAmount" );
japod@57:         }
japod@57:     }
japod@57:     
japod@57:     public boolean hasNext() {
japod@57:         return true;
japod@57:     }
japod@57: 
japod@57:     public BigDecimal next() {
japod@57:         final BigDecimal result = currentValue;
japod@57:         
japod@57:         currentValue = currentValue.add( step );
japod@57:         final int stepSign = step.signum();
japod@57:         final int currentMinusZigSign = currentValue.compareTo( zigBounce );
japod@57:         if ( stepSign * currentMinusZigSign >= 0 ) {
japod@57:             final BigDecimal temp = zigBounce;
japod@57:             zigBounce = zagBounce;
japod@57:             zagBounce = temp;
japod@57:             step = step.negate();
japod@57:         }
japod@57:         
japod@57:         return result;
japod@57:     }
japod@57: 
japod@57:     public void remove() {
japod@57:         throw new UnsupportedOperationException("Removal is not supported.");
japod@57:     }
japod@57:     
japod@57: }