package org.apidesign.apifest08.currency;

 import java.util.Currency;

 import java.util.Date;

 import org.apidesign.apifest08.currency.Convertor.ConversionRequest;

 import org.apidesign.apifest08.currency.Convertor.ConversionResult;

 /**

  * This {@link Convertor} delegates to an underlying one, provided that the request specifies time between from (included) and till (excluded).

  * Otherwise it just refuses to convert.

  * @author jdvorak

  */

 public class TimeRangeSpecificConvertor extends DelegatingConvertor {

     private final Date from;

     private final Date till;

     /**

      * A new time range specific convertor.

      * @param old the underlying convertor one delegates to

      * @param from the beginning of the time interval

      * @param till the end of the time interval

      * @throws IllegalArgumentException unless from comes before till

      */

     public TimeRangeSpecificConvertor( final Convertor old, final Date from, final Date till ) {

         super( old );

         this.from = from;

         this.till = till;

         if (! from.before( till ) ) {

             throw new IllegalArgumentException( "from must come before till" );

         }

     }

     /**

      * The beginning of the time interval.

      */

     public Date getFrom() {

         return from;

     }

     /**

      * The end of the time interval.

      */

     public Date getTill() {

         return till;

     }

     /**

      * The conversion method.

      * Takes a {@link TimeSpecificConversionRequest}, other {@link ConversionRequest}s will result in an exception being thrown.

      * @param req the request; must not be null; must be {@link TimeSpecificConversionRequest} or a subclass thereof

      * @return the response

      * @throws IllegalRequestSubtypeException iff req is not instance of {@link TimeSpecificConversionRequest}

      */

     @Override

     public ConversionResult convert( final ConversionRequest req ) {

         if ( req instanceof TimeSpecificConversionRequest ) {

             final Date time = ( (TimeSpecificConversionRequest) req ).getTime();

             if ( ( from == null || !from.after(time) ) && ( till == null || time.before(till) ) ) {

                 return super.convert( req );

             } else {

                 return new ConversionResult( null );

             }

         } else {

             throw new IllegalRequestSubtypeException( this.getClass().getName() + ".convert() requires a TimeSpecificConversionRequest to be passed in" );

         }

     }

     /**

      * The request for converting a monetary amount into another currency using the conditions that apply at a particular time.

      * Immutable.

      */

     public static class TimeSpecificConversionRequest extends Convertor.ConversionRequest {

         private final Date time;

         /**

          * A request to convert srcAmount into tgtCurrency at the current time.

          * @param srcAmount the source amount; must not be null

          * @param tgtCurrency the currency we want it in afterwards; must not be null

          */

         public TimeSpecificConversionRequest( final MonetaryAmount srcAmount, final Currency tgtCurrency ) {

             this( srcAmount, tgtCurrency, new Date() );

         }

         /**

          * A request to convert srcAmount into tgtCurrency at given time.

          * @param srcAmount the source amount; must not be null

          * @param tgtCurrency the currency we want it in afterwards; must not be null

          * @param time the time instant when the conversion is to be carried out

          */

         public TimeSpecificConversionRequest( final MonetaryAmount srcAmount, final Currency tgtCurrency, final Date time ) {

             super( srcAmount, tgtCurrency );

             this.time = time;

             if ( time == null ) {

                 throw new NullPointerException( "The time of conversion" );

             }

         }

         /**

          * The time as of which the conversion is to be carried out.

          */

         public Date getTime() {

             return time;

         }

     }

 }