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;

        }

    }

}