package org.apidesign.apifest08.currency;

import java.math.BigDecimal;

import java.math.RoundingMode;

/**

 * This class encapsulates settings for currency conversion

 * We can use it eg. for uptime options etc. in future versions

 *

 * @author Ladislav Vitasek

 */

final public class ConversionProperties {

    private final ConversionRatioProvider conversionRatioProvider;

    private final RoundingMode roundingMode;

    /**

     * Returns conversion constants - conversion operation is invertable

     * Default

     */

    private final static class FixedBidirectionalRatioConversion implements ConversionRatioProvider {

        private final BigDecimal currency1ToCurrency2Constant;

        private final BigDecimal currency2ToCurrency1Constant;

        private static final int SCALE_MAX_DEFAULT = 20;

        /**

         * Constructor

         * @param ratioConstant fixed ratio constant

         * @param mode math rounding mode

         * @throws IllegalArgumentException if conversion value is <= 0

         */

        private FixedBidirectionalRatioConversion(BigDecimal ratioConstant, RoundingMode mode) {

            if (ratioConstant.compareTo(BigDecimal.ZERO) <= 0)

                throw new IllegalArgumentException("Conversion value cannot be <= 0");

            this.currency1ToCurrency2Constant = ratioConstant;

            this.currency2ToCurrency1Constant = BigDecimal.ONE.setScale(SCALE_MAX_DEFAULT).divide(ratioConstant, mode);

        }

        public BigDecimal getCurrency1ToCurrency2Constant() {

            return currency1ToCurrency2Constant;

        }

        public BigDecimal getCurrency2ToCurrency1Constant() {

            return currency2ToCurrency1Constant;

        }

    }

    /**

     * Returns new instance Conversion properties - fixed conversion ratio - both directions

     * Default max scale is set to 20

     *

     * @param conversionConstant value of constant for conversion

     * @param roundingMode       math rounding mode

     * @return new instance of ConversionProperties class

     * @throws IllegalArgumentException if conversion constant is <= 0 

     * @see org.apidesign.apifest08.currency.ConversionProperties.FixedBidirectionalRatioConversion

     */

    public static ConversionProperties create(BigDecimal conversionConstant, RoundingMode roundingMode) {

        return create(new FixedBidirectionalRatioConversion(conversionConstant, roundingMode), roundingMode);

    }

    /**

     * Returns new instance Conversion properties

     *

     * @param conversionRatioProvider provider for conversion constants

     * @param roundingMode       math rounding mode

     * @return new instance of ConversionProperties class

     */

    public static ConversionProperties create(ConversionRatioProvider conversionRatioProvider, RoundingMode roundingMode) {

        if (conversionRatioProvider == null || roundingMode == null)

            throw new NullPointerException();

        return new ConversionProperties(conversionRatioProvider, roundingMode);

    }

    /**

     * Returns new instance Conversion properties with values set to conversionConstant=BigDecimal.ONE

     * and roundingMode=RoundingMode.HALF_EVEN

     * 

     * Conversion is bidirectional.

     *

     * @return

     */

    public static ConversionProperties createDefault() {

        return create(BigDecimal.ONE, RoundingMode.HALF_EVEN);

    }

    private ConversionProperties(ConversionRatioProvider conversionRatioProvider, RoundingMode roundingMode) {

        this.conversionRatioProvider = conversionRatioProvider;

        this.roundingMode = roundingMode;

    }

    public RoundingMode getRoundingMode() {

        return roundingMode;

    }

    public ConversionRatioProvider getConversionRatioProvider() {

        return conversionRatioProvider;

    }

}