/*
 *  Copyright (c) 2012, 2013, Credit Suisse (Anatole Tresch), Werner Keil.
 *
 *  Licensed under the Apache License, Version 2.0 (the "License");
 *  you may not use this file except in compliance with the License.
 *  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 */
package org.javamoney.calc;

import javax.money.MonetaryAmount;

import org.javamoney.moneta.Money;

import java.util.function.Predicate;


/**
 * Platform RI: This class decorates an arbitrary {@link MonetaryAmount}
 * instance and ensure no negative values can be created using this instance.
 * Though there are many constraints possible for
 * <p>
 * As required by the {@link MonetaryAmount} interface, this class is
 * <ul>
 * <li>immutable</li>
 * <li>final</li>
 * <li>thread-safe/li>
 * <li>serializable</li>
 * </ul>
 *
 * @author Anatole Tresch
 * @author Werner Keil
 */
public final class ValidatedAmount {

    /**
     * The shared unsigned predicate.
     */
    private static final UnsignedPredicate UNSIGNED_PREDICATE = new UnsignedPredicate();

    /**
     * Creates an unsigned {@link MonetaryAmount} based on the given
     * {@link MonetaryAmount}.
     *
     * @param amount
     * @return an ansigned instance, that can never be negative.
     */
    public static MonetaryAmount unsignedAmount(MonetaryAmount amount) {
        return new ValidatedMoney(amount, UNSIGNED_PREDICATE);
    }

    /**
     * Creates an predicated {@link MonetaryAmount} based on the given
     * {@link MonetaryAmount}.
     *
     * @param amount The amount to decorated.
     * @return a predicated instance, that ensures the given predicate is always
     * ensured on all operations.
     */
    public static MonetaryAmount of(MonetaryAmount amount,
                                    Predicate<MonetaryAmount> predicate) {
        return new ValidatedMoney(amount, predicate);
    }

    /**
     * MonetaryPredicate used for unsigned amounts.
     *
     * @author Anatole Tresch
     */
    private static final class UnsignedPredicate implements
            Predicate<MonetaryAmount> {
        public boolean test(MonetaryAmount amount) {
            return Money.from(amount).signum() >= 0;
        }
    }
}