/*
 * Copyright (c) 2014 Cisco Systems, Inc. and others.  All rights reserved.
 *
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Public License v1.0 which accompanies this distribution,
 * and is available at http://www.eclipse.org/legal/epl-v10.html
 */
package org.opendaylight.yangtools.concepts.util;

import java.math.BigDecimal;
import java.math.BigInteger;
import java.util.Collections;
import java.util.HashSet;
import java.util.Set;
import java.util.concurrent.atomic.AtomicInteger;
import java.util.concurrent.atomic.AtomicLong;

import org.opendaylight.yangtools.concepts.Immutable;
import org.opendaylight.yangtools.concepts.Mutable;

public class Immutables {

    private Immutables() {
        throw new UnsupportedOperationException("Helper class");
    }

    public static final Set<Class<?>> KNOWN_IMMUTABLES = Immutables.<Class<?>> asHashSet(
            //
            Integer.class, Short.class, BigDecimal.class, BigInteger.class, Byte.class, Character.class, Double.class,
            Float.class);

    /**
     * Determines if object is known to be immutable
     * 
     * Note: This method may return false to immutable objects which
     * immutability is not known, was defined not using concepts term.
     * 
     * @param o
     *            Reference to check
     * @return true if object is known to be immutable false otherwise.
     */
    public static boolean isImmutable(Object o) {
        if (o == null) {
            throw new IllegalArgumentException("Object should not be null");
        }
        if (o instanceof Mutable) {
            return false;
        } else if (o instanceof Immutable) {
            return true;
        } else if (o instanceof String) {
            return true;
        } else if (KNOWN_IMMUTABLES.contains(o.getClass())) {
            return true;
        }
        return false;
    }

    private static boolean isNumberImmutable(Number o) {
        if(o instanceof AtomicInteger) {
            return false;
        } else if(o instanceof AtomicLong) {
            return false;
        } else if(o instanceof Short) {
            return true;
        }
        return false;
    }

    @SafeVarargs
    private static <E> Set<E> asHashSet(E... list) {
        HashSet<E> ret = new HashSet<>();
        for (E e : list) {
            ret.add(e);
        }
        return Collections.unmodifiableSet(ret);
    }
}