/*******************************************************************************
 * Copyright (c) 1998, 2015 Oracle and/or its affiliates. All rights reserved.
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Public License v1.0 and Eclipse Distribution License v. 1.0
 * which accompanies this distribution.
 * The Eclipse Public License is available at http://www.eclipse.org/legal/epl-v10.html
 * and the Eclipse Distribution License is available at
 * http://www.eclipse.org/org/documents/edl-v10.php.
 *
 * Contributors:
 *     Oracle - initial API and implementation from Oracle TopLink
******************************************************************************/
package org.eclipse.persistence.tools.workbench.utility.filters;

import java.io.Serializable;

import org.eclipse.persistence.tools.workbench.utility.string.StringTools;


/**
 * Simple, abstract implementation of <code>Filter</code>
 * that holds on to a criterion object that can be used in the
 * <code>accept(Object)</code> or <code>reject(Object)</code>
 * methods. Subclasses can override either of these methods,
 * depending on which is easier to implement. Note that at least
 * one of these methods <em>must</em> be overridden or
 * an infinite loop will occur. If both of them are overridden,
 * only the <code>accept(Object)</code> method will be used.
 * <p>
 * Simplifies the implementation of straightforward inner classes.
 * Here is an example of a filter that can be used by a
 * <code>FilteringIterator</code> to return only those strings
 * in the nested iterator start with "prefix":
 * <pre>
 *    Filter filter = new SimpleFilter("prefix") {
 *        public boolean accept(Object next) {
 *            return ((String) next).startsWith((String) criterion);
 *        }
 *    };
 * </pre>
 */
public abstract class SimpleFilter
    implements Filter, Cloneable, Serializable
{
    protected final Object criterion;

    private static final long serialVersionUID = 1L;


    /**
     * More useful constructor. The specified criterion can
     * be used by a subclass to "accept" or "reject" objects.
     */
    protected SimpleFilter(Object criterion) {
        super();
        this.criterion = criterion;
    }

    /**
     * Construct a simple filter with a null criterion
     */
    protected SimpleFilter() {
        this(null);
    }

    /**
     * Return whether the the specified object should be "rejected".
     * The semantics of "rejected" is determined by the client.
     */
    protected boolean reject(Object next) {
        return ! this.accept(next);
    }

    /**
     * Return whether the the specified object should be "accepted".
     * The semantics of "accepted" is determined by the client.
     */
    public boolean accept(Object next) {
        return ! this.reject(next);
    }

    /**
     * @see Object#clone()
     */
    public Object clone() {
        try {
            return super.clone();
        } catch (CloneNotSupportedException ex) {
            throw new InternalError();
        }
    }

    /**
     * @see Object#equals(Object)
     */
    public boolean equals(Object o) {
        if ( ! (o instanceof SimpleFilter)) {
            return false;
        }
        SimpleFilter other = (SimpleFilter) o;
        return (this.criterion == null) ?
            (other.criterion == null) : this.criterion.equals(other.criterion);
    }

    /**
     * @see Object#hashCode()
     */
    public int hashCode() {
        return (this.criterion == null) ? 0 : this.criterion.hashCode();
    }

    /**
     * @see Object#toString()
     */
    public String toString() {
        return StringTools.buildToStringFor(this, this.criterion);
    }

}