/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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.apache.tinkerpop.gremlin.structure.util.reference;

import org.apache.tinkerpop.gremlin.structure.Element;
import org.apache.tinkerpop.gremlin.structure.Graph;
import org.apache.tinkerpop.gremlin.structure.util.ElementHelper;
import org.apache.tinkerpop.gremlin.structure.util.Attachable;
import org.apache.tinkerpop.gremlin.structure.util.empty.EmptyGraph;

import java.io.Serializable;

/**
 * @author Marko A. Rodriguez (http://markorodriguez.com)
 */
public abstract class ReferenceElement<E extends Element> implements Element, Serializable, Attachable<E> {

    protected static final String EMPTY_STRING = "";

    protected Object id;

    protected ReferenceElement() {

    }

    public ReferenceElement(final Element element) {
        this.id = element.id();
    }

    @Override
    public Object id() {
        return this.id;
    }

    @Override
    public String label() {
        return EMPTY_STRING;
    }

    @Override
    public Graph graph() {
        return EmptyGraph.instance();
    }

    @Override
    public int hashCode() {
        return ElementHelper.hashCode(this);
    }

    @SuppressWarnings("EqualsWhichDoesntCheckParameterClass")
    @Override
    public boolean equals(final Object other) {
        return ElementHelper.areEqual(this, other);
    }

    public E get() {
        return (E) this;
    }
}