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This project contains some of the configurable modules used within the Heritrix application to crawl the web. The modules in this project can be used in applications other than Heritrix, however.

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/*
 *  This file is part of the Heritrix web crawler (crawler.archive.org).
 *
 *  Licensed to the Internet Archive (IA) by one or more individual 
 *  contributors. 
 *
 *  The IA 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.archive.modules.extractor;

import java.io.Serializable;


/**
 * The context of link discovery.  Different subclasses represent different
 * kinds of contexts.
 * 
 * @author pjack
 */
public abstract class LinkContext implements Serializable {
    private static final long serialVersionUID = 4117965561244539334L;


    /** Class for representing handy default LinkContext values. */
    public static class SimpleLinkContext extends LinkContext {

        private static final long serialVersionUID = 1L;

        private String desc;
        
        public SimpleLinkContext(String desc) {
            this.desc = desc;
        }
        
        public String toString() {
            return desc;
        }
    }

    /** Stand-in value for embeds without other context. */
    final public static LinkContext EMBED_MISC
     = new SimpleLinkContext("=EMBED_MISC");

    /** Stand-in value for JavaScript-discovered urls without other context. */
    final public static LinkContext JS_MISC
     = new SimpleLinkContext("=JS_MISC");
    
    /** Stand-in value for navlink urls without other context. */
    final public static LinkContext NAVLINK_MISC
     = new SimpleLinkContext("=NAVLINK_MISC");
    
    /** 
     * Stand-in value for speculative/aggressively extracted urls without 
     * other context. 
     */
    final public static LinkContext SPECULATIVE_MISC
     = new SimpleLinkContext("=SPECULATIVE_MISC");

    /** 
     * Stand-in value for inferred urls without  other context. 
     */
    final public static LinkContext INFERRED_MISC
        = new SimpleLinkContext("=INFERRED_MISC");
    
    /** Stand-in value for prerequisite urls without other context. */
    final public static LinkContext PREREQ_MISC
     = new SimpleLinkContext("=PREREQ_MISC");

    public boolean equals(Object o) {
        if (o == this) {
            return true;
        }
        if (!(o instanceof LinkContext)) {
            return false;
        }
        return o.toString().equals(toString());
    }
    
    
    public int hashCode() {
        return toString().hashCode();
    }
}