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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;


/**
 * XPath-like context for HTML discovered URIs.
 * 
 * @author pjack
 */
public class HTMLLinkContext extends LinkContext {
    
    private static final long serialVersionUID = 1L;

    
    final public static HTMLLinkContext META = new HTMLLinkContext("meta");
    final public static HTMLLinkContext A_HREF = new HTMLLinkContext("a", "href");
    final public static HTMLLinkContext IMG_SRC = new HTMLLinkContext("img", "src");
    final public static HTMLLinkContext IMG_SRCSET = new HTMLLinkContext("img", "srcset");
    final public static HTMLLinkContext SOURCE_SRCSET = new HTMLLinkContext("source", "srcset");
    final public static HTMLLinkContext SCRIPT_SRC = new HTMLLinkContext("script", "src");
    final public static HTMLLinkContext META_HREF = new HTMLLinkContext("meta", "href");
    
    
    /**
     * The HTML path to the URL.
     */
    private final String path;
    
    /**
     * return an instance of HTMLLinkContext for attribute {@code attr} in
     * element {@code el}. returns pre-allocated shared instance for common case,
     * or new instance for others.
     * @param el element name
     * @param attr attribute name
     * @return instance of HTMLLinkContext
     */
    public static HTMLLinkContext get(CharSequence el, CharSequence attr) {
        if (attr.equals("href") || attr.equals("HREF")) {
            if (el.equals("a") || el.equals("A")) return A_HREF;
            if (el.equals("meta") || el.equals("META")) return META_HREF;
        } else if (attr.equals("src") || attr.equals("SRC")) {
            if (el.equals("img") || attr.equals("IMG")) return IMG_SRC;
            if (el.equals("script") || attr.equals("SCRIPT")) return SCRIPT_SRC;
        } else if (attr.equals("srcset") || attr.equals("SRCSET")) {
            if (el.equals("img") || attr.equals("IMG")) return IMG_SRCSET;
            if (el.equals("source") || attr.equals("SOURCE")) return SOURCE_SRCSET;
        }
        return new HTMLLinkContext(el, attr);
    }
    /**
     * return an instance of HTMLLinkContext for path {@code path}.
     * returns pre-allocated shared instance for common case, or new instance for others.
     * TODO: most code calling this method builds path by concatenating element name
     * and attribute name. consider changing such code to call {@link #get(CharSequence, CharSequence)}
     * instead. 
     * @param path element and attribute in XLink-like path notation
     * @return instance of HTMLLinkContext
     */
    public static HTMLLinkContext get(String path) {
        if (path.equalsIgnoreCase("a/@href")) return A_HREF;
        if (path.equalsIgnoreCase("meta/@href")) return META_HREF;
        if (path.equalsIgnoreCase("img/@src")) return IMG_SRC;
        if (path.equalsIgnoreCase("img/@srcset")) return IMG_SRCSET;
        if (path.equalsIgnoreCase("source/@srcset")) return SOURCE_SRCSET;
        if (path.equalsIgnoreCase("script/@src")) return SCRIPT_SRC;
        return new HTMLLinkContext(path);
    }
    /**
     * Constructor.
     * 
     * @param path   an XPath-like context, eg "A\@HREF"
     */
    protected HTMLLinkContext(String path) {
        // FIXME: Verify that path really is XPath-like
        this.path = path;
    }

    
    protected HTMLLinkContext(CharSequence element, CharSequence attribute) {
        if (attribute == null) {
            this.path = "";
        } else {
            this.path = element + "/@" + attribute;
        }
    }
    
    @Override
    public String toString() {
        return path;
    }
}