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LDPath Functions for HTML content.
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/**
 * Copyright (C) 2013 Salzburg Research.
 *
 * Licensed 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 at.newmedialab.ldpath.model.functions;

import at.newmedialab.ldpath.api.backend.RDFBackend;
import at.newmedialab.ldpath.api.functions.SelectorFunction;
import at.newmedialab.ldpath.model.transformers.StringTransformer;
import at.newmedialab.ldpath.util.Collections;
import org.jsoup.Jsoup;
import org.jsoup.safety.Whitelist;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.util.ArrayList;
import java.util.Collection;
import java.util.Iterator;
import java.util.List;

/**
 * Function to clean up HTML and remove all script and style elements from the content.
 * 
 * Author: Sebastian Schaffert
 */
public class CleanHtmlFunction extends SelectorFunction {

    private final StringTransformer transformer = new StringTransformer();

    private Logger log = LoggerFactory.getLogger(CleanHtmlFunction.class);

    public CleanHtmlFunction() {
    }

    /**
     * Apply the function to the list of nodes passed as arguments and return the result as type T.
     * Throws IllegalArgumentException if the function cannot be applied to the nodes passed as argument
     * or the number of arguments is not correct.
     *
     * @param args a list of KiWiNodes
     * @return
     */
    @Override
    public Collection apply(RDFBackend backend, Node context, Collection... args) throws IllegalArgumentException {
        Iterator it;
        if(args.length < 1){
            log.debug("clean HTML from context {}",context);
            it = java.util.Collections.singleton(context).iterator();
        } else {
            log.debug("clean HTML from parameters");
            it = Collections.iterator(args);
        }
        List result = new ArrayList();
        while(it.hasNext()) {
            Node node = it.next();
            String cleaned = Jsoup.clean(transformer.transform(backend, node), Whitelist.basic());
            result.add(backend.createLiteral(cleaned));
        }
        return result;
    }

    /**
     * Return the name of the NodeFunction for registration in the function registry
     *
     * @return
     * @param backend
     */
    @Override
    public String getLocalName() {
        return "cleanHtml";
    }

    /**
     * A string describing the signature of this node function, e.g. "fn:content(uris : Nodes) : Nodes". The
     * syntax for representing the signature can be chosen by the implementer. This method is for informational
     * purposes only.
     *
     * @return
     */
    @Override
    public String getSignature() {
        return "fn:cleanHtml(content: LiteralList) : LiteralList";
    }

    /**
     * A short human-readable description of what the node function does.
     *
     * @return
     */
    @Override
    public String getDescription() {
        return "Function to clean up HTML and remove all script and style elements from the content. Can be used in-path, using the current context nodes as argument.";
    }
}