/*
 *  eXist Open Source Native XML Database: Extension module
 *  Copyright (C) 2008 Josef Willenborg
 *  jwillenborg@mpiwg-berlin.mpg.de
 *  http://www.mpiwg-berlin.mpg.de
 *  
 *  This program is free software; you can redistribute it and/or
 *  modify it under the terms of the GNU Lesser General Public License
 *  as published by the Free Software Foundation; either version 2
 *  of the License, or (at your option) any later version.
 *  
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU Lesser General Public License for more details.
 *  
 *  You should have received a copy of the GNU Lesser General Public License
 *  along with this program; if not, write to the Free Software
 *  Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 *  
 *  $Id: TextModule.java $
 */
package org.exist.xquery.modules.mpdltext;

import java.io.UnsupportedEncodingException;
import java.util.ArrayList;

import org.exist.dom.QName;
import org.exist.memtree.DocumentImpl;
import org.exist.memtree.MemTreeBuilder;
import org.exist.xquery.BasicFunction;
import org.exist.xquery.Cardinality;
import org.exist.xquery.FunctionSignature;
import org.exist.xquery.XPathException;
import org.exist.xquery.XQueryContext;
import org.exist.xquery.value.Sequence;
import org.exist.xquery.value.SequenceType;
import org.exist.xquery.value.Type;

/**
 * @author Josef Willenborg (jwillenborg@mpiwg-berlin.mpg.de)
 */
public class GetBig5EncodedTerms extends BasicFunction {

	public final static FunctionSignature signature =
		new FunctionSignature(
			new QName("get-big5-encoded-terms", MPDLTextModule.NAMESPACE_URI, MPDLTextModule.PREFIX),
			"bla bla",
			new SequenceType[] { new SequenceType(Type.STRING, Cardinality.ZERO_OR_MORE) },
			new SequenceType(Type.NODE, Cardinality.EXACTLY_ONE));

	public GetBig5EncodedTerms(XQueryContext context) {
		super(context, signature);
	}

	public Sequence eval(Sequence[] args, Sequence contextSequence) throws XPathException {
    Sequence luceneQueryStringSeq = args[0];
    String luceneQueryString = "";
		if (luceneQueryStringSeq.isEmpty())
			return Sequence.EMPTY_SEQUENCE;
		luceneQueryString = luceneQueryStringSeq.getStringValue();
		ArrayList<String> queryTerms = getTermsFromLuceneQuery(luceneQueryString);
    int size = queryTerms.size();
    MemTreeBuilder builder = context.getDocumentBuilder();
    builder.startElement("", "big5-mappings", "big5-mappings", null);
    for (int i=0; i<size; i++) {
      String queryTerm = queryTerms.get(i);
      String big5EncodedQueryTerm = encodeBig5(queryTerm);
      builder.startElement("", "big5-mapping", "big5-mapping", null);
      builder.startElement("", "term", "term", null);
      builder.characters(queryTerm);
      builder.endElement();
      builder.startElement("", "mapping", "mapping", null);
      builder.characters(big5EncodedQueryTerm);
      builder.endElement();
      builder.endElement();
    }
    builder.endElement();
    DocumentImpl doc = ((DocumentImpl)builder.getDocument());

		return doc;
	}
	
  // TODO method is only simple: proof all Lucene cases
  private ArrayList<String> getTermsFromLuceneQuery(String queryString) {
    ArrayList<String> terms = new ArrayList<String>();
    String[] variantTokens = queryString.split(" ");  // TODO throw the phrases away (e.g.: "bla bla bla")
    for (int i = 0; i < variantTokens.length; i++) {
      String token = variantTokens[i];
      if (! (token.contains("*") || token.contains("?") || token.contains("~") || token.contains("-") || token.contains("+") || token.contains("^") || token.contains("OR") || token.contains("AND") || token.contains("NOT"))) {
        terms.add(token);
      }
    }
    return terms;
  }

  private String encodeBig5(String inputStr) {
    String resultStr = "";
    String charset = "big5";
    try {
      byte[] resultBytes = inputStr.getBytes(charset);
      for (int i=0; i < resultBytes.length; i++) {
        byte b = resultBytes[i];
        int unsigned = unsignedByteToInt(b);
        String hexStr = Integer.toHexString(unsigned);
        resultStr = resultStr + "%" + hexStr;
      }
    } catch (UnsupportedEncodingException e) {
      
    }
    return resultStr;
  }

  private int unsignedByteToInt(byte b) {
    return (int) b & 0xFF;
  }

}