/*
 * eXist Open Source Native XML Database
 * Copyright (C) 2005-2009 The eXist Project
 * http://exist-db.org
 *
 * 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., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
 *  
 *  $Id$
 */
package org.exist.xquery.functions;

import org.apache.log4j.Logger;

import org.exist.dom.QName;
import org.exist.util.XMLChar;
import org.exist.xquery.BasicFunction;
import org.exist.xquery.Cardinality;
import org.exist.xquery.Dependency;
import org.exist.xquery.Function;
import org.exist.xquery.FunctionSignature;
import org.exist.xquery.Profiler;
import org.exist.xquery.XPathException;
import org.exist.xquery.XQueryContext;
import org.exist.xquery.value.FunctionReturnSequenceType;
import org.exist.xquery.value.FunctionParameterSequenceType;
import org.exist.xquery.value.NumericValue;
import org.exist.xquery.value.Sequence;
import org.exist.xquery.value.SequenceIterator;
import org.exist.xquery.value.SequenceType;
import org.exist.xquery.value.StringValue;
import org.exist.xquery.value.Type;

/**
 *
 * @author wolf
 * 
 */
public class FunCodepointsToString extends BasicFunction {
	protected static final Logger logger = Logger.getLogger(FunCodepointsToString.class);
	public final static FunctionSignature signature =
		new FunctionSignature(
				new QName("codepoints-to-string", Function.BUILTIN_FUNCTION_NS, ModuleImpl.PREFIX),
				"Creates an xs:string from a sequence of code points. Returns the zero-length string if " +
				"$codepoints is the empty sequence. If any of the code points in $codepoints is not a legal XML character, " +
				"an error is raised",
				new SequenceType[] {
                    new FunctionParameterSequenceType("codepoints", Type.INTEGER, Cardinality.ZERO_OR_MORE, "The codepoints as a sequence of xs:integer values"),
				},
				new FunctionReturnSequenceType(Type.STRING, Cardinality.EXACTLY_ONE, "the string constructed from the codepoints if valid"));
	
	public FunCodepointsToString(XQueryContext context) {
		super(context, signature);
	}

	public Sequence eval(Sequence[] args, Sequence contextSequence) throws XPathException {
        if (context.getProfiler().isEnabled()) {
            context.getProfiler().start(this);       
            context.getProfiler().message(this, Profiler.DEPENDENCIES, "DEPENDENCIES", Dependency.getDependenciesName(this.getDependencies()));
            if (contextSequence != null)
                context.getProfiler().message(this, Profiler.START_SEQUENCES, "CONTEXT SEQUENCE", contextSequence);
        }
        
        Sequence result;
		if (args[0].isEmpty())
			result = StringValue.EMPTY_STRING;
        else {
    		StringBuilder buf = new StringBuilder();    		
    		for (SequenceIterator i = args[0].iterate(); i.hasNext(); ) {
                long next = ((NumericValue)i.nextItem()).getLong();
    			if (next < 0 || next > Integer.MAX_VALUE || !XMLChar.isValid((int)next)) {
                    logger.error("err:FOCH0001: Codepoint " +
                                 next +
                                 " is not a valid character.");
    				throw new XPathException(this, "err:FOCH0001: Codepoint " + next + 
                            " is not a valid character.");
    			}
    			if (next < 65536) {
                    buf.append((char)next);
                }
                else {  // output a surrogate pair
                	buf.append(XMLChar.highSurrogate((int) next));
                    buf.append(XMLChar.lowSurrogate((int) next));
                }
    		}
    		result = new StringValue(buf.toString());
        }
        
        if (context.getProfiler().isEnabled()) 
            context.getProfiler().end(this, "", result);        
        
        return result;
	}
}