/*
 * DocumentFunction.java
 * Copyright (C) 2004 The Free Software Foundation
 * 
 * This file is part of GNU JAXP, a library.
 *
 * GNU JAXP is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 * 
 * GNU JAXP 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 General Public License for more details.
 * 
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 *
 * Linking this library statically or dynamically with other modules is
 * making a combined work based on this library.  Thus, the terms and
 * conditions of the GNU General Public License cover the whole
 * combination.
 *
 * As a special exception, the copyright holders of this library give you
 * permission to link this library with independent modules to produce an
 * executable, regardless of the license terms of these independent
 * modules, and to copy and distribute the resulting executable under
 * terms of your choice, provided that you also meet, for each linked
 * independent module, the terms and conditions of the license of that
 * module.  An independent module is a module which is not derived from
 * or based on this library.  If you modify this library, you may extend
 * this exception to your version of the library, but you are not
 * obliged to do so.  If you do not wish to do so, delete this
 * exception statement from your version. 
 */

package gnu.xml.transform;

import java.io.InputStream;
import java.io.IOException;
import java.net.URL;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.Iterator;
import java.util.List;
import java.util.TreeSet;
import javax.xml.transform.ErrorListener;
import javax.xml.transform.TransformerException;
import javax.xml.transform.URIResolver;
import javax.xml.transform.dom.DOMSource;
import javax.xml.xpath.XPathFunction;
import javax.xml.xpath.XPathFunctionException;
import org.w3c.dom.Document;
import org.w3c.dom.Node;
import gnu.xml.xpath.Constant;
import gnu.xml.xpath.Expr;
import gnu.xml.xpath.Function;
import gnu.xml.xpath.IdFunction;

/**
 * The XSLT <code>document()</code>function.
 *
 * @author <a href='mailto:dog@gnu.org'>Chris Burdess</a>
 */
final class DocumentFunction
  extends Expr
  implements Function, XPathFunction
{

  final Stylesheet stylesheet;
  final Node base;
  List args;
  List values;

  DocumentFunction(Stylesheet stylesheet, Node base)
  {
    this.stylesheet = stylesheet;
    this.base = base;
  }

  public Object evaluate(List args)
    throws XPathFunctionException
  {
    values = args;
    return evaluate(null, 1, 1);
  }

  public void setArguments(List args)
  {
    this.args = args;
  }
  
  public Object evaluate(Node context, int pos, int len)
  {
    int arity = args.size();
    if (values == null)
      {
        values = new ArrayList(arity);
        for (int i = 0; i < arity; i++)
          {
            Expr arg = (Expr) args.get(i);
            values.add(arg.evaluate(context, pos, len));
          }
      }
    Object ret;
    switch (arity)
      {
      case 1:
        Object arg = values.get(0);
        if (arg instanceof Collection)
          {
            Collection ns = (Collection) arg;
            Collection acc = new TreeSet();
            for (Iterator i = ns.iterator(); i.hasNext(); )
              {
                Node node = (Node) i.next();
                String s = Expr.stringValue(node);
                acc.addAll(document(s, node.getBaseURI()));
              }
            ret = acc;
          }
        else
          {
            String s = Expr._string(context, arg);
            ret = document(s, base.getBaseURI());
          }
        break;
      case 2:
        Object arg1 = values.get(0);
        Object arg2 = values.get(1);
        if (!(arg2 instanceof Collection))
          {
            throw new RuntimeException("second argument is not a node-set");
          }
        Collection arg2ns = (Collection) arg2;
        String base2 = arg2ns.isEmpty() ? null :
          ((Node) arg2ns.iterator().next()).getBaseURI();
        if (arg1 instanceof Collection)
          {
            Collection arg1ns = (Collection) arg1;
            Collection acc = new TreeSet();
            for (Iterator i = arg1ns.iterator(); i.hasNext(); )
              {
                Node node = (Node) i.next();
                String s = Expr.stringValue(node);
                acc.addAll(document(s, base2));
              }
            ret = acc;
          }
        else
          {
            String s = Expr._string(context, arg1);
            ret = document(s, base2);
          }
        break;
      default:
        throw new RuntimeException("invalid arity");
      }
    values = null;
    return ret;
  }

  /**
   * The XSL <code>document</code> function.
   * @see XSLT 12.1
   * @param uri the URI from which to retrieve nodes
   * @param base the base URI for relative URIs
   */
  Collection document(String uri, String base)
  {
    if ("".equals(uri) || uri == null)
      {
        uri = this.base.getBaseURI();
      }
    
    // Get fragment
    Expr fragment = null;
    int hi = uri.indexOf('#');
    if (hi != -1)
      {
        String f = uri.substring(hi + 1);
        uri = uri.substring(0, hi);
        // TODO handle xpointer() here
        // this only handles IDs
        fragment = new IdFunction(new Constant(f));
      }

    // Get document source
    try
      {
        DOMSource source;
        XSLURIResolver resolver = stylesheet.factory.resolver;
        synchronized (resolver)
          {
            if (stylesheet.transformer != null)
              {
                resolver.setUserResolver(stylesheet.transformer.uriResolver);
                resolver.setUserListener(stylesheet.transformer.errorListener);
              }
            source = resolver.resolveDOM(null, base, uri);
          }
        Node node = source.getNode();
        if (fragment == null)
          {
            return Collections.singleton(node);
          }
        else
          {
            Object ret = fragment.evaluate(node, 1, 1);
            if (!(ret instanceof Collection))
              {
                // XXX Report error?
                return Collections.EMPTY_SET;
              }
            return (Collection) ret;
          }
      }
    catch (TransformerException e)
      {
        String msg = "can't open " + uri;
        if (base != null)
          {
            msg += " with base " + base;
          }
        throw new RuntimeException(msg);
      }
  }

  public Expr clone(Object context)
  {
    Stylesheet s = stylesheet;
    if (context instanceof Stylesheet)
      {
        s = (Stylesheet) context;
      }
    DocumentFunction f = new DocumentFunction(s, base);
    int len = args.size();
    List args2 = new ArrayList(len);
    for (int i = 0; i < len; i++)
      {
        args2.add(((Expr) args.get(i)).clone(context));
      }
    f.setArguments(args2);
    return f;
  }
  
}
