package com.jclark.xsl.expr;

import com.jclark.xsl.om.*;
import java.net.URL;

class DocumentFunction implements Function {
  public ConvertibleExpr makeCallExpr(ConvertibleExpr args[], final Node exprNode)
    throws ParseException {
    if (args.length != 1 && args.length != 2)
      throw new ParseException("expected one or two arguments");
    ConvertibleExpr e = args[0];
    final NodeSetExpr base = (args.length == 1
			      ? null
			      : args[1].makeNodeSetExpr());
    if (e instanceof NodeSetExpr) {
      final NodeSetExpr nse = (NodeSetExpr)e;
      return new ConvertibleNodeSetExpr() {
	public NodeIterator eval(Node node, ExprContext context) throws XSLException {
	  return document(context,
			  nse.eval(node, context),
			  base == null
			  ? null
			  : base.eval(node, context).next());
	}
      };
    }
    else if (e instanceof VariantExpr) {
      final VariantExpr ve = (VariantExpr)e;
      return new ConvertibleNodeSetExpr() {
	public NodeIterator eval(Node node, ExprContext context) throws XSLException {
	  Variant v = ve.eval(node, context);
	  if (v.isNodeSet())
	    return document(context,
			    v.convertToNodeSet(),
			    base == null
			    ? null
			    : base.eval(node, context).next());
	  else {
	    Node baseNode = v.getBaseNode();
	    if (baseNode == null)
	      baseNode = exprNode;
	    return document(context,
			    v.convertToString(),
			    base == null
			    ? baseNode
			    : base.eval(node, context).next());
	  }
	}
      };
    }
    else {
      final StringExpr se = e.makeStringExpr();
      return new ConvertibleNodeSetExpr() {
	public NodeIterator eval(Node node, ExprContext context) 
	  throws XSLException {
	  return document(context,
			  se.eval(node, context),
			  base == null
			  ? exprNode
			  : base.eval(node, context).next());
	}
      };
    }
  }
  
  
  private static final NodeIterator document(ExprContext context, NodeIterator iter, Node baseNode) throws XSLException {
    NodeIterator[] iters = new NodeIterator[1];
    int len = 0;
    for (;;) {
      Node node = iter.next();
      if (node == null)
	break;
      if (len == iters.length) {
	NodeIterator[] oldIters = iters;
	iters = new NodeIterator[iters.length*2];
	System.arraycopy(oldIters, 0, iters, 0, oldIters.length);
      }
      iters[len++] = document(context,
			      Converter.toString(node),
			      baseNode == null ? node : baseNode);
    }
    if (len > 1)
      return new MergeNodeIterator(iters, len);
    if (len == 1)
      return iters[0];
    return new SingleNodeIterator(null);
  }

  private static final NodeIterator document(ExprContext context, String urlRef, Node baseNode) throws XSLException {
    return context.getDocument(baseNode == null ? null : baseNode.getURL(),
			       urlRef);
  }
}