package com.jclark.xsl.expr;

import com.jclark.xsl.om.*;

class SequenceComposeNodeIterator implements NodeIterator {
  private final NodeIterator iter1;
  private NodeIterator iter2;
  private final NodeSetExpr expr;
  private final ExprContext context;

  SequenceComposeNodeIterator(NodeIterator iter, NodeSetExpr expr, ExprContext context) {
    this.iter1 = iter;
    this.expr = expr;
    this.context = context;
    this.iter2 = new NullNodeIterator();
  }

  public Node next() throws XSLException {
    for (;;) {
      Node node = iter2.next();
      if (node != null)
	return node;
      node = iter1.next();
      if (node == null)
	break;
      iter2 = expr.eval(node, context);
    }
    return null;
  }
}