package org.pdf4j.saxon.expr;
import org.pdf4j.saxon.om.Item;
import org.pdf4j.saxon.om.NodeInfo;
import org.pdf4j.saxon.om.SequenceIterator;
import org.pdf4j.saxon.om.SingletonIterator;
import org.pdf4j.saxon.pattern.AnyNodeTest;
import org.pdf4j.saxon.trans.XPathException;
import org.pdf4j.saxon.type.ItemType;
import org.pdf4j.saxon.type.TypeHierarchy;
/**
* A node set expression that will always return zero or one nodes
*/
public abstract class SingleNodeExpression extends Expression {
/**
* Type-check the expression.
*/
public Expression typeCheck(ExpressionVisitor visitor, ItemType contextItemType) throws XPathException {
if (contextItemType == null) {
XPathException err = new XPathException("Cannot select a node here: the context item is undefined");
err.setErrorCode("XPDY0002");
err.setIsTypeError(true);
err.setLocator(this);
throw err;
}
if (contextItemType.isAtomicType()) {
XPathException err = new XPathException("Cannot select a node here: the context item is an atomic value");
err.setErrorCode("XPTY0020");
err.setIsTypeError(true);
err.setLocator(this);
throw err;
}
return this;
}
/**
* Perform optimisation of an expression and its subexpressions.
* <p/>
* <p>This method is called after all references to functions and variables have been resolved
* to the declaration of the function or variable, and after all type checking has been done.</p>
*
* @param visitor an expression visitor
* @param contextItemType the static type of "." at the point where this expression is invoked.
* The parameter is set to null if it is known statically that the context item will be undefined.
* If the type of the context item is not known statically, the argument is set to
* {@link org.pdf4j.saxon.type.Type#ITEM_TYPE}
* @return the original expression, rewritten if appropriate to optimize execution
* @throws XPathException if an error is discovered during this phase
* (typically a type error)
*/
public Expression optimize(ExpressionVisitor visitor, ItemType contextItemType) throws XPathException {
// repeat the check: in XSLT insufficient information is available the first time
return typeCheck(visitor, contextItemType);
}
/**
* Specify that the expression returns a singleton
*/
public int computeCardinality() {
return StaticProperty.ALLOWS_ZERO_OR_ONE;
}
/**
* Determine the data type of the items returned by this expression
* @return Type.NODE
* @param th the type hierarchy cache
*/
public ItemType getItemType(TypeHierarchy th) {
return AnyNodeTest.getInstance();
}
/**
* Determine which aspects of the context the expression depends on. The result is
* a bitwise-or'ed value composed from constants such as StaticProperty.VARIABLES and
* StaticProperty.CURRENT_NODE
*/
public int getIntrinsicDependencies() {
return StaticProperty.DEPENDS_ON_CONTEXT_ITEM;
}
public int computeSpecialProperties() {
return StaticProperty.ORDERED_NODESET |
StaticProperty.CONTEXT_DOCUMENT_NODESET |
StaticProperty.SINGLE_DOCUMENT_NODESET |
StaticProperty.NON_CREATIVE;
}
/**
* Get the single node to which this expression refers. Returns null if the node-set is empty
*/
public abstract NodeInfo getNode(XPathContext context) throws XPathException;
/**
* Evaluate the expression in a given context to return an iterator
* @param context the evaluation context
*/
public SequenceIterator iterate(XPathContext context) throws XPathException {
return SingletonIterator.makeIterator(getNode(context));
}
public Item evaluateItem(XPathContext context) throws XPathException {
return getNode(context);
}
public boolean effectiveBooleanValue(XPathContext context) throws XPathException {
return getNode(context) != null;
}
}
//
// The contents of this file are subject to the Mozilla Public License Version 1.0 (the "License");
// you may not use this file except in compliance with the License. You may obtain a copy of the
// License at http://www.mozilla.org/MPL/
//
// Software distributed under the License is distributed on an "AS IS" basis,
// WITHOUT WARRANTY OF ANY KIND, either express or implied.
// See the License for the specific language governing rights and limitations under the License.
//
// The Original Code is: all this file.
//
// The Initial Developer of the Original Code is Michael H. Kay.
//
// Portions created by (your name) are Copyright (C) (your legal entity). All Rights Reserved.
//
// Contributor(s): none.
//