XPathExpression.java

package org.openrosa.client.xpath;

import java.io.Serializable;
import java.util.Vector;

import com.google.gwt.xml.client.Node;
/**
 * @author Cosmin
 * 
 */
public class XPathExpression implements Serializable
{
	/**
	 * Generated serialization ID.
	 */
	private static final long serialVersionUID = 2204726896219201531L;
	
	String[] locationStepStringsArray;
	XPathLocationStep[] locationStepArray;
	Vector resultNodeSet;
	String expression = null;
	Node startNode = null;
		
	public XPathExpression (Node startNode, String expression){
		Vector<String> tmp = new Vector<String>();

		this.startNode = startNode;
		this.expression = expression;
		
		//I do not support function name in the start
		//of an xpath expression
		
		//parse
		if(expression.startsWith("//")) {
			//this way of handling "//" is obviously incomplete
			//but we allow it like this because of the lacking resources
			tmp.addElement("//");
			expression = new String(expression.toCharArray(), 2, expression.length()-2);
		} else if(expression.startsWith("/")) {
			tmp.addElement("/");
			//trace the root element
			expression = new String(expression.toCharArray(), 1, expression.length()-1);
		} 
		//System.out.println("Expression "+expression+" start node is "+start);
		
		//because there is no support for StringTokenizer
		//on j2me we remove this
		/*
		StringTokenizer st = new StringTokenizer(expression, "/");
		locationStepStringsArray = new String[st.countTokens()];
		for(int i = 0; i < locationStepStringsArray.length; i++) {
			locationStepStringsArray[i] = st.nextToken();
			System.out.println("location step: "+locationStepStringsArray[i]);
		}
		*/
		for(int start = 0, end = 0; end < expression.length()-1 && end!=-1; start = end+1) {
			end = expression.indexOf("/", start);
			
			if(end != -1){
				String token = expression.substring(start,end);
				if(token.indexOf('@') >= 0 && token.indexOf(']') < 0){
					//end = expression.indexOf("/", end + 1);
					end = expression.indexOf("]", end + 1) + 1;
				}
			}
			
			//System.out.println("start = "+start+" end = "+end);
			String s = new String(expression.toCharArray(), start, 
					(end!=-1?end:expression.length())-start);
			
			if(s.indexOf('@') > 0)
				addAttributeSteps(s,tmp);
			else
				tmp.addElement(s);
		}
		locationStepStringsArray = new String[tmp.size()];
		tmp.copyInto(locationStepStringsArray);
		tmp = null;
		
		//the result node set should contain nodes
		//with regard to the starting poing of the xpath expression
		//for now just pass the root of the document
		resultNodeSet = new Vector<Node>();
		resultNodeSet.addElement(startNode);
		
		boolean attributeFound = false;
		Vector<Object> prevResults = null;
		
		//start processing every location
		for(int j=0; j < locationStepStringsArray.length; j++)
		{
			prevResults = new Vector<Object>();
			
			String locationStepString = locationStepStringsArray[j];
			if(locationStepString.indexOf('@') >= 0){
				if(attributeFound)
					prevResults = resultNodeSet;
				attributeFound = true;
			}
			else
				attributeFound = false;
			
			XPathLocationStep locationStep = new XPathLocationStep(locationStepString);

			resultNodeSet = locationStep.getResult(resultNodeSet, prevResults);
		}
	}
	
	private void addAttributeSteps(String step, Vector<String> list){
		int posBeg = 0;
		int posEnd = step.indexOf(" and ");
		/*if(posEnd > 0){ //TODO Need to support more than two and expressions
			list.addElement(step.substring(posBeg, posEnd+1).trim() + "]");
			
			posBeg = posEnd + 5;
			posEnd = step.indexOf(']',posBeg);
			list.addElement(step.substring(0, step.indexOf('@'))+step.substring(posBeg, posEnd+1));
			
			posBeg = posEnd + 1;
			posEnd = step.indexOf(']',posBeg);
		}
		else*/
			posEnd = step.indexOf(']',posBeg);
		
		while(posEnd > 0){
			list.addElement(step.substring(posBeg, posEnd+1));
			posBeg = posEnd + 1;
			if(posBeg >= step.length())
				break;
			posEnd = step.indexOf(']',posBeg);
		}
	}
	
	public Vector<Node> getResult(){
		return resultNodeSet;
	}
}