package com.nailabs.abac.credential;

import com.nailabs.abac.test.Debug;
import edu.stanford.peer.rbtm.credential.*;
import edu.stanford.rt.credential.CredentialDomain;
import org.w3c.dom.*;
import org.xml.sax.*;

// imports for loading xml documents BEGIN
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.DocumentBuilder;

import javax.xml.transform.Transformer;
import javax.xml.transform.TransformerFactory;
import javax.xml.transform.TransformerException;
import javax.xml.transform.TransformerConfigurationException;

import javax.xml.transform.dom.DOMSource; 
import javax.xml.transform.stream.StreamResult; 

import java.io.*;
// imports for loading xml documents END


/** 
 * A credential which can handle XML persistent representations of RTML
 * credentials. 
 */
public class RtmlCredential extends StaticCredential {
    /** 
     * the domain for this credential. note: a domain may contain multiple
     * credentials.
     */
    protected transient CredentialDomain credDomain;
    
    /**
     * constructor for an unparsed credential that is part of a domain.
     */
    public RtmlCredential(String cred, CredentialDomain domain)
        throws CredentialParsingException {
        super(cred);
        credDomain = domain;
    }

    /**
     * parsed  constructor for a static credential that is part of a domain 
     */
    public RtmlCredential(Role l, EntityExpression r, CredentialDomain domain){
        super(l, r);
        credDomain = domain;
    }

    /** public accessor for the credential domain */
    public CredentialDomain getCredentialDomain() {
        return credDomain;
    }   

    /** convert the DOM from the credential domain into XML */
    public String toXML() { 
        ByteArrayOutputStream bytesOut = new ByteArrayOutputStream();
        PrintStream out = new PrintStream(bytesOut);
        try {
            // Use a Transformer for output
            TransformerFactory tFactory = TransformerFactory.newInstance();
            Transformer transformer = tFactory.newTransformer();
            DOMSource source = 
                new DOMSource(credDomain.getCredentialElement());
            StreamResult result = new StreamResult(out);
            transformer.transform(source, result);
        }
        catch (Exception ex) {
            // Error generated by the parser
            System.out.println ("* Transformation error");
            System.out.println("  " + ex.getMessage() );
            // Use the contained exception, if any
            //Throwable x = (ex.getException() != null)? ex.getException(): ex;
            //x.printStackTrace();
        }
        return bytesOut.toString();
    }


    /** a utility method for loading an xml credential */
    public static org.w3c.dom.Element getDomElement(String xml) {
        ByteArrayInputStream bias =  new ByteArrayInputStream(xml.getBytes());
        DocumentBuilderFactory factory =
            DocumentBuilderFactory.newInstance();
        Document document = null;

        try {
            DocumentBuilder builder = factory.newDocumentBuilder();
             document = builder.parse(bias);
        }
        catch (Exception ex) {
            // Error generated by the parser
            System.out.println ("* Document loading error");
            System.out.println("  " + ex.getMessage() );
            
        } 
        NodeList list = document.getElementsByTagName("Credential");
        for(int i = 0; i < list.getLength(); i++) {
            Node cNode = list.item(i);
            Debug.debug("rtml", "cNode = " + cNode.getNodeName());
            if(cNode instanceof Element) {
                return (Element)cNode;
            }
        }
        return null;
    }

}