/*
 * File: UserServlet.java
 * 
 * Copyright 2009 Muradora
 * 
 * Licensed under the Apache License, Version 2.0 (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.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 * License for the specific language governing permissions and limitations under
 * the License.
 */

package org.fcrepo.server.jaas;

import java.io.IOException;
import java.io.OutputStream;
import java.util.Map;
import java.util.Set;

import javax.security.auth.Subject;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.ParserConfigurationException;

import org.apache.log4j.Logger;
import org.fcrepo.server.jaas.util.DataUtils;
import org.fcrepo.server.jaas.util.SubjectUtils;
import org.w3c.dom.Document;
import org.w3c.dom.Element;

/**
 * This servlet produces an XML representation of a currently logged in user.
 * The User is logged in if they have authenticated using the JAAS
 * authentication filter. The XML representation is the same as that of the
 * XMLUsersFile that is used by fedora by default. This servlet provides a
 * technology agnostic way over providing applications with user attributes that
 * might be required for performing various user-centric activities like sending
 * them emails. This servlet should always be protected by the filter for
 * authentication.
 * 
 * @author nish.naidoo@gmail.com
 */
public class UserServlet
        extends HttpServlet {

    private static final long serialVersionUID = -6735420697733987757L;

    private static final Logger log = Logger.getLogger(UserServlet.class);

    private static final String SESSION_SUBJECT_KEY =
            "javax.security.auth.subject";

    private DocumentBuilder documentBuilder = null;

    /*
     * (non-Javadoc)
     * @see javax.servlet.GenericServlet#init()
     */
    @Override
    public void init() throws ServletException {
        try {
            DocumentBuilderFactory documentBuilderFactory =
                    DocumentBuilderFactory.newInstance();
            documentBuilderFactory.setNamespaceAware(true);
            documentBuilder = documentBuilderFactory.newDocumentBuilder();
        } catch (ParserConfigurationException pce) {
            log.error("Unable to initialise UserServlet: " + pce.getMessage(),
                      pce);
        }
    }

    /*
     * (non-Javadoc)
     * @see
     * javax.servlet.http.HttpServlet#doPost(javax.servlet.http.HttpServletRequest
     * , javax.servlet.http.HttpServletResponse)
     */
    @Override
    public void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        doGet(request, response);
    }

    /*
     * (non-Javadoc)
     * @see
     * javax.servlet.http.HttpServlet#doGet(javax.servlet.http.HttpServletRequest
     * , javax.servlet.http.HttpServletResponse)
     */
    @Override
    public void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        Subject subject =
                (Subject) request.getSession()
                        .getAttribute(SESSION_SUBJECT_KEY);

        java.security.Principal principal = request.getUserPrincipal();
        String userId = null;
        if (principal == null || principal.getName() == null
                || "".equals(principal.getName())) {
            userId = "anonymous";
        } else {
            userId = principal.getName();
        }

        Document doc = documentBuilder.newDocument();
        doc.setXmlVersion("1.0");

        Element root = doc.createElement("user");
        root.setAttribute("id", userId);

        doc.appendChild(root);

        Map<String, Set<String>> attributes =
                SubjectUtils.getAttributes(subject);

        if (attributes != null && attributes.size() > 0) {
            for (String attr : attributes.keySet()) {
                Element attribute = doc.createElement("attribute");
                attribute.setAttribute("name", attr);
                root.appendChild(attribute);

                for (String value : attributes.get(attr)) {
                    Element v = doc.createElement("value");
                    v.appendChild(doc.createTextNode(value));
                    attribute.appendChild(v);
                }
            }
        }

        byte[] output = null;
        try {
            output = DataUtils.format(doc).getBytes();
        } catch (Exception e) {
            log.error("Error obtaining user information: " + e.getMessage(), e);
        }

        response.setContentType("text/xml");
        response.setContentLength(output.length);
        OutputStream out = response.getOutputStream();
        out.write(output);
        out.flush();
        out.close();
    }
}