package at.gv.egovernment.moa.id.proxy.servlet;

import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.IOException;
import java.io.PrintWriter;
import java.io.StringWriter;
import java.net.HttpURLConnection;
import java.net.URLEncoder;
import java.util.Enumeration;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;

import javax.net.ssl.SSLSocketFactory;
import javax.servlet.RequestDispatcher;
import javax.servlet.ServletConfig;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

import at.gv.egovernment.moa.id.AuthenticationException;
import at.gv.egovernment.moa.id.BuildException;
import at.gv.egovernment.moa.id.MOAIDException;
import at.gv.egovernment.moa.id.ParseException;
import at.gv.egovernment.moa.id.ServiceException;
import at.gv.egovernment.moa.id.config.ConfigurationException;
import at.gv.egovernment.moa.id.config.ConnectionParameter;
import at.gv.egovernment.moa.id.config.proxy.ProxyConfigurationProvider;
import at.gv.egovernment.moa.id.config.proxy.OAConfiguration;
import at.gv.egovernment.moa.id.config.proxy.OAProxyParameter;
import at.gv.egovernment.moa.id.data.AuthenticationData;
import at.gv.egovernment.moa.id.data.CookieManager;
import at.gv.egovernment.moa.id.proxy.ConnectionBuilder;
import at.gv.egovernment.moa.id.proxy.ConnectionBuilderFactory;
import at.gv.egovernment.moa.id.proxy.LoginParameterResolver;
import at.gv.egovernment.moa.id.proxy.LoginParameterResolverException;
import at.gv.egovernment.moa.id.proxy.LoginParameterResolverFactory;
import at.gv.egovernment.moa.id.proxy.MOAIDProxyInitializer;
import at.gv.egovernment.moa.id.proxy.NotAllowedException;
import at.gv.egovernment.moa.id.proxy.invoke.GetAuthenticationDataInvoker;
import at.gv.egovernment.moa.id.util.MOAIDMessageProvider;
import at.gv.egovernment.moa.id.util.SSLUtils;
import at.gv.egovernment.moa.logging.Logger;
import at.gv.egovernment.moa.util.Base64Utils;

/**
 * Servlet requested for logging in at an online application,
 * and then for proxying requests to the online application.
 * @author Paul Ivancsics
 * @version $Id$
 */
public class ProxyServlet extends HttpServlet {
  /** Name of the Parameter for the Target */
  private static final String PARAM_TARGET = "Target";
  /** Name of the Parameter for the SAMLArtifact */  
  private static final String PARAM_SAMLARTIFACT = "SAMLArtifact";

  /** Name of the Attribute for the PublicURLPrefix */  
  private static final String ATT_PUBLIC_URLPREFIX = "PublicURLPrefix";
  /** Name of the Attribute for the RealURLPrefix */  
  private static final String ATT_REAL_URLPREFIX = "RealURLPrefix";
  /** Name of the Attribute for the SSLSocketFactory */  
  private static final String ATT_SSL_SOCKET_FACTORY = "SSLSocketFactory";
  /** Name of the Attribute for the LoginHeaders */  
  private static final String ATT_LOGIN_HEADERS = "LoginHeaders";
  /** Name of the Attribute for the LoginParameters */  
  private static final String ATT_LOGIN_PARAMETERS = "LoginParameters";
	/** Name of the Attribute for the SAMLARTIFACT */  
	private static final String ATT_SAML_ARTIFACT = "SamlArtifact";

  /**
   * @see javax.servlet.http.HttpServlet#service(HttpServletRequest, HttpServletResponse)
   */
  protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

    Logger.debug("getRequestURL:" + req.getRequestURL().toString());
    try {
      if (req.getParameter(PARAM_SAMLARTIFACT) != null && req.getParameter(PARAM_TARGET) != null) {

				// check if SAML Artifact was already used in this session (in case of page reload)
				HttpSession session = req.getSession();
				if(null != session && req.getParameter(PARAM_SAMLARTIFACT).equals(session.getAttribute(ATT_SAML_ARTIFACT))) {
					tunnelRequest(req, resp); 
				} else
				// it is the first time that the SAML Artifact was used
					login(req, resp);
      }
      else
        tunnelRequest(req, resp);
    }
    catch (MOAIDException ex) {
			handleError(ex.getMessage(), ex, req, resp);
    }
    catch (Throwable ex) {
			handleError(ex.getMessage(), ex, req, resp);
    } 
  }

  /**
   * Login to online application at first call of servlet for a user session.<br/>
   * <ul>
   * <li>Acquires authentication data from the MOA-ID Auth component.</li>
   * <li>Reads configuration data for the online application.</li>
   * <li>Resolves login parameters.</li>
   * <li>Sets up an SSLSocketFactory in case of a secure connection to the online application.</li>
   * <li>For a stateless online application, stores data in the HttpSession.</li>
   * <li>Tunnels the request to the online application.</li>
   * </ul> 
   * @param req
   * @param resp
   * @throws ConfigurationException when wrong configuration is encountered
   * @throws ProxyException when wrong configuration is encountered
   * @throws BuildException while building the request for MOA-ID Auth
   * @throws ServiceException while invoking MOA-ID Auth
   * @throws ParseException while parsing the response from MOA-ID Auth
   */
  private void login(HttpServletRequest req, HttpServletResponse resp) throws ConfigurationException, ProxyException, BuildException, ServiceException, ParseException, AuthenticationException {

    String samlArtifact = req.getParameter(PARAM_SAMLARTIFACT);
    Logger.debug("moa-id-proxy login " + PARAM_SAMLARTIFACT + ": " + samlArtifact);
    // String target = req.getParameter(PARAM_TARGET); parameter given but not processed

    // get authentication data from the MOA-ID Auth component
		AuthenticationData authData;
    try {
    	authData = new GetAuthenticationDataInvoker().getAuthenticationData(samlArtifact);
    } catch (ServiceException ex) {
      throw new ProxyException("proxy.14", new Object[] {ex.getMessage()}, ex);
    } catch (ProxyException ex) {
			throw new ProxyException("proxy.14", new Object[] {ex.getMessage()}, ex);
    }
    
    String urlRequested = req.getRequestURL().toString();

    // read configuration data
    ProxyConfigurationProvider proxyConf = ProxyConfigurationProvider.getInstance();
    OAProxyParameter oaParam = proxyConf.getOnlineApplicationParameter(urlRequested);
    if (oaParam == null) {
      throw new ProxyException("proxy.02", new Object[] { urlRequested });
    }
    String publicURLPrefix = oaParam.getPublicURLPrefix();
    Logger.debug("OA: " + publicURLPrefix);
    OAConfiguration oaConf = oaParam.getOaConfiguration();
    ConnectionParameter oaConnParam = oaParam.getConnectionParameter();
    String realURLPrefix = oaConnParam.getUrl();

    // resolve login parameters to be forwarded to online application 
    LoginParameterResolver lpr =
      LoginParameterResolverFactory.getLoginParameterResolver(publicURLPrefix);
    String clientIPAddress = req.getRemoteAddr();
    Map loginHeaders = null;
    Map loginParameters = null;
    try {
      if (oaConf.getAuthType().equals(OAConfiguration.PARAM_AUTH))
        loginParameters = lpr.getAuthenticationParameters(oaConf, authData, clientIPAddress);
      else
        loginHeaders = lpr.getAuthenticationHeaders(oaConf, authData, clientIPAddress);

    } catch (LoginParameterResolverException ex) {
      throw new ProxyException("proxy.13", new Object[] { publicURLPrefix });
    } catch (NotAllowedException e) {
      throw new ProxyException("proxy.15", new Object[] { });
    }

    // setup SSLSocketFactory for communication with the online application
    SSLSocketFactory ssf = null;
    if (oaConnParam.isHTTPSURL()) {
      try {
        ssf = SSLUtils.getSSLSocketFactory(proxyConf, oaConnParam);
      } catch (Throwable ex) {
        throw new ProxyException(
          "proxy.05",
          new Object[] { oaConnParam.getUrl(), ex.toString()},
          ex);
      }
    }

    try {
      // for stateless online application, store data in HttpSession
      String loginType = oaConf.getLoginType();
      Logger.debug("Login type: " + loginType);
      if (loginType.equals(OAConfiguration.LOGINTYPE_STATELESS)) {
        
        HttpSession session = req.getSession();
        int sessionTimeOut = oaParam.getSessionTimeOut();
        if (sessionTimeOut == 0)
          sessionTimeOut = 60 * 60; // default 1 h
        session.setMaxInactiveInterval(sessionTimeOut);
        session.setAttribute(ATT_PUBLIC_URLPREFIX, publicURLPrefix);
        session.setAttribute(ATT_REAL_URLPREFIX, realURLPrefix);
        session.setAttribute(ATT_SSL_SOCKET_FACTORY, ssf);
        session.setAttribute(ATT_LOGIN_HEADERS, loginHeaders);
        session.setAttribute(ATT_LOGIN_PARAMETERS, loginParameters);
        session.setAttribute(ATT_SAML_ARTIFACT, samlArtifact);
        Logger.debug("moa-id-proxy: HTTPSession angelegt");
      }
      
     
      // tunnel request to the online application
      int respcode =
        tunnelRequest(
          req,
          resp,
          loginHeaders,
          loginParameters,
          publicURLPrefix,
          realURLPrefix,
          ssf);
      if (respcode == 401) {
        Logger.debug("Got 401, trying again");

        respcode =
          tunnelRequest(
            req,
            resp,
            loginHeaders,
            loginParameters,
            publicURLPrefix,
            realURLPrefix,
            ssf);
        if (respcode == 401)
          throw new ProxyException("proxy.12", new Object[] { realURLPrefix });
      }
    } catch (ProxyException ex) {
      throw new ProxyException("proxy.12", new Object[] { realURLPrefix });
    
    } catch (Throwable ex) {
      throw new ProxyException("proxy.04", new Object[] { urlRequested, ex.toString()}, ex);
    }
  }

  /**
   * Tunnels a request to the stateless online application using data stored in the HTTP session.
   * @param req HTTP request
   * @param resp HTTP response
   * @throws IOException if an I/O error occurs
   */
  private void tunnelRequest(HttpServletRequest req, HttpServletResponse resp) throws ProxyException, IOException {

    Logger.debug("Tunnel request (stateless)");
    HttpSession session = req.getSession(false);
       
    if (session == null)
      throw new ProxyException("proxy.07", null);
    String publicURLPrefix = (String) session.getAttribute(ATT_PUBLIC_URLPREFIX);
		//A sesssion is automatically created when forwarded 1st time to errorpage-proxy.jsp (with the handleError method)
		//additional check if publicURLPrefix is OK, if not throw an Exception
		if (publicURLPrefix == null)
			throw new ProxyException("proxy.07", null);
		 
    String realURLPrefix = (String) session.getAttribute(ATT_REAL_URLPREFIX);
    SSLSocketFactory ssf = (SSLSocketFactory) session.getAttribute(ATT_SSL_SOCKET_FACTORY);
    Map loginHeaders = (Map) session.getAttribute(ATT_LOGIN_HEADERS);
    Map loginParameters = (Map) session.getAttribute(ATT_LOGIN_PARAMETERS);
    if (publicURLPrefix == null || realURLPrefix == null)
      throw new ProxyException("proxy.08", new Object[] { req.getRequestURL().toString()});
      
    int respcode = tunnelRequest(req, resp, loginHeaders, loginParameters, publicURLPrefix, realURLPrefix, ssf);
    if (respcode == 401) 
      {
      Logger.debug("Got 401, trying again");
      respcode = tunnelRequest(req, resp, loginHeaders, loginParameters, publicURLPrefix, realURLPrefix, ssf);
      if (respcode == 401)
        throw new ProxyException("proxy.12", new Object[] { realURLPrefix});        
      }
 }  

/**
 * Tunnels a request to the online application using given URL mapping and SSLSocketFactory.
 * This method returns the ResponseCode of the request to the online application. 
 * @param req HTTP request
 * @param resp HTTP response
 * @param loginHeaders header field/values to be inserted for purposes of authentication; 
 *         may be <code>null</code>
 * @param loginParameters parameter name/values to be inserted for purposes of authentication; 
 *         may be <code>null</code>
 * @param publicURLPrefix prefix of request URL to be substituted for the <code>realURLPrefix</code>
 * @param realURLPrefix prefix of online application URL to substitute the <code>publicURLPrefix</code>
 * @param ssf SSLSocketFactory to use
 * @throws IOException if an I/O error occurs
 */
private int tunnelRequest(HttpServletRequest req, HttpServletResponse resp, Map loginHeaders, Map loginParameters, String publicURLPrefix, String realURLPrefix, SSLSocketFactory ssf)
  throws IOException {

  // collect headers from request
  Map headers = new HashMap();
  for (Enumeration enum = req.getHeaderNames(); enum.hasMoreElements();) {
    String headerKey = (String) enum.nextElement();
    //We ignore any Basic-Auth-Headers from the client
    if (headerKey.equalsIgnoreCase("Authorization"))
    { Logger.debug("Ignoring authorization-header from browser: " +req.getHeader(headerKey) );
    }
    else
      headers.put(headerKey, req.getHeader(headerKey));
  }
  // collect login headers, possibly overwriting headers from request
  if (loginHeaders != null) {
    for (Iterator iter = loginHeaders.keySet().iterator(); iter.hasNext();) {
      String headerKey = (String) iter.next();
      headers.put(headerKey, loginHeaders.get(headerKey));
    }
  }
  // collect parameters from request
  Map parameters = new HashMap();
  for (Enumeration enum = req.getParameterNames(); enum.hasMoreElements();) {
    String paramName = (String) enum.nextElement();
    parameters.put(paramName, req.getParameter(paramName));
  }
  // collect login parameters, possibly overwriting parameters from request
  if (loginParameters != null) {
    for (Iterator iter = loginParameters.keySet().iterator(); iter.hasNext();) {
      String paramName = (String) iter.next();
      parameters.put(paramName, loginParameters.get(paramName));
    }
  }

  headers.remove("content-length");
  parameters.remove(PARAM_SAMLARTIFACT);
  parameters.remove(PARAM_TARGET);

  ConnectionBuilder cb = ConnectionBuilderFactory.getConnectionBuilder(publicURLPrefix);
  HttpURLConnection conn = cb.buildConnection(req, publicURLPrefix, realURLPrefix, ssf, parameters);
  
  //Set Cookies...
  
   String cookieString = CookieManager.getInstance().getCookie(req.getSession().getId());
  if (cookieString!=null)  
    {
      //If we get Cookies from Client, we put them throgh if they dont exist/conflict with the stored Cookies 
       for (Iterator iter = headers.keySet().iterator(); iter.hasNext();) {
          String headerKey = (String) iter.next();
          String headerValue = (String) headers.get(headerKey);
          if (headerKey.equalsIgnoreCase("Cookie"))
          CookieManager.getInstance().saveOldCookies(req.getSession().getId(), headerValue);
       }
       cookieString = CookieManager.getInstance().getCookie(req.getSession().getId());
       headers.put("cookie", cookieString);       
    }
  
  // set headers as request properties of URLConnection
  for (Iterator iter = headers.keySet().iterator(); iter.hasNext();) {
    String headerKey = (String) iter.next();
    String headerValue = (String) headers.get(headerKey);
    conn.setRequestProperty(headerKey, headerValue);    
    Logger.debug("Req header " + headerKey + ": " + headers.get(headerKey));
    if (Logger.isDebugEnabled() && isBasicAuthenticationHeader(headerKey, headerValue)) {
      String credentials = headerValue.substring(6);
      String userIDPassword = new String(Base64Utils.decode(credentials, false));
      Logger.debug(":UserID:Password: :" + userIDPassword + ":");
    }
  }
  // Write out parameters into output stream of URLConnection.
  // On GET request, do not send parameters in any case,
  // otherwise HttpURLConnection would send a POST.
  if (!"get".equalsIgnoreCase(req.getMethod()) && !parameters.isEmpty()) {
    boolean firstParam = true;
    StringWriter sb = new StringWriter();
    for (Iterator iter = parameters.keySet().iterator(); iter.hasNext();) {
      String paramname = (String) iter.next();
      String value = URLEncoder.encode((String) parameters.get(paramname));
      if (firstParam)
        firstParam = false;
      else
        sb.write("&");
      sb.write(paramname);
      sb.write("=");
      sb.write(value);
      Logger.debug("Req param " + paramname + ": " + value);
    }
    PrintWriter reqOut = new PrintWriter(conn.getOutputStream());
    reqOut.write(sb.toString());
    reqOut.flush();
    reqOut.close();
  }
  // connect
  conn.connect();

  // Read response status and content type.
  // If the connection returns a 401 disconnect and return
  // otherwise the attempt to read data from that connection
  // will result in an error
  
  if (conn.getResponseCode()==HttpURLConnection.HTTP_UNAUTHORIZED)
  {    
   Logger.debug("Found 401... searching cookies");
   String headerKey;
   
  int i = 1;
  CookieManager cm = CookieManager.getInstance();
  while ((headerKey = conn.getHeaderFieldKey(i)) != null) {
    String headerValue = conn.getHeaderField(i);
    if (headerKey.equalsIgnoreCase("set-cookie"))
     { cm.saveCookie(req.getSession().getId(), headerValue);
       cm.add401(req.getSession().getId(),headerValue);
       Logger.debug("Cookie " + headerValue);
       Logger.debug("CookieSession " + req.getSession().getId());
     }
    i++;
  }
  
  conn.disconnect();
   return conn.getResponseCode();       
  }
  resp.setStatus(conn.getResponseCode());
  resp.setContentType(conn.getContentType());

  // Read response headers
  // Omit response header "content-length" if response header "Transfer-encoding: chunked" is set.
  // Otherwise, the connection will not be kept alive, resulting in subsequent missing requests.
  // See JavaDoc of javax.servlet.http.HttpServlet:
  // When using HTTP 1.1 chunked encoding (which means that the response has a Transfer-Encoding header), do not set the Content-Length header.
  Map respHeaders = new HashMap();
  boolean chunked = false;
  String contentLengthKey = null;
  String transferEncodingKey = null;
  int i = 1;
  String headerKey;
  while ((headerKey = conn.getHeaderFieldKey(i)) != null) {
    String headerValue = conn.getHeaderField(i);
    respHeaders.put(headerKey, headerValue);
    if (isTransferEncodingChunkedHeader(headerKey, headerValue)) {
      chunked = true;
      transferEncodingKey = headerKey;
    }
     CookieManager cm = CookieManager.getInstance();
     if (headerKey.equalsIgnoreCase("set-cookie"))
     { cm.saveCookie(req.getSession().getId(), headerValue);
       Logger.debug("Cookie " + headerValue);
       Logger.debug("CookieSession " + req.getSession().getId());
     }
    if ("content-length".equalsIgnoreCase(headerKey))
      contentLengthKey = headerKey;
    Logger.debug("Resp header " + headerKey + ": " + headerValue);
    i++;
  }
  if (chunked && contentLengthKey != null) {
    respHeaders.remove(transferEncodingKey);
    Logger.debug("Resp header " + transferEncodingKey + " REMOVED");
  }

  //Get a Hash-Map of all 401-set-cookies
  HashMap cookies401 = CookieManager.getInstance().get401(req.getSession().getId());
  
  for (Iterator iter = respHeaders.keySet().iterator(); iter.hasNext();) {
    headerKey = (String) iter.next();
    
    if (headerKey.equalsIgnoreCase("Set-Cookie"))        
        {
        String headerValue = (String) respHeaders.get(headerKey);
        Logger.debug("Found 'Set-Cookie' in ResponseHeaders: " + headerValue);
        if(!cookies401.containsKey(headerValue.substring(0, headerValue.indexOf("="))))
        { 
          // If we dont already have a Set-Cookie-Value for THAT Cookie we create one...
          CookieManager.getInstance().add401(req.getSession().getId(), headerValue);
        }
    }    
  }
  
  //write out all Responseheaders != "set-cookie"
  for (Iterator iter = respHeaders.keySet().iterator(); iter.hasNext();) {
    headerKey = (String) iter.next();
    if (!headerKey.equalsIgnoreCase("Set-Cookie")) 
    resp.addHeader(headerKey, (String) respHeaders.get(headerKey));
  }
  
  //write out all Responseheaders = "set-cookie"  
  cookies401 = CookieManager.getInstance().get401(req.getSession().getId());
  Iterator cookie_i = cookies401.values().iterator();
  while (cookie_i.hasNext()) {
    String element = (String) cookie_i.next();
    resp.addHeader("Set-Cookie", element);
  }
  //Delete all "Set-Cookie" - Values
  CookieManager.getInstance().clear401(req.getSession().getId());    
  
  // read response stream
  Logger.debug("Resp from " + conn.getURL().toString() + ": status " + conn.getResponseCode());
  // Load content unless the server lets us know that the content is NOT MODIFIED...
  if (conn.getResponseCode()!=HttpURLConnection.HTTP_NOT_MODIFIED)
    {
    BufferedInputStream respIn = new BufferedInputStream(conn.getInputStream());
    Logger.debug("Got Inputstream");
    BufferedOutputStream respOut = new BufferedOutputStream(resp.getOutputStream());
    Logger.debug("Got Outputstream");
    int ch;
    while ((ch = respIn.read()) >= 0)
      respOut.write(ch);
    respOut.close();
    respIn.close();
    }
   else
   Logger.debug("Found 304 NOT MODIFIED...");
   conn.disconnect();
   Logger.debug("Request done");
  
  
  return conn.getResponseCode();
}
/**
 * Determines whether a HTTP header is a basic authentication header of the kind "Authorization: Basic ..."
 * 
 * @param headerKey header name
 * @param headerValue header value
 * @return true for a basic authentication header
 */
private boolean isBasicAuthenticationHeader(String headerKey, String headerValue) {
  if (!"authorization".equalsIgnoreCase(headerKey))
    return false;
  if (headerValue.length() < "basic".length())
    return false;
  String authenticationSchema = headerValue.substring(0, "basic".length());
  return "basic".equalsIgnoreCase(authenticationSchema);
}
/**
 * Determines whether a HTTP header is "Transfer-encoding" header with value containing "chunked" 
 *  
 * @param headerKey header name
 * @param headerValue header value
 * @return true for a "Transfer-encoding: chunked" header
 */
private boolean isTransferEncodingChunkedHeader(String headerKey, String headerValue) {
  if (!"transfer-encoding".equalsIgnoreCase(headerKey))
    return false;
  return headerValue.indexOf("chunked") >= 0 || headerValue.indexOf("Chunked") >= 0 || headerValue.indexOf("CHUNKED") >= 0;
}

/**
 * Calls the web application initializer.
 * 
 * @see javax.servlet.Servlet#init(ServletConfig)
 */
public void init(ServletConfig servletConfig) throws ServletException {
	super.init(servletConfig);
  try {
    MOAIDProxyInitializer.initialize();
    Logger.info(MOAIDMessageProvider.getInstance().getMessage("proxy.00", null));
  }
  catch (Exception ex) {
    Logger.fatal(MOAIDMessageProvider.getInstance().getMessage("proxy.06", null), ex);
    throw new ServletException(ex);
  }
}

/**
 * Handles an error. <br>
 * <ul>
 * <li>Logs the error</li>
 * <li>Places error message and exception thrown into the request 
 * 		 as request attributes (to be used by <code>"/errorpage-proxy.jsp"</code>)</li>
 * <li>Sets HTTP status 500 (internal server error)</li>
 * </ul>
 * 
 * @param errorMessage error message
 * @param exceptionThrown exception thrown
 * @param req servlet request
 * @param resp servlet response
 */
protected void handleError(
	String errorMessage, Throwable exceptionThrown, HttpServletRequest req, HttpServletResponse resp) {

		
	if(null != errorMessage) {
		Logger.error(errorMessage);
		req.setAttribute("ErrorMessage", errorMessage	);	
	}
	
	if (null != exceptionThrown) {
		if(null == errorMessage) errorMessage = exceptionThrown.getMessage();
		Logger.error(errorMessage, exceptionThrown);
		//req.setAttribute("ExceptionThrown", exceptionThrown);
	}
				
	//forward this to errorpage-proxy.jsp wher the HTML error page is generated
	ServletContext context = getServletContext();
	RequestDispatcher dispatcher = context.getRequestDispatcher("/errorpage-proxy.jsp");
	try {
		dispatcher.forward(req, resp);
	} catch (ServletException e) {
		Logger.error(e);
	} catch (IOException e) {
		Logger.error(e);
	}
		
}

}