/*
 *  Copyright 1999-2004 The Apache Software Foundation
 *
 *  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.apache.jasper.servlet;

import java.io.File;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.util.Enumeration;
import java.util.Hashtable;

import javax.servlet.Servlet;
import javax.servlet.ServletConfig;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.SingleThreadModel;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.jsp.JspFactory;

import org.apache.jasper.Constants;
import org.apache.jasper.EmbededServletOptions;
import org.apache.jasper.JasperException;
import org.apache.jasper.JspCompilationContext;
import org.apache.jasper.JspEngineContext;
import org.apache.jasper.Options;
import org.apache.jasper.compiler.Compiler;
import org.apache.jasper.compiler.Mangler;
import org.apache.jasper.runtime.HttpJspBase;
import org.apache.jasper.runtime.JspFactoryImpl;
import org.apache.tomcat.util.log.Log;

/**
 * The JSP engine (a.k.a Jasper)! 
 *
 * @author Anil K. Vijendran
 * @author Harish Prabandham
 * @author Marc A. Saegesser
 */
public class JspServlet extends HttpServlet {

    Log loghelper = Log.getLog("JASPER_LOG", "JspServlet");

    /**
     * Adds reference counting to the JSP implementation servlet.  This
     * is required to handle the case where a JSP implementation servlet
     * is executing requests on several threads when a new implementation
     * arrives (the JSP source was updated).  We need to wait until all
     * the requests complete before calling the implementation servlet's
     * destroy() method.
     */
    class JspCountedServlet extends HttpServlet
    {
        private Servlet servlet = null;
        private int threadCount = 0;
        private boolean destroyed = false;

        public JspCountedServlet(Servlet servlet)
        {
            this.servlet = servlet;
        }

        public void init(ServletConfig config) throws ServletException, JasperException
        {
            try{
                servlet.init(config);
            }catch(NullPointerException e){
                throw new JasperException(e);
            }
        }

        public void service(HttpServletRequest req, HttpServletResponse res) throws ServletException, IOException, JasperException
        {
            try{
                incrementCount();
                if(servlet instanceof SingleThreadModel){
                    synchronized(servlet){
                        servlet.service(req, res);
                    }
                } else {
                    servlet.service(req, res);
                }
            }catch(NullPointerException e){
                throw new JasperException(e);
            }finally{
                decrementCount();
            }
        }

        /*
         * Flags this servlet for destrction once all active requests have completed.
         * After calling this method it is invalid to call service().
         */
        public void destroy()
        {
            destroyed = true;
            if(getCount() == 0)
                doDestroy();
        }

        private void doDestroy()
        {
            try{
                servlet.destroy();
                servlet = null;
            }catch(NullPointerException e){
            }
        }

        private synchronized void incrementCount()
        {
            threadCount++;
        }

        private synchronized void decrementCount()
        {
            if(threadCount <= 0){
                Constants.message("jsp.error.badcount", Log.ERROR);
                return;
            }

            --threadCount;
            if(threadCount == 0 && destroyed)
                doDestroy();
        }

        private synchronized int getCount()
        {
            return threadCount;
        }
    }

    class JspServletWrapper {
        JspCountedServlet theServlet;
	String jspUri;
	boolean isErrorPage;
	Class servletClass;
	
	JspServletWrapper(String jspUri, boolean isErrorPage) {
	    this.jspUri = jspUri;
	    this.isErrorPage = isErrorPage;
	    this.theServlet = null;
	}
	
        public synchronized void instantiateServlet(Class servletClass) throws JasperException, ServletException
        {
            try {
                this.servletClass = servletClass;

                // If we're replacing an existing JSP Implementation class, then
                // schedule it for destruction
                if(theServlet != null)
                    theServlet.destroy();

                // Create an instance of the JSP implementation class
                Servlet servlet = (Servlet) servletClass.newInstance();
                // Set the class loader
                if(servlet instanceof HttpJspBase) {
                    ((HttpJspBase)servlet).setClassLoader(JspServlet.this.parentClassLoader);
                }

                // Wrap this servlet in a counted servlet
                theServlet = new JspCountedServlet(servlet);

                // Call the JSP Implementation servlet's init() method.  This
                // will cause the page's jspInit() method to be invoked if one exists.
                theServlet.init(JspServlet.this.config);

            } catch(Exception ex) {
                throw new JasperException(ex);
            }

        }

        public synchronized Servlet getServlet()
        {
            return theServlet;
        }

        public synchronized boolean isInstantiated()
        {
            return theServlet != null;
        }

	private void loadIfNecessary(HttpServletRequest req, HttpServletResponse res) 
            throws JasperException, ServletException, FileNotFoundException 
        {
            // First try context attribute; if that fails then use the 
            // classpath init parameter. 

            // Should I try to concatenate them if both are non-null?

            String cp = (String) context.getAttribute(Constants.SERVLET_CLASSPATH);

            String accordingto;

            if (cp == null || cp.equals("")) {
                accordingto = "according to the init parameter";
                cp = options.getClassPath();
            } else 
                accordingto = "according to the Servlet Engine";
            
            Constants.message("jsp.message.cp_is", 
                              new Object[] { 
                                  accordingto,
                                  cp == null ? "" : cp
                              }, 
                              Log.INFORMATION);

            loadJSP(jspUri, cp, isErrorPage, req, res);
	}
	
	public void service(HttpServletRequest request, 
			    HttpServletResponse response,
			    boolean precompile)
	    throws ServletException, IOException, FileNotFoundException 
	{
            Servlet servlet = null;
            try {
                loadIfNecessary(request, response);
                servlet = getServlet();

		// If a page is to only to be precompiled return.
		if (precompile)
		    return;

		if (servlet instanceof SingleThreadModel) {
		    // sync on the wrapper so that the freshness
		    // of the page is determined right before servicing
		    synchronized (this) {
			servlet.service(request, response);
		    }
		} else {
		    servlet.service(request, response);
		}

            } catch (FileNotFoundException ex) {
		try {
                    if (insecure_TMI) {
                        response.sendError(HttpServletResponse.SC_NOT_FOUND, 
                                           Constants.getString
                                           ("jsp.error.file.not.found.TMI", 
                                            new Object[] {
                                                ex.getMessage()
                                            }));
                    } else {
                        response.sendError(HttpServletResponse.SC_NOT_FOUND, 
                                           Constants.getString
                                           ("jsp.error.file.not.found", 
                                            new Object[] {
                                                // Too Much Information -- ex.getMessage()
                                            }));
                    }
		} catch (IllegalStateException ise) {
                    // logs are presumed to be secure, thus the TMI info can be logged
		    Constants.jasperLog.log(Constants.getString
					    ("jsp.error.file.not.found.TMI",
					     new Object[] {
						 ex.getMessage()
					     }), ex,
					    Log.ERROR);
		    // rethrow FileNotFoundException so someone higher up can handle
                    if (insecure_TMI)
                        throw ex;
                    else
			throw new FileNotFoundException(Constants.getString
                                           ("jsp.error.file.not.found", 
                                            new Object[] {
                                                // Too Much Information -- ex.getMessage()
                                            }));
		}
                return;
            }
	}

        public void destroy()
        {
            if(theServlet != null)
                theServlet.destroy();
        }
    }
	
	
    protected ServletContext context = null;
    protected Hashtable jsps = new Hashtable();
    //    protected Hashtable loadedJSPs = new Hashtable();
    protected ServletConfig config;
    protected JasperLoader loader;
    protected Options options;
    protected ClassLoader parentClassLoader;
    protected ServletEngine engine;
    protected String serverInfo;
    
    /** Set to true to provide Too Much Information on errors */
    private final boolean insecure_TMI = false;

    static boolean firstTime = true;
    static boolean jdk12=false;
    static {
	try {
	    Class.forName( "java.security.PrivilegedAction" );
	    jdk12=true;
	} catch(Throwable ex ) {
	}
    }

    public void init(ServletConfig config)
	throws ServletException
    {
	super.init(config);
	this.config = config;
	this.context = config.getServletContext();
        this.serverInfo = context.getServerInfo();
        
	options = new EmbededServletOptions(config, context);

	parentClassLoader = (ClassLoader) context.getAttribute(Constants.SERVLET_CLASS_LOADER);
	if (parentClassLoader == null)
	    parentClassLoader = this.getClass().getClassLoader();
            
	// getClass().getClassLoader() returns null in JDK 1.1.6/1.1.8
	if (parentClassLoader != null) {
            Constants.message("jsp.message.parent_class_loader_is", 
                              new Object[] {
                                  parentClassLoader.toString()
                              }, Log.DEBUG);
            }
	else {
            Constants.message("jsp.message.parent_class_loader_is", 
                              new Object[] {
                                  ""
                              }, Log.DEBUG);
	}
	if( loader==null ) {
	    if( jdk12 ) {
		try {
		    Class ld=Class.forName("org.apache.jasper.servlet.JasperLoader12");
		    loader=(JasperLoader)ld.newInstance();
		} catch(Throwable t ) {
		    loghelper.log("Loading org.apache.jasper.servlet.JasperLoader12", t);
		}
	    }
	    if( loader==null )
		loader = new org.apache.jasper.servlet.JasperLoader();

	    loader.setParentClassLoader(parentClassLoader);
	    loader.setOptions(options);
	    Object pd=context.getAttribute("org.apache.tomcat.protection_domain");
	    loader.setProtectionDomain( pd );
	}
	if (firstTime) {
	    firstTime = false;
	    Constants.message("jsp.message.scratch.dir.is", 
			      new Object[] { 
				  options.getScratchDir().toString() 
			      }, Log.INFORMATION );
	    Constants.message("jsp.message.dont.modify.servlets", Log.INFORMATION);
	    JspFactory.setDefaultFactory(new JspFactoryImpl());
	}
    }

    private void serviceJspFile(HttpServletRequest request, 
      				HttpServletResponse response, String jspUri, 
				Throwable exception, boolean precompile) 
	throws ServletException, IOException
    {
	boolean isErrorPage = exception != null;
        JspServletWrapper wrapper = null;

        /*
         * Several threads may be handling requests for the same jspUri.
         * Only one of them is allowed to create the JspServletWrapper.
         */
        synchronized(jsps){
            wrapper = (JspServletWrapper) jsps.get(jspUri);
            if (wrapper == null) {
                wrapper = new JspServletWrapper(jspUri, isErrorPage);
                jsps.put(jspUri, wrapper);
            }
        }
	
	wrapper.service(request, response, precompile);
    }


    boolean preCompile(HttpServletRequest request) 
        throws ServletException 
    {
        boolean precompile = false;
        String precom = null;
        String qString = request.getQueryString();
        // Avoid calling getParameter() unless precompile string is found
        // in query string.  Allows post data to remain unread per the
        // servlet spec if the precompile string is not found.
        if (qString != null && qString.indexOf(Constants.PRECOMPILE) >= 0)
            precom = request.getParameter(Constants.PRECOMPILE);
        
        if (precom != null) {
            if (precom.equals("true")) 
                precompile = true;
            else if (precom.equals("false")) 
                precompile = false;
            else {
		    // This is illegal.
		    throw new ServletException("Can't have request parameter " +
					       Constants.PRECOMPILE + " set to " + precom);
            }
        } else if (qString != null && (qString.startsWith(Constants.PRECOMPILE) ||
                                     qString.indexOf("&" + Constants.PRECOMPILE)
                                     != -1))
            precompile = true;

        return precompile;
    }
    
    

    public void service (HttpServletRequest request, 
    			 HttpServletResponse response)
	throws ServletException, IOException
    {
	try {
            String includeUri 
                = (String) request.getAttribute(Constants.INC_SERVLET_PATH);

            String jspUri;

            if (includeUri == null)
		jspUri = request.getServletPath();
            else
                jspUri = includeUri;

//	    System.out.println("JspServletWrapper: " + includeUri + " " +
//                            jspUri + 
// 			       (String) request.getAttribute(
//                                  Constants.INC_REQUEST_URI));

            boolean precompile = preCompile(request);

	    Log jasperLog = Constants.jasperLog;
	    
            if (jasperLog != null &&
		jasperLog.getLevel() >= Log.INFORMATION)
		{
		    jasperLog.log("JspEngine --> "+jspUri);
		    jasperLog.log("\t     ServletPath: "+request.getServletPath());
		    jasperLog.log("\t        PathInfo: "+request.getPathInfo());
		    jasperLog.log("\t        RealPath: "
				  +getServletConfig().getServletContext().getRealPath(jspUri));
		    jasperLog.log("\t      RequestURI: "+request.getRequestURI());
		    jasperLog.log("\t     QueryString: "+request.getQueryString());
		    jasperLog.log("\t  Request Params: ");
                    // If not precompiling and method is POST, avoid reading POST data.
                    if ( !precompile && request.getMethod().equals("POST") )
                        jasperLog.log("Parameters not read because method is POST");
                    else {
                        Enumeration e = request.getParameterNames();
                        while (e.hasMoreElements()) {
                            String name = (String) e.nextElement();
                            jasperLog.log("\t\t "+name+" = "+request.getParameter(name));
                        }
                    }
		}
            serviceJspFile(request, response, jspUri, null, precompile);
	} catch (RuntimeException e) {
	    throw e;
	} catch (ServletException e) {
	    throw e;
	} catch (IOException e) {
	    throw e;
	} catch (Throwable e) {
	    throw new ServletException(e);
	}

	// It's better to throw the exception - we don't
	// know if we can deal with sendError ( buffer may be
	// commited )
	// catch (Throwable t) {
	// 	    unknownException(response, t);
	// 	}
    }

    public void destroy() {
	if (Constants.jasperLog != null)
	    Constants.jasperLog.log("JspServlet.destroy()", Log.INFORMATION);

	Enumeration servlets = jsps.elements();
	while (servlets.hasMoreElements()) 
	    ((JspServletWrapper) servlets.nextElement()).destroy();
    }


    /*  Check if we need to reload a JSP page.
     *
     *  Side-effect: re-compile the JSP page.
     *
     *  @param classpath explicitly set the JSP compilation path.
     *  @return true if JSP files is newer
     */
    boolean loadJSP(String jspUri, String classpath, 
	boolean isErrorPage, HttpServletRequest req, HttpServletResponse res) 
	throws JasperException, FileNotFoundException 
    {
	// Loader knows how to set the right priviledges, and call
	// doLoadeJsp
	return loader.loadJSP( this,jspUri, classpath, isErrorPage, req, res );
    }

    /*  Check if we need to reload a JSP page.
     *
     *  Side-effect: re-compile the JSP page.
     *
     *  @param classpath explicitly set the JSP compilation path.
     *  @return true if JSP files is newer
     */

    /*
     * A word about the thread synchronization below.  The call to 
     * compiler.isOutDated() is outside the synchronization block on purpose.  
     * The expectation is that for the vast majority of cases the JSP source file 
     * will not have changed and there will be no need to recompile the 
     * implementation class.  For those cases when a compile is required, we 
     * enter a block that is synchronized on the JspServletWrapper object for 
     * this JSP page.  Because the initial out dated check is unsynchronized, it 
     * is possible for more than one request to attempt to enter the synchronized 
     * compile block.  The compile() method contains performs an outdated check 
     * of its own.  The first thread into the block will cause a compile, the 
     * subsequent threads will essentially skip the compilation and instantiation 
     * steps.  
     * 
     * One other thing to note is that there is a window of time between the 
     * compiler.compile() call and the end of the synchronized block where a new 
     * thread entering doLoadJSP() will be told that that implementation class is 
     * up to date even though the code in the synchronized block has not 
     * completed loading and instantiating the class.  In this case doLoadJSP() 
     * will return false without attempting to compile the class.  This is OK 
     * because the JspServletWrapper.getServlet() method used by the 
     * JspServletWrapper.service() method is synchronized.  Thus, the service 
     * method will not receive the servlet class until it has been completely loaded and 
     * instantiated.  
     * 
     * The bottom line is that we avoid synchronizing a fairly expensive 
     * operation (isOutDated) but pay a small price of some unnecessary 
     * compilation attempts in the atypical case of a modified JSP file.  
     */
    protected boolean doLoadJSP(String jspUri, String classpath, 
                                boolean isErrorPage, HttpServletRequest req, HttpServletResponse res) 
    throws JasperException, FileNotFoundException 
    {
        JspServletWrapper jsw=(JspServletWrapper) jsps.get(jspUri);
        if( jsw==null ) {
            throw new JasperException("Can't happen - JspServletWrapper=null");
        }
        JspCompilationContext ctxt = new JspEngineContext(loader, classpath,
                                                          context, jspUri, 
                                                          isErrorPage, options,
                                                          req, res);
        boolean outDated = false; 

        Compiler compiler = null;
        synchronized(jsw){
            /*
             * Creating a compiler opens the associated .class file (if it exists)
             * and reads the actual class name.  If we allow a compiler to be
             * created while a compile is going on then bad things can happen.
             */
            compiler = ctxt.createCompiler();
        }

        try {


            outDated = compiler.isOutDated();
            if(!jsw.isInstantiated() || outDated ) {
                synchronized(jsw){
                    outDated = compiler.compile();
                    if(!jsw.isInstantiated() || outDated) {
                        if( null ==ctxt.getServletClassName() ) {
                            compiler.computeServletClassName();
                        }
                        jsw.instantiateServlet(loader.loadClass(ctxt.getFullClassName()));
                    }
                }
            }
        } catch(FileNotFoundException ex) {
            compiler.removeGeneratedFiles();
            throw ex;
        } catch(JasperException ex) {
            throw ex;
        } catch(ClassNotFoundException cex) {
                throw new JasperException(Constants.getString("jsp.error.unable.load"), 
                                          cex);
        } catch(Exception ex) {
            throw new JasperException(Constants.getString("jsp.error.unable.compile"),
                                      ex);
        }

        return outDated;
    }

        /**
     * Determines whether the current JSP class is older than the JSP file
     * from whence it came
     */
    public boolean isOutDated(File jsp, JspCompilationContext ctxt,
			      Mangler mangler ) {
        File jspReal = null;
	boolean outDated;
	
        jspReal = new File(ctxt.getRealPath(jsp.getPath()));

        File classFile = new File(mangler.getClassFileName());
        if (classFile.exists()) {
            outDated = classFile.lastModified() < jspReal.lastModified();
        } else {
            outDated = true;
        }

        return outDated;
    }

}