/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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.struts2.jasper.servlet;

import java.io.FileNotFoundException;
import java.io.IOException;
import java.net.URL;

import javax.servlet.Servlet;
import javax.servlet.ServletConfig;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.SingleThreadModel;
import javax.servlet.UnavailableException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.jsp.tagext.TagInfo;

import org.apache.struts2.jasper.JasperException;
import org.apache.struts2.jasper.JspCompilationContext;
import org.apache.struts2.jasper.Options;
import org.apache.struts2.jasper.compiler.ErrorDispatcher;
import org.apache.struts2.jasper.compiler.JavacErrorDetail;
import org.apache.struts2.jasper.compiler.JspRuntimeContext;
import org.apache.struts2.jasper.compiler.Localizer;
import org.apache.struts2.jasper.runtime.JspSourceDependent;
import org.apache.struts2.jasper.runtime.InstanceHelper;
import org.apache.juli.logging.Log;
import org.apache.juli.logging.LogFactory;
import org.apache.tomcat.InstanceManager;

/**
 * The JSP engine (a.k.a Jasper).
 *
 * The servlet container is responsible for providing a
 * URLClassLoader for the web application context Jasper
 * is being used in. Jasper will try get the Tomcat
 * ServletContext attribute for its ServletContext class
 * loader, if that fails, it uses the parent class loader.
 * In either case, it must be a URLClassLoader.
 *
 * @author Anil K. Vijendran
 * @author Harish Prabandham
 * @author Remy Maucherat
 * @author Kin-man Chung
 * @author Glenn Nielsen
 * @author Tim Fennell
 */

public class JspServletWrapper {

    // Logger
    private Log log = LogFactory.getLog(JspServletWrapper.class);

    private Servlet theServlet;
    private String jspUri;
    private Class servletClass;
    private Class tagHandlerClass;
    private JspCompilationContext ctxt;
    private long available = 0L;
    private ServletConfig config;
    private Options options;
    private boolean firstTime = true;
    private boolean reload = true;
    private boolean isTagFile;
    private int tripCount;
    private JasperException compileException;
    private long servletClassLastModifiedTime;
    private long lastModificationTest = 0L;

    /*
     * JspServletWrapper for JSP pages.
     */
    public JspServletWrapper(ServletConfig config, Options options, String jspUri,
                      boolean isErrorPage, JspRuntimeContext rctxt)
            throws JasperException {

	this.isTagFile = false;
        this.config = config;
        this.options = options;
        this.jspUri = jspUri;
        ctxt = new JspCompilationContext(jspUri, isErrorPage, options,
					 config.getServletContext(),
					 this, rctxt, null);
    }

    /*
     * JspServletWrapper for tag files.
     */
    public JspServletWrapper(ServletContext servletContext,
			     Options options,
			     String tagFilePath,
			     TagInfo tagInfo,
			     JspRuntimeContext rctxt,
			     URL tagFileJarUrl)
	    throws JasperException {

	this.isTagFile = true;
        this.config = null;	// not used
        this.options = options;
	this.jspUri = tagFilePath;
	this.tripCount = 0;
        ctxt = new JspCompilationContext(jspUri, tagInfo, options,
					 servletContext, this, rctxt,
					 tagFileJarUrl);
    }

    public JspCompilationContext getJspEngineContext() {
        return ctxt;
    }

    public void setReload(boolean reload) {
        this.reload = reload;
    }

    public Servlet getServlet()
        throws ServletException, IOException, FileNotFoundException
    {
        if (reload) {
            synchronized (this) {
                // Synchronizing on jsw enables simultaneous loading
                // of different pages, but not the same page.
                if (reload) {
                    // This is to maintain the original protocol.
                    destroy();
                    
                    Servlet servlet = null;
                    
                    try {
                        servletClass = ctxt.load();
                        servlet = (Servlet) servletClass.newInstance();
                        final InstanceManager instanceManager = InstanceHelper.getServletInstanceManager(config);
                        if (instanceManager != null) {
                            InstanceHelper.postConstruct(instanceManager, servlet);
                        }
                    } catch (IllegalAccessException e) {
                        throw new JasperException(e);
                    } catch (InstantiationException e) {
                        throw new JasperException(e);
                    } catch (Exception e) {
                        throw new JasperException(e);
                    }
                    
                    servlet.init(config);

                    if (!firstTime) {
                        ctxt.getRuntimeContext().incrementJspReloadCount();
                    }

                    theServlet = servlet;
                    reload = false;
                }
            }    
        }
        return theServlet;
    }

    public ServletContext getServletContext() {
        return config.getServletContext();
    }

    /**
     * Sets the compilation exception for this JspServletWrapper.
     *
     * @param je The compilation exception
     */
    public void setCompilationException(JasperException je) {
        this.compileException = je;
    }

    /**
     * Sets the last-modified time of the servlet class file associated with
     * this JspServletWrapper.
     *
     * @param lastModified Last-modified time of servlet class
     */
    public void setServletClassLastModifiedTime(long lastModified) {
        if (this.servletClassLastModifiedTime < lastModified) {
            synchronized (this) {
                if (this.servletClassLastModifiedTime < lastModified) {
                    this.servletClassLastModifiedTime = lastModified;
                    reload = true;
                }
            }
        }
    }

    /**
     * Compile (if needed) and load a tag file
     */
    public Class loadTagFile() throws JasperException {

        try {
            if (ctxt.isRemoved()) {
                throw new FileNotFoundException(jspUri);
            }
            if (options.getDevelopment() || firstTime ) {
                synchronized (this) {
                    firstTime = false;
                    ctxt.compile();
                }
            } else {
                if (compileException != null) {
                    throw compileException;
                }
            }

            if (reload) {
                tagHandlerClass = ctxt.load();
                reload = false;
            }
        } catch (FileNotFoundException ex) {
            throw new JasperException(ex);
	}

	return tagHandlerClass;
    }

    /**
     * Compile and load a prototype for the Tag file.  This is needed
     * when compiling tag files with circular dependencies.  A prototpe
     * (skeleton) with no dependencies on other other tag files is
     * generated and compiled.
     */
    public Class loadTagFilePrototype() throws JasperException {

	ctxt.setPrototypeMode(true);
	try {
	    return loadTagFile();
	} finally {
	    ctxt.setPrototypeMode(false);
	}
    }

    /**
     * Get a list of files that the current page has source dependency on.
     */
    public java.util.List getDependants() {
        try {
            Object target;
            if (isTagFile) {
                if (reload) {
                    tagHandlerClass = ctxt.load();
                    reload = false;
                }
                target = tagHandlerClass.newInstance();
            } else {
                target = getServlet();
            }
            if (target != null && target instanceof JspSourceDependent) {
                return ((java.util.List) ((JspSourceDependent) target).getDependants());
            }
        } catch (Throwable ex) {
        }
        return null;
    }

    public boolean isTagFile() {
	return this.isTagFile;
    }

    public int incTripCount() {
	return tripCount++;
    }

    public int decTripCount() {
	return tripCount--;
    }

    public void service(HttpServletRequest request, 
                        HttpServletResponse response,
                        boolean precompile)
	    throws ServletException, IOException, FileNotFoundException {
        
        try {

            if (ctxt.isRemoved()) {
                throw new FileNotFoundException(jspUri);
            }

            if ((available > 0L) && (available < Long.MAX_VALUE)) {
                if (available > System.currentTimeMillis()) {
                    response.setDateHeader("Retry-After", available);
                    response.sendError
                        (HttpServletResponse.SC_SERVICE_UNAVAILABLE,
                         Localizer.getMessage("jsp.error.unavailable"));
                    return;
                } else {
                    // Wait period has expired. Reset.
                    available = 0;
                }
            }

            /*
             * (1) Compile
             */
            if (options.getDevelopment() || firstTime ) {
                synchronized (this) {
                    firstTime = false;

                    // The following sets reload to true, if necessary
                    ctxt.compile();
                }
            } else {
                if (compileException != null) {
                    // Throw cached compilation exception
                    throw compileException;
                }
            }

            /*
             * (2) (Re)load servlet class file
             */
            getServlet();

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

        } catch (ServletException ex) {
            if (options.getDevelopment()) {
                throw handleJspException(ex);
            } else {
                throw ex;
            }
        } catch (IOException ex) {
            if (options.getDevelopment()) {
                throw handleJspException(ex);
            } else {
                throw ex;
            }
        } catch (IllegalStateException ex) {
            if (options.getDevelopment()) {
                throw handleJspException(ex);
            } else {
                throw ex;
            }
        } catch (Exception ex) {
            if (options.getDevelopment()) {
                throw handleJspException(ex);
            } else {
                throw new JasperException(ex);
            }
        }

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

        } catch (UnavailableException ex) {
            String includeRequestUri = (String)
                request.getAttribute("javax.servlet.include.request_uri");
            if (includeRequestUri != null) {
                // This file was included. Throw an exception as
                // a response.sendError() will be ignored by the
                // servlet engine.
                throw ex;
            } else {
                int unavailableSeconds = ex.getUnavailableSeconds();
                if (unavailableSeconds <= 0) {
                    unavailableSeconds = 60;        // Arbitrary default
                }
                available = System.currentTimeMillis() +
                    (unavailableSeconds * 1000L);
                response.sendError
                    (HttpServletResponse.SC_SERVICE_UNAVAILABLE, 
                     ex.getMessage());
            }
        } catch (ServletException ex) {
            if(options.getDevelopment()) {
                throw handleJspException(ex);
            } else {
                throw ex;
            }
        } catch (IOException ex) {
            if(options.getDevelopment()) {
                throw handleJspException(ex);
            } else {
                throw ex;
            }
        } catch (IllegalStateException ex) {
            if(options.getDevelopment()) {
                throw handleJspException(ex);
            } else {
                throw ex;
            }
        } catch (Exception ex) {
            if(options.getDevelopment()) {
                throw handleJspException(ex);
            } else {
                throw new JasperException(ex);
            }
        }
    }

    public void destroy() {
        if (theServlet != null) {
            theServlet.destroy();
            final InstanceManager instanceManager = InstanceHelper.getServletInstanceManager(config);
            if (instanceManager != null) {
                try {
                    InstanceHelper.preDestroy(instanceManager, theServlet);
                } catch (Exception e) {
                    // Log any exception, since it can't be passed along
                    log.error(Localizer.getMessage("jsp.error.file.not.found",
                           e.getMessage()), e);
                }
            }
        }
    }

    /**
     * @return Returns the lastModificationTest.
     */
    public long getLastModificationTest() {
        return lastModificationTest;
    }
    /**
     * @param lastModificationTest The lastModificationTest to set.
     */
    public void setLastModificationTest(long lastModificationTest) {
        this.lastModificationTest = lastModificationTest;
    }

    /**
     * <p>Attempts to construct a JasperException that contains helpful information
     * about what went wrong. Uses the JSP compiler system to translate the line
     * number in the generated servlet that originated the exception to a line
     * number in the JSP.  Then constructs an exception containing that
     * information, and a snippet of the JSP to help debugging.
     * Please see http://issues.apache.org/bugzilla/show_bug.cgi?id=37062 and
     * http://www.tfenne.com/jasper/ for more details.
     *</p>
     *
     * @param ex the exception that was the cause of the problem.
     * @return a JasperException with more detailed information
     */
    protected JasperException handleJspException(Exception ex) {
        try {
            Throwable realException = ex;
            if (ex instanceof ServletException) {
                realException = ((ServletException) ex).getRootCause();
            }

            // First identify the stack frame in the trace that represents the JSP
            StackTraceElement[] frames = realException.getStackTrace();
            StackTraceElement jspFrame = null;

            for (int i=0; i<frames.length; ++i) {
                if ( frames[i].getClassName().equals(this.getServlet().getClass().getName()) ) {
                    jspFrame = frames[i];
                    break;
                }
            }

            if (jspFrame == null) {
                // If we couldn't find a frame in the stack trace corresponding
                // to the generated servlet class, we can't really add anything
                return new JasperException(ex);
            }
            else {
                int javaLineNumber = jspFrame.getLineNumber();
                JavacErrorDetail detail = ErrorDispatcher.createJavacError(
                        jspFrame.getMethodName(),
                        this.ctxt.getCompiler().getPageNodes(),
                        null,
                        javaLineNumber,
                        ctxt);

                // If the line number is less than one we couldn't find out
                // where in the JSP things went wrong
                int jspLineNumber = detail.getJspBeginLineNumber();
                if (jspLineNumber < 1) {
                    throw new JasperException(ex);
                }

                if (options.getDisplaySourceFragment()) {
                    return new JasperException(Localizer.getMessage
                            ("jsp.exception", detail.getJspFileName(),
                                    "" + jspLineNumber) +
                                    "\n\n" + detail.getJspExtract() +
                                    "\n\nStacktrace:", ex);
                    
                } else {
                    return new JasperException(Localizer.getMessage
                            ("jsp.exception", detail.getJspFileName(),
                                    "" + jspLineNumber), ex);
                }
            }
        } catch (Exception je) {
            // If anything goes wrong, just revert to the original behaviour
            if (ex instanceof JasperException) {
                return (JasperException) ex;
            } else {
                return new JasperException(ex);
            }
        }
    }

}
