/*
 * 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.jasper.runtime;

import java.io.IOException;
import java.io.Writer;
import java.security.AccessController;
import java.security.PrivilegedAction;
import java.security.PrivilegedActionException;
import java.security.PrivilegedExceptionAction;
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.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
import javax.servlet.jsp.JspException;
import javax.servlet.jsp.JspFactory;
import javax.servlet.jsp.JspWriter;
import javax.servlet.jsp.PageContext;
import javax.servlet.jsp.el.ELException;
import javax.servlet.jsp.el.ExpressionEvaluator;
import javax.servlet.jsp.el.VariableResolver;
import javax.servlet.jsp.tagext.BodyContent;

import org.apache.commons.el.ExpressionEvaluatorImpl;
import org.apache.commons.el.VariableResolverImpl;
import org.apache.jasper.Constants;
import org.apache.jasper.compiler.Localizer;
import org.apache.jasper.security.SecurityUtil;

/**
 * Implementation of the PageContext class from the JSP spec.
 * Also doubles as a VariableResolver for the EL.
 *
 * @author Anil K. Vijendran
 * @author Larry Cable
 * @author Hans Bergsten
 * @author Pierre Delisle
 * @author Mark Roth
 * @author Jan Luehe
 */
public class PageContextImpl extends PageContext implements VariableResolver {

    // The expression evaluator, for evaluating EL expressions.
    private static ExpressionEvaluatorImpl elExprEval
        = new ExpressionEvaluatorImpl(false);

    // The variable resolver, for evaluating EL expressions.
    private VariableResolverImpl variableResolver;

    private BodyContentImpl[] outs;
    private int depth;

    // per-servlet state
    private Servlet servlet;
    private ServletConfig config;
    private ServletContext context;
    private String errorPageURL;

    // page-scope attributes
    private transient Hashtable        attributes;

    // per-request state
    private transient ServletRequest request;
    private transient ServletResponse response;
    private transient HttpSession session;
    private boolean isIncluded;

    // initial output stream
    private transient JspWriter out;
    private transient JspWriterImpl baseOut;

    /*
     * Constructor.
     */
    PageContextImpl(JspFactory factory) {
        this.variableResolver = new VariableResolverImpl(this);
        this.outs = new BodyContentImpl[0];
        this.attributes = new Hashtable(16);
        this.depth = -1;
    }

    public void initialize(Servlet servlet,
                           ServletRequest request,
                           ServletResponse response,
                           String errorPageURL,
                           boolean needsSession,
                           int bufferSize,
                           boolean autoFlush) throws IOException {

        _initialize(servlet, request, response, errorPageURL, needsSession,
                    bufferSize, autoFlush);
    }

    private void _initialize(Servlet servlet,
                             ServletRequest request,
                             ServletResponse response,
                             String errorPageURL,
                             boolean needsSession,
                             int bufferSize,
                             boolean autoFlush) throws IOException {

        // initialize state
        this.servlet = servlet;
        this.config = servlet.getServletConfig();
        this.context = config.getServletContext();
        this.errorPageURL = errorPageURL;
        this.request = request;
        this.response = response;


        // Setup session (if required)
        if (request instanceof HttpServletRequest && needsSession)
            this.session = ((HttpServletRequest)request).getSession();
        if (needsSession && session == null)
            throw new IllegalStateException
                ("Page needs a session and none is available");

        // initialize the initial out ...
        depth = -1;
        if (this.baseOut == null) {
            this.baseOut = new JspWriterImpl(response, bufferSize, autoFlush);
        } else {
            this.baseOut.init(response, bufferSize, autoFlush);
        }
        this.out = baseOut;

        // register names/values as per spec
        setAttribute(OUT, this.out);
        setAttribute(REQUEST, request);
        setAttribute(RESPONSE, response);

        if (session != null)
            setAttribute(SESSION, session);

        setAttribute(PAGE, servlet);
        setAttribute(CONFIG, config);
        setAttribute(PAGECONTEXT, this);
        setAttribute(APPLICATION, context);

        isIncluded = request.getAttribute(
            "javax.servlet.include.servlet_path") != null;
    }

    public void release() {
        out = baseOut;
        try {
            if (isIncluded) {
                ((JspWriterImpl)out).flushBuffer();
                // push it into the including jspWriter
            } else {
                // Old code:
                //out.flush();
                // Do not flush the buffer even if we're not included (i.e.
                // we are the main page. The servlet will flush it and close
                // the stream.
                ((JspWriterImpl)out).flushBuffer();
            }
        } catch (IOException ex) {
            context.log(
                "PageContextImpl.release(): Internal error flushing buffer");
        }

        servlet = null;
        config = null;
        context = null;
        errorPageURL = null;
        request = null;
        response = null;
        depth = -1;
        baseOut.recycle();
        session = null;

        attributes.clear();
    }

    public Object getAttribute(final String name) {

        if (name == null) {
            throw new NullPointerException(
                    Localizer.getMessage("jsp.error.attribute.null_name"));
        }

        if (SecurityUtil.isPackageProtectionEnabled()){
            return AccessController.doPrivileged(new PrivilegedAction(){
                public Object run(){
                    return doGetAttribute(name);
                }
            });
        } else {
            return doGetAttribute(name);
        }

    }

    private Object doGetAttribute(String name){
        return attributes.get(name);
    }

    public Object getAttribute(final String name, final int scope) {

        if (name == null) {
            throw new NullPointerException(
                    Localizer.getMessage("jsp.error.attribute.null_name"));
        }

        if (SecurityUtil.isPackageProtectionEnabled()){
            return AccessController.doPrivileged(new PrivilegedAction(){
                public Object run(){
                    return doGetAttribute(name, scope);
                }
            });
        } else {
            return doGetAttribute(name, scope);
        }

    }

    private Object doGetAttribute(String name, int scope){
        switch (scope) {
            case PAGE_SCOPE:
            return attributes.get(name);

            case REQUEST_SCOPE:
            return request.getAttribute(name);

            case SESSION_SCOPE:
            if (session == null) {
                throw new IllegalStateException(
                        Localizer.getMessage("jsp.error.page.noSession"));
            }
            return session.getAttribute(name);

            case APPLICATION_SCOPE:
            return context.getAttribute(name);

            default:
            throw new IllegalArgumentException("Invalid scope");
        }
    }

    public void setAttribute(final String name, final Object attribute) {

        if (name == null) {
            throw new NullPointerException(
                    Localizer.getMessage("jsp.error.attribute.null_name"));
        }

        if (SecurityUtil.isPackageProtectionEnabled()){
            AccessController.doPrivileged(new PrivilegedAction(){
                public Object run(){
                    doSetAttribute(name, attribute);
                    return null;
                }
            });
        } else {
            doSetAttribute(name, attribute);
        }
    }

    private void doSetAttribute(String name, Object attribute){
        if (attribute != null) {
            attributes.put(name, attribute);
        } else {
            removeAttribute(name, PAGE_SCOPE);
        }
    }

    public void setAttribute(final String name, final Object o, final int scope) {

        if (name == null) {
            throw new NullPointerException(
                    Localizer.getMessage("jsp.error.attribute.null_name"));
        }

        if (SecurityUtil.isPackageProtectionEnabled()){
            AccessController.doPrivileged(new PrivilegedAction(){
                public Object run(){
                    doSetAttribute(name, o, scope);
                    return null;
                }
            });
        } else {
            doSetAttribute(name, o, scope);
        }

    }

    private void doSetAttribute(String name, Object o, int scope ){
        if (o != null) {
            switch (scope) {
            case PAGE_SCOPE:
            attributes.put(name, o);
            break;

            case REQUEST_SCOPE:
            request.setAttribute(name, o);
            break;

            case SESSION_SCOPE:
            if (session == null) {
                throw new IllegalStateException(
                        Localizer.getMessage("jsp.error.page.noSession"));
            }
            session.setAttribute(name, o);
            break;

            case APPLICATION_SCOPE:
            context.setAttribute(name, o);
            break;

            default:
            throw new IllegalArgumentException("Invalid scope");
            }
        } else {
            removeAttribute(name, scope);
        }
    }

    public void removeAttribute(final String name, final int scope) {

        if (name == null) {
            throw new NullPointerException(
                    Localizer.getMessage("jsp.error.attribute.null_name"));
        }
        if (SecurityUtil.isPackageProtectionEnabled()){
            AccessController.doPrivileged(new PrivilegedAction(){
                public Object run(){
                    doRemoveAttribute(name, scope);
                    return null;
                }
            });
        } else {
            doRemoveAttribute(name, scope);
        }
    }

    private void doRemoveAttribute(String name, int scope){
        switch (scope) {
        case PAGE_SCOPE:
            attributes.remove(name);
            break;

        case REQUEST_SCOPE:
            request.removeAttribute(name);
            break;

        case SESSION_SCOPE:
            if (session == null) {
            throw new IllegalStateException(
                        Localizer.getMessage("jsp.error.page.noSession"));
            }
            session.removeAttribute(name);
            break;

        case APPLICATION_SCOPE:
            context.removeAttribute(name);
            break;
            
        default:
            throw new IllegalArgumentException("Invalid scope");
        }
    }

    public int getAttributesScope(final String name) {

        if (name == null) {
            throw new NullPointerException(
                    Localizer.getMessage("jsp.error.attribute.null_name"));
        }

        if (SecurityUtil.isPackageProtectionEnabled()){
            return ((Integer)AccessController.doPrivileged(new PrivilegedAction(){
                public Object run(){
                    return new Integer(doGetAttributeScope(name));
                }
            })).intValue();
        } else {
            return doGetAttributeScope(name);
        }
    }

    private int doGetAttributeScope(String name){
        if (attributes.get(name) != null)
            return PAGE_SCOPE;

        if (request.getAttribute(name) != null)
            return REQUEST_SCOPE;

        if (session != null) {
            try {
                if (session.getAttribute(name) != null)
                    return SESSION_SCOPE;
            } catch(IllegalStateException ise) {
                // Session has been invalidated.
                // Ignore and fall through to application scope.
            }
        }

        if (context.getAttribute(name) != null)
            return APPLICATION_SCOPE;

        return 0;
    }

    public Object findAttribute(final String name) {
        if (SecurityUtil.isPackageProtectionEnabled()){
            return AccessController.doPrivileged(new PrivilegedAction(){
                public Object run(){
                    if (name == null) {
                        throw new NullPointerException(
                                Localizer.getMessage("jsp.error.attribute.null_name"));
                    }

                    return doFindAttribute(name);
                }
            });
        } else {
            if (name == null) {
                throw new NullPointerException(
                        Localizer.getMessage("jsp.error.attribute.null_name"));
            }

            return doFindAttribute(name);
        }
    }

    private Object doFindAttribute(String name){

        Object o = attributes.get(name);
        if (o != null)
            return o;

        o = request.getAttribute(name);
        if (o != null)
            return o;

        if (session != null) {
            try {
                o = session.getAttribute(name);
            } catch(IllegalStateException ise) {
                // Session has been invalidated.
                // Ignore and fall through to application scope.
            }
            if (o != null)
                return o;
        }

        return context.getAttribute(name);
    }


    public Enumeration getAttributeNamesInScope(final int scope) {
        if (SecurityUtil.isPackageProtectionEnabled()){
            return (Enumeration)
                    AccessController.doPrivileged(new PrivilegedAction(){
                public Object run(){
                    return doGetAttributeNamesInScope(scope);
                }
            });
        } else {
            return doGetAttributeNamesInScope(scope);
        }
    }

    private Enumeration doGetAttributeNamesInScope(int scope){
        switch (scope) {
        case PAGE_SCOPE:
            return attributes.keys();
            
        case REQUEST_SCOPE:
            return request.getAttributeNames();

        case SESSION_SCOPE:
            if (session == null) {
            throw new IllegalStateException(
                        Localizer.getMessage("jsp.error.page.noSession"));
            }
            return session.getAttributeNames();

        case APPLICATION_SCOPE:
            return context.getAttributeNames();

        default:
            throw new IllegalArgumentException("Invalid scope");
        }
    }

    public void removeAttribute(final String name) {

        if (name == null) {
            throw new NullPointerException(
                    Localizer.getMessage("jsp.error.attribute.null_name"));
        }

        if (SecurityUtil.isPackageProtectionEnabled()){
            AccessController.doPrivileged(new PrivilegedAction(){
                public Object run(){
                    doRemoveAttribute(name);
                    return null;
                }
            });
        } else {
            doRemoveAttribute(name);
        }
        }


    private void doRemoveAttribute(String name){
        removeAttribute(name, PAGE_SCOPE);
        removeAttribute(name, REQUEST_SCOPE);
        if( session != null ) {
            try {
                removeAttribute(name, SESSION_SCOPE);
            } catch(IllegalStateException ise) {
                // Session has been invalidated.
                // Ignore and fall throw to application scope.
            }
        }
        removeAttribute(name, APPLICATION_SCOPE);
    }

    public JspWriter getOut() {
        return out;
    }

    public HttpSession getSession() { return session; }
    public Servlet getServlet() { return servlet; }
    public ServletConfig getServletConfig() { return config; }
    public ServletContext getServletContext() {
        return config.getServletContext();
    }
    public ServletRequest getRequest() { return request; }
    public ServletResponse getResponse() { return response; }


    /**
     * Returns the exception associated with this page
     * context, if any.
     * <p/>
     * Added wrapping for Throwables to avoid ClassCastException:
     * see Bugzilla 31171 for details.
     *
     * @return The Exception associated with this page context, if any.
     */
    public Exception getException() {
        Throwable t = JspRuntimeLibrary.getThrowable(request);

        // Only wrap if needed
        if((t != null) && (! (t instanceof Exception))) {
            t = new JspException(t);
        }

        return (Exception) t;
    }


    public Object getPage() { return servlet; }


    private final String getAbsolutePathRelativeToContext(String relativeUrlPath) {
        String path = relativeUrlPath;

        if (!path.startsWith("/")) {
            String uri = (String)
                request.getAttribute("javax.servlet.include.servlet_path");
            if (uri == null)
                uri = ((HttpServletRequest) request).getServletPath();
            String baseURI = uri.substring(0, uri.lastIndexOf('/'));
            path = baseURI+'/'+path;
        }

        return path;
    }

    public void include(String relativeUrlPath)
                throws ServletException, IOException {
        JspRuntimeLibrary.include(request, response, relativeUrlPath, out,
                                  true);
    }

    public void include(final String relativeUrlPath, final boolean flush)
                throws ServletException, IOException {
        if (SecurityUtil.isPackageProtectionEnabled()){
            try{
                AccessController.doPrivileged(new PrivilegedExceptionAction(){
                    public Object run() throws Exception{
                        doInclude(relativeUrlPath, flush);
                        return null;
                    }
                });
            } catch (PrivilegedActionException e){
                Exception ex =  e.getException();
                if (ex instanceof IOException){
                    throw (IOException)ex;
                } else {
                    throw (ServletException)ex;
                }
            }
        } else {
            doInclude(relativeUrlPath, flush);
        }
    }

    private void doInclude(String relativeUrlPath, boolean flush)
                throws ServletException, IOException {
        JspRuntimeLibrary.include(request, response, relativeUrlPath, out,
                                  flush);
    }

    public VariableResolver getVariableResolver() {
        return this;
    }

    public void forward(final String relativeUrlPath)
        throws ServletException, IOException {
        if (SecurityUtil.isPackageProtectionEnabled()){
            try{
                AccessController.doPrivileged(new PrivilegedExceptionAction(){
                    public Object run() throws Exception{
                        doForward(relativeUrlPath);
                        return null;
                    }
                });
            } catch (PrivilegedActionException e){
                Exception ex =  e.getException();
                if (ex instanceof IOException){
                    throw (IOException)ex;
                } else {
                    throw (ServletException)ex;
                }
            }
        } else {
            doForward(relativeUrlPath);
        }
    }

    private void doForward(String relativeUrlPath)
        throws ServletException, IOException{

        // JSP.4.5 If the buffer was flushed, throw IllegalStateException
        try {
            out.clear();
        } catch (IOException ex) {
            IllegalStateException ise =
                new IllegalStateException(Localizer.getMessage(
                            "jsp.error.attempt_to_clear_flushed_buffer"));
            ise.initCause(ex);
            throw ise;
        }

        // Make sure that the response object is not the wrapper for include
        while (response instanceof ServletResponseWrapperInclude) {
            response = ((ServletResponseWrapperInclude)response).getResponse();
        }

        final String path = getAbsolutePathRelativeToContext(relativeUrlPath);
        String includeUri
            = (String) request.getAttribute(Constants.INC_SERVLET_PATH);
            
        if (includeUri != null)
            request.removeAttribute(Constants.INC_SERVLET_PATH);
        try {
            context.getRequestDispatcher(path).forward(request, response);
        } finally {
            if (includeUri != null)
                request.setAttribute(Constants.INC_SERVLET_PATH, includeUri);
            request.setAttribute(Constants.FORWARD_SEEN, "true");
        }
    }

    public BodyContent pushBody() {
        return (BodyContent) pushBody(null);
    }

    public JspWriter pushBody(Writer writer) {
        depth++;
        if (depth >= outs.length) {
            BodyContentImpl[] newOuts = new BodyContentImpl[depth + 1];
            for (int i=0; i<outs.length; i++) {
                newOuts[i] = outs[i];
            }
            newOuts[depth] = new BodyContentImpl(out);
            outs = newOuts;
        }

        outs[depth].setWriter(writer);
        out = outs[depth];

        // Update the value of the "out" attribute in the page scope
        // attribute namespace of this PageContext
        setAttribute(OUT, out);

        return outs[depth];
    }

    public JspWriter popBody() {
        depth--;
        if (depth >= 0) {
            out = outs[depth];
        } else {
            out = baseOut;
        }

        // Update the value of the "out" attribute in the page scope
        // attribute namespace of this PageContext
        setAttribute(OUT, out);

        return out;
    }

    /**
     * Provides programmatic access to the ExpressionEvaluator.
     * The JSP Container must return a valid instance of an
     * ExpressionEvaluator that can parse EL expressions.
     */
    public ExpressionEvaluator getExpressionEvaluator() {
        return elExprEval;
    }

    public void handlePageException(Exception ex)
        throws IOException, ServletException
    {
        // Should never be called since handleException() called with a
        // Throwable in the generated servlet.
        handlePageException((Throwable) ex);
    }

    public void handlePageException(final Throwable t)
        throws IOException, ServletException
    {
        if (t == null)
            throw new NullPointerException("null Throwable");

        if (SecurityUtil.isPackageProtectionEnabled()){
            try{
                AccessController.doPrivileged(new PrivilegedExceptionAction(){
                    public Object run() throws Exception{
                        doHandlePageException(t);
                        return null;
                    }
                });
            } catch (PrivilegedActionException e){
                Exception ex =  e.getException();
                if (ex instanceof IOException){
                    throw (IOException)ex;
                } else {
                    throw (ServletException)ex;
                }
            }
        } else {
            doHandlePageException(t);
        }

    }

    private void doHandlePageException(Throwable t)
        throws IOException, ServletException {

        if (errorPageURL != null && !errorPageURL.equals("")) {

            /*
             * Set request attributes.
             * Do not set the javax.servlet.error.exception attribute here
             * (instead, set in the generated servlet code for the error page)
             * in order to prevent the ErrorReportValve, which is invoked as
             * part of forwarding the request to the error page, from
             * throwing it if the response has not been committed (the response
             * will have been committed if the error page is a JSP page).
             */
            request.setAttribute("javax.servlet.jsp.jspException", t);
            request.setAttribute("javax.servlet.error.status_code",
                new Integer(HttpServletResponse.SC_INTERNAL_SERVER_ERROR));
            request.setAttribute("javax.servlet.error.request_uri",
            ((HttpServletRequest) request).getRequestURI());
            request.setAttribute("javax.servlet.error.servlet_name",
                     config.getServletName());
            try {
                forward(errorPageURL);
            } catch (IllegalStateException ise) {
                include(errorPageURL);
            }

            // The error page could be inside an include.

            Object newException = request.getAttribute("javax.servlet.error.exception");

            // t==null means the attribute was not set.
            if( (newException!= null) && (newException==t) ) {
                request.removeAttribute("javax.servlet.error.exception");
            }

            // now clear the error code - to prevent double handling.
            request.removeAttribute("javax.servlet.error.status_code");
            request.removeAttribute("javax.servlet.error.request_uri");
            request.removeAttribute("javax.servlet.error.status_code");
            request.removeAttribute("javax.servlet.jsp.jspException");

        } else {
            // Otherwise throw the exception wrapped inside a ServletException.
            // Set the exception as the root cause in the ServletException
            // to get a stack trace for the real problem
            if (t instanceof IOException) throw (IOException)t;
            if (t instanceof ServletException) throw (ServletException)t;
            if (t instanceof RuntimeException) throw (RuntimeException)t;

            Throwable rootCause = null;
            if (t instanceof JspException) {
                rootCause = ((JspException) t).getRootCause();
            } else if (t instanceof ELException) {
                rootCause = ((ELException) t).getRootCause();
            }

            if (rootCause != null) {
                throw new ServletException(t.getClass().getName() + ": " + 
                                           t.getMessage(), rootCause);
            }
                 
            throw new ServletException(t);
        }
    }

    /**
     * VariableResolver interface
     */
    public Object resolveVariable(String pName) throws ELException {
        return variableResolver.resolveVariable(pName);
    }

    /**
     * XML-escape the given string.
     *
     * @param s The string to escape
     * @return The escape string
     */
    private static String XmlEscape(String s) {
        if (s == null) {
            return null;
        }

        StringBuffer sb = new StringBuffer();
        for(int i = 0; i < s.length(); i++) {
            char c = s.charAt(i);
            if (c == '<') {
                sb.append("&lt;");
            } else if (c == '>') {
                sb.append("&gt;");
            } else if (c == '\'') {
                sb.append("&#039;");        // &apos;
            } else if (c == '&') {
                sb.append("&amp;");
            } else if (c == '"') {
                sb.append("&#034;");        // &quot;
            } else {
                sb.append(c);
            }
        }
        return sb.toString();
    }

    /**
     * Proprietary method to evaluate EL expressions.
     * XXX - This method should go away once the EL interpreter moves
     * out of JSTL and into its own project.  For now, this is necessary
     * because the standard machinery is too slow.
     *
     * @param expression The expression to be evaluated
     * @param expectedType The expected resulting type
     * @param pageContext The page context
     * @param functionMap Maps prefix and name to Method
     * @return The result of the evaluation
     */
    public static Object proprietaryEvaluate(final String expression, 
                                             final Class expectedType,
                                             final PageContext pageContext,
                                             final ProtectedFunctionMapper functionMap,
                                             final boolean escape)
        throws ELException
    {
        Object retValue;
        if (SecurityUtil.isPackageProtectionEnabled()){
            try {
                retValue = AccessController.doPrivileged(
                        new PrivilegedExceptionAction(){

                    public Object run() throws Exception{
                        return elExprEval.evaluate(expression,
                                                   expectedType,
                                                   pageContext.getVariableResolver(),
                                                   functionMap);
                    }
                });
            } catch (PrivilegedActionException ex) {
                Exception realEx = ex.getException();
                if (realEx instanceof ELException) {
                    throw (ELException) realEx;
                } else {
                    throw new ELException(realEx);
                }
            }
        } else {
            retValue = elExprEval.evaluate(expression,
                                           expectedType,
                                           pageContext.getVariableResolver(),
                                           functionMap);
        }
        if (escape) {
            retValue = XmlEscape(retValue.toString());
        }

        return retValue;
    }

}