/*
 * 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.catalina.valves;

import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.Writer;
import java.util.Scanner;
import java.util.concurrent.atomic.AtomicBoolean;

import javax.servlet.RequestDispatcher;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServletResponse;

import org.apache.catalina.connector.Request;
import org.apache.catalina.connector.Response;
import org.apache.catalina.util.ErrorPageSupport;
import org.apache.catalina.util.IOTools;
import org.apache.catalina.util.ServerInfo;
import org.apache.catalina.util.TomcatCSS;
import org.apache.coyote.ActionCode;
import org.apache.tomcat.util.ExceptionUtils;
import org.apache.tomcat.util.descriptor.web.ErrorPage;
import org.apache.tomcat.util.res.StringManager;
import org.apache.tomcat.util.security.Escape;

/**
 * Implementation of a Valve that outputs HTML error pages.
 * <p>
 * This Valve should be attached at the Host level, although it will work if attached to a Context.
 * <p>
 * HTML code from the Cocoon 2 project.
 */
public class ErrorReportValve extends ValveBase {

    private boolean showReport = true;

    private boolean showServerInfo = true;

    private final ErrorPageSupport errorPageSupport = new ErrorPageSupport();


    // ------------------------------------------------------ Constructor

    public ErrorReportValve() {
        super(true);
    }


    // --------------------------------------------------------- Public Methods

    /**
     * Invoke the next Valve in the sequence. When the invoke returns, check the response state. If the status code is
     * greater than or equal to 400 or an uncaught exception was thrown then the error handling will be triggered.
     *
     * @param request  The servlet request to be processed
     * @param response The servlet response to be created
     *
     * @exception IOException      if an input/output error occurs
     * @exception ServletException if a servlet error occurs
     */
    @Override
    public void invoke(Request request, Response response) throws IOException, ServletException {

        // Perform the request
        getNext().invoke(request, response);

        if (response.isCommitted()) {
            if (response.setErrorReported()) {
                // Error wasn't previously reported, but we can't write an error
                // page because the response has already been committed.

                // See if IO is allowed
                AtomicBoolean ioAllowed = new AtomicBoolean(true);
                response.getCoyoteResponse().action(ActionCode.IS_IO_ALLOWED, ioAllowed);

                if (ioAllowed.get()) {
                    // I/O is currently still allowed. Flush any data that is
                    // still to be written to the client.
                    try {
                        response.flushBuffer();
                    } catch (Throwable t) {
                        ExceptionUtils.handleThrowable(t);
                    }
                    // Now close immediately to signal to the client that
                    // something went wrong
                    response.getCoyoteResponse().action(ActionCode.CLOSE_NOW,
                            request.getAttribute(RequestDispatcher.ERROR_EXCEPTION));
                }
            }
            return;
        }

        Throwable throwable = (Throwable) request.getAttribute(RequestDispatcher.ERROR_EXCEPTION);

        // If an async request is in progress and is not going to end once this
        // container thread finishes, do not process any error page here.
        if (request.isAsync() && !request.isAsyncCompleting()) {
            return;
        }

        if (throwable != null && !response.isError()) {
            // Make sure that the necessary methods have been called on the
            // response. (It is possible a component may just have set the
            // Throwable. Tomcat won't do that but other components might.)
            // These are safe to call at this point as we know that the response
            // has not been committed.
            response.reset();
            response.sendError(HttpServletResponse.SC_INTERNAL_SERVER_ERROR);
        }

        // One way or another, response.sendError() will have been called before
        // execution reaches this point and suspended the response. Need to
        // reverse that so this valve can write to the response.
        response.setSuspended(false);

        try {
            report(request, response, throwable);
        } catch (Throwable tt) {
            ExceptionUtils.handleThrowable(tt);
        }
    }


    // ------------------------------------------------------ Protected Methods


    /**
     * Return the error page associated with the specified status and exception.
     *
     * @param statusCode the status code
     * @param throwable  the exception
     *
     * @return the associated error page
     */
    protected ErrorPage findErrorPage(int statusCode, Throwable throwable) {
        ErrorPage errorPage = null;
        if (throwable != null) {
            errorPage = errorPageSupport.find(throwable);
        }
        if (errorPage == null) {
            errorPage = errorPageSupport.find(statusCode);
        }
        if (errorPage == null) {
            // Default error page
            errorPage = errorPageSupport.find(0);
        }
        return errorPage;
    }


    /**
     * Prints out an error report.
     *
     * @param request   The request being processed
     * @param response  The response being generated
     * @param throwable The exception that occurred (which possibly wraps a root cause exception
     */
    protected void report(Request request, Response response, Throwable throwable) {

        int statusCode = response.getStatus();

        // Do nothing on a 1xx, 2xx and 3xx status
        // Do nothing if anything has been written already
        // Do nothing if the response hasn't been explicitly marked as in error
        // and that error has not been reported.
        if (statusCode < 400 || response.getContentWritten() > 0 || !response.setErrorReported()) {
            return;
        }

        // If an error has occurred that prevents further I/O, don't waste time
        // producing an error report that will never be read
        AtomicBoolean result = new AtomicBoolean(false);
        response.getCoyoteResponse().action(ActionCode.IS_IO_ALLOWED, result);
        if (!result.get()) {
            return;
        }

        ErrorPage errorPage = findErrorPage(statusCode, throwable);

        if (errorPage != null) {
            if (sendErrorPage(errorPage.getLocation(), response)) {
                // If the page was sent successfully, don't write the standard
                // error page.
                return;
            }
        }

        String message = Escape.htmlElementContent(response.getMessage());
        if (message == null) {
            if (throwable != null) {
                String exceptionMessage = throwable.getMessage();
                if (exceptionMessage != null && !exceptionMessage.isEmpty()) {
                    try (Scanner scanner = new Scanner(exceptionMessage)) {
                        message = Escape.htmlElementContent(scanner.nextLine());
                    }
                }
            }
            if (message == null) {
                message = "";
            }
        }

        // Do nothing if there is no reason phrase for the specified status code and
        // no error message provided
        String reason = null;
        String description = null;
        StringManager smClient = StringManager.getManager(Constants.Package, request.getLocales());
        response.setLocale(smClient.getLocale());
        try {
            reason = smClient.getString("http." + statusCode + ".reason");
            description = smClient.getString("http." + statusCode + ".desc");
        } catch (Throwable t) {
            ExceptionUtils.handleThrowable(t);
        }
        if (reason == null || description == null) {
            if (message.isEmpty()) {
                return;
            } else {
                reason = smClient.getString("errorReportValve.unknownReason");
                description = smClient.getString("errorReportValve.noDescription");
            }
        }

        StringBuilder sb = new StringBuilder();

        sb.append("<!doctype html><html lang=\"");
        sb.append(smClient.getLocale().getLanguage()).append("\">");
        sb.append("<head>");
        sb.append("<title>");
        sb.append(smClient.getString("errorReportValve.statusHeader", String.valueOf(statusCode), reason));
        sb.append("</title>");
        sb.append("<style type=\"text/css\">");
        sb.append(TomcatCSS.TOMCAT_CSS);
        sb.append("</style>");
        sb.append("</head><body>");
        sb.append("<h1>");
        sb.append(smClient.getString("errorReportValve.statusHeader", String.valueOf(statusCode), reason))
                .append("</h1>");
        if (isShowReport()) {
            sb.append("<hr class=\"line\" />");
            sb.append("<p><b>");
            sb.append(smClient.getString("errorReportValve.type"));
            sb.append("</b> ");
            if (throwable != null) {
                sb.append(smClient.getString("errorReportValve.exceptionReport"));
            } else {
                sb.append(smClient.getString("errorReportValve.statusReport"));
            }
            sb.append("</p>");
            if (!message.isEmpty()) {
                sb.append("<p><b>");
                sb.append(smClient.getString("errorReportValve.message"));
                sb.append("</b> ");
                sb.append(message).append("</p>");
            }
            sb.append("<p><b>");
            sb.append(smClient.getString("errorReportValve.description"));
            sb.append("</b> ");
            sb.append(description);
            sb.append("</p>");
            if (throwable != null) {
                String stackTrace = getPartialServletStackTrace(throwable);
                sb.append("<p><b>");
                sb.append(smClient.getString("errorReportValve.exception"));
                sb.append("</b></p><pre>");
                sb.append(Escape.htmlElementContent(stackTrace));
                sb.append("</pre>");

                int loops = 0;
                Throwable rootCause = throwable.getCause();
                while (rootCause != null && (loops < 10)) {
                    stackTrace = getPartialServletStackTrace(rootCause);
                    sb.append("<p><b>");
                    sb.append(smClient.getString("errorReportValve.rootCause"));
                    sb.append("</b></p><pre>");
                    sb.append(Escape.htmlElementContent(stackTrace));
                    sb.append("</pre>");
                    // In case root cause is somehow heavily nested
                    rootCause = rootCause.getCause();
                    loops++;
                }

                sb.append("<p><b>");
                sb.append(smClient.getString("errorReportValve.note"));
                sb.append("</b> ");
                sb.append(smClient.getString("errorReportValve.rootCauseInLogs"));
                sb.append("</p>");

            }
            sb.append("<hr class=\"line\" />");
        }
        if (isShowServerInfo()) {
            sb.append("<h3>").append(ServerInfo.getServerInfo()).append("</h3>");
        }
        sb.append("</body></html>");

        try {
            try {
                response.setContentType("text/html");
                response.setCharacterEncoding("utf-8");
            } catch (Throwable t) {
                ExceptionUtils.handleThrowable(t);
                if (container.getLogger().isDebugEnabled()) {
                    container.getLogger().debug(sm.getString("errorReportValve.contentTypeFail"), t);
                }
            }
            Writer writer = response.getReporter();
            if (writer != null) {
                // If writer is null, it's an indication that the response has
                // been hard committed already, which should never happen
                writer.write(sb.toString());
                response.finishResponse();
            }
        } catch (IOException | IllegalStateException e) {
            // Ignore
        }

    }


    /**
     * Print out a partial servlet stack trace (truncating at the last occurrence of javax.servlet.).
     *
     * @param t The stack trace to process
     *
     * @return the stack trace relative to the application layer
     */
    protected String getPartialServletStackTrace(Throwable t) {
        StringBuilder trace = new StringBuilder();
        trace.append(t.toString()).append(System.lineSeparator());
        StackTraceElement[] elements = t.getStackTrace();
        int pos = elements.length;
        for (int i = elements.length - 1; i >= 0; i--) {
            if ((elements[i].getClassName().startsWith("org.apache.catalina.core.ApplicationFilterChain")) &&
                    (elements[i].getMethodName().equals("internalDoFilter"))) {
                pos = i;
                break;
            }
        }
        for (int i = 0; i < pos; i++) {
            if (!(elements[i].getClassName().startsWith("org.apache.catalina.core."))) {
                trace.append('\t').append(elements[i].toString()).append(System.lineSeparator());
            }
        }
        return trace.toString();
    }


    private boolean sendErrorPage(String location, Response response) {
        File file = new File(location);
        if (!file.isAbsolute()) {
            file = new File(getContainer().getCatalinaBase(), location);
        }
        if (!file.isFile() || !file.canRead()) {
            getContainer().getLogger().warn(sm.getString("errorReportValve.errorPageNotFound", location));
            return false;
        }

        // Hard coded for now. Consider making this optional. At Valve level or
        // page level?
        response.setContentType("text/html");
        response.setCharacterEncoding("UTF-8");

        try (OutputStream os = response.getOutputStream(); InputStream is = new FileInputStream(file)) {
            IOTools.flow(is, os);
        } catch (IOException ioe) {
            getContainer().getLogger().warn(sm.getString("errorReportValve.errorPageIOException", location), ioe);
            return false;
        }

        return true;
    }


    /**
     * Enables/Disables full error reports
     *
     * @param showReport <code>true</code> to show full error data
     */
    public void setShowReport(boolean showReport) {
        this.showReport = showReport;
    }

    public boolean isShowReport() {
        return showReport;
    }

    /**
     * Enables/Disables server info on error pages
     *
     * @param showServerInfo <code>true</code> to show server info
     */
    public void setShowServerInfo(boolean showServerInfo) {
        this.showServerInfo = showServerInfo;
    }

    public boolean isShowServerInfo() {
        return showServerInfo;
    }


    public boolean setProperty(String name, String value) {
        if (name.startsWith("errorCode.")) {
            int code = Integer.parseInt(name.substring(10));
            ErrorPage ep = new ErrorPage();
            ep.setErrorCode(code);
            ep.setLocation(value);
            errorPageSupport.add(ep);
            return true;
        } else if (name.startsWith("exceptionType.")) {
            String className = name.substring(14);
            ErrorPage ep = new ErrorPage();
            ep.setExceptionType(className);
            ep.setLocation(value);
            errorPageSupport.add(ep);
            return true;
        }
        return false;
    }

    public String getProperty(String name) {
        String result;
        if (name.startsWith("errorCode.")) {
            int code = Integer.parseInt(name.substring(10));
            ErrorPage ep = errorPageSupport.find(code);
            if (ep == null) {
                result = null;
            } else {
                result = ep.getLocation();
            }
        } else if (name.startsWith("exceptionType.")) {
            String className = name.substring(14);
            ErrorPage ep = errorPageSupport.find(className);
            if (ep == null) {
                result = null;
            } else {
                result = ep.getLocation();
            }
        } else {
            result = null;
        }
        return result;
    }
}
