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/**
 * Logback: the reliable, generic, fast and flexible logging framework.
 * Copyright (C) 1999-2015, QOS.ch. All rights reserved.
 *
 * This program and the accompanying materials are dual-licensed under
 * either the terms of the Eclipse Public License v1.0 as published by
 * the Eclipse Foundation
 *
 *   or (per the licensee's choosing)
 *
 * under the terms of the GNU Lesser General Public License version 2.1
 * as published by the Free Software Foundation.
 */
package ch.qos.logback.classic.net;

import java.io.IOException;
import java.io.OutputStream;
import java.net.SocketException;
import java.net.UnknownHostException;

import ch.qos.logback.classic.PatternLayout;
import ch.qos.logback.classic.pattern.SyslogStartConverter;
import ch.qos.logback.classic.spi.ILoggingEvent;
import ch.qos.logback.classic.spi.IThrowableProxy;
import ch.qos.logback.classic.spi.StackTraceElementProxy;
import ch.qos.logback.classic.util.LevelToSyslogSeverity;
import ch.qos.logback.core.CoreConstants;
import ch.qos.logback.core.Layout;
import ch.qos.logback.core.net.SyslogAppenderBase;
import ch.qos.logback.core.net.SyslogOutputStream;

/**
 * This appender can be used to send messages to a remote syslog daemon.
 * 
 * For more information about this appender, please refer to the online manual
 * at http://logback.qos.ch/manual/appenders.html#SyslogAppender
 *
 * @author Ceki Gülcü
 */
public class SyslogAppender extends SyslogAppenderBase {

    static final public String DEFAULT_SUFFIX_PATTERN = "[%thread] %logger %msg";
    static final public String DEFAULT_STACKTRACE_PATTERN = "" + CoreConstants.TAB;

    PatternLayout stackTraceLayout = new PatternLayout();
    String stackTracePattern = DEFAULT_STACKTRACE_PATTERN;

    boolean throwableExcluded = false;

    public void start() {
        super.start();
        setupStackTraceLayout();
    }

    String getPrefixPattern() {
        return "%syslogStart{" + getFacility() + "}%nopex{}";
    }

    @Override
    public SyslogOutputStream createOutputStream() throws SocketException, UnknownHostException {
        return new SyslogOutputStream(getSyslogHost(), getPort());
    }

    /**
     * Convert a level to equivalent syslog severity. Only levels for printing
     * methods i.e. DEBUG, WARN, INFO and ERROR are converted.
     *
     * @see ch.qos.logback.core.net.SyslogAppenderBase#getSeverityForEvent(java.lang.Object)
     */
    @Override
    public int getSeverityForEvent(Object eventObject) {
        ILoggingEvent event = (ILoggingEvent) eventObject;
        return LevelToSyslogSeverity.convert(event);
    }

    @Override
    protected void postProcess(Object eventObject, OutputStream sw) {
        if (throwableExcluded)
            return;

        ILoggingEvent event = (ILoggingEvent) eventObject;
        IThrowableProxy tp = event.getThrowableProxy();

        if (tp == null)
            return;

        String stackTracePrefix = stackTraceLayout.doLayout(event);
        boolean isRootException = true;
        while (tp != null) {
            StackTraceElementProxy[] stepArray = tp.getStackTraceElementProxyArray();
            try {
                handleThrowableFirstLine(sw, tp, stackTracePrefix, isRootException);
                isRootException = false;
                for (StackTraceElementProxy step : stepArray) {
                    StringBuilder sb = new StringBuilder();
                    sb.append(stackTracePrefix).append(step);
                    sw.write(sb.toString().getBytes());
                    sw.flush();
                }
            } catch (IOException e) {
                break;
            }
            tp = tp.getCause();
        }
    }

    // LOGBACK-411 and LOGBACK-750
    private void handleThrowableFirstLine(OutputStream sw, IThrowableProxy tp, String stackTracePrefix,
            boolean isRootException) throws IOException {
        StringBuilder sb = new StringBuilder().append(stackTracePrefix);

        if (!isRootException) {
            sb.append(CoreConstants.CAUSED_BY);
        }
        sb.append(tp.getClassName()).append(": ").append(tp.getMessage());
        sw.write(sb.toString().getBytes());
        sw.flush();
    }

    boolean stackTraceHeaderLine(StringBuilder sb, boolean topException) {

        return false;
    }

    public Layout buildLayout() {
        PatternLayout layout = new PatternLayout();
        layout.getInstanceConverterMap().put("syslogStart", SyslogStartConverter::new);
        if (suffixPattern == null) {
            suffixPattern = DEFAULT_SUFFIX_PATTERN;
        }
        layout.setPattern(getPrefixPattern() + suffixPattern);
        layout.setContext(getContext());
        layout.start();
        return layout;
    }

    private void setupStackTraceLayout() {
        stackTraceLayout.getInstanceConverterMap().put("syslogStart", SyslogStartConverter::new);

        stackTraceLayout.setPattern(getPrefixPattern() + stackTracePattern);
        stackTraceLayout.setContext(getContext());
        stackTraceLayout.start();
    }

    public boolean isThrowableExcluded() {
        return throwableExcluded;
    }

    /**
     * Setting throwableExcluded to true causes no Throwable's stack trace data to
     * be sent to the syslog daemon. By default, stack trace data is sent to syslog
     * daemon.
     *
     * @param throwableExcluded
     * @since 1.0.4
     */
    public void setThrowableExcluded(boolean throwableExcluded) {
        this.throwableExcluded = throwableExcluded;
    }

    /**
     * See {@link #setStackTracePattern(String).
     *
     * @return the stackTraceSuffixPattern
     * @since 1.0.4
     */
    public String getStackTracePattern() {
        return stackTracePattern;
    }

    /**
     * Stack trace lines are sent to the syslog server separately from the main
     * message For stack trace lines, the stackTracePattern is used instead of
     * {@link #suffixPattern}. The stackTracePattern option allows
     * specification of a separate format for the non-standardized part of stack
     * trace lines.
     *
     * @param stackTracePattern
     * @since 1.0.4
     */
    public void setStackTracePattern(String stackTracePattern) {
        this.stackTracePattern = stackTracePattern;
    }
}