/**
 * 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.core.net;

import java.io.IOException;
import java.io.OutputStream;
import java.net.SocketException;
import java.net.UnknownHostException;
import java.nio.charset.Charset;

import ch.qos.logback.core.AppenderBase;
import ch.qos.logback.core.CoreConstants;
import ch.qos.logback.core.Layout;

/**
 * Base class for SyslogAppender.
 * 
 * @author Ceki G&uuml;lc&uuml;
 * 
 * @param <E>
 */
public abstract class SyslogAppenderBase<E> extends AppenderBase<E> {

    final static String SYSLOG_LAYOUT_URL = CoreConstants.CODES_URL + "#syslog_layout";
    final static int MAX_MESSAGE_SIZE_LIMIT = 65000;

    Layout<E> layout;
    String facilityStr;
    String syslogHost;
    protected String suffixPattern;
    SyslogOutputStream sos;
    int port = SyslogConstants.SYSLOG_PORT;
    int maxMessageSize;
    Charset charset;

    public void start() {
        int errorCount = 0;
        if (facilityStr == null) {
            addError("The Facility option is mandatory");
            errorCount++;
        }

        if (charset == null) {
            // Using defaultCharset() preserves the previous behavior when String.getBytes()
            // was
            // called without arguments
            charset = Charset.defaultCharset();
        }

        try {
            sos = createOutputStream();

            final int systemDatagramSize = sos.getSendBufferSize();
            if (maxMessageSize == 0) {
                maxMessageSize = Math.min(systemDatagramSize, MAX_MESSAGE_SIZE_LIMIT);
                addInfo("Defaulting maxMessageSize to [" + maxMessageSize + "]");
            } else if (maxMessageSize > systemDatagramSize) {
                addWarn("maxMessageSize of [" + maxMessageSize
                        + "] is larger than the system defined datagram size of [" + systemDatagramSize + "].");
                addWarn("This may result in dropped logs.");
            }
        } catch (UnknownHostException e) {
            addError("Could not create SyslogWriter", e);
            errorCount++;
        } catch (SocketException e) {
            addWarn("Failed to bind to a random datagram socket. Will try to reconnect later.", e);
        }

        if (layout == null) {
            layout = buildLayout();
        }

        if (errorCount == 0) {
            super.start();
        }
    }

    abstract public SyslogOutputStream createOutputStream() throws UnknownHostException, SocketException;

    abstract public Layout<E> buildLayout();

    abstract public int getSeverityForEvent(Object eventObject);

    @Override
    protected void append(E eventObject) {
        if (!isStarted()) {
            return;
        }

        try {
            String msg = layout.doLayout(eventObject);
            if (msg == null) {
                return;
            }
            if (msg.length() > maxMessageSize) {
                msg = msg.substring(0, maxMessageSize);
            }
            sos.write(msg.getBytes(charset));
            sos.flush();
            postProcess(eventObject, sos);
        } catch (IOException ioe) {
            addError("Failed to send diagram to " + syslogHost, ioe);
        }
    }

    protected void postProcess(Object event, OutputStream sw) {

    }

    /**
     * Returns the integer value corresponding to the named syslog facility.
     * 
     * @throws IllegalArgumentException if the facility string is not recognized
     */
    static public int facilityStringToint(String facilityStr) {
        if ("KERN".equalsIgnoreCase(facilityStr)) {
            return SyslogConstants.LOG_KERN;
        } else if ("USER".equalsIgnoreCase(facilityStr)) {
            return SyslogConstants.LOG_USER;
        } else if ("MAIL".equalsIgnoreCase(facilityStr)) {
            return SyslogConstants.LOG_MAIL;
        } else if ("DAEMON".equalsIgnoreCase(facilityStr)) {
            return SyslogConstants.LOG_DAEMON;
        } else if ("AUTH".equalsIgnoreCase(facilityStr)) {
            return SyslogConstants.LOG_AUTH;
        } else if ("SYSLOG".equalsIgnoreCase(facilityStr)) {
            return SyslogConstants.LOG_SYSLOG;
        } else if ("LPR".equalsIgnoreCase(facilityStr)) {
            return SyslogConstants.LOG_LPR;
        } else if ("NEWS".equalsIgnoreCase(facilityStr)) {
            return SyslogConstants.LOG_NEWS;
        } else if ("UUCP".equalsIgnoreCase(facilityStr)) {
            return SyslogConstants.LOG_UUCP;
        } else if ("CRON".equalsIgnoreCase(facilityStr)) {
            return SyslogConstants.LOG_CRON;
        } else if ("AUTHPRIV".equalsIgnoreCase(facilityStr)) {
            return SyslogConstants.LOG_AUTHPRIV;
        } else if ("FTP".equalsIgnoreCase(facilityStr)) {
            return SyslogConstants.LOG_FTP;
        } else if ("NTP".equalsIgnoreCase(facilityStr)) {
            return SyslogConstants.LOG_NTP;
        } else if ("AUDIT".equalsIgnoreCase(facilityStr)) {
            return SyslogConstants.LOG_AUDIT;
        } else if ("ALERT".equalsIgnoreCase(facilityStr)) {
            return SyslogConstants.LOG_ALERT;
        } else if ("CLOCK".equalsIgnoreCase(facilityStr)) {
            return SyslogConstants.LOG_CLOCK;
        } else if ("LOCAL0".equalsIgnoreCase(facilityStr)) {
            return SyslogConstants.LOG_LOCAL0;
        } else if ("LOCAL1".equalsIgnoreCase(facilityStr)) {
            return SyslogConstants.LOG_LOCAL1;
        } else if ("LOCAL2".equalsIgnoreCase(facilityStr)) {
            return SyslogConstants.LOG_LOCAL2;
        } else if ("LOCAL3".equalsIgnoreCase(facilityStr)) {
            return SyslogConstants.LOG_LOCAL3;
        } else if ("LOCAL4".equalsIgnoreCase(facilityStr)) {
            return SyslogConstants.LOG_LOCAL4;
        } else if ("LOCAL5".equalsIgnoreCase(facilityStr)) {
            return SyslogConstants.LOG_LOCAL5;
        } else if ("LOCAL6".equalsIgnoreCase(facilityStr)) {
            return SyslogConstants.LOG_LOCAL6;
        } else if ("LOCAL7".equalsIgnoreCase(facilityStr)) {
            return SyslogConstants.LOG_LOCAL7;
        } else {
            throw new IllegalArgumentException(facilityStr + " is not a valid syslog facility string");
        }
    }

    /**
     * Returns the value of the <b>SyslogHost</b> option.
     */
    public String getSyslogHost() {
        return syslogHost;
    }

    /**
     * The <b>SyslogHost</b> option is the name of the syslog host where log
     * output should go.
     * 
     * <b>WARNING</b> If the SyslogHost is not set, then this appender will fail.
     */
    public void setSyslogHost(String syslogHost) {
        this.syslogHost = syslogHost;
    }

    /**
     * Returns the string value of the <b>Facility</b> option.
     * 
     * See {@link #setFacility} for the set of allowed values.
     */
    public String getFacility() {
        return facilityStr;
    }

    /**
     * The <b>Facility</b> option must be set one of the strings KERN, USER, MAIL,
     * DAEMON, AUTH, SYSLOG, LPR, NEWS, UUCP, CRON, AUTHPRIV, FTP, NTP, AUDIT,
     * ALERT, CLOCK, LOCAL0, LOCAL1, LOCAL2, LOCAL3, LOCAL4, LOCAL5, LOCAL6, LOCAL7.
     * Case is not important.
     * 
     * <p>
     * See {@link ch.qos.logback.core.net.SyslogConstants SyslogConstants} and RFC
     * 3164 for more information about the <b>Facility</b> option.
     */
    public void setFacility(String facilityStr) {
        if (facilityStr != null) {
            facilityStr = facilityStr.trim();
        }
        this.facilityStr = facilityStr;
    }

    /**
     * 
     * @return
     */
    public int getPort() {
        return port;
    }

    /**
     * The port number on the syslog server to connect to. Normally, you would not
     * want to change the default value, that is 514.
     */
    public void setPort(int port) {
        this.port = port;
    }

    public int getMaxMessageSize() {
        return maxMessageSize;
    }

    /**
     * Maximum size for the syslog message (in characters); messages longer than
     * this are truncated. The default value is 65400 (which is near the maximum for
     * syslog-over-UDP). Note that the value is characters; the number of bytes may
     * vary if non-ASCII characters are present.
     */
    public void setMaxMessageSize(int maxMessageSize) {
        this.maxMessageSize = maxMessageSize;
    }

    public Layout<E> getLayout() {
        return layout;
    }

    public void setLayout(Layout<E> layout) {
        addWarn("The layout of a SyslogAppender cannot be set directly. See also " + SYSLOG_LAYOUT_URL);
    }

    @Override
    public void stop() {
        if (sos != null) {
            sos.close();
        }
        super.stop();
    }

    /**
     * See {@link #setSuffixPattern #setSuffixPattern(String)}.
     * 
     * @return
     */
    public String getSuffixPattern() {
        return suffixPattern;
    }

    /**
     * The <b>suffixPattern</b> option specifies the format of the non-standardized
     * part of the message sent to the syslog server.
     * 
     * @param suffixPattern
     */
    public void setSuffixPattern(String suffixPattern) {
        this.suffixPattern = suffixPattern;
    }

    /**
     * Returns the Charset used to encode String messages into byte sequences when
     * writing to syslog.
     */
    public Charset getCharset() {
        return charset;
    }

    /**
     * The Charset to use when encoding messages into byte sequences.
     *
     * @param charset
     */
    public void setCharset(Charset charset) {
        this.charset = charset;
    }
}
