/*
 * 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.commons.logging.impl;

import java.io.InputStream;
import java.io.Serializable;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.security.AccessController;
import java.security.PrivilegedAction;
import java.text.DateFormat;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.Properties;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogConfigurationException;

/**
 * Simple implementation of Log that sends all enabled log messages,
 * for all defined loggers, to System.err.  The following system properties
 * are supported to configure the behavior of this logger:
 * <ul>
 * <li><code>org.apache.commons.logging.simplelog.defaultlog</code> -
 *     Default logging detail level for all instances of SimpleLog.
 *     Must be one of ("trace", "debug", "info", "warn", "error", or "fatal").
 *     If not specified, defaults to "info". </li>
 * <li><code>org.apache.commons.logging.simplelog.log.xxxxx</code> -
 *     Logging detail level for a SimpleLog instance named "xxxxx".
 *     Must be one of ("trace", "debug", "info", "warn", "error", or "fatal").
 *     If not specified, the default logging detail level is used.</li>
 * <li><code>org.apache.commons.logging.simplelog.showlogname</code> -
 *     Set to <code>true</code> if you want the Log instance name to be
 *     included in output messages. Defaults to <code>false</code>.</li>
 * <li><code>org.apache.commons.logging.simplelog.showShortLogname</code> -
 *     Set to <code>true</code> if you want the last component of the name to be
 *     included in output messages. Defaults to <code>true</code>.</li>
 * <li><code>org.apache.commons.logging.simplelog.showdatetime</code> -
 *     Set to <code>true</code> if you want the current date and time
 *     to be included in output messages. Default is <code>false</code>.</li>
 * <li><code>org.apache.commons.logging.simplelog.dateTimeFormat</code> -
 *     The date and time format to be used in the output messages.
 *     The pattern describing the date and time format is the same that is
 *     used in <code>java.text.SimpleDateFormat</code>. If the format is not
 *     specified or is invalid, the default format is used.
 *     The default format is <code>yyyy/MM/dd HH:mm:ss:SSS zzz</code>.</li>
 * </ul>
 * <p>
 * In addition to looking for system properties with the names specified
 * above, this implementation also checks for a class loader resource named
 * <code>"simplelog.properties"</code>, and includes any matching definitions
 * from this resource (if it exists).
 *
 * @version $Id: SimpleLog.html 915605 2014-07-09 20:22:43Z tn $
 */
public class SimpleLog implements Log, Serializable {

    /** Serializable version identifier. */
    private static final long serialVersionUID = 136942970684951178L;

    // ------------------------------------------------------- Class Attributes

    /** All system properties used by <code>SimpleLog</code> start with this */
    static protected final String systemPrefix = "org.apache.commons.logging.simplelog.";

    /** Properties loaded from simplelog.properties */
    static protected final Properties simpleLogProps = new Properties();

    /** The default format to use when formating dates */
    static protected final String DEFAULT_DATE_TIME_FORMAT = "yyyy/MM/dd HH:mm:ss:SSS zzz";

    /** Include the instance name in the log message? */
    static volatile protected boolean showLogName = false;

    /** Include the short name ( last component ) of the logger in the log
     *  message. Defaults to true - otherwise we'll be lost in a flood of
     *  messages without knowing who sends them.
     */
    static volatile protected boolean showShortName = true;

    /** Include the current time in the log message */
    static volatile protected boolean showDateTime = false;

    /** The date and time format to use in the log message */
    static volatile protected String dateTimeFormat = DEFAULT_DATE_TIME_FORMAT;

    /**
     * Used to format times.
     * <p>
     * Any code that accesses this object should first obtain a lock on it,
     * ie use synchronized(dateFormatter); this requirement was introduced
     * in 1.1.1 to fix an existing thread safety bug (SimpleDateFormat.format
     * is not thread-safe).
     */
    static protected DateFormat dateFormatter = null;

    // ---------------------------------------------------- Log Level Constants

    /** "Trace" level logging. */
    public static final int LOG_LEVEL_TRACE  = 1;
    /** "Debug" level logging. */
    public static final int LOG_LEVEL_DEBUG  = 2;
    /** "Info" level logging. */
    public static final int LOG_LEVEL_INFO   = 3;
    /** "Warn" level logging. */
    public static final int LOG_LEVEL_WARN   = 4;
    /** "Error" level logging. */
    public static final int LOG_LEVEL_ERROR  = 5;
    /** "Fatal" level logging. */
    public static final int LOG_LEVEL_FATAL  = 6;

    /** Enable all logging levels */
    public static final int LOG_LEVEL_ALL    = LOG_LEVEL_TRACE - 1;

    /** Enable no logging levels */
    public static final int LOG_LEVEL_OFF    = LOG_LEVEL_FATAL + 1;

    // ------------------------------------------------------------ Initializer

    private static String getStringProperty(String name) {
        String prop = null;
        try {
            prop = System.getProperty(name);
        } catch (SecurityException e) {
            // Ignore
        }
        return prop == null ? simpleLogProps.getProperty(name) : prop;
    }

    private static String getStringProperty(String name, String dephault) {
        String prop = getStringProperty(name);
        return prop == null ? dephault : prop;
    }

    private static boolean getBooleanProperty(String name, boolean dephault) {
        String prop = getStringProperty(name);
        return prop == null ? dephault : "true".equalsIgnoreCase(prop);
    }

    // Initialize class attributes.
    // Load properties file, if found.
    // Override with system properties.
    static {
        // Add props from the resource simplelog.properties
        InputStream in = getResourceAsStream("simplelog.properties");
        if(null != in) {
            try {
                simpleLogProps.load(in);
                in.close();
            } catch(java.io.IOException e) {
                // ignored
            }
        }

        showLogName = getBooleanProperty(systemPrefix + "showlogname", showLogName);
        showShortName = getBooleanProperty(systemPrefix + "showShortLogname", showShortName);
        showDateTime = getBooleanProperty(systemPrefix + "showdatetime", showDateTime);

        if(showDateTime) {
            dateTimeFormat = getStringProperty(systemPrefix + "dateTimeFormat",
                                               dateTimeFormat);
            try {
                dateFormatter = new SimpleDateFormat(dateTimeFormat);
            } catch(IllegalArgumentException e) {
                // If the format pattern is invalid - use the default format
                dateTimeFormat = DEFAULT_DATE_TIME_FORMAT;
                dateFormatter = new SimpleDateFormat(dateTimeFormat);
            }
        }
    }

    // ------------------------------------------------------------- Attributes

    /** The name of this simple log instance */
    protected volatile String logName = null;
    /** The current log level */
    protected volatile int currentLogLevel;
    /** The short name of this simple log instance */
    private volatile String shortLogName = null;

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

    /**
     * Construct a simple log with given name.
     *
     * @param name log name
     */
    public SimpleLog(String name) {
        logName = name;

        // Set initial log level
        // Used to be: set default log level to ERROR
        // IMHO it should be lower, but at least info ( costin ).
        setLevel(SimpleLog.LOG_LEVEL_INFO);

        // Set log level from properties
        String lvl = getStringProperty(systemPrefix + "log." + logName);
        int i = String.valueOf(name).lastIndexOf(".");
        while(null == lvl && i > -1) {
            name = name.substring(0,i);
            lvl = getStringProperty(systemPrefix + "log." + name);
            i = String.valueOf(name).lastIndexOf(".");
        }

        if(null == lvl) {
            lvl =  getStringProperty(systemPrefix + "defaultlog");
        }

        if("all".equalsIgnoreCase(lvl)) {
            setLevel(SimpleLog.LOG_LEVEL_ALL);
        } else if("trace".equalsIgnoreCase(lvl)) {
            setLevel(SimpleLog.LOG_LEVEL_TRACE);
        } else if("debug".equalsIgnoreCase(lvl)) {
            setLevel(SimpleLog.LOG_LEVEL_DEBUG);
        } else if("info".equalsIgnoreCase(lvl)) {
            setLevel(SimpleLog.LOG_LEVEL_INFO);
        } else if("warn".equalsIgnoreCase(lvl)) {
            setLevel(SimpleLog.LOG_LEVEL_WARN);
        } else if("error".equalsIgnoreCase(lvl)) {
            setLevel(SimpleLog.LOG_LEVEL_ERROR);
        } else if("fatal".equalsIgnoreCase(lvl)) {
            setLevel(SimpleLog.LOG_LEVEL_FATAL);
        } else if("off".equalsIgnoreCase(lvl)) {
            setLevel(SimpleLog.LOG_LEVEL_OFF);
        }
    }

    // -------------------------------------------------------- Properties

    /**
     * Set logging level.
     *
     * @param currentLogLevel new logging level
     */
    public void setLevel(int currentLogLevel) {
        this.currentLogLevel = currentLogLevel;
    }

    /**
     * Get logging level.
     */
    public int getLevel() {
        return currentLogLevel;
    }

    // -------------------------------------------------------- Logging Methods

    /**
     * Do the actual logging.
     * <p>
     * This method assembles the message and then calls <code>write()</code>
     * to cause it to be written.
     *
     * @param type One of the LOG_LEVEL_XXX constants defining the log level
     * @param message The message itself (typically a String)
     * @param t The exception whose stack trace should be logged
     */
    protected void log(int type, Object message, Throwable t) {
        // Use a string buffer for better performance
        final StringBuffer buf = new StringBuffer();

        // Append date-time if so configured
        if(showDateTime) {
            final Date now = new Date();
            String dateText;
            synchronized(dateFormatter) {
                dateText = dateFormatter.format(now);
            }
            buf.append(dateText);
            buf.append(" ");
        }

        // Append a readable representation of the log level
        switch(type) {
            case SimpleLog.LOG_LEVEL_TRACE: buf.append("[TRACE] "); break;
            case SimpleLog.LOG_LEVEL_DEBUG: buf.append("[DEBUG] "); break;
            case SimpleLog.LOG_LEVEL_INFO:  buf.append("[INFO] ");  break;
            case SimpleLog.LOG_LEVEL_WARN:  buf.append("[WARN] ");  break;
            case SimpleLog.LOG_LEVEL_ERROR: buf.append("[ERROR] "); break;
            case SimpleLog.LOG_LEVEL_FATAL: buf.append("[FATAL] "); break;
        }

        // Append the name of the log instance if so configured
        if(showShortName) {
            if(shortLogName == null) {
                // Cut all but the last component of the name for both styles
                final String slName = logName.substring(logName.lastIndexOf(".") + 1);
                shortLogName = slName.substring(slName.lastIndexOf("/") + 1);
            }
            buf.append(String.valueOf(shortLogName)).append(" - ");
        } else if(showLogName) {
            buf.append(String.valueOf(logName)).append(" - ");
        }

        // Append the message
        buf.append(String.valueOf(message));

        // Append stack trace if not null
        if(t != null) {
            buf.append(" <");
            buf.append(t.toString());
            buf.append(">");

            final java.io.StringWriter sw = new java.io.StringWriter(1024);
            final java.io.PrintWriter pw = new java.io.PrintWriter(sw);
            t.printStackTrace(pw);
            pw.close();
            buf.append(sw.toString());
        }

        // Print to the appropriate destination
        write(buf);
    }

    /**
     * Write the content of the message accumulated in the specified
     * <code>StringBuffer</code> to the appropriate output destination.  The
     * default implementation writes to <code>System.err</code>.
     *
     * @param buffer A <code>StringBuffer</code> containing the accumulated
     *  text to be logged
     */
    protected void write(StringBuffer buffer) {
        System.err.println(buffer.toString());
    }

    /**
     * Is the given log level currently enabled?
     *
     * @param logLevel is this level enabled?
     */
    protected boolean isLevelEnabled(int logLevel) {
        // log level are numerically ordered so can use simple numeric
        // comparison
        return logLevel >= currentLogLevel;
    }

    // -------------------------------------------------------- Log Implementation

    /**
     * Logs a message with
     * <code>org.apache.commons.logging.impl.SimpleLog.LOG_LEVEL_DEBUG</code>.
     *
     * @param message to log
     * @see org.apache.commons.logging.Log#debug(Object)
     */
    public final void debug(Object message) {
        if (isLevelEnabled(SimpleLog.LOG_LEVEL_DEBUG)) {
            log(SimpleLog.LOG_LEVEL_DEBUG, message, null);
        }
    }

    /**
     * Logs a message with
     * <code>org.apache.commons.logging.impl.SimpleLog.LOG_LEVEL_DEBUG</code>.
     *
     * @param message to log
     * @param t log this cause
     * @see org.apache.commons.logging.Log#debug(Object, Throwable)
     */
    public final void debug(Object message, Throwable t) {
        if (isLevelEnabled(SimpleLog.LOG_LEVEL_DEBUG)) {
            log(SimpleLog.LOG_LEVEL_DEBUG, message, t);
        }
    }

    /**
     * Logs a message with <code>org.apache.commons.logging.impl.SimpleLog.LOG_LEVEL_TRACE</code>.
     *
     * @param message to log
     * @see org.apache.commons.logging.Log#trace(Object)
     */
    public final void trace(Object message) {
        if (isLevelEnabled(SimpleLog.LOG_LEVEL_TRACE)) {
            log(SimpleLog.LOG_LEVEL_TRACE, message, null);
        }
    }

    /**
     * Logs a message with <code>org.apache.commons.logging.impl.SimpleLog.LOG_LEVEL_TRACE</code>.
     *
     * @param message to log
     * @param t log this cause
     * @see org.apache.commons.logging.Log#trace(Object, Throwable)
     */
    public final void trace(Object message, Throwable t) {
        if (isLevelEnabled(SimpleLog.LOG_LEVEL_TRACE)) {
            log(SimpleLog.LOG_LEVEL_TRACE, message, t);
        }
    }

    /**
     * Logs a message with <code>org.apache.commons.logging.impl.SimpleLog.LOG_LEVEL_INFO</code>.
     *
     * @param message to log
     * @see org.apache.commons.logging.Log#info(Object)
     */
    public final void info(Object message) {
        if (isLevelEnabled(SimpleLog.LOG_LEVEL_INFO)) {
            log(SimpleLog.LOG_LEVEL_INFO,message,null);
        }
    }

    /**
     * Logs a message with <code>org.apache.commons.logging.impl.SimpleLog.LOG_LEVEL_INFO</code>.
     *
     * @param message to log
     * @param t log this cause
     * @see org.apache.commons.logging.Log#info(Object, Throwable)
     */
    public final void info(Object message, Throwable t) {
        if (isLevelEnabled(SimpleLog.LOG_LEVEL_INFO)) {
            log(SimpleLog.LOG_LEVEL_INFO, message, t);
        }
    }

    /**
     * Logs a message with <code>org.apache.commons.logging.impl.SimpleLog.LOG_LEVEL_WARN</code>.
     *
     * @param message to log
     * @see org.apache.commons.logging.Log#warn(Object)
     */
    public final void warn(Object message) {
        if (isLevelEnabled(SimpleLog.LOG_LEVEL_WARN)) {
            log(SimpleLog.LOG_LEVEL_WARN, message, null);
        }
    }

    /**
     * Logs a message with <code>org.apache.commons.logging.impl.SimpleLog.LOG_LEVEL_WARN</code>.
     *
     * @param message to log
     * @param t log this cause
     * @see org.apache.commons.logging.Log#warn(Object, Throwable)
     */
    public final void warn(Object message, Throwable t) {
        if (isLevelEnabled(SimpleLog.LOG_LEVEL_WARN)) {
            log(SimpleLog.LOG_LEVEL_WARN, message, t);
        }
    }

    /**
     * Logs a message with <code>org.apache.commons.logging.impl.SimpleLog.LOG_LEVEL_ERROR</code>.
     *
     * @param message to log
     * @see org.apache.commons.logging.Log#error(Object)
     */
    public final void error(Object message) {
        if (isLevelEnabled(SimpleLog.LOG_LEVEL_ERROR)) {
            log(SimpleLog.LOG_LEVEL_ERROR, message, null);
        }
    }

    /**
     * Logs a message with <code>org.apache.commons.logging.impl.SimpleLog.LOG_LEVEL_ERROR</code>.
     *
     * @param message to log
     * @param t log this cause
     * @see org.apache.commons.logging.Log#error(Object, Throwable)
     */
    public final void error(Object message, Throwable t) {
        if (isLevelEnabled(SimpleLog.LOG_LEVEL_ERROR)) {
            log(SimpleLog.LOG_LEVEL_ERROR, message, t);
        }
    }

    /**
     * Log a message with <code>org.apache.commons.logging.impl.SimpleLog.LOG_LEVEL_FATAL</code>.
     *
     * @param message to log
     * @see org.apache.commons.logging.Log#fatal(Object)
     */
    public final void fatal(Object message) {
        if (isLevelEnabled(SimpleLog.LOG_LEVEL_FATAL)) {
            log(SimpleLog.LOG_LEVEL_FATAL, message, null);
        }
    }

    /**
     * Logs a message with <code>org.apache.commons.logging.impl.SimpleLog.LOG_LEVEL_FATAL</code>.
     *
     * @param message to log
     * @param t log this cause
     * @see org.apache.commons.logging.Log#fatal(Object, Throwable)
     */
    public final void fatal(Object message, Throwable t) {
        if (isLevelEnabled(SimpleLog.LOG_LEVEL_FATAL)) {
            log(SimpleLog.LOG_LEVEL_FATAL, message, t);
        }
    }

    /**
     * Are debug messages currently enabled?
     * <p>
     * This allows expensive operations such as <code>String</code>
     * concatenation to be avoided when the message will be ignored by the
     * logger.
     */
    public final boolean isDebugEnabled() {
        return isLevelEnabled(SimpleLog.LOG_LEVEL_DEBUG);
    }

    /**
     * Are error messages currently enabled?
     * <p>
     * This allows expensive operations such as <code>String</code>
     * concatenation to be avoided when the message will be ignored by the
     * logger.
     */
    public final boolean isErrorEnabled() {
        return isLevelEnabled(SimpleLog.LOG_LEVEL_ERROR);
    }

    /**
     * Are fatal messages currently enabled?
     * <p>
     * This allows expensive operations such as <code>String</code>
     * concatenation to be avoided when the message will be ignored by the
     * logger.
     */
    public final boolean isFatalEnabled() {
        return isLevelEnabled(SimpleLog.LOG_LEVEL_FATAL);
    }

    /**
     * Are info messages currently enabled?
     * <p>
     * This allows expensive operations such as <code>String</code>
     * concatenation to be avoided when the message will be ignored by the
     * logger.
     */
    public final boolean isInfoEnabled() {
        return isLevelEnabled(SimpleLog.LOG_LEVEL_INFO);
    }

    /**
     * Are trace messages currently enabled?
     * <p>
     * This allows expensive operations such as <code>String</code>
     * concatenation to be avoided when the message will be ignored by the
     * logger.
     */
    public final boolean isTraceEnabled() {
        return isLevelEnabled(SimpleLog.LOG_LEVEL_TRACE);
    }

    /**
     * Are warn messages currently enabled?
     * <p>
     * This allows expensive operations such as <code>String</code>
     * concatenation to be avoided when the message will be ignored by the
     * logger.
     */
    public final boolean isWarnEnabled() {
        return isLevelEnabled(SimpleLog.LOG_LEVEL_WARN);
    }

    /**
     * Return the thread context class loader if available.
     * Otherwise return null.
     *
     * The thread context class loader is available for JDK 1.2
     * or later, if certain security conditions are met.
     *
     * @exception LogConfigurationException if a suitable class loader
     * cannot be identified.
     */
    private static ClassLoader getContextClassLoader() {
        ClassLoader classLoader = null;

        try {
            // Are we running on a JDK 1.2 or later system?
            final Method method = Thread.class.getMethod("getContextClassLoader", (Class[]) null);

            // Get the thread context class loader (if there is one)
            try {
                classLoader = (ClassLoader)method.invoke(Thread.currentThread(), (Class[]) null);
            } catch (IllegalAccessException e) {
                // ignore
            } catch (InvocationTargetException e) {
                /**
                 * InvocationTargetException is thrown by 'invoke' when
                 * the method being invoked (getContextClassLoader) throws
                 * an exception.
                 *
                 * getContextClassLoader() throws SecurityException when
                 * the context class loader isn't an ancestor of the
                 * calling class's class loader, or if security
                 * permissions are restricted.
                 *
                 * In the first case (not related), we want to ignore and
                 * keep going.  We cannot help but also ignore the second
                 * with the logic below, but other calls elsewhere (to
                 * obtain a class loader) will trigger this exception where
                 * we can make a distinction.
                 */
                if (e.getTargetException() instanceof SecurityException) {
                    // ignore
                } else {
                    // Capture 'e.getTargetException()' exception for details
                    // alternate: log 'e.getTargetException()', and pass back 'e'.
                    throw new LogConfigurationException
                        ("Unexpected InvocationTargetException", e.getTargetException());
                }
            }
        } catch (NoSuchMethodException e) {
            // Assume we are running on JDK 1.1
            // ignore
        }

        if (classLoader == null) {
            classLoader = SimpleLog.class.getClassLoader();
        }

        // Return the selected class loader
        return classLoader;
    }

    private static InputStream getResourceAsStream(final String name) {
        return (InputStream)AccessController.doPrivileged(
            new PrivilegedAction() {
                public Object run() {
                    ClassLoader threadCL = getContextClassLoader();

                    if (threadCL != null) {
                        return threadCL.getResourceAsStream(name);
                    } else {
                        return ClassLoader.getSystemResourceAsStream(name);
                    }
                }
            });
    }
}