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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

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 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

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 * accompanied this code).

 *

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package java.util.logging;

/**

 * <tt>Handler</tt> that buffers requests in a circular buffer in memory.

 * <p>

 * Normally this <tt>Handler</tt> simply stores incoming <tt>LogRecords</tt>

 * into its memory buffer and discards earlier records.  This buffering

 * is very cheap and avoids formatting costs.  On certain trigger

 * conditions, the <tt>MemoryHandler</tt> will push out its current buffer

 * contents to a target <tt>Handler</tt>, which will typically publish

 * them to the outside world.

 * <p>

 * There are three main models for triggering a push of the buffer:

 * <ul>

 * <li>

 * An incoming <tt>LogRecord</tt> has a type that is greater than

 * a pre-defined level, the <tt>pushLevel</tt>. </li>

 * <li>

 * An external class calls the <tt>push</tt> method explicitly. </li>

 * <li>

 * A subclass overrides the <tt>log</tt> method and scans each incoming

 * <tt>LogRecord</tt> and calls <tt>push</tt> if a record matches some

 * desired criteria. </li>

 * </ul>

 * <p>

 * <b>Configuration:</b>

 * By default each <tt>MemoryHandler</tt> is initialized using the following

 * <tt>LogManager</tt> configuration properties where <tt>&lt;handler-name&gt;</tt>

 * refers to the fully-qualified class name of the handler.

 * If properties are not defined

 * (or have invalid values) then the specified default values are used.

 * If no default value is defined then a RuntimeException is thrown.

 * <ul>

 * <li>   &lt;handler-name&gt;.level

 *        specifies the level for the <tt>Handler</tt>

 *        (defaults to <tt>Level.ALL</tt>). </li>

 * <li>   &lt;handler-name&gt;.filter

 *        specifies the name of a <tt>Filter</tt> class to use

 *        (defaults to no <tt>Filter</tt>). </li>

 * <li>   &lt;handler-name&gt;.size

 *        defines the buffer size (defaults to 1000). </li>

 * <li>   &lt;handler-name>.push

 *        defines the <tt>pushLevel</tt> (defaults to <tt>level.SEVERE</tt>). </li>

 * <li>   &lt;handler-name&gt;.target

 *        specifies the name of the target <tt>Handler </tt> class.

 *        (no default). </li>

 * </ul>

 * <p>

 * For example, the properties for {@code MemoryHandler} would be:

 * <ul>

 * <li>   java.util.logging.MemoryHandler.level=INFO </li>

 * <li>   java.util.logging.MemoryHandler.formatter=java.util.logging.SimpleFormatter </li>

 * </ul>

 * <p>

 * For a custom handler, e.g. com.foo.MyHandler, the properties would be:

 * <ul>

 * <li>   com.foo.MyHandler.level=INFO </li>

 * <li>   com.foo.MyHandler.formatter=java.util.logging.SimpleFormatter </li>

 * </ul>

 * <p>

 * @since 1.4

 */

public class MemoryHandler extends Handler {

    private final static int DEFAULT_SIZE = 1000;

    private Level pushLevel;

    private int size;

    private Handler target;

    private LogRecord buffer[];

    int start, count;

    // Private method to configure a MemoryHandler from LogManager

    // properties and/or default values as specified in the class

    // javadoc.

    private void configure() {

        LogManager manager = LogManager.getLogManager();

        String cname = getClass().getName();

        pushLevel = manager.getLevelProperty(cname +".push", Level.SEVERE);

        size = manager.getIntProperty(cname + ".size", DEFAULT_SIZE);

        if (size <= 0) {

            size = DEFAULT_SIZE;

        }

        setLevel(manager.getLevelProperty(cname +".level", Level.ALL));

        setFilter(manager.getFilterProperty(cname +".filter", null));

        setFormatter(manager.getFormatterProperty(cname +".formatter", new SimpleFormatter()));

    }

    /**

     * Create a <tt>MemoryHandler</tt> and configure it based on

     * <tt>LogManager</tt> configuration properties.

     */

    public MemoryHandler() {

        sealed = false;

        configure();

        sealed = true;

        LogManager manager = LogManager.getLogManager();

        String handlerName = getClass().getName();

        String targetName = manager.getProperty(handlerName+".target");

        if (targetName == null) {

            throw new RuntimeException("The handler " + handlerName

                    + " does not specify a target");

        }

        Class<?> clz;

        try {

            clz = ClassLoader.getSystemClassLoader().loadClass(targetName);

            target = (Handler) clz.newInstance();

        } catch (ClassNotFoundException | InstantiationException | IllegalAccessException e) {

            throw new RuntimeException("MemoryHandler can't load handler target \"" + targetName + "\"" , e);

        }

        init();

    }

    // Initialize.  Size is a count of LogRecords.

    private void init() {

        buffer = new LogRecord[size];

        start = 0;

        count = 0;

    }

    /**

     * Create a <tt>MemoryHandler</tt>.

     * <p>

     * The <tt>MemoryHandler</tt> is configured based on <tt>LogManager</tt>

     * properties (or their default values) except that the given <tt>pushLevel</tt>

     * argument and buffer size argument are used.

     *

     * @param target  the Handler to which to publish output.

     * @param size    the number of log records to buffer (must be greater than zero)

     * @param pushLevel  message level to push on

     *

     * @throws IllegalArgumentException if size is <= 0

     */

    public MemoryHandler(Handler target, int size, Level pushLevel) {

        if (target == null || pushLevel == null) {

            throw new NullPointerException();

        }

        if (size <= 0) {

            throw new IllegalArgumentException();

        }

        sealed = false;

        configure();

        sealed = true;

        this.target = target;

        this.pushLevel = pushLevel;

        this.size = size;

        init();

    }

    /**

     * Store a <tt>LogRecord</tt> in an internal buffer.

     * <p>

     * If there is a <tt>Filter</tt>, its <tt>isLoggable</tt>

     * method is called to check if the given log record is loggable.

     * If not we return.  Otherwise the given record is copied into

     * an internal circular buffer.  Then the record's level property is

     * compared with the <tt>pushLevel</tt>. If the given level is

     * greater than or equal to the <tt>pushLevel</tt> then <tt>push</tt>

     * is called to write all buffered records to the target output

     * <tt>Handler</tt>.

     *

     * @param  record  description of the log event. A null record is

     *                 silently ignored and is not published

     */

    public synchronized void publish(LogRecord record) {

        if (!isLoggable(record)) {

            return;

        }

        int ix = (start+count)%buffer.length;

        buffer[ix] = record;

        if (count < buffer.length) {

            count++;

        } else {

            start++;

            start %= buffer.length;

        }

        if (record.getLevel().intValue() >= pushLevel.intValue()) {

            push();

        }

    }

    /**

     * Push any buffered output to the target <tt>Handler</tt>.

     * <p>

     * The buffer is then cleared.

     */

    public synchronized void push() {

        for (int i = 0; i < count; i++) {

            int ix = (start+i)%buffer.length;

            LogRecord record = buffer[ix];

            target.publish(record);

        }

        // Empty the buffer.

        start = 0;

        count = 0;

    }

    /**

     * Causes a flush on the target <tt>Handler</tt>.

     * <p>

     * Note that the current contents of the <tt>MemoryHandler</tt>

     * buffer are <b>not</b> written out.  That requires a "push".

     */

    public void flush() {

        target.flush();

    }

    /**

     * Close the <tt>Handler</tt> and free all associated resources.

     * This will also close the target <tt>Handler</tt>.

     *

     * @exception  SecurityException  if a security manager exists and if

     *             the caller does not have <tt>LoggingPermission("control")</tt>.

     */

    public void close() throws SecurityException {

        target.close();

        setLevel(Level.OFF);

    }

    /**

     * Set the <tt>pushLevel</tt>.  After a <tt>LogRecord</tt> is copied

     * into our internal buffer, if its level is greater than or equal to

     * the <tt>pushLevel</tt>, then <tt>push</tt> will be called.

     *

     * @param newLevel the new value of the <tt>pushLevel</tt>

     * @exception  SecurityException  if a security manager exists and if

     *             the caller does not have <tt>LoggingPermission("control")</tt>.

     */

    public void setPushLevel(Level newLevel) throws SecurityException {

        if (newLevel == null) {

            throw new NullPointerException();

        }

        LogManager manager = LogManager.getLogManager();

        checkPermission();

        pushLevel = newLevel;

    }

    /**

     * Get the <tt>pushLevel</tt>.

     *

     * @return the value of the <tt>pushLevel</tt>

     */

    public synchronized Level getPushLevel() {

        return pushLevel;

    }

    /**

     * Check if this <tt>Handler</tt> would actually log a given

     * <tt>LogRecord</tt> into its internal buffer.

     * <p>

     * This method checks if the <tt>LogRecord</tt> has an appropriate level and

     * whether it satisfies any <tt>Filter</tt>.  However it does <b>not</b>

     * check whether the <tt>LogRecord</tt> would result in a "push" of the

     * buffer contents. It will return false if the <tt>LogRecord</tt> is null.

     * <p>

     * @param record  a <tt>LogRecord</tt>

     * @return true if the <tt>LogRecord</tt> would be logged.

     *

     */

    public boolean isLoggable(LogRecord record) {

        return super.isLoggable(record);

    }

}