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package org.nakedobjects.metamodel.commons.logging;

import java.util.Date;

import org.apache.log4j.AppenderSkeleton;
import org.apache.log4j.Level;
import org.apache.log4j.Logger;
import org.apache.log4j.helpers.CyclicBuffer;
import org.apache.log4j.helpers.OptionConverter;
import org.apache.log4j.spi.LoggingEvent;
import org.apache.log4j.spi.TriggeringEventEvaluator;
import org.nakedobjects.metamodel.commons.about.AboutNakedObjects;


class DefaultEvaluator implements TriggeringEventEvaluator {
    public boolean isTriggeringEvent(final LoggingEvent event) {
        return event.getLevel().isGreaterOrEqual(Level.ERROR);
    }
}

public abstract class SnapshotAppender extends AppenderSkeleton {
    private int bufferSize = 512;
    protected CyclicBuffer buffer = new CyclicBuffer(bufferSize);
    private boolean locationInfo = false;
    protected TriggeringEventEvaluator triggerEvaluator;
    private boolean addInfo;

    /**
     * The default constructor will instantiate the appender with a {@link TriggeringEventEvaluator} that will
     * trigger on events with level ERROR or higher.
     */
    public SnapshotAppender() {
        this(new DefaultEvaluator());
    }

    public SnapshotAppender(final TriggeringEventEvaluator evaluator) {
        this.triggerEvaluator = evaluator;
    }

    @Override
    public void append(final LoggingEvent event) {
        if (shouldAppend()) {
            event.getThreadName();
            event.getNDC();
            if (locationInfo) {
                event.getLocationInformation();
            }
            buffer.add(event);
            if (triggerEvaluator.isTriggeringEvent(event)) {
                writeSnapshot(buffer);
            }
        }
    }

    public void forceSnapshot() {
        writeSnapshot(buffer);
    }

    /**
     * Send the contents of the cyclic buffer as an web server posting.
     */
    private void writeSnapshot(final CyclicBuffer buffer) {
        final StringBuffer details = new StringBuffer();
        final String header = layout.getHeader();
        if (header != null) {
            details.append(header);
        }

        if (addInfo) {
            final String user = System.getProperty("user.name");
            final String system = System.getProperty("os.name") + " (" + System.getProperty("os.arch") + ") "
                    + System.getProperty("os.version");
            final String java = System.getProperty("java.vm.name") + " " + System.getProperty("java.vm.version");
            final String version = AboutNakedObjects.getFrameworkVersion();

            final LoggingEvent infoEvent = new LoggingEvent("", Logger.getRootLogger(), Level.INFO, "Snapshot:- " + new Date()
                    + "\n\t" + user + "\n\t" + system + "\n\t" + java + "\n\t" + version, null);
            details.append(layout.format(infoEvent));
        }

        final int len = buffer.length();
        String message = "";
        for (int i = 0; i < len; i++) {
            final LoggingEvent event = buffer.get();
            message = event.getLoggerName() + ": " + event.getMessage();
            details.append(layout.format(event));
            if (layout.ignoresThrowable()) {
                final String[] s = event.getThrowableStrRep();
                if (s != null) {
                    for (int j = 0; j < s.length; j++) {
                        details.append(s[j]);
                        details.append('\n');
                    }
                }
            }
        }

        final String footer = layout.getFooter();
        if (footer != null) {
            details.append(footer);
        }

        writeSnapshot(message, details.toString());
    }

    protected abstract void writeSnapshot(final String message, final String details);

    synchronized public void close() {
        this.closed = true;
    }

    public int getBufferSize() {
        return bufferSize;
    }

    public String getEvaluatorClass() {
        return triggerEvaluator == null ? null : triggerEvaluator.getClass().getName();
    }

    public boolean getLocationInfo() {
        return locationInfo;
    }

    /**
     * returns true to show that this appender requires a {@linkorg.apache.log4j.Layout layout}.
     */
    public boolean requiresLayout() {
        return true;
    }

    public void setBufferSize(final int bufferSize) {
        this.bufferSize = bufferSize;
        buffer.resize(bufferSize);
    }

    public void setEvaluatorClass(final String value) {
        triggerEvaluator = (TriggeringEventEvaluator) OptionConverter.instantiateByClassName(value,
                TriggeringEventEvaluator.class, triggerEvaluator);
    }

    public void setAddInfo(final boolean addInfo) {
        this.addInfo = addInfo;
    }

    public void setLocationInfo(final boolean locationInfo) {
        this.locationInfo = locationInfo;
    }

    protected boolean shouldAppend() {
        if (triggerEvaluator == null) {
            errorHandler.error("No TriggeringEventEvaluator is set for appender [" + name + "].");
            return false;
        }

        if (layout == null) {
            errorHandler.error("No layout set for appender named [" + name + "].");
            return false;
        }

        return true;
    }
}
// Copyright (c) Naked Objects Group Ltd.