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Contains the core Hudson code and view files to render HTML.
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/*******************************************************************************
 *
 * Copyright (c) 2004-2009 Oracle Corporation.
 *
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 * 
 *    Kohsuke Kawaguchi, Seiji Sogabe, Thomas J. Black
 *
 *
 *******************************************************************************/ 

package hudson.util;

import hudson.Util;
import hudson.model.Node;

import java.io.IOException;

import org.kohsuke.stapler.export.ExportedBean;
import org.kohsuke.stapler.export.Exported;

/**
 * Represents a clock difference. Immutable.
 *
 * @author Kohsuke Kawaguchi
 */
@ExportedBean
public final class ClockDifference {

    /**
     * The difference in milliseconds.
     *
     * Positive value means the slave is behind the master, negative value means
     * the slave is ahead of the master.
     */
    @Exported
    public final long diff;

    public ClockDifference(long value) {
        this.diff = value;
    }

    /**
     * Returns true if the difference is big enough to be considered dangerous.
     */
    public boolean isDangerous() {
        return Math.abs(diff) > 5000;
    }

    /**
     * Gets the absolute value of {@link #diff}.
     */
    public long abs() {
        return Math.abs(diff);
    }

    /**
     * Gets the clock difference in HTML string.
     */
    @Override
    public String toString() {
        if (-1000 < diff && diff < 1000) {
            return Messages.ClockDifference_InSync();  // clock is in sync
        }
        long abs = Math.abs(diff);

        String s = Util.getTimeSpanString(abs);
        if (diff < 0) {
            s += Messages.ClockDifference_Ahead();
        } else {
            s += Messages.ClockDifference_Behind();
        }

        return s;
    }

    public String toHtml() {
        String s = toString();
        if (isDangerous()) {
            s = Util.wrapToErrorSpan(s);
        }
        return s;
    }

    public static String toHtml(Node d) {
        try {
            if (d == null) {
                return FAILED_HTML;
            }
            return d.getClockDifference().toHtml();
        } catch (IOException e) {
            return FAILED_HTML;
        } catch (InterruptedException e) {
            return FAILED_HTML;
        }
    }

    /**
     * Gets the clock difference in HTML string. This version handles null
     * {@link ClockDifference}.
     */
    public static String toHtml(ClockDifference d) {
        if (d == null) {
            return FAILED_HTML;
        }
        return d.toHtml();
    }
    public static final ClockDifference ZERO = new ClockDifference(0);
    private static final String FAILED_HTML =
            "" + Messages.ClockDifference_Failed() + "";
}