/*******************************************************************************
 *
 * Copyright (c) 2004-2011 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:
 *
 *    Inc., Kohsuke Kawaguchi, Seiji Sogabe, Winston Prakash
 *
 *
 *******************************************************************************/ 

package hudson.node_monitors;

import hudson.Util;
import hudson.Extension;
import hudson.model.Computer;
import hudson.model.Hudson;
import hudson.remoting.Callable;
import org.eclipse.hudson.jna.NativeAccessException;
import org.eclipse.hudson.jna.NativeUtils;
import org.eclipse.hudson.jna.NativeSystemMemory;
import net.sf.json.JSONObject;

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

import java.io.IOException;

/**
 * Checks the swap space availability.
 *
 * @author Kohsuke Kawaguchi
 * @sine 1.233
 */
public class SwapSpaceMonitor extends NodeMonitor {

    /**
     * Returns the HTML representation of the space.
     */
    public String toHtml(NativeSystemMemory usage) {
        if (usage.getAvailableSwapSpace() == -1) {
            return "N/A";
        }

        long free = usage.getAvailableSwapSpace();
        free /= 1024L;   // convert to KB
        free /= 1024L;   // convert to MB
        if (free > 256 || usage.getTotalSwapSpace() < usage.getAvailableSwapSpace() * 5) {
            return free + "MB"; // if we have more than 256MB free or less than 80% filled up, it's OK
        }
        // Otherwise considered dangerously low.
        return Util.wrapToErrorSpan(free + "MB");
    }

    public long toMB(NativeSystemMemory usage) {
        if (usage.getAvailableSwapSpace() == -1) {
            return -1;
        }

        long free = usage.getAvailableSwapSpace();
        free /= 1024L;   // convert to KB
        free /= 1024L;   // convert to MB
        return free;
    }

    @Override
    public String getColumnCaption() {
        // Hide this column from non-admins
        return Hudson.getInstance().hasPermission(Hudson.ADMINISTER) ? super.getColumnCaption() : null;
    }
    @Extension
    public static final AbstractNodeMonitorDescriptor<NativeSystemMemory> DESCRIPTOR = new AbstractNodeMonitorDescriptor<NativeSystemMemory>() {
        protected NativeSystemMemory monitor(Computer c) throws IOException, InterruptedException {
            final NativeUtils  nativeUtils = NativeUtils.getInstance();
            return c.getChannel().call(new MonitorTask(nativeUtils));
        }

        public String getDisplayName() {
            return Messages.SwapSpaceMonitor_DisplayName();
        }

        @Override
        public NodeMonitor newInstance(StaplerRequest req, JSONObject formData) throws FormException {
            return new SwapSpaceMonitor();
        }
    };

    /**
     * Obtains the string that represents the architecture.
     */
    private static class MonitorTask implements Callable<NativeSystemMemory, IOException> {

        private static final long serialVersionUID = 1L;
        private static boolean warned = false;
        private NativeUtils nativeUtils;

        private MonitorTask(NativeUtils nativeUtils) {
            this.nativeUtils = nativeUtils;
        }

        public NativeSystemMemory call() throws IOException {

            try {
                return new MemoryUsage(nativeUtils.getSystemMemory());
            } catch (NativeAccessException exc) {
                if (!warned) {
                    // report the problem just once, and avoid filling up the log with the same error. see HUDSON-2194.
                    warned = true;
                    throw new IOException(exc);
                } else {
                    return null;
                }
            }

        }
    }

    /**
     * Memory Usage.
     *
     * <p> {@link MemoryUsage} + stapler annotations.
     */
    @ExportedBean
    public static class MemoryUsage implements NativeSystemMemory {

        NativeSystemMemory systemMemory;

        public MemoryUsage(NativeSystemMemory mem) {
            systemMemory = mem;
        }

        /**
         * Total physical memory of the system, in bytes.
         */
        @Exported
        public long getTotalPhysicalMemory() {
            return systemMemory.getTotalPhysicalMemory();
        }

        /**
         * Of the total physical memory of the system, available bytes.
         */
        @Exported
        public long getAvailablePhysicalMemory() {
            return systemMemory.getAvailablePhysicalMemory();
        }

        /**
         * Total number of swap space in bytes.
         */
        @Exported
        public long getTotalSwapSpace() {
            return systemMemory.getTotalSwapSpace();
        }

        /**
         * Available swap space in bytes.
         */
        @Exported
        public long getAvailableSwapSpace() {
            return systemMemory.getAvailableSwapSpace();
        }
    }
}