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/*
 License:

 blueprint-sdk is licensed under the terms of Eclipse Public License(EPL) v1.0
 (http://www.eclipse.org/legal/epl-v10.html)


 Distribution:

 Maven Central - https://search.maven.org/artifact/io.github.lempel/blueprint-sdk
 MVN Repository - https://mvnrepository.com/artifact/io.github.lempel/blueprint-sdk
 */

package blueprint.sdk.util.jvm;

import java.lang.management.ManagementFactory;
import java.lang.management.RuntimeMXBean;
import java.util.List;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import blueprint.sdk.util.Terminatable;

/**
 * Monitors memory usage

 * For better result, please set -Xmx argument.

 *
 * @author [email protected]
 * @since 2009. 3. 2.
 */
public class MemoryMonitor implements Terminatable, Runnable {
    private static final Logger L = LoggerFactory.getLogger(MemoryMonitor.class);

    /**
     * check interval - 10sec
     */
    private static final int INTERVAL = 10000;
    /**
     * memory usage limit to warn - 80%
     */
    private static final int WARNING_USAGE = 80;
    /**
     * maximum tolerable warnings - 6times
     */
    private static final int MAX_WARNINGS = 6;

    private boolean running = false;
    private transient boolean terminated = false;
    private boolean trace = false;

    @SuppressWarnings("WeakerAccess")
    public MemoryMonitor() {
        super();
    }

    @SuppressWarnings("WeakerAccess")
    public MemoryMonitor(boolean trace) {
        super();

        this.trace = trace;
    }

    /**
     * @return current heap usage in percent
     */
    public static int getMemoryUsage() {
        Runtime rtime = Runtime.getRuntime();
        long total = rtime.maxMemory();
        long used = rtime.totalMemory() - rtime.freeMemory();
        double ratio = (double) used / (double) total;
        return (int) (ratio * 100d);
    }

    /**
     * @return true if -Xmx is set
     */
    @SuppressWarnings("WeakerAccess")
    public static boolean isXmxSet() {
        boolean result = false;

        RuntimeMXBean RuntimemxBean = ManagementFactory.getRuntimeMXBean();
        List arguments = RuntimemxBean.getInputArguments();
        for (String arg : arguments) {
            if (arg.toLowerCase().startsWith("-xmx")) {
                result = true;
                break;
            }
        }

        return result;
    }

    public boolean isValid() {
        return running;
    }

    public boolean isTerminated() {
        return terminated;
    }

    public void terminate() {
        running = false;
    }

    public void start() {
        Thread thr = new Thread(this);
        thr.setName(this.getClass().getName());
        thr.setDaemon(true);
        thr.start();
    }

    public void run() {
        running = true;

        boolean interrupted = false;
        int warnCount = 0;
        boolean xmx = isXmxSet();

        while (running) {
            try {
                if (!interrupted) {
                    Runtime rtime = Runtime.getRuntime();
                    long total = rtime.maxMemory();
                    long used = rtime.totalMemory() - rtime.freeMemory();
                    double ratio = (double) used / (double) total;
                    int percent = (int) (ratio * 100d);

                    if (percent >= WARNING_USAGE) {
                        warnCount++;
                        if (warnCount >= MAX_WARNINGS) {
                            L.error("LOW MEMORY!! Memory usage is Critical. " + percent + "%");
                            if (xmx) {
                                L.error("RECOMMEND: 1. Increase -Xmx value");
                            } else {
                                L.error("RECOMMEND: 1. Set -Xmx value");
                            }
                            L.error("RECOMMEND: 2. Check for memory leak");
                            L.error("RECOMMEND: 3. Install more RAM");
                            warnCount = 0;
                        } else {
                            L.warn("Memory usage: " + percent + "% - " + (used / 1024 / 1024) + "M");
                        }
                    } else {
                        warnCount = 0;
                    }

                    if (trace) {
                        L.info("Memory usage: " + percent + "% - " + (used / 1024 / 1024) + "M");
                    }
                }
            } catch (OutOfMemoryError oom) {
                L.error("OutOfMemoryError", oom);
            }

            try {
                Thread.sleep(INTERVAL);
                interrupted = false;
            } catch (InterruptedException e) {
                interrupted = true;
            }
        }

        terminated = true;
    }
}