package gc;

import java.lang.management.ManagementFactory;
import com.sun.management.OperatingSystemMXBean;
import java.lang.management.ThreadMXBean;
import java.lang.management.MemoryMXBean;
import java.lang.management.GarbageCollectorMXBean;
import java.util.*;

public class GCUtils {
	private OperatingSystemMXBean operatingSystem;
	private ThreadMXBean thread;
	private MemoryMXBean memory;
	private List<GarbageCollectorMXBean> gcBeans;
	
	private int processorCount;
	private long lastCpuTime;
	private long lastNanoTime;
	private final ArrayList<String> youngGenCollectorNames;
	private final ArrayList<String> oldGenCollectorNames;
	
	public GCUtils() {
		operatingSystem = (OperatingSystemMXBean)ManagementFactory.getOperatingSystemMXBean();
		thread = ManagementFactory.getThreadMXBean();
		memory = ManagementFactory.getMemoryMXBean();
		gcBeans = ManagementFactory.getGarbageCollectorMXBeans();
		
		processorCount = operatingSystem.getAvailableProcessors();
		lastCpuTime = operatingSystem.getProcessCpuTime();
		lastNanoTime = System.nanoTime();
		
		youngGenCollectorNames = new ArrayList();
		youngGenCollectorNames.add("Copy");
		youngGenCollectorNames.add("ParNew");
		youngGenCollectorNames.add("PS Scavenge");
		
		youngGenCollectorNames.add("Garbage collection optimized for short pausetimes Young Collector");
		youngGenCollectorNames.add("Garbage collection optimized for throughput Young Collector");
		youngGenCollectorNames.add("Garbage collection optimized for deterministic pausetimes Young Collector");
		
		oldGenCollectorNames = new ArrayList();
		oldGenCollectorNames.add("MarkSweepCompact");
		oldGenCollectorNames.add("PS MarkSweep");
		oldGenCollectorNames.add("ConcurrentMarkSweep");
		
		oldGenCollectorNames.add("Garbage collection optimized for short pausetimes Old Collector");
		oldGenCollectorNames.add("Garbage collection optimized for throughput Old Collector");
		oldGenCollectorNames.add("Garbage collection optimized for deterministic pausetimes Old Collector");
	}
	
	public String getUsedCpu() {
		long cpuTime = operatingSystem.getProcessCpuTime();
		long time = System.nanoTime();
		double pct = (cpuTime - lastCpuTime) / (double)(time - lastNanoTime) / processorCount;
		lastCpuTime = cpuTime;
		lastNanoTime = time;
		return String.format("%.2f%%", pct*100);
	}
	
	public long getUsedHeap() {
		return memory.getHeapMemoryUsage().getUsed() >> 20;
	}
	
	public long getCommittedHeap() {
		return memory.getHeapMemoryUsage().getCommitted() >> 20;
	}
	
	private static void printGC(GarbageCollectorMXBean gc) {
		String gcName = gc.getName();
		long gcCnt = gc.getCollectionCount();
		long gcTime = gc.getCollectionTime();
		System.out.println(String.format("%s: gc count %d, gc time %d.", gcName, gcCnt, gcTime));
		System.out.println(Arrays.toString(gc.getMemoryPoolNames()));
	}
	
	public void printYoungGC() {
		for (int i = 0; i < gcBeans.size(); i++) {
			GarbageCollectorMXBean gc = (GarbageCollectorMXBean)gcBeans.get(i);
			if (youngGenCollectorNames.contains(gc.getName())) {
				printGC(gc);
			}
		}
	}
	
	public void printFullGC() {
		for (int i = 0; i < gcBeans.size(); i++) {
			GarbageCollectorMXBean gc = (GarbageCollectorMXBean)gcBeans.get(i);
			if (oldGenCollectorNames.contains(gc.getName())) {
				printGC(gc);
			}
		}
	}
	
	public long getYoungGCCount() {
		long gcCount = 0L;
		for (int i = 0; i < gcBeans.size(); i++) {
			GarbageCollectorMXBean gc = (GarbageCollectorMXBean)gcBeans.get(i);
			if (youngGenCollectorNames.contains(gc.getName())) {
				gcCount += gc.getCollectionCount();
			}
		}
		return gcCount;
	}
	
	public long getFullGCCount() {
		long gcCount = 0L;
		for (int i = 0; i < gcBeans.size(); i++) {
			GarbageCollectorMXBean gc = (GarbageCollectorMXBean)gcBeans.get(i);
			if (oldGenCollectorNames.contains(gc.getName())) {
				gcCount += gc.getCollectionCount();
			}
		}
		return gcCount;
	}
	
	public long getYoungGCTime() {
		long gcTime = 0L;
		for (int i = 0; i < gcBeans.size(); i++) {
			GarbageCollectorMXBean gc = (GarbageCollectorMXBean)gcBeans.get(i);
			if (youngGenCollectorNames.contains(gc.getName())) {
				gcTime += gc.getCollectionTime();
			}
		}
		return gcTime;
	}
	
	public long getFullGCTime() {
		long gcTime = 0L;
		for (int i = 0; i < gcBeans.size(); i++) {
			GarbageCollectorMXBean gc = (GarbageCollectorMXBean)gcBeans.get(i);
			if (oldGenCollectorNames.contains(gc.getName())) {
				gcTime += gc.getCollectionTime();
			}

		}
		return gcTime;
	}
	
	public static void main(String[] args) {
		GCUtils gc = new GCUtils();
		System.out.println(String.format("cpu %s.", gc.getUsedCpu()));
		System.out.println(String.format("Used heap %dM.", gc.getUsedHeap()));
		System.out.println(String.format("Committed heap %dM.", gc.getCommittedHeap()));
		gc.printYoungGC();
		gc.printFullGC();
	}
}