package jalview.bin;

import java.lang.management.ManagementFactory;
import java.lang.management.OperatingSystemMXBean;

public class MemoryPercent
{

  protected static long getPhysicalMemory()
  {
    final OperatingSystemMXBean o = ManagementFactory
            .getOperatingSystemMXBean();

    try
    {
      if (o instanceof com.sun.management.OperatingSystemMXBean)
      {
        final com.sun.management.OperatingSystemMXBean osb = (com.sun.management.OperatingSystemMXBean) o;
        return osb.getTotalPhysicalMemorySize();
      }
    } catch (NoClassDefFoundError e)
    {
      // com.sun.management.OperatingSystemMXBean doesn't exist in this JVM
      System.err.println(
              "No com.sun.management.OperatingSystemMXBean: cannot get total physical memory size");
    }

    // We didn't get a com.sun.management.OperatingSystemMXBean.
    return -1;
  }

  public static long memPercentAmount(int percent)
  {
    return memPercentAmount((float)percent);
  }
  public static long memPercentAmount(float percent)
  {
    long memPercentAmount = -1;

    long physicalMem = getPhysicalMemory();
    if (physicalMem > MemorySetting.applicationMinMemory)
    {
      // try and set at least applicationMinMemory and thereafter ensure
      // leaveFreeMinMemory is left for the OS

      memPercentAmount = (long) ((physicalMem * percent) / 100F);

      // check for memory left for OS
      if (physicalMem - memPercentAmount < MemorySetting.leaveFreeMinMemory)
      {
        memPercentAmount = physicalMem - MemorySetting.leaveFreeMinMemory;
      }

      // check for minimum application memsize
      if (memPercentAmount < MemorySetting.applicationMinMemory)
      {
        memPercentAmount = MemorySetting.applicationMinMemory;
      }
    } else {
      // not enough memory for application, just try and grab what we can!
      memPercentAmount = physicalMem;
    }

    return memPercentAmount;
  }

}