package jalview.bin;

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

public class MemorySetting
{
  public static final long leaveFreeMinMemory = 536870912; // 0.5 GB

  public static final long applicationMinMemory = 536870912; // 0.5 GB

  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
      Cache.log.error("No com.sun.management.OperatingSystemMXBean");
    }

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

  public static long memPercent(int percent)
  {
    long memPercent = -1;

    long physicalMem = getPhysicalMemory();
    if (physicalMem > applicationMinMemory)
    {
      // try and set at least applicationMinMemory and thereafter ensure
      // leaveFreeMinMemory is left for the OS
      memPercent = Math.max(applicationMinMemory,
              physicalMem - Math.max(physicalMem * (100 - percent) / 100,
                      leaveFreeMinMemory));
    }

    return memPercent;
  }

}