/**
    * Oshi (https://github.com/dblock/oshi)
    * 
    * Copyright (c) 2010 - 2015 The Oshi Project Team
    * 
    * 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:
   * dblock[at]dblock[dot]org
   * alessandro[at]perucchi[dot]org
   * widdis[at]gmail[dot]com
   * https://github.com/dblock/oshi/graphs/contributors
   */
  package oshi.software.os.linux.proc;
  
  import java.io.IOException;
  import java.util.List;
  
  import oshi.hardware.Memory;
  import oshi.software.os.linux.Libc;
  import oshi.software.os.linux.Libc.Sysinfo;
  import oshi.util.FileUtil;
  
  import com.sun.jna.LastErrorException;
  import com.sun.jna.Native;
  
  /**
   * Memory obtained by /proc/meminfo and sysinfo.totalram
   * 
   * @author alessandro[at]perucchi[dot]org
   * @author widdis[at]gmail[dot]com
   */
  public class GlobalMemory implements Memory {
  
  	private long totalMemory = 0;
  
  	@Override
  	public long getAvailable() {
  		long availableMemory = 0;
  		List<String> memInfo = null;
  		try {
  			memInfo = FileUtil.readFile("/proc/meminfo");
  		} catch (IOException e) {
  			System.err.println("Problem with: /proc/meminfo");
  			System.err.println(e.getMessage());
  			return availableMemory;
  		}
  		for (String checkLine : memInfo) {
  			// If we have MemAvailable, it trumps all. See code in
  			// https://git.kernel.org/cgit/linux/kernel/git/torvalds/
  			// linux.git/commit/?id=34e431b0ae398fc54ea69ff85ec700722c9da773
  			if (checkLine.startsWith("MemAvailable:")) {
  				String[] memorySplit = checkLine.split("\\s+");
  				availableMemory = parseMeminfo(memorySplit);
  				break;
  			} else
  			// Otherwise we combine MemFree + Active(file), Inactive(file), and
  			// SReclaimable. Free+cached is no longer appropriate. MemAvailable
  			// reduces these values using watermarks to estimate when swapping
  			// is prevented, omitted here for simplicity (assuming 0 swap).
  			if (checkLine.startsWith("MemFree:")) {
  				String[] memorySplit = checkLine.split("\\s+");
  				availableMemory += parseMeminfo(memorySplit);
  			} else if (checkLine.startsWith("Active(file):")) {
  				String[] memorySplit = checkLine.split("\\s+");
  				availableMemory += parseMeminfo(memorySplit);
  			} else if (checkLine.startsWith("Inactive(file):")) {
  				String[] memorySplit = checkLine.split("\\s+");
  				availableMemory += parseMeminfo(memorySplit);
  			} else if (checkLine.startsWith("SReclaimable:")) {
  				String[] memorySplit = checkLine.split("\\s+");
  				availableMemory += parseMeminfo(memorySplit);
  			}
  		}
  		return availableMemory;
  	}
  
  	@Override
  	public long getTotal() {
  		if (this.totalMemory == 0) {
  			Sysinfo info = new Sysinfo();
  			if (0 != Libc.INSTANCE.sysinfo(info))
  				throw new LastErrorException("Error code: "
  						+ Native.getLastError());
  			this.totalMemory = info.totalram.longValue() * info.mem_unit;
  		}
  		return this.totalMemory;
  	}
  
  	private long parseMeminfo(String[] memorySplit) {
  		if (memorySplit.length < 2) {
  			return 0l;
  		}
  		long memory = new Long(memorySplit[1]).longValue();
  		if (memorySplit.length > 2 && memorySplit[2].equals("kB")) {
  			memory *= 1024;
 		}
 		return memory;
 	}
 }