/**
 * title:  Network Delay Calculator
 * author: Matt Rankin, 2007
 */
public class NetworkDelay{
   static char type;
   static double packetSize,bitrate,distance,velocity,util;
   public static void main(String[] argv){
      if(argv.length<3 || argv.length>5)
         type='h';
      else
         type=(argv[0].matches("-[spuUh]"))?argv[0].charAt(1):'h';
      switch(type){
         case 's':
            System.out.println("Transmission delay = "+send(argv[1],argv[2])+
                               " seconds");
            break;
         case 'p':
            System.out.println("Propagation delay = "+prop(argv[1],argv[2])+
                               " seconds");
            break;
         case 'u':
            util=util(send(argv[1],argv[2]),prop(argv[3],argv[4]));
            System.out.println("Utilisation = "+round(util,2)+
                               "%\nThroughput = "+through(util*bitrate));
            break;
         case 'U':
            util=utilSW(send(argv[1],argv[2]),prop(argv[3],argv[4]));
            System.out.println("Utilisation = "+round(util,2)+
                               "%\nThroughput = "+through(util*bitrate));
            break;
         case 'h':
            System.out.println(help());
            break;
      }
      System.exit(0);
   }
   static double send(String p1,String p2){
      try{
         packetSize=Double.parseDouble(p1);
         bitrate=Double.parseDouble(p2);
      }catch(NumberFormatException e){
         epicFail();
      }
      return packetSize/bitrate;
   }
   static double prop(String p1,String p2){
      try{
         distance=Double.parseDouble(p1);
         switch(p2.charAt(0)){
            case 'r':
               velocity=299792458;
               break;
            case 'w':
               velocity=199861638;
               break;
            default:epicFail();
         }
      }catch(Exception e){
         epicFail();
      }
      return distance/velocity;
   }
   static double util(double s,double p){
      return 100*s/(s+(2*p));
   }
   static double utilSW(double s,double p){
      return 1/(1+(2*(p/s)));
   }
   static String through(double ebps){
      StringBuffer out=new StringBuffer(1024);
      double mb=Math.pow(2,20);
      if(ebps<Math.pow(2,24)){
         out.append(round(ebps,2)+"bps");
         if(ebps>=mb)
            out.append(" ("+round(ebps/mb,2)+"MB/s)");
      }else
         out.append(round(ebps/mb,2)+"MB/s");
      return out.toString();
   }
   static double round(double x,int y){
      double z=Math.pow(10,y);
      return Math.round(x*z)/z;
   }
   static String help(){
      String h;
      h="Calculates network transmission and propagation delay, and also the\n"+
      "overall utilisation percentage and effective throughput.\n\n"+
      "   NetworkDelay -[spuUh] [ packet bitrate | distance velocity ]\n\n"+
      "   -s         Transmission delay\n"+
      "   -p         Propagation delay\n"+
      "   -u         Network Utilisation\n"+
      "   -U         Network Utilisation (stop-n-wait protocol)\n"+
      "   -h         Help\n"+
      "   packet     Packet size (in bits)\n"+
      "   bitrate    Bits per second\n"+
      "   distance   In metres\n"+
      "   velocity   Wire or radio [r | w]\n\n"+
      "Transmission delay requires the 'packet' and 'bitrate' parameters.\n"+
      "Propagation delay requires the 'distance' and 'velocity'. Ensure that\n"+
      "'velocity' is 'r' (speed of light) or 'w' (2/3 speed of light).\n\n"+
      "Network utilisation requires all four parameters in the order shown\n"+
      "in the syntax above.";
      return h;
   }
   static void epicFail(){
      System.err.println("Epic fail!");
      System.exit(0);
   }
}