/**
 * title:  Bandwidth Calculator
 * author: Matt Rankin, 2007
 */
public class Bandwidth{
   static char type;
   static double hertz,depth,signal,noise,dB,bitrate;
   public static void main(String[] argv){
      if(argv.length<3 || argv.length>3)
         type='h';
      else
         type=(argv[0].matches("-[nsh]"))?argv[0].charAt(1):'h';
      switch(type){
         case 'n':
            try{
               hertz=Double.parseDouble(argv[1]);
               depth=Double.parseDouble(argv[2]);
            }catch(NumberFormatException e){
               epicFail();
            }
            bitrate=nyquist(hertz,depth);
            System.out.println("bitrate = "+bitrate+"bps");
            break;
         case 's':
            hertz=Double.parseDouble(argv[1]);
            if(argv[2].matches("\\d+:\\d+")){
               String[] ratio=argv[2].split(":");
               signal=Double.parseDouble(ratio[0]);
               noise=Double.parseDouble(ratio[1]);
            }else{
               dB=Double.parseDouble(argv[2]);
               signal=Math.pow(10,dB/10);
               noise=1;
            }
            bitrate=shannon(hertz,signal,noise);
            System.out.println("bitrate = "+bitrate+"bps");
            break;
         case 'h':
            System.out.println(help());
            break;
      }
      System.exit(0);
   }
   static double nyquist(double h,double d){
      return 2*h*logb(d,2);
   }
   static double shannon(double h,double s,double n){
      double e=Math.pow(10,4);
      return Math.round(e*h*logb((1+(s/n)),2))/e;
   }
   static double logb(double d,double b){
      return Math.log(d)/Math.log(b);
   }
   static String help(){
      String h;
      h="Calculates channel bandwidth capacity using either Nyquist's or "+
      "Shannon's\ntheorem.\n\n"+
      "   Bandwidth -[nsh] hertz [depth | [dB | SNR]]\n\n"+
      "   -n         Use Nyquist's Theorem\n"+
      "   -s         Use Shannon's Theorem\n"+
      "   -h         Help\n"+
      "   hertz      Channel bandwidth in cyles per second\n"+
      "   depth      No. of signalling symbols (2 for binary)\n"+
      "   dB         Signal strength in decibels\n"+
      "   SNR        Signal-to-Noise ratio (syntax: 's:n')\n\n"+
      "Nyquist's theorem requires the 'hertz' and 'depth' parameters to\n"+
      "calculate the maximum bitrate of a noise-free bandwidth-limited\n"+
      "channel. Shannon's theorem applies to a bandwidth-limited noisy\n"+
      "channel without respect to the number of signal cycles used, and uses\n"+
      "the 'hertz' and 'dB' or 'SNR' parameters.";
      return h;
   }
   static void epicFail(){
      System.err.println("Epic fail!");
      System.exit(0);
   }
}