/**
 * title: Caesar Cipher
 * author: Matt Rankin, 2007
 */
import java.io.*;
public class Caesar{
   static char type;
   static int key;
   static String input;
   public static void main(String[] argv){
      if(argv.length<1 || argv.length>4){
         System.out.println(help());
         System.exit(0);
      }
      type=(argv[0].matches("-[edDh]"))?argv[0].charAt(1):'h';
      switch(type){
         case 'h':
            System.out.println(help());
            System.exit(0);
            break;
         case 'e':
            key=getKey(argv[1]);
            input=getInput(argv).toLowerCase();
            System.out.println("\nPlaintext:\n\n"+input+"\n\nCiphertext("+
                               Math.abs(key)+"):\n\n"+
                               shift(input,key).toUpperCase());
            break;
         case 'd':
            key=getKey(argv[1])*-1;
            input=getInput(argv).toUpperCase();
            System.out.println("\nCiphertext:\n\n"+input+"\n\nPlaintext("+
                               Math.abs(key)+"):\n\n"+
                               shift(input,key).toLowerCase());
            break;
         case 'D':
            input=getInput(argv).toUpperCase();
            System.out.println("\nCiphertext:\n\n"+input+"\n\nPlaintexts:\n");
            for(int i=1;i<26;i++){
               System.out.println(shift(input,i*-1).toLowerCase()+" ("+i+")\n");
            }
            break;
      }
      System.exit(0);
   }
   static int getKey(String param){
      if(!param.matches("\\d+"))
         epicFail("Invalid key!");
      return Integer.parseInt(param)%26;
   }
   static String getInput(String[] params){
      StringBuffer str=new StringBuffer(65536);
      int x=-1;
      for(int i=0;i<params.length;i++)
         if(params[i].matches("-f"))
            x=i;
      if(x!=-1){
         try{
            BufferedReader file=new BufferedReader(new FileReader(params[x+1]));
            while(file.ready()){
               String line=file.readLine();
               int length=line.length();
               for(int i=0;i<length;i++){
                  char ch=line.charAt(i);
                  if(Character.isLetterOrDigit(ch)||Character.isWhitespace(ch))
                     str.append(ch);
               }
               str.append("\n");
            }
         }catch(Exception e){
            epicFail(e.getMessage());
         }
      }else{
         int z=params.length-1;
         int length=params[z].length();
         for(int i=0;i<length;i++){
            char ch=params[z].charAt(i);
            if(Character.isLetterOrDigit(ch)||Character.isWhitespace(ch))
               str.append(ch);
         }
      }
      return str.toString().trim();
   }
   static String shift(String in,int key){
      int length=in.length();
      StringBuffer out=new StringBuffer(length);
      String alphabet=new String("abcdefghijklmnopqrstuvwxyz");
      for(int i=0;i<length;i++){
         char ch=Character.toLowerCase(in.charAt(i));
         int index=alphabet.indexOf(ch);
         if(index!=-1){
            index+=key;
            int substitute=(index<0)?index+26:index%26;
            out.append(alphabet.charAt(substitute));
         }else
            out.append(ch);
      }
      return out.toString();
   }
   static String help(){
      String h;
      h="Encrypts and decrypts the Caesar Cipher\n\n"+
      "   Caesar -[edDh] [key] [-f filename|\"string\"]\n\n"+
      "   -e          Encrypt input\n"+
      "   -d          Decrypt input\n"+
      "   -D          Brute-force decrypt\n"+
      "   -h          This help menu\n"+
      "   key         The shift size\n"+
      "   -f filename Path to the file to process\n"+
      "   \"string\"    String to process\n\n"+
      "The 'key' parameter is required for normal encryption and decryption\n"+
      "functions, but not for the brute-force functions, since all 26\n"+
      "possible keys are tried.\n\nFor input strings that contain spaces,\n"+
      "quotation marks must be used.";
      return h;
   }
   static void epicFail(String error){
      System.err.println("Epic fail!\n\n"+error);
      System.exit(0);
   }
}