RosettaCodeData/Task/Caesar-cipher/Zonnon/caesar-cipher.zonnon

module Caesar;
const
   size = 25;

type
   Operation = (code,decode);

procedure C_D(s:string;k:integer;op: Operation): string;
var
   i,key: integer;
   resp: string;
   n,c: char;
begin
   resp := "";
   if op = Operation.decode then key := k else key := (26 - k) end;
   for i := 0 to len(s) - 1 do
      c := cap(s[i]);
      if (c >= 'A') & (c <= 'Z') then
         resp := resp +
            string(char(integer('A') + ((integer(c) - integer('A') + key )) mod 26));
      else
         resp := resp + string(c)
      end;
   end;
   return  resp
end C_D;

procedure {public} Cipher(s:string;k:integer):string;
var
   i: integer;
   resp: string;
   n,c: char;
begin
   return C_D(s,k,Operation.code)
end Cipher;

procedure {public} Decipher(s:string;k:integer):string;
var
   i: integer;
   resp: string;
   n,c: char;
begin
   return C_D(s,k,Operation.decode)
end Decipher;

var
   txt,cipher,decipher: string;

begin
   txt := "HI";cipher := Caesar.Cipher(txt,2);decipher := Caesar.Decipher(cipher,2);
   writeln(txt," -c-> ",cipher," -d-> ",decipher);
   txt := "ZA";cipher := Caesar.Cipher(txt,2);decipher := Caesar.Decipher(cipher,2);
   writeln(txt," -c-> ",cipher," -d-> ",decipher);
   txt := "The five boxing wizards jump quickly";
   cipher := Caesar.Cipher(txt,2);decipher := Caesar.Decipher(cipher,2);
   writeln(txt," -c-> ",cipher," -d-> ",decipher)
end Caesar.