/*
  Copyright (c) 2003 Jan-Klaas Kollhof
  
  This file is part of the JavaScript o lait library(jsolait).
  
  jsolait is free software; you can redistribute it and/or modify
  it under the terms of the GNU Lesser General Public License as published by
  the Free Software Foundation; either version 2.1 of the License, or
  (at your option) any later version.
 
  This software is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  GNU Lesser General Public License for more details.
 
  You should have received a copy of the GNU Lesser General Public License
  along with this software; if not, write to the Free Software
  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
*/ 

/**
    Cryptography module.
    Provides String encryption/decryption and hashing. 
*/
Module("crypto", "0.1.2", function(mod){
    /**
        Returns all all available encrypters.
        @return  An array of encrypters names.
    */
    mod.listEncrypters=function(){
        var c=[];
        for(var attr in String.prototype){
            if(attr.slice(0, 8) == "encrypt_"){
                c.push(attr.slice(8));
            }
        }
        return c;
    }
    /**
        Returns all all available decrypters.
        @return  An array of decrypters names.
    */
    mod.listDecrypters=function(){
        var c=[];
        for(var attr in String.prototype){
            if(attr.slice(0, 8) == "decrypt_"){
                c.push(attr.slice(8));
            }
        }
        return c;
    }
    
    /**
        Encrypts a string.
        Parameters but the crypdec parameter are forwardet to the crypdec.
        @param codec  The codec to use.
    */
    String.prototype.encrypt=function(crydec){
        var n = "encrypt_" + crydec;
        if(String.prototype[n]){
            var args=[];
            for(var i=1;i<arguments.length;i++){
                args[i-1] = arguments[i];
            }
            return String.prototype[n].apply(this, args);
        }else{
            throw new mod.Exception("Decrypter '%s' not found.".format(crydec));
        }
    }
    /**
        Decrypts a string.
        Parameters but the crypdec parameter are forwardet to the crypdec.
        @param codec  The codec to use.
    */
    String.prototype.decrypt=function(crydec){
        var n = "decrypt_" + crydec;
        if(String.prototype[n]){
            var args=[];
            for(var i=1;i<arguments.length;i++){
                args[i-1] = arguments[i];
            }
            return String.prototype[n].apply(this, args);
        }else{
            throw new mod.Exception("Encrypter '%s' not found.".format(crydec));
        }
    }
    
    /**
        Encrypts a string using XOR.
        The whole String will be XORed with the key. 
        If the key is shorter than the String then it will be multiplied to fit the length of the String.
        @param key  The key to use for encryption.
    */
    String.prototype.encrypt_xor=function(key){
        var e=new Array(this.length);
        var l=key.length;
        for(var i=0;i<this.length;i++){
            e[i] = String.fromCharCode(this.charCodeAt(i) ^ key.charCodeAt(i % l));
        }
        return e.join("");
    }
    /**
        Decrypts a string using XOR.
        Since XORing is symetric it is the same as the encrypter.
        @param key  The key to use for decryption.
    */
    String.prototype.decrypt_xor=String.prototype.encrypt_xor;
    /**
        Encrypts a string using the ARC4 algorithm.
        @param key  The key to use for encryption.
    */
    String.prototype.encrypt_rc4=function(key){
        //generate substitution box
        var sbox = new Array (256);
        for (var i=0; i<256; i++){
             sbox[i]=i;
        }
        
        //swap things around 
        var j=0;
        for (var i=0; i < 256; i++) {
             j = (j + sbox[i] + key.charCodeAt(i % key.length)) % 256;
             var tmp = sbox[i];
             sbox[i] = sbox[j];
             sbox[j] = tmp;
        }
        
        //calculate the result
        var i=256;    
        var j=256;
        var rslt=new Array(this.length);
        for (var k=0; k < this.length; k++) {
            i = (i + 1) % 256;
            j = (j + sbox[i]) % 256;
            var tmp = sbox[i];
            sbox[i] = sbox[j];
            sbox[j] = tmp;
            t = (sbox[i] + sbox[j]) % 256;
            rslt[k] = String.fromCharCode(this.charCodeAt(k) ^ sbox[t]);
        }
        return rslt.join("");
    }
    /**
        Decrypts a string using the ARC4 algorithm.
        Since it is symetric it is the same as the encrypter.
        @param key  The key to use for decryption.
    */
    String.prototype.decrypt_rc4=String.prototype.encrypt_rc4;
})
