/*
    NXT address class, simple version (check only).

    Version: 1.0, license: Public Domain, coder: NxtChg (admin@nxtchg.com).
*/

function NxtAddress()
{
        var codeword = [1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0];
        var syndrome = [0,0,0,0,0];

        var gexp = [ 1, 2, 4, 8, 16, 5, 10, 20, 13, 26, 17, 7, 14, 28, 29, 31, 27, 19, 3, 6, 12, 24, 21, 15, 30, 25, 23, 11, 22, 9, 18, 1 ];
        var glog = [ 0, 0, 1, 18, 2, 5, 19, 11, 3, 29, 6, 27, 20, 8, 12, 23, 4, 10, 30, 17, 7, 22, 28, 26, 21, 25, 9, 16, 13, 14, 24, 15 ];

        var cwmap = [ 3, 2, 1, 0, 7, 6, 5, 4, 13, 14, 15, 16, 12, 8, 9, 10, 11 ];

        var alphabet = '23456789ABCDEFGHJKLMNPQRSTUVWXYZ';
        //var alphabet = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ345679';

        function gmult(a, b)
        {
                if(a == 0 || b == 0) return 0;

                var idx = (glog[a] + glog[b]) % 31;

                return gexp[idx];
        }//__________________________

        function encode()
        {
                var p = [0,0,0,0];

                for(var i = 12; i >= 0; i--)
                {
                        var fb = codeword[i] ^ p[3];

                        p[3] = p[2] ^ gmult(30, fb);
                        p[2] = p[1] ^ gmult( 6, fb);
                        p[1] = p[0] ^ gmult( 9, fb);
                        p[0] =        gmult(17, fb);
                }

                codeword[13] = p[0]; codeword[14] = p[1];
                codeword[15] = p[2]; codeword[16] = p[3];
        }//__________________________

        function reset()
        {
                for(var i = 0; i < 17; i++) codeword[i] = 0;

                codeword[0] = 1;
        }

        this.ok = function()
        {
                var sum = 0;

                for(var i = 1; i < 5; i++)
                {
                        for(var j = 0, t = 0; j < 31; j++)
                        {
                    if(j > 12 && j < 27) continue;

                                pos = j; if(j > 26) pos -= 14;

                                t ^= gmult(codeword[pos], gexp[(i*j)%31]);
                        }

                        sum |= t; syndrome[i] = t;
                }

                return (sum == 0);
        }//__________________________

        function from_acc(acc)
        {
                var inp = [], out = [], pos = 0, len = acc.length;

                if(len == 20 && acc.charAt(0) != '1') return false;

                for(var i = 0; i < len; i++)
                {
                        inp[i] = acc.charCodeAt(i) - '0'.charCodeAt(0);
                }

                do // base 10 to base 32 conversion
                {
                        var divide = 0, newlen = 0;

                        for(i = 0; i < len; i++)
                        {
                                divide = divide * 10 + inp[i];

                                if(divide >= 32)
                                {
                                        inp[newlen++] = divide >> 5; divide &= 31;
                                }
                                else if(newlen > 0)
                                {
                                        inp[newlen++] = 0;
                                }
                        }

                        len = newlen; out[pos++] = divide;
                }
                while(newlen);

                for(i = 0; i < 13; i++) // copy to codeword in reverse, pad with 0's
                {
                        codeword[i] = (--pos >= 0 ? out[i] : 0);
                }

                encode();

                return true;
        }//__________________________

        this.toString = function(prefix)
        {
                var out = (prefix ? 'NXT-' : '');

                for(var i = 0; i < 17; i++)
                {
                        out += alphabet[codeword[cwmap[i]]];

                        if((i & 3) == 3 && i < 13) out += '-';
                }

                return out;
        }//__________________________

        this.account_id = function()
        {
                var out = '', inp = [], len = 13;

                for(var i = 0; i < 13; i++)
                {
                        inp[i] = codeword[12-i];
                }

                do // base 32 to base 10 conversion
                {
                        var divide = 0, newlen = 0;

                        for(i = 0; i < len; i++)
                        {
                                divide = divide * 32 + inp[i];

                                if(divide >= 10)
                                {
                                        inp[newlen++] = Math.floor(divide / 10); divide %= 10;
                                }
                                else if(newlen > 0)
                                {
                                        inp[newlen++] = 0;
                                }
                        }

                        len = newlen; out += String.fromCharCode(divide + '0'.charCodeAt(0));
                }
                while(newlen);

                return out.split("").reverse().join("");
        }//__________________________

        this.set = function(adr, allow_accounts)
        {
                if(typeof allow_accounts === 'undefined') allow_accounts = true;

                var len = 0; reset();

                adr = adr.replace(/(^\s+)|(\s+$)/g, '').toUpperCase();

                if(adr.indexOf('NXT-') == 0) adr = adr.substr(4);

                if(adr.match(/^\d{6,20}$/g)) // account id
                {
                        if(allow_accounts) return from_acc(adr);
                }
                else // address
                {
                        for(var i = 0; i < adr.length; i++)
                        {
                                var pos = alphabet.indexOf(adr[i]);

                                if(pos >= 0)
                                {
                                        if(len > 16) return false;

                                        codeword[cwmap[len++]] = pos;
                                }
                        }
                }

                return (len == 17 ? this.ok() : false);
        }
}