joshuaferrara/node-csgo

'use strict';

var packJS = require('./pack.js');
var StringIO = require('./stringio.js');
var BigNumber = require('bignumber.js');
BigNumber.config({
    DECIMAL_PLACES: 43,
    EXPONENTIAL_AT: 50
});

class ByteReader {
    constructor(io) {
        this.io = io;
    }

    get read_int64() {
        var temp = this.io.read(8);
        var unpacked = packJS.unpack("C*", temp);
        var result = new BigNumber(0);
        Object.keys(unpacked).forEach(function(key) {
            var index = key - 1;
            var byte = unpacked[key];

            var a = new BigNumber(256).toPower(new BigNumber(index));
            var b = new BigNumber(byte).times(a);

            result = result.plus(b)
        });
        return result.toString();
    }

    get read_short() {
        var temp = this.io.read(2);
        var unpacked = packJS.unpack("S*", temp);
        return unpacked[''].toString();
    }
}

class SharecodeDecoder {
    constructor(code) {
        this.code = this.sanitize_code(code);
        this.originalCode = code;

        this.DICTIONARY = "ABCDEFGHJKLMNOPQRSTUVWXYZabcdefhijkmnopqrstuvwxyz23456789";
        this.DICTIONARY_LENGTH = this.DICTIONARY.length
    }

    decode() {
        var reader         = new ByteReader(this.io);
        var matchId     = reader.read_int64;
        var outcomeId    = reader.read_int64;
        var tokenId     = reader.read_short;

        return {
            matchId: matchId,
            outcomeId: outcomeId,
            tokenId: tokenId
        };
    }

    sanitize_code(str) {
        return str.replace(/CSGO|\-/g, '');
    }

    get io() {
        return new StringIO.StringIO(this.decoded_code);
    }

    get decoded_code() {
        var self = this;
        var result = new Array(18).fill(0);
        var reversed = this.code.split('').reverse();
        reversed.forEach(function(char, index) {
            var addval = self.DICTIONARY.indexOf(char);
            var tmp = new Array(18).fill(0);
            var carry = 0;
            var v = 0;
            for(var t = 17; t >= 0; t--) {
                carry = 0;
                for(var s = t; s >= 0; s--) {
                    if(t - s == 0) {
                        v = tmp[s] + result[t] * 57;
                    }else {
                        v = 0;
                    }
                    v = v + carry;
                    carry = v >> 8;
                    tmp[s] = v & 0xFF;
                }
            }
            result = tmp;
            carry = 0;

            for(var t = 17; t >= 0; t--) {
                if(t == 17) {
                    v = result[t] + addval;
                }else {
                    v = result[t];
                }
                v = v + carry;
                carry = v >> 8;
                result[t] = v & 0xFF;
            }
        });

        result.unshift('C*');
        return packJS.pack.apply(this, result);    
    }
}

exports.SharecodeDecoder = SharecodeDecoder;