/**
 * Created by jimiz on 2017/3/28.
 */

let scMathUtil = {
    innerRoundTo: function(num, digit){
        let lFactor = Math.pow(10, digit);
        let fOffSet = 0.5;
        let sign = '';
        if (num < 0){
            sign = '-';
            num = Math.abs(num);
        }
        let result = Math.floor((num / lFactor) + fOffSet).toString();
        let iLength = result.length;
        let r1 = result.substring(0, iLength + digit);
        let r2 = result.substring(iLength + digit, iLength);
        return Number(sign + r1 + '.' + r2);
    },
    floatToBin: function(num) {
        return num.toString(2);
    },
    binToFloat: function(bin) {
        let result = 0;
        let iLength = bin.length;
        let sign = '';
        if (iLength > 0 && bin[0]==='-'){
            sign = '-';
            bin = bin.substring(1, iLength);
        }
        iLength = bin.length;
        let iDot = bin.indexOf('.');
        if (iDot >= 0) {
            for (let i = 0; i < iLength; i++) {
                let num = Number(bin[i]);
                let idx = iDot - i;
                if (idx === 0) {
                    continue
                };
                if (idx > 0) {
                    idx -= 1
                };
                let r = Math.pow(2, idx);
                result += num * r;
            }
        }
        else {
            result = parseInt(bin, 2);
        };
        return sign + result;
    },
    zeroString: function(length){
        let result = '';
        for (let i = 0; i < length; i++){
            result = result + '0';
        };
        return result;
    },    
    incMantissa: function(bin){
        let result = bin;
        let iDot = bin.indexOf('.');
        if (iDot < 0){return result};
        // 二进制浮点数带小数位数最大长度
        let floatLength = 53;
        let iLength = bin.length;
        // 长度小于53说明该二进制数尾数长度小于Double类型限制，未被截断，无需进位
        if (iLength < floatLength) {
            return result;
        }
        let iLength = bin.length;
        for (let i = iLength - 1; i > iDot; i--){
            let num = Number(bin[i]);
            if (num === 0){
                num = 1;
                let bin1 = bin.substring(0, i);
                let bin2 = this.zeroString(iLength - (i + 1));//bin.substring(i + 1, iLength);
                result = bin1 + num.toString() + bin2;
                break;
            }

        };
        return result;
    },
    roundTo: function(num, digit){
        let me = this;
        return me.innerRoundTo(me.binToFloat(me.incMantissa(me.floatToBin(num))), digit);
    }
};

Number.prototype.toDecimal = function (ADigit) {
    //return parseFloat(this.toFixed(ADigit));
    digit = (ADigit && typeof(ADigit) === 'number' && Number.isInteger(ADigit) && ADigit >= 0) ? -ADigit : -2;
    // var s = scMathUtil.roundTo(this, digit);
    // console.log('Number: ' + this + '   Digit: ' + digit + '    Result: ' + s);
    // return parseFloat(s);
    return scMathUtil.roundTo(this, digit);
};