price formatter

formatter

/* 
    expected functionality:
    // 1002.0   -> 1,002
    // 1002.1   -> 1,002.10
    // 1002.666 -> 1,002.66
*/
fun legacyFormatPrice(value: Double) {
  return if (this.rem(1) == 0.0)
            String.format("%,.0f", value)
        else
            String.format("%,.2f", value)
}

fun formatPrice(value: Double, addSeparator: Boolean): String {
    val fractionSize = 2
    val separatorSize = 3

    val fraction = BigDecimal((value % 1f) * 10.0.pow(fractionSize.toDouble()))
        .setScale(0, RoundingMode.HALF_UP)
        .toInt()
    val integer = BigDecimal(value)
        .setScale(0, RoundingMode.DOWN)

    val builder = StringBuilder().append(integer)
    val chunks = builder.length / separatorSize
    if (addSeparator) {
        var i = chunks * separatorSize
        while (i > 0) {
            val position = builder.length - i
            if (position > 0)
                builder.insert(position, ",")
            i -= separatorSize
        }
    }

    if (fraction > 0) {
        builder.append(".")
        var i = fractionSize - fraction.toString().length
        while (i > 0) {
            builder.append(0)
            i--
        }
        builder.append(fraction)
    }
    return builder.toString()
}