mobile bill assessment

class ExampleUnitTest {
    @Test
    fun test8Hours1Min(){
        val calBill = calculateMobileBill("2020-07-06 00:00:01", "2020-07-06 08:01:00")
        assertEquals(calBill, 602.0, 0.0)
    }
    @Test
    fun test1Second(){
        val calBill = calculateMobileBill("2020-07-06 00:00:00", "2020-07-06 00:00:01")
        assertEquals(calBill, 1.0, 0.0)
    }
    @Test
    fun test10Second(){
        val calBill = calculateMobileBill("2020-07-06 00:00:00", "2020-07-06 00:00:10")
        assertEquals(calBill, 1.0, 0.0)
    }
    @Test
    fun test2MinuteAnd10Second(){
        val calBill = calculateMobileBill("2020-07-06 00:00:00", "2020-07-06 00:02:10")
        assertEquals(calBill, 3.0, 0.0)
    }
    @Test
    fun test24Hours(){
        val calBill = calculateMobileBill("2020-07-06 00:00:00", "2020-07-06 23:59:01")
        assertEquals(calBill, 3600.0, 0.0)
    }
    @Test
    fun test2Days(){
        val calBill = calculateMobileBill("2020-07-06 00:00:00", "2020-07-07 23:59:01")
        assertEquals(calBill, (3600.0 *2), 0.0)
    }
    fun calculateMobileBill(startDateAndTime: String?, endDateAndTime: String?): Double {

        val format: DateTimeFormatter = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss")
        val start: LocalDateTime = LocalDateTime.parse(startDateAndTime, format)
        val end: LocalDateTime = LocalDateTime.parse(endDateAndTime, format)
        var totalBill = 0.0

        Stream.iterate(start, { date -> date.plusDays(1) })
            .limit(ChronoUnit.DAYS.between(start, end) + 1)
            .forEach {
                println("start "+start)
                println("end "+end)
                println("--------------")

                val hourEnd = end.toLocalTime().hour
                val minuteEnd = end.toLocalTime().minute
                val secondEnd = end.toLocalTime().second

                if (end.toLocalTime().hour<6){
                    totalBill = calculateBlockBill(totalBill, secondEnd, minuteEnd, hourEnd, 1)
                }else if (end.toLocalTime().hour<12){
                    val remainHours = hourEnd - 6
                    totalBill = calculateBlockBill( totalBill = totalBill, hour = 6, prices = 1)
                    totalBill = calculateBlockBill(totalBill = totalBill, hour = remainHours, minute = minuteEnd, second = secondEnd, prices = 2)
                }else if (end.toLocalTime().hour<18){
                    val remainHours = hourEnd - 12
                    totalBill = calculateBlockBill( totalBill = totalBill, hour = 12, prices = 2)
                    totalBill = calculateBlockBill(totalBill = totalBill, hour = remainHours, minute = minuteEnd, second = secondEnd, prices = 3)
                }else if (end.toLocalTime().hour<24){
                    val remainHours = hourEnd - 18
                    totalBill = calculateBlockBill( totalBill = totalBill, hour = 12, prices = 3)
                    totalBill = calculateBlockBill(totalBill = totalBill, hour = remainHours, minute = minuteEnd, second = secondEnd, prices = 4)
                }
            }
       return totalBill
    }

    private fun calculateBlockBill(totalBill: Double = 0.0, second: Int=0, minute: Int=0, hour: Int=0, prices: Int=0): Double {
        var bill = totalBill
        bill += if (second == 0) 0 else 1 * prices
        bill += if (minute == 0) 0 else minute * prices
        bill += if (hour == 0) 0 else hour * prices * 60
        return bill
    }