Retrieve the total number of hours within a designated time frame that falls within a different time frame

Question

Retrieve the total number of hours within a designated time frame that falls within a different time frame

Having a difficult time with this, let me present you with a scenario:

A waiter at a restaurant earns $15/hour, but between 9:00 PM and 2:30 AM, he gets paid an additional $3/hour. I have the 'start' and 'end' of the shift as Date objects, and I want to calculate how many hours of that extra paid period are within the shift, if any. The start and end times of the shift can vary, which makes it challenging.

I managed to make it work using a lot of if statements, but I know that's not the most efficient way. Here is the code snippet link, but it's quite messy (involving two different time periods with extra pay). Does anyone have a better idea of how to calculate this? Are there any classes or methods that could assist in this calculation?

static calculateShiftSalary(shift: Shift, employee: Employee): Shift {
    const extraPaidStart = 22
    const extraPaidEnd= 2.5 // meaning 02:30 o'clock -of the next day here

    let start:Date = shift.startDate
    let end:Date = shift.endDate

    let extraHours:number = 
          getNumberOfExtraPaidHours(start,end,extraPaidStart,extraPaidEnd)
}

So, for example, if the shift is between 8:00 PM and 11:30 PM, 'extraHours' would be 1.5. If the shift is between 11:00 PM and 2:00 AM, 'extraHours' would be 3 hours.

Feel free to change 'extraPaidStart' and 'extraPaidEnd' to Date objects if that would be more beneficial.

javascript algorithm typescript

Answer 1

Answer №1

Let's start with the simplest scenario: When our worker only works for one day, a timetable where overtime extends into the night would be laid out as follows:

extra paid ---|-- regular paying ---------|---- extra paid ---
      |--------- working time -----------------------------|
      |--- 1 -------|--------------- 2 ----------------|---- 3 ---|

When the extra time spans just one day, it becomes even simpler:

|----------- regular paying -------|------ extra paid ----|----|
    |------ working time -----------------|
    |-----  1 -----------------------------|- 2 -|

We now have three ranges to calculate when determining the worker's pay, all in minutes:

 function paymentRange(payment: number, start: number, end: number) {
    return function calculatePayment(startWorking: number, endWorking: number) {
      if(start < end) { 
        const rangeStart = Math.max(start, startWorking);
        const rangeEnd = Math.min(end, endWorking);
        return Math.max(rangeEnd - rangeStart, 0) / 60 * payment;
    } else {
       const morning =  Math.max(end - startWorking, 0);
       const evening = Math.max(endWorking - start, 0)
       return (morning + evening) / 60 * payment;
  }
 }
}

To combine multiple payments, we use:

 function combinedPayment(...payments) {
   return (start, end) => payments.reduce((sum, payment) => sum + payment(start, end), 0);
 }

To calculate the payment for one day, we can simply do this:

 const calculatePayment = combinedPayment(
   paymentRange(3/*$*/, 22/*h*/ * 60, 2/*h*/ * 60 + 30/*min*/),
   paymentRange(15/*$*/, 0/*min*/, 24/*h*/ * 60)
);

 // If he worked from 1h to 22h:
calculatePayment(1/*h*/ * 60, 22/*h*/ * 60)

Next, we need to break down the date range into days and calculate payments accordingly:

 const dateToMins = date => date.getHours() * 60 + date.getMinutes();

const toWholeDay = date => new Date(date.getFullYear(), date.getMonth(), date.getDate(), 0, 0, 0);
const min = (a, b) => new Date(Math.min(+a, +b));
const max = (a, b) => new Date(Math.max(+a, +b));

 function paymentForDateRange(payment, start: Date, end: Date) {
  let pay = 0;
  let today = toWholeDay(start);
  while(+today < +end) {
    const nextDay = new Date(today + 1000 * 60 * 60 * 24);
    const startWorking = max(start, today);
    const endWorking = min(end, nextDay);
    pay += payment(dateToMins(startWorking), dateToMins(endWorking));
   today = nextDay;
  }
  return pay;
}

Finally, we can execute:

paymentForDateRange(calculatePayment, new Date(), new Date())

PS: While every part has not been fully tested, there may be some inconsistencies

Answer 2

Let's start with the simplest scenario: When our worker only works for one day, a timetable where overtime extends into the night would be laid out as follows:

extra paid ---|-- regular paying ---------|---- extra paid ---
      |--------- working time -----------------------------|
      |--- 1 -------|--------------- 2 ----------------|---- 3 ---|

When the extra time spans just one day, it becomes even simpler:

|----------- regular paying -------|------ extra paid ----|----|
    |------ working time -----------------|
    |-----  1 -----------------------------|- 2 -|

We now have three ranges to calculate when determining the worker's pay, all in minutes:

 function paymentRange(payment: number, start: number, end: number) {
    return function calculatePayment(startWorking: number, endWorking: number) {
      if(start < end) { 
        const rangeStart = Math.max(start, startWorking);
        const rangeEnd = Math.min(end, endWorking);
        return Math.max(rangeEnd - rangeStart, 0) / 60 * payment;
    } else {
       const morning =  Math.max(end - startWorking, 0);
       const evening = Math.max(endWorking - start, 0)
       return (morning + evening) / 60 * payment;
  }
 }
}

To combine multiple payments, we use:

 function combinedPayment(...payments) {
   return (start, end) => payments.reduce((sum, payment) => sum + payment(start, end), 0);
 }

To calculate the payment for one day, we can simply do this:

 const calculatePayment = combinedPayment(
   paymentRange(3/*$*/, 22/*h*/ * 60, 2/*h*/ * 60 + 30/*min*/),
   paymentRange(15/*$*/, 0/*min*/, 24/*h*/ * 60)
);

 // If he worked from 1h to 22h:
calculatePayment(1/*h*/ * 60, 22/*h*/ * 60)

Next, we need to break down the date range into days and calculate payments accordingly:

 const dateToMins = date => date.getHours() * 60 + date.getMinutes();

const toWholeDay = date => new Date(date.getFullYear(), date.getMonth(), date.getDate(), 0, 0, 0);
const min = (a, b) => new Date(Math.min(+a, +b));
const max = (a, b) => new Date(Math.max(+a, +b));

 function paymentForDateRange(payment, start: Date, end: Date) {
  let pay = 0;
  let today = toWholeDay(start);
  while(+today < +end) {
    const nextDay = new Date(today + 1000 * 60 * 60 * 24);
    const startWorking = max(start, today);
    const endWorking = min(end, nextDay);
    pay += payment(dateToMins(startWorking), dateToMins(endWorking));
   today = nextDay;
  }
  return pay;
}

Finally, we can execute:

paymentForDateRange(calculatePayment, new Date(), new Date())

PS: While every part has not been fully tested, there may be some inconsistencies

Retrieve the total number of hours within a designated time frame that falls within a different time frame

Answer №1

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