export const MIN_REMINDER_FREQUENCY_MINUTES = 5;
export const MAX_REMINDER_FREQUENCY_MINUTES = 720;

export const parseTimeToMinutes = (time: string): number | null => {
  const [hours, minutes] = time.split(':').map(Number);
  if (
    Number.isNaN(hours) ||
    Number.isNaN(minutes) ||
    hours < 0 ||
    hours > 23 ||
    minutes < 0 ||
    minutes > 59
  ) {
    return null;
  }

  return hours * 60 + minutes;
};

export interface ReminderValidationParams {
  frequencyMinutes: number;
  startTime: string;
  endTime: string;
}

export const validateReminderInputs = ({
  frequencyMinutes,
  startTime,
  endTime,
}: ReminderValidationParams): { frequency?: string; timeRange?: string } => {
  const errors: { frequency?: string; timeRange?: string } = {};
  const frequency = Number(frequencyMinutes);

  if (
    !Number.isInteger(frequency) ||
    frequency < MIN_REMINDER_FREQUENCY_MINUTES ||
    frequency > MAX_REMINDER_FREQUENCY_MINUTES
  ) {
    errors.frequency = `Choose a value between ${MIN_REMINDER_FREQUENCY_MINUTES} and ${MAX_REMINDER_FREQUENCY_MINUTES} minutes.`;
  }

  const startMinutes = parseTimeToMinutes(startTime);
  const endMinutes = parseTimeToMinutes(endTime);

  if (
    startMinutes === null ||
    endMinutes === null ||
    endMinutes <= startMinutes
  ) {
    errors.timeRange = 'End time must be later than start time.';
  }

  return errors;
};