calendar/packages/lib/isOutOfBounds.tsx

import dayjs from "@calcom/dayjs";
import type { EventType } from "@calcom/prisma/client";
import { PeriodType } from "@calcom/prisma/enums";

import { ROLLING_WINDOW_PERIOD_MAX_DAYS_TO_CHECK } from "./constants";
import logger from "./logger";
import { safeStringify } from "./safeStringify";

export class BookingDateInPastError extends Error {
  constructor(message = "Attempting to book a meeting in the past.") {
    super(message);
  }
}

function guardAgainstBookingInThePast(date: Date) {
  if (date >= new Date()) {
    // Date is in the future.
    return;
  }
  throw new BookingDateInPastError();
}

/**
 * Dates passed to this function are timezone neutral.
 */
export function calculatePeriodLimits({
  periodType,
  periodDays,
  periodCountCalendarDays,
  periodStartDate,
  periodEndDate,
  /**
   * These dates will be considered in the same utfcOffset as provided
   */
  allDatesWithBookabilityStatusInBookerTz,
  eventUtcOffset,
  bookerUtcOffset,
  /**
   * This is temporary till we find a way to provide allDatesWithBookabilityStatus in handleNewBooking without re-computing availability.
   * It is okay for handleNewBooking to pass it as true as the frontend won't allow selecting a timeslot that is out of bounds of ROLLING_WINDOW
   * But for the booking that happen through API, we absolutely need to check the ROLLING_WINDOW limits.
   */
  _skipRollingWindowCheck,
}: Pick<
  EventType,
  "periodType" | "periodDays" | "periodCountCalendarDays" | "periodStartDate" | "periodEndDate"
> & {
  allDatesWithBookabilityStatusInBookerTz: Record<string, { isBookable: boolean }> | null;
  eventUtcOffset: number;
  bookerUtcOffset: number;
  _skipRollingWindowCheck?: boolean;
}): PeriodLimits {
  const currentTime = dayjs();
  const currentTimeInEventTz = currentTime.utcOffset(eventUtcOffset);
  const currentTimeInBookerTz = currentTime.utcOffset(bookerUtcOffset);
  periodDays = periodDays || 0;
  const log = logger.getSubLogger({ prefix: ["calculatePeriodLimits"] });
  log.debug(
    safeStringify({
      periodType,
      periodDays,
      periodCountCalendarDays,
      periodStartDate: periodStartDate,
      periodEndDate: periodEndDate,
      currentTime: currentTimeInEventTz.format(),
    })
  );

  switch (periodType) {
    case PeriodType.ROLLING: {
      // We use booker's timezone to calculate the end of the rolling period(for both ROLLING and ROLLING_WINDOW). This is because we want earliest possible timeslot to be available to be booked which could be on an earlier day(compared to event timezone) as per booker's timezone.
      // So, if 2 day rolling period is set and 2024-07-24T8:30:00 slot is available in event timezone, the corresponding slot in GMT-11 would be 2024-07-24T21:30:00. So, 24th should be bookable for that timeslot, which could only be made available if we consider things in booker timezone.
      const rollingEndDay = periodCountCalendarDays
        ? currentTimeInBookerTz.add(periodDays, "days")
        : currentTimeInBookerTz.businessDaysAdd(periodDays);
      // The future limit talks in terms of days so we take the end of the day here to consider the entire day
      return {
        endOfRollingPeriodEndDayInBookerTz: rollingEndDay.endOf("day"),
        startOfRangeStartDayInEventTz: null,
        endOfRangeEndDayInEventTz: null,
      };
    }

    case PeriodType.ROLLING_WINDOW: {
      if (_skipRollingWindowCheck) {
        return {
          endOfRollingPeriodEndDayInBookerTz: null,
          startOfRangeStartDayInEventTz: null,
          endOfRangeEndDayInEventTz: null,
        };
      }

      if (!allDatesWithBookabilityStatusInBookerTz) {
        throw new Error("`allDatesWithBookabilityStatus` is required");
      }

      const endOfRollingPeriodEndDayInBookerTz = getRollingWindowEndDate({
        startDateInBookerTz: currentTimeInBookerTz,
        daysNeeded: periodDays,
        allDatesWithBookabilityStatusInBookerTz,
        countNonBusinessDays: periodCountCalendarDays,
      });

      return {
        endOfRollingPeriodEndDayInBookerTz,
        startOfRangeStartDayInEventTz: null,
        endOfRangeEndDayInEventTz: null,
      };
    }

    case PeriodType.RANGE: {
      // We take the start of the day for the start of the range and endOf the day for end of range, so that entire days are covered
      // We use organizer's timezone here(in contrast with ROLLING/ROLLING_WINDOW where number of days is available and not the specific date objects).
      // This is because in case of range the start and end date objects are determined by the organizer, so we should consider the range in organizer/event's timezone.
      const startOfRangeStartDayInEventTz = dayjs(periodStartDate).utcOffset(eventUtcOffset).startOf("day");
      const endOfRangeEndDayInEventTz = dayjs(periodEndDate).utcOffset(eventUtcOffset).endOf("day");

      return {
        endOfRollingPeriodEndDayInBookerTz: null,
        startOfRangeStartDayInEventTz,
        endOfRangeEndDayInEventTz,
      };
    }
  }

  return {
    endOfRollingPeriodEndDayInBookerTz: null,
    startOfRangeStartDayInEventTz: null,
    endOfRangeEndDayInEventTz: null,
  };
}

export function getRollingWindowEndDate({
  startDateInBookerTz,
  daysNeeded,
  allDatesWithBookabilityStatusInBookerTz,
  countNonBusinessDays,
}: {
  /**
   * It should be provided in the same utcOffset as the dates in `allDatesWithBookabilityStatus`
   * This is because we do a lookup by day in `allDatesWithBookabilityStatus`
   */
  startDateInBookerTz: dayjs.Dayjs;
  daysNeeded: number;
  allDatesWithBookabilityStatusInBookerTz: Record<string, { isBookable: boolean }>;
  countNonBusinessDays: boolean | null;
}) {
  const log = logger.getSubLogger({ prefix: ["getRollingWindowEndDate"] });
  log.debug("called:", safeStringify({ startDay: startDateInBookerTz.format(), daysNeeded }));
  let counter = 1;
  let rollingEndDay;
  const startOfStartDayInEventTz = startDateInBookerTz.startOf("day");
  // It helps to break out of the loop if we don't find enough bookable days.
  const maxDaysToCheck = ROLLING_WINDOW_PERIOD_MAX_DAYS_TO_CHECK;

  let bookableDaysCount = 0;

  let startOfIterationDay = startOfStartDayInEventTz;
  // Add periodDays to currentDate, skipping non-bookable days.
  while (bookableDaysCount < daysNeeded) {
    // What if we don't find any bookable days. We should break out of the loop after a certain number of days.
    if (counter > maxDaysToCheck) {
      break;
    }

    const onlyDateOfIterationDay = startOfIterationDay.format("YYYY-MM-DD");

    const isBookable = !!allDatesWithBookabilityStatusInBookerTz[onlyDateOfIterationDay]?.isBookable;

    if (isBookable) {
      bookableDaysCount++;
      rollingEndDay = startOfIterationDay;
    }

    log.silly(
      `Loop Iteration: ${counter}`,
      safeStringify({
        iterationDayBeginning: startOfIterationDay.format(),
        isBookable,
        bookableDaysCount,
        rollingEndDay: rollingEndDay?.format(),
        allDatesWithBookabilityStatusInBookerTz,
      })
    );

    startOfIterationDay = countNonBusinessDays
      ? startOfIterationDay.add(1, "days")
      : startOfIterationDay.businessDaysAdd(1);

    counter++;
  }

  /**
   * We can't just return null(if rollingEndDay couldn't be obtained) and allow days farther than ROLLING_WINDOW_PERIOD_MAX_DAYS_TO_CHECK to be booked as that would mean there is no future limit
   * The future limit talks in terms of days so we take the end of the day here to consider the entire day
   */
  const endOfLastDayOfWindowInBookerTz = (rollingEndDay ?? startOfIterationDay).endOf("day");
  log.debug("Returning rollingEndDay", endOfLastDayOfWindowInBookerTz.format());

  return endOfLastDayOfWindowInBookerTz;
}

/**
 * To be used when we work on Timeslots(and not Dates) to check boundaries
 * It ensures that the time isn't in the past and also checks if the time is within the minimum booking notice.
 * Note: It throws error that needs to be caught by caller.
 */
export function isTimeOutOfBounds({
  time,
  minimumBookingNotice,
}: {
  time: dayjs.ConfigType;
  minimumBookingNotice?: number;
}) {
  const date = dayjs(time);

  guardAgainstBookingInThePast(date.toDate());

  if (minimumBookingNotice) {
    const minimumBookingStartDate = dayjs().add(minimumBookingNotice, "minutes");
    if (date.isBefore(minimumBookingStartDate)) {
      return true;
    }
  }

  return false;
}

/**
 * Wrapper over isTimeOutOfBounds to return a status object.
 * Note: It doesn't throw any error and can be safely used
 */
export function getPastTimeAndMinimumBookingNoticeBoundsStatus({
  time,
  minimumBookingNotice,
}: {
  time: dayjs.ConfigType;
  minimumBookingNotice?: number;
}): {
  isOutOfBounds: boolean;
  reason: "minBookNoticeViolation" | "slotInPast" | null;
} {
  try {
    const isOutOfBounds = isTimeOutOfBounds({ time, minimumBookingNotice });
    return {
      isOutOfBounds,
      reason: isOutOfBounds ? "minBookNoticeViolation" : null,
    };
  } catch (error) {
    if (error instanceof BookingDateInPastError) {
      return {
        isOutOfBounds: true,
        reason: "slotInPast",
      };
    }
    throw error;
  }
}

type PeriodLimits = {
  endOfRollingPeriodEndDayInBookerTz: dayjs.Dayjs | null;
  startOfRangeStartDayInEventTz: dayjs.Dayjs | null;
  endOfRangeEndDayInEventTz: dayjs.Dayjs | null;
};

export function isTimeViolatingFutureLimit({
  time,
  periodLimits,
}: {
  time: string | Date | number;
  periodLimits: PeriodLimits;
}) {
  const log = logger.getSubLogger({ prefix: ["isTimeViolatingFutureLimit"] });

  const dateObj = new Date(time);
  if (periodLimits.endOfRollingPeriodEndDayInBookerTz) {
    const isAfterRollingEndDay =
      dateObj.valueOf() > periodLimits.endOfRollingPeriodEndDayInBookerTz.valueOf();

    if (isAfterRollingEndDay)
      log.warn(
        "Booking is out of bounds due to rolling period end day.",
        safeStringify({
          formattedDate: dateObj.toISOString(),
          isAfterRollingEndDay,
          endOfRollingPeriodEndDayTs: periodLimits.endOfRollingPeriodEndDayInBookerTz.valueOf(),
        })
      );
    return isAfterRollingEndDay;
  }

  if (periodLimits.startOfRangeStartDayInEventTz && periodLimits.endOfRangeEndDayInEventTz) {
    const isBeforeRangeStart = dateObj.valueOf() < periodLimits.startOfRangeStartDayInEventTz.valueOf();
    const isAfterRangeEnd = dateObj.valueOf() > periodLimits.endOfRangeEndDayInEventTz.valueOf();
    if (isBeforeRangeStart || isAfterRangeEnd)
      log.warn(
        "Booking is out of bounds due to range start and end.",
        safeStringify({
          formattedDate: dateObj.toISOString(),
          isBeforeRangeStart,
          isAfterRangeEnd,
          startOfRangeStartDayInEventTz: periodLimits.startOfRangeStartDayInEventTz.toDate().toISOString(),
          endOfRangeEndDayInEventTz: periodLimits.endOfRangeEndDayInEventTz.toDate().toISOString(),
        })
      );
    return isBeforeRangeStart || isAfterRangeEnd;
  }
  return false;
}

export default function isOutOfBounds(
  time: NonNullable<dayjs.ConfigType>,
  {
    periodType,
    periodDays,
    periodCountCalendarDays,
    periodStartDate,
    periodEndDate,
    eventUtcOffset,
    bookerUtcOffset,
  }: Pick<
    EventType,
    "periodType" | "periodDays" | "periodCountCalendarDays" | "periodStartDate" | "periodEndDate"
  > & {
    eventUtcOffset: number;
    bookerUtcOffset: number;
  },
  minimumBookingNotice?: number
) {
  const log = logger.getSubLogger({ prefix: ["isOutOfBounds"] });
  const isOutOfBoundsByTime = isTimeOutOfBounds({ time, minimumBookingNotice });
  const periodLimits = calculatePeriodLimits({
    periodType,
    periodDays,
    periodCountCalendarDays,
    periodStartDate,
    periodEndDate,
    allDatesWithBookabilityStatusInBookerTz: null, // Temporary workaround
    _skipRollingWindowCheck: true,
    eventUtcOffset,
    bookerUtcOffset,
  });

  const isOutOfBoundsByPeriod = isTimeViolatingFutureLimit({
    time: dayjs.isDayjs(time) ? time.toDate() : time,
    periodLimits,
  });

  if (isOutOfBoundsByTime) {
    log.warn(
      "Booking is out of bounds due to minimum booking notice.",
      safeStringify({ minimumBookingNotice })
    );
    return true;
  }

  if (isOutOfBoundsByPeriod) {
    log.warn("Booking is out of bounds due to period restrictions", safeStringify({ periodLimits }));
    return true;
  }

  return false;
}