slot-engine

name	slot-engine
description	The pure `computeAvailableSlots` function — inputs, outputs, invariants, and debugging guide.

Slot engine

import { computeAvailableSlots } from "@agent-native/scheduling/core"

Inputs

• Event type config (duration, buffers, minimum notice, period, limits, slot interval)
• Schedule (timezone + weekly availability + date overrides)
• Busy intervals (UTC, aggregated from external calendars + existing bookings)
• Booking counts by bucket (day/week/month/year) for limit enforcement
• Time range to compute over
• Optional seats-per-slot + seats-taken map
• Viewer timezone (for limit bucketing, if it differs from the schedule)

Output

• Array of Slot { start: ISO, end: ISO, available: boolean, seatsRemaining?, hostEmail? }

Invariants

The function guarantees, in order:

1. No slot falls in the past (now + minimumBookingNotice is the floor).
2. No slot overlaps a busy interval (with buffers applied).
3. No slot falls outside the schedule's available intervals for that day.
4. No slot exceeds a booking limit.
5. No slot falls outside the event's period (rolling/range).
6. DST-safe: we convert to UTC using the schedule's timezone before doing any interval arithmetic.

Debugging

If a slot is unexpectedly missing:

1. Check the schedule's weekly availability for that day-of-week in the schedule's timezone (not UTC — weekends can shift across the date line).
2. Check date overrides for that local date (empty intervals = fully blocked).
3. Check merged busy intervals for overlap, including the before/after buffer expansion.
4. Check booking limits: a single existing booking can close a day.
5. Check period caps: rolling periods restrict how far in the future slots appear.

If a slot is unexpectedly present:

1. Check that now is being passed correctly (defaults to new Date()).
2. Check that busy intervals from providers are in UTC.
3. Confirm slot interval matches what you expect (default = duration).