Implements the "heart" of the app per IMPLEMENTATION_PLAN.md §6 Phase 2,
no UI yet by design:
- app/lib/time.ts: Luxon-based wall-clock helpers. slotDateTime() builds a
slot's instant from calendar-date + minutes-from-midnight by setting
hour/minute fields directly rather than adding an elapsed-time duration
to midnight — the latter is wrong by exactly one hour for any wall-clock
time on a spring-forward day, since a real elapsed-time addition crosses
the lost hour. Also detects and rejects wall-clock times that don't exist
in a spring-forward gap (Luxon silently rolls these forward instead of
invalidating them, so this required an explicit post-set field check).
- app/services/scheduling.server.ts: getAvailability(), a pure function
(no DB/Shopify calls — every input injected, including `now`) that
applies slot templates, date overrides, blackout dates, cutoff/lead-time,
and capacity to produce the bookable slots per date. Excludes unavailable
slots entirely rather than flagging them, per PRODUCT_STRATEGY.md §2.
- app/services/capacity.server.ts: remainingCapacity()/hasCapacity() — kept
as pure functions over an injected `consumed` count so this doesn't need
to change once Phase 4 adds real Booking/SlotHold-backed consumption.
41 unit tests total (up from 8), including DST regression tests that would
fail against a naive "midnight + elapsed minutes" implementation, an
ambiguous-time (fall-back) case, a nonexistent-time (spring-forward gap)
case, and a getAvailability run across the actual 2024 spring-forward date
verifying both the UTC offset change and that wall-clock hours stay correct
on both sides of it.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
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