julian
33c4ea1e91
Two halves of one anti-fraud design.
(A) Operator-issued entry — when the physical entry button is broken, an
operator can issue an entry ticket so a real car isn't blocked out of the lot.
This hands the operator-adversary a mint, so it is:
- PRESENCE-GATED like the physical button: a real car must be present (radar/
loop AND camera busy). Enforced BOTH sides — the server re-checks current
presence so a direct POST can't bypass a disabled button; no presence loop
=> feature unavailable; a no-presence attempt signs an anomaly.
- FLAGGED: vehicle_entry source=manual + operatorInitiated + operator, PLUS a
companion entry.operatorIssued anomaly (the adversary path always leaves a
red-flag row).
- capacity-OVERRIDE allowed but stamped lotFull (a broken button mustn't trap
a legit car).
New session:create permission (migration 0019 -> operator role, admin-
revocable), POST /api/entry/issue (open-shift gated), EntryFlow.
issueForOperator; the fraud-critical print->sign->open->snapshot sequence is
factored into one shared #issueTicket (button + operator). UI: the entry
BarrierLight becomes a clickable issue-control when presence+permission+shift
meet (confirm -> issue).
(B) Exit plate-swap reconciliation — defends the ticket-swap fraud the mint
enables (paid car let out on a fresh $0 ticket, original ticket lingers
"inside", occupancy drifts up by phantom cars). The plate is the invariant:
ExitFlow.#reconcilePlateAtExit compares the exiting plate against all OPEN
sessions' entry plates, EXACT + HIGH-CONFIDENCE only (>=0.85; a fuzzy read never
gates — ANPR is advisory). On a match under a DIFFERENT ticket:
- BOOTH path: returns swap_suspected + signs exit.plateSwapSuspected; the
pay/exit modal shows a red warning + "Override & release" (override signs an
attributed exit.plateSwapOverride). Flag+override, never a silent hard block
(exit fails-open; a plate is never the sole gate).
- READER path (no operator): log-only anomaly + fail-open.
Extended BoothExitResult + /api/exit (override); boothExit client returns a
structured swap result.
Verified: full monorepo build/lint/test green (229 server tests incl. 4 new:
hold-on-swap, override-releases-with-attribution, low-confidence-no-warning,
own-plate-no-warning). New wiki: operator-issued-entry.md +
plate-reconciliation.md; cross-linked from entry-exit-points, capacity-
occupancy, index. Preserves "a plate never OPENS a barrier alone — and now never
TRAPS a car alone either."
Claude-Session: https://claude.ai/code/session_01Xcm6ikLgGoCxxHrxtjkk5V
88 lines
5.1 KiB
Markdown
88 lines
5.1 KiB
Markdown
---
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type: concept
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tags: [parking, domain, business, occupancy]
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sources: []
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updated: 2026-06-15
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status: open
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---
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# Capacity & Occupancy
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How many vehicles are inside, how many spaces remain, and what happens when the lot is full.
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## Occupancy is a projection (like everything else)
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`occupancy = count(open [[parking-session|sessions]])` — an entry with no matching exit. It is a
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**fold over the signed [[append-only-event-chain]]**, never a hand-maintained counter (a counter is
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editable and drifts; the chain is the truth). Spaces-free = `capacity − occupancy`.
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- **`capacity`** is admin-set per site (and per **zone/level** if the lot has sections — model a
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`zone` on capacity + on the entry so multi-level is a later addition, not a rewrite).
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- Permit concurrency (`maxConcurrent`, see [[subscription]]) is the same kind of fold, scoped to one
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permit's open sessions.
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## Full → refuse entry + FULL sign
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- When `occupancy ≥ capacity`, the entry flow **refuses** (no `vehicle_entry`, no barrier open) and
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can drive a **"FULL" sign** (a relay/output, via the device adapter layer).
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- **Safety/policy nuance:** "full" blocks *entry* only — **exit always works** ([[fail-state-safety]]:
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exit fails open; never trap a vehicle). Permit holders may be allowed in past a "transient full"
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threshold (reserve spaces for subscribers) — an optional policy knob.
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- **Counting drift is real:** tailgating (two cars, one entry) and missed reads make the live count
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diverge from physical reality. The count is the *system's* occupancy; periodic ground-truth (a
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loop count, or the [[opencv-anpr-service|vision]] count) reconciles it — surfaced as an anomaly,
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not silently corrected.
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- **A DELIBERATE drift attack — the ticket swap:** a paid car let out on a fresh $0 ticket leaves its
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original ticket "inside" forever, inflating occupancy by phantom cars. Defended by
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[[plate-reconciliation]] (the exiting plate is already open under the original ticket → flag/hold).
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## Reserved subscriber spots (admin toggle, built 2026-06-20)
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By default occupancy counts only cars **physically inside** — a subscriber who isn't parked frees
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their spot to transients, and the operator handles any overflow by valet/key-juggling. A site can
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instead **hold a spot for every active subscriber**, so the lot reads "full" to transients sooner and
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the subscriber's place is guaranteed:
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- `site_config.reserve_subscriber_spots` (bool, default off). When ON,
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`reservedSubscriberSpots(db)` sums, over every **active** subscription (status active AND
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`now ∈ [validFrom, validTo]`), `max(0, quantity − itsCarsCurrentlyInside)` — i.e. it reserves only
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the **not-yet-parked** portion of each subscription's [[subscription|quantity]] (a parked
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subscriber already occupies a real spot; counting them twice would over-reserve).
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- `getOccupancy` gains `reserved` + `effectiveFree = capacity − count − reserved`. The transient FULL
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gate becomes **`count + reserved ≥ capacity`**. Subscribers are still **never** gated by full
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(their flow ignores it) — reservation only tightens the *transient* gate.
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- OFF = the prior behaviour exactly (`reserved = 0`).
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## "Full" is a soft, operator-configurable policy
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Refusing at capacity is the **default**, not an absolute. An operator may opt into
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**[[valet-overcapacity|valet over-capacity]]** — accept the car into operator custody (keys handed
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over, stacked beyond the marked count) instead of refusing. So the FULL gate is a policy knob
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(refuse vs. valet-accept), set by the operator per site. Valet is a manned-mode feature with its
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own custody/session shape — see [[valet-overcapacity]] (deferred).
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## As-built (2026-06-16)
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- **Occupancy** = `occupancyCount` (`apps/server/src/occupancy.ts`): a fold over the ledger —
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entries minus exits per identity, count those `> 0`. `getOccupancy` returns `{count, capacity,
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free, full}`.
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- **Capacity** is a single-row `site_config` table (admin-set; `null` = uncapped). Routes
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(`routes/site.ts`): `GET /api/occupancy` + `GET /api/site-config` (any role), `PUT /api/site-config`
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(admin; non-negative int or null).
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- **FULL gate** is in the **transient entry flow**: `occupancy.full` → refuse (no ticket, no
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`vehicle_entry`, no open) + signed `anomaly`. **Permit entry is NOT gated** here — subscribers are
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admitted past transient-full (their own `maxConcurrent` still applies); occupancy can read
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over-capacity (`free` negative) when permits enter a full lot, as intended.
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- **UI** `SiteSettings`: live occupancy + FULL badge (everyone); capacity editor (admin).
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- Verified: fill to cap → 3rd transient refused; permit still admitted past full; exit frees a
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slot; RBAC (operator can't set capacity); verifyChain ok. Physical FULL-sign relay output is
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**deferred** (needs a sign device).
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## Open
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- Zone/level granularity at launch vs. single capacity number.
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- Reserve-for-permits **threshold** (a soft transient cap below the hard capacity) — currently
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permits are simply ungated; a tunable threshold is the richer version.
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- Physical FULL-sign relay output (a sign-device role).
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- The valet over-capacity mode + custody model ([[valet-overcapacity]]).
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