julian
e579fe5b6e
Occupancy is a fold over the signed ledger (entries minus exits per identity);
getOccupancy returns {count, capacity, free, full}. Capacity is a single-row
site_config table (admin-set; null = uncapped; migration 0001, additive).
FULL gate lives in the transient entry flow: when full, refuse (no ticket, no
vehicle_entry, no open) and sign an anomaly. Permit entry is NOT gated --
subscribers are admitted past transient-full (their own maxConcurrent still
applies), so occupancy can read over capacity by design (reserve-for-permits).
Routes: GET /api/occupancy + GET /api/site-config (any role), PUT
/api/site-config (admin; non-negative int or null). Web SiteSettings: live
occupancy + FULL badge (everyone), capacity editor (admin).
Verified: fill to cap -> 3rd transient refused; permit admitted past full; exit
frees a slot; RBAC (operator can't set, -5 -> 400); verifyChain ok. Physical
FULL-sign relay output deferred.
50 lines
1.8 KiB
TypeScript
50 lines
1.8 KiB
TypeScript
import { eq, ledgerEvents, siteConfig, type Db } from "@parking/db";
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// Occupancy = a FOLD over the signed ledger: the count of vehicle_entry events
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// with no matching vehicle_exit. Never a hand-maintained counter (which is
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// editable + drifts) — the chain is the truth. See wiki/concepts/capacity-occupancy.md.
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export interface Occupancy {
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/** Cars currently inside (open sessions). */
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readonly count: number;
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/** Admin-set nominal capacity, or null = no limit. */
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readonly capacity: number | null;
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/** capacity − count, or null when uncapped. Can read 0 (or below) when full. */
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readonly free: number | null;
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/** True when count ≥ capacity (always false when uncapped). */
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readonly full: boolean;
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}
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/** Count cars inside: entries minus exits, per identity, over the ledger. */
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export function occupancyCount(db: Db): number {
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const rows = db
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.select({ type: ledgerEvents.type, identity: ledgerEvents.identity })
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.from(ledgerEvents)
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.all();
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const balance = new Map<string, number>();
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for (const r of rows) {
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if (r.type === "vehicle_entry") balance.set(r.identity ?? "", (balance.get(r.identity ?? "") ?? 0) + 1);
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else if (r.type === "vehicle_exit") balance.set(r.identity ?? "", (balance.get(r.identity ?? "") ?? 0) - 1);
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}
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let open = 0;
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for (const v of balance.values()) if (v > 0) open += 1;
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return open;
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}
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/** Admin-set capacity (null = uncapped). */
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export function siteCapacity(db: Db): number | null {
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const row = db.select().from(siteConfig).where(eq(siteConfig.id, 1)).get();
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return row?.capacity ?? null;
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}
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export function getOccupancy(db: Db): Occupancy {
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const count = occupancyCount(db);
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const capacity = siteCapacity(db);
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return {
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count,
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capacity,
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free: capacity == null ? null : capacity - count,
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full: capacity != null && count >= capacity,
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};
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}
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