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parking_solution/wiki/concepts/device-adapter-pattern.md
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julian bfe64032d8 Initial scaffold: Turborepo monorepo + design wiki
Turborepo (pnpm workspaces) with all dependencies pinned to latest
mutually-compatible versions: turbo 2.9, TypeScript 6, Fastify 5,
React 19, Vite 8, better-sqlite3 12 + Drizzle ORM 0.45.

Layout:
- apps/server   Fastify backend (local JWT auth + role guard, /health)
- apps/web      React 19 + Vite 8 operator SPA
- packages/db   Drizzle schema on SQLite/WAL; append-only events + users
- packages/devices  reader/printer/relay adapter interfaces (intent-only relay)
- packages/shared   shared domain types

Architecture constraints from the design wiki are encoded in the scaffold:
append-only hash-chained + signed event log, device-agnostic adapters,
"a barrier is not a door" (relay expresses intent only), fully-local
offline-first auth.

wiki/ is an LLM-maintained Obsidian knowledge base (28 pages) ingested
from the architecture & design notes, with its own maintenance schema.

Verified: pnpm install, full turbo build (5/5), server boots and serves
/health, drizzle-kit generates the initial migration.
2026-06-14 00:34:11 +02:00

1.1 KiB

type, tags, sources, updated
type tags sources updated
concept
parking
architecture
devices
parking-system-architecture
2026-06-14

Device-Adapter Pattern

How the system stays device-agnostic: business logic talks only to interfaces, never to a device SDK. Each physical device is an adapter implementing one interface; swapping hardware means writing a new adapter and nothing else changes. Implemented as isolated fastify plugins emitting onto a shared internal event bus. (See parking-system-architecture §5.)

interface CardReaderDevice {
  connect(): Promise<void>
  onCardRead(cb: (cardNumber: string, door: number) => void): void
  disconnect(): Promise<void>
}
interface PrinterDevice {
  printTicket(data: TicketData): Promise<void>
  checkStatus(): Promise<'ready' | 'offline' | 'paper_out'>
}
interface RelayDevice {
  pulseOpen(doorId: number): Promise<void>   // intent only — see safety note
  getDoorStatus(doorId: number): Promise<'open' | 'closed'>
}

Note the RelayDevice expresses intent only — see the barrier-not-a-door safety principle. The choice of which adapter to trust is the trust-boundary decision.