import { devices, eq, type Db } from "@parking/db";
import type { FastifyBaseLogger } from "fastify";
import type { DeviceReadEvent, ReadOutcome } from "./device-events.js";
import type { ExitFlow } from "./exit-flow.js";
import type { SubscriptionFlow } from "./subscription-flow.js";
import { relayForDevice } from "./device-resolve.js";

// Routes a credential read (ticket scan / plate / card) to the right flow. A read
// can mean a subscription entry/exit OR a transient exit, so we dispatch by WHAT the
// credential is (decision 2026-06-15):
//   - matches a subscription (card/QR/bound plate) → SUBSCRIPTION flow,
//   - else → transient EXIT flow (open ticket session → exit, else reject+log).
//
// The reader is BOUND to a controller relay (config.controllerId + relay), so a read
// resolves to exactly the barrier it sits at, and the direction is inherited from
// that relay (see entry-exit-points.md). The resolved relay is handed to the flow so
// it opens that exact barrier. An "entry" reader drives the entry side, an "exit"
// reader the exit side; "both" defers to the flow's own inference (subscription:
// session state; transient: exit).

export class ReadDispatcher {
  readonly #db: Db;
  readonly #exit: ExitFlow;
  readonly #subscription: SubscriptionFlow;
  readonly #logger: FastifyBaseLogger;

  constructor(db: Db, exit: ExitFlow, subscription: SubscriptionFlow, logger: FastifyBaseLogger) {
    this.#db = db;
    this.#exit = exit;
    this.#subscription = subscription;
    this.#logger = logger;
  }

  async dispatch(e: DeviceReadEvent): Promise<ReadOutcome> {
    const reader = this.#db.select().from(devices).where(eq(devices.id, e.deviceId)).get();
    if (!reader || !reader.enabled) {
      return { accepted: false, reason: "read from unknown/disabled device" };
    }
    const resolved = relayForDevice(this.#db, reader);
    if (!resolved) {
      return { accepted: false, reason: "reader not bound to a barrier (no relay to open)" };
    }

    const sub = this.#subscription.match(e);
    if (sub) {
      return this.#subscription.run(resolved, e, sub);
    }
    // Not a subscription → transient ticket exit. An ENTRY reader can't produce a
    // transient exit (transient entry is the button flow, not a reader), so reject+log
    // rather than treat an entry scan as an exit.
    if (resolved.direction === "entry") {
      return { accepted: false, direction: "entry", reason: "entry reader: no transient entry via reader" };
    }
    return this.#exit.handleAt(resolved, e);
  }
}