import { EventEmitter } from "node:events";
import type { PrinterStatus } from "@parking/devices";
import type { LedgerEventRow } from "@parking/db";

// Internal event bus for device-originated events (button presses, etc.).
// Hardware drivers / inbound device pushes emit here; business logic (entry
// flow, event-log) subscribes — keeping the HTTP/transport layer thin and the
// app device-agnostic. See wiki/entities/fastify.md.

export interface DeviceInputEvent {
  readonly driverId: string; // e.g. "dingtian"
  readonly deviceId: string; // which configured device (devices id)
  readonly input: number; // 1-based input/channel
  readonly edge: "on" | "off"; // active / inactive
  readonly at: string; // ISO-8601 (server receive time)
  readonly source: "push" | "poll";
}

// A credential read: a ticket scanned at exit, a plate from LPR, a card at a reader.
// Drives identity-based flows (exit validation, subscriptions, pay-station lookup). `kind`
// mirrors IdentitySource. See parking-session.md.
export interface DeviceReadEvent {
  readonly driverId: string;
  readonly deviceId: string; // devices id of the reader/scanner/camera
  readonly value: string; // the ticket id / plate / card number
  readonly kind: "ticket" | "plate" | "qr" | "card";
  readonly at: string; // ISO-8601
}

/**
 * The decision a read produced. Returned by the read flows so a SYNCHRONOUS reader
 * (e.g. the QR reader, whose HTTP reply drives its beep + output) can answer the
 * device. A fire-and-forget reader simply ignores it. See wiki/entities/gee-qr-er80.md.
 */
export interface ReadOutcome {
  /** Was the vehicle admitted/exited (barrier opened)? Drives the reader's beep. */
  readonly accepted: boolean;
  /** Which way it went, when known (subscription/exit infer this). */
  readonly direction?: "entry" | "exit";
  /** Human-readable reason (for logs / the reader UI), esp. on reject. */
  readonly reason?: string;
}

/** A printer's status as tracked by the live monitor (status + identity). */
export interface PrinterStatusEvent {
  readonly deviceId: string; // devices id
  readonly driverId: string;
  readonly role?: string; // entry-dispenser | booth-receipt
  readonly status: PrinterStatus;
}

/**
 * The unified live status of ANY configured device — what the booth footer shows.
 * Every enabled device is polled: printers via their rich `readStatus()`
 * (paper/cover/cutter), all other categories via the generic `healthCheck()`
 * reachability probe. `state` is the common traffic-light; `detail` carries the
 * human summary (e.g. "paper out", or an unreachable error). See device-monitor.ts
 * and wiki/concepts/device-status-monitoring.md.
 */
export interface DeviceStatusEvent {
  readonly deviceId: string; // devices id
  readonly driverId: string;
  readonly category: "access" | "reader" | "camera" | "printer" | "vision";
  /**
   * The device's ROLE descriptor for the footer label — NOT the vendor. A
   * direction-style token the client localises and pairs with the category, so the
   * chip reads e.g. "Lexuesi hyrje" / "Kamera dalje" / "Printer kabina":
   *   - reader/camera: "entry" | "exit" | "both" (inherited from its bound relay)
   *   - access:        "entry" | "exit" | "both" | "mixed" (from its relays[])
   *   - printer:       "lane" (entry-dispenser) | "booth" (booth-receipt)
   *   - undetermined:  null (chip shows the category alone)
   */
  readonly roleKind: "entry" | "exit" | "both" | "mixed" | "lane" | "booth" | null;
  readonly state: "ready" | "degraded" | "offline";
  readonly detail?: string;
  readonly checkedAt: string; // ISO-8601
}

/** Lane occupancy from a camera's vehicle detection — a per-direction "busy/free"
 *  the booth shows as barrier lights. ADVISORY ONLY: a detection is a hint, never a
 *  gate (it never blocks a ticket or opens a barrier). "busy" is set by a vehicle
 *  `active` event; it auto-clears to "free" after a timeout (this camera class sends
 *  no leave/`inactive` signal — see wiki/entities/lpr-camera.md). */
export interface LaneStatusEvent {
  readonly entry: boolean; // true = busy (a vehicle is at the entry vicinity)
  readonly exit: boolean; // true = busy (a vehicle is at the exit vicinity)
}

class DeviceEventBus extends EventEmitter {
  emitInput(event: DeviceInputEvent): void {
    this.emit("input", event);
  }
  onInput(cb: (event: DeviceInputEvent) => void): () => void {
    this.on("input", cb);
    return () => this.off("input", cb);
  }

  /** A credential read (ticket scan, plate, card). */
  emitRead(event: DeviceReadEvent): void {
    this.emit("read", event);
  }
  onRead(cb: (event: DeviceReadEvent) => void): () => void {
    this.on("read", cb);
    return () => this.off("read", cb);
  }

  /** Emitted by the printer monitor whenever a printer's status CHANGES. */
  emitPrinterStatus(event: PrinterStatusEvent): void {
    this.emit("printer-status", event);
  }
  onPrinterStatus(cb: (event: PrinterStatusEvent) => void): () => void {
    this.on("printer-status", cb);
    return () => this.off("printer-status", cb);
  }

  /** Emitted by the device monitor whenever ANY device's unified status CHANGES
   *  (all categories — relays, readers, cameras, printers). Drives the booth
   *  device-status footer over the WS. */
  emitDeviceStatus(event: DeviceStatusEvent): void {
    this.emit("device-status", event);
  }
  onDeviceStatus(cb: (event: DeviceStatusEvent) => void): () => void {
    this.on("device-status", cb);
    return () => this.off("device-status", cb);
  }

  /**
   * Emitted AFTER a signed business event is appended to the ledger (entry, exit,
   * payment, void, …). The payload is the persisted row — business facts only, no
   * secrets — so it is safe to fan out to authenticated booth clients over the WS.
   * This is a read-side notification ONLY: it never feeds back into append/sign/
   * chain logic. See event-log.ts (emitted from EventLog.append) and routes/ws.ts.
   */
  emitLedger(event: LedgerEventRow): void {
    this.emit("ledger", event);
  }
  onLedger(cb: (event: LedgerEventRow) => void): () => void {
    this.on("ledger", cb);
    return () => this.off("ledger", cb);
  }

  /** Emitted whenever a lane's busy/free state CHANGES (from camera vehicle
   *  detection). Drives the booth's barrier lights. Advisory only. */
  emitLaneStatus(event: LaneStatusEvent): void {
    this.emit("lane-status", event);
  }
  onLaneStatus(cb: (event: LaneStatusEvent) => void): () => void {
    this.on("lane-status", cb);
    return () => this.off("lane-status", cb);
  }
}

/** Process-wide device event bus. */
export const deviceEvents = new DeviceEventBus();