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

// 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 (lane_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 at a lane: a ticket scanned at exit, a plate from LPR, a card
// at a reader. Drives identity-based flows (exit validation, and later permits /
// pay-station lookup). `kind` mirrors IdentitySource. See parking-session.md.
export interface DeviceReadEvent {
  readonly driverId: string;
  readonly deviceId: string; // lane_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
}

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

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) at a lane. */
  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);
  }
}

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