import { AdaptorSubscribeTypeFn } from "../types.ts";
import Adaptor from "./adaptor.ts";
import {
  Codec,
  connect,
  ConnectionOptions,
  NatsConnection,
  StringCodec,
  Subscription,
} from "nats";

export default class NatsAdaptor implements Adaptor {
  private options: ConnectionOptions;

  private nc?: NatsConnection;

  private callbacks: Record<string, AdaptorSubscribeTypeFn>;

  private sc: Codec<string>;

  private sub?: Subscription;

  constructor(options: ConnectionOptions) {
    this.options = options;
    this.sc = StringCodec();
    this.callbacks = {};
  }

  async listen(serviceName: string) {
    this.nc = await connect(this.options);

    this.sub = this.nc.subscribe(`${serviceName}.*`);
    (async (sub: Subscription) => {
      for await (const msg of sub) {
        const res = await this.callbacks[msg.subject](this.sc.decode(msg.data));
        msg.respond(this.sc.encode(res));
      }
    })(this.sub);
  }

  subscribe(subject: string, fn: AdaptorSubscribeTypeFn) {
    this.callbacks[subject] = fn;
  }

  async request(subject: string, req: string): Promise<string> {
    if (this.nc) {
      const msg = await this.nc.request(subject, this.sc.encode(req));
      return this.sc.decode(msg.data);
    }

    throw new Error("nats connection is not initialized");
  }

  async stop(): Promise<void> {
    await this.nc?.drain();
  }
}