flynn/src/channels/registry.ts

/**
 * Channel registry — manages adapter lifecycle and message routing.
 *
 * The ChannelRegistry holds all registered channel adapters and routes
 * inbound messages through a single MessageHandler. Each adapter's
 * onMessage callback is wired at registration time so that messages
 * flow through handleInbound → messageHandler → reply.
 */

import type {
  ChannelAdapter,
  InboundMessage,
  MessageHandler,
  OutboundMessage,
} from './types.js';

export class ChannelRegistry {
  private adapters: Map<string, ChannelAdapter> = new Map();
  private messageHandler?: MessageHandler;

  /** Register an adapter. Throws if name already registered. */
  register(adapter: ChannelAdapter): void {
    if (this.adapters.has(adapter.name)) {
      throw new Error(`Channel adapter '${adapter.name}' is already registered`);
    }

    // Wire the adapter's onMessage to route through our messageHandler
    adapter.onMessage((msg) => this.handleInbound(msg));
    this.adapters.set(adapter.name, adapter);
  }

  /** Unregister an adapter by name. Calls disconnect() if connected. */
  async unregister(name: string): Promise<void> {
    const adapter = this.adapters.get(name);
    if (!adapter) return;

    if (adapter.status === 'connected' || adapter.status === 'connecting') {
      await adapter.disconnect();
    }

    this.adapters.delete(name);
  }

  /** Get an adapter by name. */
  get(name: string): ChannelAdapter | undefined {
    return this.adapters.get(name);
  }

  /** List all registered adapters. */
  list(): ChannelAdapter[] {
    return Array.from(this.adapters.values());
  }

  /** Set the message handler that all adapters route inbound messages to. */
  setMessageHandler(handler: MessageHandler): void {
    this.messageHandler = handler;
  }

  /** Start all registered adapters. Logs errors per adapter, doesn't throw. */
  async startAll(): Promise<void> {
    const adapters = Array.from(this.adapters.values());
    const results = await Promise.allSettled(
      adapters.map((a) => a.connect()),
    );

    for (const [i, result] of results.entries()) {
      if (result.status === 'rejected') {
        console.error(
          `Failed to start channel '${adapters[i].name}':`,
          result.reason,
        );
      }
    }
  }

  /** Stop all registered adapters. */
  async stopAll(): Promise<void> {
    const adapters = Array.from(this.adapters.values());
    const results = await Promise.allSettled(
      adapters.map((a) => a.disconnect()),
    );

    for (const [i, result] of results.entries()) {
      if (result.status === 'rejected') {
        console.error(
          `Failed to stop channel '${adapters[i].name}':`,
          result.reason,
        );
      }
    }
  }

  /** Internal: route an inbound message to the message handler. */
  private handleInbound(msg: InboundMessage): void {
    if (!this.messageHandler) {
      console.warn(`No message handler set, dropping message from '${msg.channel}'`);
      return;
    }

    const adapter = this.adapters.get(msg.channel);
    if (!adapter) {
      console.warn(`Unknown channel '${msg.channel}' in inbound message`);
      return;
    }

    // Create a reply function bound to this message's channel and sender
    const reply = async (response: OutboundMessage): Promise<void> => {
      await adapter.send(msg.senderId, response);
    };

    // Fire and forget — errors are logged, not propagated
    this.messageHandler(msg, reply).catch((err: unknown) => {
      console.error(`Error handling message from '${msg.channel}':`, err);
    });
  }
}