feat(gateway): add plugin host module

apps/gateway/src/plugin/plugin.module.ts

@@ -0,0 +1,90 @@
+import {
+  Global,
+  Inject,
+  Logger,
+  Module,
+  type OnModuleDestroy,
+  type OnModuleInit,
+} from '@nestjs/common';
+import { DiscordPlugin } from '@mosaic/discord-plugin';
+import { PluginService } from './plugin.service.js';
+import type { IChannelPlugin } from './plugin.interface.js';
+
+export const PLUGIN_REGISTRY = Symbol('PLUGIN_REGISTRY');
+
+class DiscordChannelPluginAdapter implements IChannelPlugin {
+  readonly name = 'discord';
+
+  constructor(private readonly plugin: DiscordPlugin) {}
+
+  async start(): Promise<void> {
+    await this.plugin.start();
+  }
+
+  async stop(): Promise<void> {
+    await this.plugin.stop();
+  }
+}
+
+const DEFAULT_GATEWAY_URL = 'http://localhost:4000';
+
+function createPluginRegistry(logger: Logger): IChannelPlugin[] {
+  const plugins: IChannelPlugin[] = [];
+  const discordToken = process.env['DISCORD_BOT_TOKEN'];
+  const discordGuildId = process.env['DISCORD_GUILD_ID'];
+  const discordGatewayUrl = process.env['DISCORD_GATEWAY_URL'] ?? DEFAULT_GATEWAY_URL;
+
+  if (discordToken) {
+    plugins.push(
+      new DiscordChannelPluginAdapter(
+        new DiscordPlugin({
+          token: discordToken,
+          guildId: discordGuildId,
+          gatewayUrl: discordGatewayUrl,
+        }),
+      ),
+    );
+  }
+
+  const telegramToken = process.env['TELEGRAM_BOT_TOKEN'];
+  const telegramGatewayUrl = process.env['TELEGRAM_GATEWAY_URL'] ?? DEFAULT_GATEWAY_URL;
+
+  if (telegramToken) {
+    logger.warn(
+      `Telegram plugin requested for ${telegramGatewayUrl}, but @mosaic/telegram-plugin is not implemented yet.`,
+    );
+  }
+
+  return plugins;
+}
+
+@Global()
+@Module({
+  providers: [
+    {
+      provide: PLUGIN_REGISTRY,
+      useFactory: (): IChannelPlugin[] => createPluginRegistry(new Logger('PluginModule')),
+    },
+    PluginService,
+  ],
+  exports: [PluginService, PLUGIN_REGISTRY],
+})
+export class PluginModule implements OnModuleInit, OnModuleDestroy {
+  private readonly logger = new Logger(PluginModule.name);
+
+  constructor(@Inject(PLUGIN_REGISTRY) private readonly plugins: IChannelPlugin[]) {}
+
+  async onModuleInit(): Promise<void> {
+    for (const plugin of this.plugins) {
+      this.logger.log(`Starting plugin: ${plugin.name}`);
+      await plugin.start();
+    }
+  }
+
+  async onModuleDestroy(): Promise<void> {
+    for (const plugin of [...this.plugins].reverse()) {
+      this.logger.log(`Stopping plugin: ${plugin.name}`);
+      await plugin.stop();
+    }
+  }
+}