feat: add Discord channel adapter (Phase 3a)
Implement ChannelAdapter for Discord using discord.js: - Bot mention filtering and mention stripping - Guild and channel allowlist filtering - Message chunking at 2000 chars - Reset command detection (!reset / reset in DMs) - 22 tests covering all behaviors
This commit is contained in:
William Valentin
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/**
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* Discord channel adapter.
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*
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* Implements the ChannelAdapter interface using discord.js v14.
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* Supports guild channels (with optional mention requirement) and DMs.
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* Messages are chunked at Discord's 2000-char limit.
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*/
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import { Client, GatewayIntentBits, Events } from 'discord.js';
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import type { Message as DiscordMessage } from 'discord.js';
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import type {
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InboundMessage,
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OutboundMessage,
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ChannelAdapter,
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ChannelStatus,
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} from '../types.js';
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/** Configuration for the Discord channel adapter. */
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export interface DiscordAdapterConfig {
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botToken: string;
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/** Guild IDs to respond in. Empty = all guilds. */
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allowedGuildIds?: string[];
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/** Channel IDs to respond in. Empty = all channels. */
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allowedChannelIds?: string[];
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/** Whether to require mention to respond in guild channels (default: true). DMs always respond. */
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requireMention?: boolean;
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}
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/**
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* Split a long message into chunks that respect Discord's 2000 char limit.
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* Prefers splitting at newlines, then spaces, then hard-cuts.
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*/
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function splitMessage(text: string, maxLength: number): string[] {
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const chunks: string[] = [];
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let remaining = text;
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while (remaining.length > 0) {
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if (remaining.length <= maxLength) {
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chunks.push(remaining);
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break;
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}
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// Try to split at a newline within the allowed window
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let splitIndex = remaining.lastIndexOf('\n', maxLength);
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if (splitIndex === -1 || splitIndex < maxLength / 2) {
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splitIndex = remaining.lastIndexOf(' ', maxLength);
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}
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if (splitIndex === -1 || splitIndex < maxLength / 2) {
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splitIndex = maxLength;
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}
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chunks.push(remaining.slice(0, splitIndex));
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remaining = remaining.slice(splitIndex).trimStart();
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}
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return chunks;
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}
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/**
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* Discord channel adapter backed by discord.js.
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*
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* Handles guild/channel filtering, optional mention requirement,
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* DM support, and message chunking for Discord's 2000-char limit.
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*/
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export class DiscordAdapter implements ChannelAdapter {
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readonly name = 'discord';
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private _status: ChannelStatus = 'disconnected';
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private client: Client | null = null;
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private messageHandler?: (msg: InboundMessage) => void;
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private config: DiscordAdapterConfig;
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get status(): ChannelStatus {
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return this._status;
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}
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constructor(config: DiscordAdapterConfig) {
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this.config = config;
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}
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/** Register the inbound message handler. Called by the registry before connect(). */
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onMessage(handler: (msg: InboundMessage) => void): void {
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this.messageHandler = handler;
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}
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/** Create the discord.js client, wire up event handlers, and log in. */
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async connect(): Promise<void> {
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this._status = 'connecting';
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this.client = new Client({
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intents: [
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GatewayIntentBits.Guilds,
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GatewayIntentBits.GuildMessages,
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GatewayIntentBits.MessageContent,
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GatewayIntentBits.DirectMessages,
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],
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});
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// ── Ready handler — resolve connect() when the bot is online ──
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const readyPromise = new Promise<void>((resolve) => {
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this.client!.on(Events.ClientReady, () => {
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console.log(`Discord bot ready as ${this.client!.user?.tag}`);
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this._status = 'connected';
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resolve();
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});
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});
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// ── Message handler — route inbound messages ──
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this.client.on(Events.MessageCreate, (message: DiscordMessage) => {
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this.handleMessage(message);
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});
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// Log in and wait for the ready event
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await this.client.login(this.config.botToken);
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await readyPromise;
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}
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/** Stop the client and clean up. */
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async disconnect(): Promise<void> {
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if (this.client) {
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this.client.destroy();
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this.client = null;
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}
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this._status = 'disconnected';
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}
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/** Send an outbound message, automatically chunking if it exceeds Discord's 2000-char limit. */
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async send(peerId: string, message: OutboundMessage): Promise<void> {
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if (!this.client) throw new Error('Discord adapter not connected');
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const channel = await this.client.channels.fetch(peerId);
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if (!channel || !('send' in channel)) {
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throw new Error(`Channel ${peerId} not found or is not a text channel`);
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}
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const text = message.text;
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const sendable = channel as { send: (content: string) => Promise<unknown> };
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if (text.length <= 2000) {
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await sendable.send(text);
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} else {
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const chunks = splitMessage(text, 2000);
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for (const chunk of chunks) {
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await sendable.send(chunk);
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}
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}
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}
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/** Internal: process an inbound Discord message. */
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private handleMessage(message: DiscordMessage): void {
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if (!this.messageHandler) return;
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// Ignore bot messages
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if (message.author.bot) return;
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const isDM = !message.guild;
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// ── Guild/channel filtering ──
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if (!isDM) {
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// Check allowed guild IDs
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if (
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this.config.allowedGuildIds &&
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this.config.allowedGuildIds.length > 0 &&
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!this.config.allowedGuildIds.includes(message.guild!.id)
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) {
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return;
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}
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// Check allowed channel IDs
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if (
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this.config.allowedChannelIds &&
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this.config.allowedChannelIds.length > 0 &&
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!this.config.allowedChannelIds.includes(message.channelId)
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) {
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return;
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}
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// ── Mention requirement in guild channels ──
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const requireMention = this.config.requireMention ?? true;
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if (requireMention && this.client?.user) {
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if (!message.mentions.has(this.client.user)) {
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return;
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}
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}
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}
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// Strip bot mention from the message text
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const text = message.content.replace(/<@!?\d+>/g, '').trim();
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// ── Reset command ──
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if (text === '!reset' || text === 'reset') {
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this.messageHandler({
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id: message.id,
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channel: 'discord',
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senderId: message.channelId,
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senderName: message.author.username,
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text: '!reset',
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timestamp: Date.now(),
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metadata: { isCommand: true, command: 'reset' },
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});
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return;
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}
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// ── Regular message ──
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this.messageHandler({
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id: message.id,
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channel: 'discord',
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senderId: message.channelId,
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senderName: message.author.username,
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text,
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timestamp: Date.now(),
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});
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}
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}
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