fix(on_message): ensure slow mode is unset after server restart (#60)

* fix(slow_mode): handle server restarts

- Check busy level if channel's current rate limit does not match server state

* fix(slow_mode): adjust server state tracking

- Track slow mode state per unique channel
- Refactor related variables to snake_case

* chore: nothing to see here

Author: theetrain

src/events/on_message/_slow_mode.ts

@@ -13,7 +13,7 @@ function debug(args: any | []) {
 }
 
 type QueueItem = { userId: string; timestamp: number };
-const messageQueueChannelMap = new Map<string, QueueItem[]>([]);
+const message_queue_channel_map = new Map<string, QueueItem[]>([]);
 
 const ONE_MINUTE = 60_000;
 const FIVE_MINUTES = 300_000;
@@ -90,7 +90,15 @@ type SlowModeActivation = {
 	expiry: number;
 };
 
-let currentSlowMode: SlowModeActivation | undefined;
+/** Track slow mode state per channel */
+const slow_mode_state_channel_map = new Map<string, SlowModeActivation>();
+
+/** Look up rate limit per user based on level. */
+function level_to_rate_limit(level: BusyLevels | -1): number {
+	return (
+		levelConfigs.find((el) => el.level === level)?.rateLimitPerUser ?? -1
+	);
+}
 
 export default async function slow_mode(message: Message): Promise<void> {
 	if (
@@ -105,44 +113,56 @@ export default async function slow_mode(message: Message): Promise<void> {
 	const now = Date.now();
 	const { channelId } = message;
 
-	if (!Array.isArray(messageQueueChannelMap.get(channelId))) {
+	if (!Array.isArray(message_queue_channel_map.get(channelId))) {
 		// instantiate array, mapped against channel id
-		messageQueueChannelMap.set(channelId, []);
+		message_queue_channel_map.set(channelId, []);
 	}
 
-	const channelMessageQueue = messageQueueChannelMap.get(channelId)!;
+	const channel_message_queue = message_queue_channel_map.get(channelId)!;
 	debug([
 		'queue on message',
 		{
-			channelMessageQueue,
-			messageQueueChannelMap,
+			channelMessageQueue: channel_message_queue,
+			messageQueueChannelMap: message_queue_channel_map,
 		},
 	]);
 
-	channelMessageQueue.push({ userId: message.author.id, timestamp: now });
+	channel_message_queue.push({ userId: message.author.id, timestamp: now });
 
 	// Remove old messages from queue
-	while (channelMessageQueue[0].timestamp < now - QUEUE_TIME_RANGE) {
-		channelMessageQueue.shift();
+	while (channel_message_queue[0].timestamp < now - QUEUE_TIME_RANGE) {
+		channel_message_queue.shift();
 	}
 
-	debug(['queue on purge', channelMessageQueue]);
+	debug(['queue on purge', channel_message_queue]);
 	const { level: newLevel, messagesUntilNextLevel } = checkBusyLevel(
 		now,
-		channelMessageQueue,
+		channel_message_queue,
 	);
 
+	// Secret joke
+	// TODO: refactor into its own hook
+	if (message.content.includes('the bot is here')) {
+		await message.react('👀');
+	}
+
 	// Return early if:
 	//
 	// - new level is equal to current level
 	// OR
 	// - new level is lower or equal to the current level AND current rate limit
 	//   hasn't expired
+	// BUT ALSO
+	// - channel has slow mode already activated
+	const currentSlowMode = slow_mode_state_channel_map.get(channelId);
 	const currentModeExpired = now > (currentSlowMode?.expiry ?? 0);
 	const currentLevel = currentSlowMode?.level ?? -1;
+	const hasStateMismatch =
+		level_to_rate_limit(currentLevel) !== message.channel.rateLimitPerUser;
 	if (
-		newLevel === currentLevel ||
-		(newLevel <= currentLevel && !currentModeExpired)
+		!hasStateMismatch &&
+		(newLevel === currentLevel ||
+			(newLevel <= currentLevel && !currentModeExpired))
 	) {
 		debug([
 			'early return due to new level not exceeding current, or current rate limit has not expired',
@@ -190,11 +210,11 @@ export default async function slow_mode(message: Message): Promise<void> {
 		await message.channel.send(targetConfig.channelMessage);
 
 	const setTime = Date.now();
-	currentSlowMode = {
+	slow_mode_state_channel_map.set(channelId, {
 		level: targetConfig.level,
 		timestamp: setTime,
 		expiry: setTime + targetConfig.timeout,
-	};
+	});
 }
 
 /** Get number of unique users in message queue */