Realtime Chat - Profanity Filter

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#1

I am wondering what would be the best method for filtering messages sent through the realtime chat sockets.

We already have a client-side filter that compares messages to a .txt list of words, but want to know if server side you can create a .lua script to do the same process and replace words. Assuming we have to register a hook, I see a ChannelMessageUpdate hook but unsure if appropriate or how to then adapt.

#2

@keiranlovett Good question, you’re on the right track. There are two message types you probably want to hook into: ChannelMessageSend (this is the main one) and ChannelMessageUpdate (only if your game clients use it).

In these hooks you should inspect the incoming message or send it to a profanity verification service, and either sanitise the text or reject the message.

I’m not sure which runtime you plan to use, but here’s an example of a Go runtime before hook that would reject bad messages.

// Inside your Go module's `InitModule` function.
if err := initializer.RegisterBeforeRt("ChannelMessageSend", func(ctx context.Context, logger runtime.Logger, db *sql.DB, nk runtime.NakamaModule, envelope *rtapi.Envelope) (*rtapi.Envelope, error) {
	message := envelope.GetChannelMessageSend()
	if strings.Contains(message.Content, "bad word") {
		// Alternatively, to sanitise instead of reject:
		// message.Content = strings.ReplaceAll(message.Content, "bad word", "****")

		// Reject the message send:
		return nil, runtime.NewError("profanity detected", 3)
	}
	return envelope, nil
}); err != nil {
	return err
}
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#3

@keiranlovett You’re on the right track with the use of before hooks. That’s how most game teams implement a profanity filter. Some example code looks like:

// This code should be inside InitModule.
if err := initializer.RegisterBeforeRt("ChannelMessageSend", beforeRtChatMessageSend); err != nil {
	return err
}

func beforeRtChatMessageSend(ctx context.Context, logger runtime.Logger, db *sql.DB, nk runtime.NakamaModule, envelope *rtapi.Envelope) (envelope2 *rtapi.Envelope, e error) {
	inputMessage := envelope.GetChannelMessageSend()

	// Profanity check the chat message input.
	inputMessage.Content = "some safe string"

	return envelope, nil
}

Hope that helps.

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