noctbot/bot/src/plugins/file_only_channel_checker.ts

import { Message, TextChannel } from "discord.js";
import { getRepository } from "typeorm";
import { FileOnlyChannel } from "@shared/db/entity/FileOnlyChannel";
import { Event, BotEventData, Plugin } from "src/model/plugin";

@Plugin
export class FileOnlyChannelChecker {
    private urlPattern = /(?:((?:https?|ftp):\/\/)|ww)(?:\S+(?::\S*)?@)?(?:(?!(?:10|127)(?:\.\d{1,3}){3})(?!(?:169\.254|192\.168)(?:\.\d{1,3}){2})(?!172\.(?:1[6-9]|2\d|3[0-1])(?:\.\d{1,3}){2})(?:[1-9]\d?|1\d\d|2[01]\d|22[0-3])(?:\.(?:1?\d{1,2}|2[0-4]\d|25[0-5])){2}(?:\.(?:[1-9]\d?|1\d\d|2[0-4]\d|25[0-4]))|(?:(?:[a-z\u00a1-\uffff0-9]-*)*[a-z\u00a1-\uffff0-9]+)(?:\.(?:[a-z\u00a1-\uffff0-9]-*)*[a-z\u00a1-\uffff0-9]+)*(?:\.(?:[a-z\u00a1-\uffff]{2,}))\.?)(?::\d{2,5})?(?:[/?#]\S*)?/;

    @Event("message")
    async processMessage(data: BotEventData, msg: Message): Promise<void> {
        if (data.actionsDone)
            return;

        const repo = getRepository(FileOnlyChannel);
        const entry = await repo.findOne(msg.channel.id);
        if (!entry)
            return;

        // Has attachments; is fine
        if (msg.attachments.size > 0)
            return;

        // Has a link
        if(this.urlPattern.test(msg.content))
            return;

        msg.delete();

        // Non-default system message (e.g. pin or thread create) => there is no one to warn, so just remove it to keep the channel clean
        if (msg.type != "DEFAULT")
            return;

        const ch = msg.guild?.channels.resolve(entry.warningMessageChannelId);
        
        if(ch instanceof TextChannel)
            ch.send(`> ${msg.content.replace(/\n/g, "\n> ")}\n\n${msg.author.toString()} Channel ${msg.channel.toString()} is only meant for sharing links and files! If you want to post text-only messages, do so in ${ch.toString()}!`);

        data.actionsDone = true;
    }
}