captcha.ts

import type { ExtendedContext } from "../typings/context";
import type { User } from "telegraf/typings/telegram-types";
import Telegraf = require("telegraf");
import HtmlUtils = require("../utils/html");
import TgUtils = require("../utils/tg");
import Log = require("../utils/log");
import UserStore = require('../stores/user');
import Files = require('fs');

let settings = {
    active: true, // If True, Bot will issue Captcha Challenges for new Members.
    challengeTimeout: 1800, // Time before Bot kicks the user for not answer, 30 minutes (1800 seconds) by default.
    kickCooldown: 300, // Time before a kicked user can attempt to join the chat again in 5 minutes (300 seconds) by default.
    strict: true, // If True, deletes all messages by unverified users that aren't answers.
    maxAttempts: 3 // Max number of attempts before kicking the unverified user.
}

// Permissions for the new user when they join the chat.
const unverifiedOptions = {
    can_send_messages: true,
    can_send_media_messages: false,
    can_send_polls: false,
    can_send_other_messages: false,
    can_add_web_page_previews: false,
    can_change_info: false,
    can_invite_users: false,
    can_pin_messages: false
}

// Permissions for the new user after they Complete the Captcha. Check 
const verifiedOptions = {
    can_send_messages: true,
    can_send_media_messages: true,
    can_send_polls: true,
    can_send_other_messages: true,
    can_add_web_page_previews: true,
    can_change_info: false,
    can_invite_users: false,
    can_pin_messages: false
}

// Arithmetic Captcha Question Parameters
const numbers = [0, 1, 2, 3, 4, 5];
const calc = {
    "+": (a: number, b: number) => a + b,
    "-": (a: number, b: number) => a - b,
    //"*": (a: number, b: number) => a * b,
};

const { Composer: C } = Telegraf;
const { html } = HtmlUtils;
const { link } = TgUtils;
const { logError } = Log;
const { getAdmins } = UserStore;
const fs = Files;

const pick = <T>(list: T[]) => list[Math.floor(Math.random() * list.length)];

type Challenge = {
    user: User;
    chat: string;
    kickTimeout: number;
    math: [string, number];
    messageId: number;
    deleteList: number[];
    attempts: number;
};

const challenge = (
    challenges: Challenge[],
    ctx: ExtendedContext,
    x: User,
): Challenge => {
    let a: number, b: number, op: keyof typeof calc, result: number;
    do {
        a = pick(numbers);
        b = pick(numbers);
        op = pick(Object.keys(calc)) as keyof typeof calc;
        result = calc[op](a, b);
    } while (result === 0);
    const c = {
        user: x,
        chat: "",
        kickTimeout: (setTimeout(() => {
            ctx
                .kickChatMember(x.id, Math.floor((Date.now() / 1000) + settings.kickCooldown))
                .catch((err) => logError("[captcha] " + err.message))
                .then(() => {
                    challenges.splice(challenges.indexOf(c), 1);
                    return ctx.deleteMessage(c.messageId);
                })
                .catch((err) => logError("[captcha] " + err.message));
        }, settings.challengeTimeout * 1000) as unknown) as number,
        math: [`${a} ${op} ${b}`, result] as [string, number],
        messageId: 0,
        deleteList: [],
        attempts: settings.maxAttempts,
    };
    return c;
};

const activeChallenges: Challenge[] = [];

const adminList: number[] = [];

const settingsFile = "./plugins/captcha.json";

// If a settings file exists, read it and update our settings with it.
fs.access(settingsFile, fs.F_OK, (err) => {
    if (err) {
        logError("[captcha] " + err.message);
        return;
    }
    fs.readFile(settingsFile, "utf-8", (err, data) => {
        if (err) {
            logError("[captcha] " + err.message);
            return;
        }
        settings = JSON.parse(data.toString());
    });
});

// Update the settings file with our current settings object.
function updateSettings() {
    const data = JSON.stringify(settings);

    fs.writeFile(settingsFile, data, (err) => {
        if (err) {
            logError("[captcha] " + err.message);
            return;
        }
    });
}

export = C.mount("message", async (ctx: ExtendedContext, next) => {
    // Populate the list of Admins
    if (adminList.length < 1) {
        const admins = await getAdmins();
        //logError(admins);
        for (let i = 0; i < admins.length; i++) {
            adminList.push(admins[i].id);
        }
        //logError(adminList);
    }

    //Plugin Commands
    if (ctx.message?.entities?.[0].type === "bot_command") {
        const text = ctx.message?.text;
        const match = text.match(/^\/([^\s]+)\s?(.+)?/);
        let args = [];
        let command = "";
        if (match !== null) {
            if (match[1]) {
                command = match[1];
            }
            if (match[2]) {
                args = match[2].split(' ');
            }
        }

        // Command arguments (/captcha).
        if (command === "captcha") {
            if (adminList.indexOf(ctx.from?.id) >= 0) {
                if (args !== null) {
                    if (args[0] === "on") { // Enable Captcha (/captcha on).
                        settings.active = true;
                        updateSettings();
                        ctx.replyWithHTML(
                            html`Captcha is now On.`
                        );
                    } else if (args[0] === "off") { // Disable Captcha (/captcha off).
                        settings.active = false;
                        updateSettings();
                        ctx.replyWithHTML(
                            html`Captcha is now Off.`
                        );
                    } else if (args[0] === "timeout") { // Change challenge timeout. (/captcha timeout <integer bigger or equal to 300>).
                        if (parseInt(args[1]) >= 300) {
                            settings.challengeTimeout = parseInt(args[1]);
                            updateSettings();
                            ctx.replyWithHTML(
                                html`Captcha cooldown kick time is now ${settings.challengeTimeout}.`
                            );
                        } else if (parseInt(args[1]) < 300) {
                            ctx.replyWithHTML(
                                html`Captcha cooldown kick time cannot be lower than 300 seconds (5 minutes).`
                            );
                        } else {
                            ctx.replyWithHTML(
                                html`Captcha cooldown kick time value is invalid.`
                            );
                        }
                    } else if (args[0] === "cooldown") { // Change kick cooldown. (/captcha cooldown <integer bigger or equal to 300>).
                        if (parseInt(args[1]) >= 300) {
                            settings.kickCooldown = parseInt(args[1]);
                            updateSettings();
                            ctx.replyWithHTML(
                                html`Captcha cooldown kick time is now ${settings.kickCooldown}.`
                            );
                        } else if (parseInt(args[1]) < 300) {
                            ctx.replyWithHTML(
                                html`Captcha cooldown kick time cannot be lower than 300 seconds (5 minutes).`
                            );
                        } else {
                            ctx.replyWithHTML(
                                html`Captcha cooldown kick time value is invalid.`
                            );
                        }
                    } else if (args[0] === "strict") { // Change Captcha strict (/captcha strict <true or false>).
                        if (args[1] == "true") {
                            settings.strict = true;
                            updateSettings();
                            ctx.replyWithHTML(
                                html`Captcha strict is enabled.`
                            );
                        } else if (args[1] == "false") {
                            settings.strict = false;
                            updateSettings();
                            ctx.replyWithHTML(
                                html`Captcha strict is disabled.`
                            );
                        }
                    } else if (args[0] === "attempts") { // Change max attempts (/captcha attempts <integer bigger or equal to 1>).
                        if (parseInt(args[1]) >= 1) {
                            settings.maxAttempts = parseInt(args[1]);
                            updateSettings();
                            ctx.replyWithHTML(
                                html`Captcha max attempts is now ${settings.maxAttempts}.`
                            );
                        } else if (parseInt(args[1]) < 1) {
                            ctx.replyWithHTML(
                                html`Captcha max attempts cannot be lower than 1 attempt.`
                            );
                        } else {
                            ctx.replyWithHTML(
                                html`Captcha max attempts value is invalid.`
                            );
                        }
                    } else if (args[0] === "settings") { // Print plugin settings (/captcha settings).
                        ctx.replyWithHTML(
                            html`Captcha settings:
                            <code>
                            active: ${settings.active}
                            challengeTimeout: ${settings.challengeTimeout}
                            kickCooldown: ${settings.kickCooldown}
                            strict: ${settings.strict}
                            maxAttempts: ${settings.maxAttempts}
                            </code>`
                        );
                    } else { // Invalid arguments, show Captcha commands.
                        ctx.replyWithHTML(
                            html`Captcha usage:
                            <code>/captcha argument value</code>\n
                            Captcha arguments:\n
                            <code>on</code> - Enables Captcha.
                            <code>off</code> - Disables Captcha.
                            <code>timeout</code> - Changes the challenge timeout, in seconds, cannot be lower than 300 seconds (5 minutes).
                            <code>cooldown</code> - Changes the kick cooldown, in seconds, cannot be lower than 300 seconds (5 minutes).
                            <code>strict</code> - Switches message deletion on challenge ending on and off, boolean, only accepts true or false.
                            <code>attempts</code> - Changes the max number of attempts, cannot be lower than 1.
                            <code>settings</code> - Shows the current settings for Captcha.`
                        );
                    }
                }
            }
            ctx.deleteMessage(ctx.message?.message_id);
        }
    }

    const members = ctx.message?.new_chat_members?.filter(
        (x) => x.username !== ctx.me
    );
    if (!members || members.length === 0) {
        const foundChallenge = activeChallenges.find(
            (x) => (x.user.id === ctx.from?.id && x.chat === String(ctx.chat?.id))
        );
        if (!foundChallenge) {
            return next();
        }
        if (Number(ctx.message?.text) === foundChallenge.math[1]) {
            //logError("Correct Answer: \n" + ctx.message?.text + " " + foundChallenge.math[1] + "\n" + ctx.chat?.id + " " + foundChallenge.chat);
            clearTimeout(foundChallenge.kickTimeout);
            activeChallenges.splice(activeChallenges.indexOf(foundChallenge), 1);
            return Promise.all([
                ctx.message?.message_id
                    ? ctx.deleteMessage(ctx.message?.message_id)
                    : Promise.resolve(true),
                ctx.deleteMessage(foundChallenge.messageId),
                foundChallenge.deleteList.forEach(number => {
                    ctx.deleteMessage(number);
                }),
                ctx.replyWithHTML(html`Thank you, ${link(ctx.from)}, please read the rules in our pinned message and enjoy the chat!`),
                ctx.telegram.restrictChatMember(ctx.chat?.id, ctx.from?.id, verifiedOptions),
            ]).catch((err) => logError("[captcha] " + err.message));
        }
        if (Number(ctx.message?.text) !== foundChallenge.math[1]) {
            //logError("Wrong Answer: \n" + ctx.message?.text + " " + foundChallenge.math[1] + "\n" + ctx.chat?.id + " " + foundChallenge.chat);
            if (foundChallenge.attempts >= 1) {
                let msg;
                return Promise.all([
                    foundChallenge.deleteList.push(ctx.message?.message_id),
                    msg = await ctx.replyWithHTML(html`Sorry, ${link(ctx.from)}, that answer is incorrect, you have ${foundChallenge.attempts} attempts left, try again!`),
                    foundChallenge.deleteList.push(msg?.message_id),
                    foundChallenge.attempts = foundChallenge.attempts - 1,
                ]).catch((err) => logError("[captcha] " + err.message));
            } else {
                clearTimeout(foundChallenge.kickTimeout);
                activeChallenges.splice(activeChallenges.indexOf(foundChallenge), 1);
                return Promise.all([
                    ctx.message?.message_id
                        ? ctx.deleteMessage(ctx.message?.message_id)
                        : Promise.resolve(true),
                    ctx.deleteMessage(foundChallenge.messageId),
                    foundChallenge.deleteList.forEach(number => {
                        ctx.deleteMessage(number);
                    }),
                    ctx.kickChatMember(ctx.from?.id, Math.floor((Date.now() / 1000) + settings.kickCooldown)),
                ]).catch((err) => logError("[captcha] " + err.message));
            }
        }
        return settings.strict
            ? ctx.message?.message_id
                ? ctx.deleteMessage(ctx.message?.message_id)
                : Promise.resolve(true)
            : next();
    }
    return Promise.all(
        members.map(async (x) => {
            if (settings.active && !x.is_bot) {
                const c = challenge(activeChallenges, ctx, x);
                activeChallenges.push(c);
                const msg = await ctx.replyWithHTML(
                    html`Welcome ${link(x)}, please solve the following arithmetic operation in ${(settings.challengeTimeout / 60)} minutes: \n\n
                <code>${c.math[0]}</code> \n\n
                Note: Results can be negative, don't forget the (-) sign if so`
                );
                c.chat = String(ctx.chat?.id);
                c.messageId = msg.message_id;
                ctx.telegram.restrictChatMember(ctx.chat?.id, ctx.from?.id, unverifiedOptions);
            }
        })
    );
});