TravBot-v3/src/events/message.ts

import Event from "../core/event";
import Command, {loadCommands} from "../core/command";
import {
    hasPermission,
    getPermissionLevel,
    PermissionNames
} from "../core/permissions";
import {Permissions, Collection} from "discord.js";
import {getPrefix} from "../core/structures";
import $ from "../core/lib";

// It's a rather hacky solution, but since there's no top-level await, I just have to make the loading conditional.
let commands: Collection<string, Command> | null = null;

export default new Event<"message">({
    async on(message) {
        // Load commands if it hasn't already done so. Luckily, it's called once at most.
        if (!commands) commands = await loadCommands();

        // Message Setup //
        if (message.author.bot) return;

        const prefix = getPrefix(message.guild);

        if (!message.content.startsWith(prefix)) {
            if (
                message.client.user &&
                message.mentions.has(message.client.user)
            )
                message.channel.send(
                    `${message.author.toString()}, my prefix on this guild is \`${prefix}\`.`
                );
            return;
        }

        const [header, ...args] = message.content
            .substring(prefix.length)
            .split(/ +/);

        if (!commands.has(header)) return;

        if (
            message.channel.type === "text" &&
            !message.channel
                .permissionsFor(message.client.user || "")
                ?.has(Permissions.FLAGS.SEND_MESSAGES)
        ) {
            let status;

            if (message.member?.hasPermission(Permissions.FLAGS.ADMINISTRATOR))
                status =
                    "Because you're a server admin, you have the ability to change that channel's permissions to match if that's what you intended.";
            else
                status =
                    "Try using a different channel or contacting a server admin to change permissions of that channel if you think something's wrong.";

            return message.author.send(
                `I don't have permission to send messages in ${message.channel.toString()}. ${status}`
            );
        }

        $.log(
            `${message.author.username}#${message.author.discriminator} executed the command "${header}" with arguments "${args}".`
        );

        // Subcommand Recursion //
        let command = commands.get(header);
        if (!command)
            return $.warn(
                `Command "${header}" was called but for some reason it's still undefined!`
            );
        const params: any[] = [];
        let isEndpoint = false;
        let permLevel = command.permission ?? Command.PERMISSIONS.NONE;

        for (let param of args) {
            if (command.endpoint) {
                if (
                    command.subcommands.size > 0 ||
                    command.user ||
                    command.number ||
                    command.any
                )
                    $.warn(
                        `An endpoint cannot have subcommands! Check ${prefix}${header} again.`
                    );
                isEndpoint = true;
                break;
            }

            const type = command.resolve(param);
            command = command.get(param);
            permLevel = command.permission ?? permLevel;

            if (type === Command.TYPES.USER) {
                const id = param.match(/\d+/g)![0];
                try {
                    params.push(await message.client.users.fetch(id));
                } catch (error) {
                    return message.channel.send(
                        `No user found by the ID \`${id}\`!`
                    );
                }
            } else if (type === Command.TYPES.NUMBER)
                params.push(Number(param));
            else if (type !== Command.TYPES.SUBCOMMAND) params.push(param);
        }

        if (!message.member)
            return $.warn(
                "This command was likely called from a DM channel meaning the member object is null."
            );

        if (!hasPermission(message.member, permLevel)) {
            const userPermLevel = getPermissionLevel(message.member);
            return message.channel.send(
                `You don't have access to this command! Your permission level is \`${PermissionNames[userPermLevel]}\` (${userPermLevel}), but this command requires a permission level of \`${PermissionNames[permLevel]}\` (${permLevel}).`
            );
        }

        if (isEndpoint) return message.channel.send("Too many arguments!");

        // Execute with dynamic library attached. //
        // The purpose of using $.bind($) is to clone the function so as to not modify the original $.
        // The cloned function doesn't copy the properties, so Object.assign() is used.
        // Object.assign() modifies the first element and returns that, the second element applies its properties and the third element applies its own overriding the second one.
        command.execute(
            Object.assign(
                $.bind($),
                {
                    args: params,
                    author: message.author,
                    channel: message.channel,
                    client: message.client,
                    guild: message.guild,
                    member: message.member,
                    message: message
                },
                $
            )
        );
    }
});