discord.js-structures/proxies/structures.js

const discord = require("discord.js");

/**
 * An extendable structure:
 * * **`GuildEmoji`**
 * * **`DMChannel`**
 * * **`TextChannel`**
 * * **`VoiceChannel`**
 * * **`CategoryChannel`**
 * * **`NewsChannel`**
 * * **`StoreChannel`**
 * * **`GuildMember`**
 * * **`Guild`**
 * * **`Message`**
 * * **`MessageReaction`**
 * * **`Presence`**
 * * **`ClientPresence`**
 * * **`VoiceState`**
 * * **`Role`**
 * * **`User`**
 * @typedef {string} ExtendableStructure
 */

/**
 * Allows for the extension of built-in Discord.js structures that are instantiated by {@link BaseManager Managers}.
 */
class Structures {
    constructor() {
        throw new Error(`The ${this.constructor.name} class may not be instantiated.`);
    }

    /**
     * Retrieves a structure class.
     * @param {string} structure Name of the structure to retrieve
     * @returns {Function}
     */
    static get(structure) {
        if (typeof structure === 'string') return structures[structure];
        throw new TypeError(`"structure" argument must be a string (received ${typeof structure})`);
    }

    /**
     * Extends a structure.
     * <warn> Make sure to extend all structures before instantiating your client.
     * Extending after doing so may not work as expected. </warn>
     * @param {ExtendableStructure} structure Name of the structure class to extend
     * @param {Function} extender Function that takes the base class to extend as its only parameter and returns the
     * extended class/prototype
     * @returns {Function} Extended class/prototype returned from the extender
     * @example
     * const { Structures } = require('discord.js');
     *
     * Structures.extend('Guild', Guild => {
     *   class CoolGuild extends Guild {
     *     constructor(client, data) {
     *       super(client, data);
     *       this.cool = true;
     *     }
     *   }
     *
     *   return CoolGuild;
     * });
     */
    static extend(structure, extender) {
        if (!structures[structure]) throw new RangeError(`"${structure}" is not a valid extensible structure.`);
        if (typeof extender !== 'function') {
            const received = `(received ${typeof extender})`;
            throw new TypeError(
                `"extender" argument must be a function that returns the extended structure class/prototype ${received}.`,
            );
        }

        const extended = extender(structures[structure]);
        if (typeof extended !== 'function') {
            const received = `(received ${typeof extended})`;
            throw new TypeError(`The extender function must return the extended structure class/prototype ${received}.`);
        }

        if (!(extended.prototype instanceof structures[structure])) {
            const prototype = Object.getPrototypeOf(extended);
            const received = `${extended.name || 'unnamed'}${prototype.name ? ` extends ${prototype.name}` : ''}`;
            throw new Error(
                'The class/prototype returned from the extender function must extend the existing structure class/prototype' +
                ` (received function ${received}; expected extension of ${structures[structure].name}).`,
            );
        }

        structures[structure] = extended;
        return extended;
    }
}

const structures = {
    GuildEmoji: discord.GuildEmoji,
    DMChannel: discord.DMChannel,
    TextChannel: discord.TextChannel,
    VoiceChannel: discord.VoiceChannel,
    CategoryChannel: discord.CategoryChannel,
    NewsChannel: discord.NewsChannel,
    StoreChannel: discord.StoreChannel,
    GuildMember: discord.GuildMember,
    Guild: discord.Guild,
    Message: discord.Message,
    MessageReaction: discord.MessageReaction,
    Presence: discord.Presence,
    ClientPresence: discord.ClientPresence,
    VoiceState: discord.VoiceState,
    Role: discord.Role,
    User: discord.User,
};

module.exports = Structures;