Plugins

As of now, modules seem a little underwhelming. It appears that sern doesn't have all the features of a standard handler, which manages permissions, categorizes, cool-downs, publishes application commands, role permissions, etc.

Many important parts that manage access and help streamline command creation to make are apparently absent. Below is an example of an event plugin, one of the types of plugins.

Typescript:

export function serenOnly(): EventPlugin<CommandType.Both> {
  return {
    type: PluginType.Event,
    async execute([ctx, args], controller) {
      if (ctx.user.id !== "182326315813306368") {
        await ctx.reply({content: "You cannot use this command"})
        return controller.stop()
      }
      return controller.next();
    }
  }
}

Javascript:

export function serenOnly() {
    return {
        type: PluginType.Event,
        async execute([ctx, args], controller) {
            if (ctx.user.id !== "182326315813306368") {
                await ctx.reply({content: "You cannot use this command"})
                return controller.stop()
            }
            return controller.next();
        }
    }
}

As part of our extensibility, the plugins feature make sern just as powerful, if not more powerful than standard handlers. Plugins modify and add new behavior to standard modules, extending customizability and implementing automation.
At the moment, there are two types of plugins:

• Command Plugins
• Event Plugins

Command Plugins

All modules are registered into sern's system. With command plugins, you can modify how commands are loaded, or do some kind of preprocessing before they are loaded.

The controller object

export interface Controller {
  next: () => Ok<void>;
  stop: () => Err<void>;
}

An instance of the above object is passed into every plugin.
This controls whether a module is stored into sern.
Typescript:

export function inDir(dir : string) : CommandPlugin<CommandType.Both> {
  return {
    type: PluginType.Command,
    async execute(wrapper, { absPath, module }, controller) {
      if(path.dirname(absPath) !== dir) {
        console.log(+new Date(),  `${module.name} is not in the correct directory!`);
        return controller.stop()
      }
      console.log(+new Date(),  `${module.name} is in the correct directory!`);
      return controller.next(); //continue
    }
  }
}

Javascript:

export function inDir(dir : string) {
  return {
    type: PluginType.Command,
    async execute(wrapper, { absPath, module }, controller) {
        if(path.dirname(absPath) !== dir) {
          console.log(+new Date(),  `${module.name} is not in the correct directory!`);
          return controller.stop()
        }
        console.log(+new Date(),  `${module.name} is in the correct directory!`);
        return controller.next(); //continue
    }
  }
}

Above, this simple plugin logs that the module has been loaded along with a timestamp.
Again, it is up to you to define plugin logic! The possibilities to customize your bots are endless.

tip

Command Plugins are good for ensuring the shape, location, and preprocessing of your commands.

Event Plugins

• An event is emitted by discord.js.
• This event is passed to all plugins (in order!!),
• If all are successful,

The command is executed. Calling controller.stop() notifies sern that this command should not be run, and this event is ignored.

So, what does a command module look like with plugins?

Typescript:

import { commandModule, CommandType } from '@sern/handler';

export default commandModule({
    type: CommandType.Both,
    plugins: [
        inDir("other"), 
        serenOnly()
    ],
    description: 'A ping command',
    //alias : [],
    execute: async (ctx, args) => {
        await ctx.reply({ content: 'Pong 🏓' });
    },
});

Javascript:

const { commandModule, CommandType } = require('@sern/handler');

exports.default = commandModule({
    type: CommandType.Both,
    plugins: [
        inDir("other"), 
        serenOnly() //The plugins in this section applied to this module!
    ],
    description: 'A ping command',
    //alias : [],
    execute: async (ctx, args) => {
        await ctx.reply({ content: 'Pong 🏓' });
    },
});

Can you predict the behavior of this command?

• Before loading into sern, this command module will check if this module is in the correct directory other.
• Before an event occurs, this command module will check if the user has the id 182326315813306368.

tip

Event Plugins are good for filtering, preconditions, parsing.

If all plugins return controller.next(), this command replies Pong 🏓