Prechecks

Learn how to use prechecks to add additional validation and checks before a command runs.

Prechecks are a powerful feature in Carbon that allow you to add additional validation and checks before a command is executed. This can be useful for implementing features like cooldowns, permission checks, or any other validation that needs to happen before the main command logic runs.

How Prechecks Work

Prechecks are implemented by overriding the preCheck method in your command class. This method is called before the main run method of your command. If the precheck returns anything other than true, the command will not execute.

Here's a basic example of a precheck:

import { Command } from "@buape/carbon"
import { CommandInteraction } from "discord.js"

export default class MyCommand extends Command {
	public override async preCheck(interaction: CommandInteraction): Promise<true | unknown> {
		// Check if the user has a specific role
		if (!interaction.member?.roles.find(x => x.id === "123456789")) {
			await interaction.reply("You don't have permission to use this command!")
			return false
		}
		return true
	}

	public override async run(interaction: CommandInteraction) {
		// Your command logic here
	}
}

Common Use Cases

Cooldowns

You can implement cooldowns using prechecks to prevent users from spamming commands:

private cooldowns = new Map<string, number>()

public override async preCheck(interaction: CommandInteraction): Promise<true | unknown> {
	const cooldown = 5000 // 5 seconds
	const now = Date.now()
	const lastUsed = this.cooldowns.get(interaction.user.id)

	if (lastUsed && now - lastUsed < cooldown) {
		await interaction.reply(`Please wait ${Math.ceil((cooldown - (now - lastUsed)) / 1000)} seconds before using this command again.`)
		return false
	}

	this.cooldowns.set(interaction.user.id, now)
	return true
}

Permission Checks

You can use prechecks to verify if a user has the necessary permissions to use a command:

public override async preCheck(interaction: CommandInteraction): Promise<true | unknown> {
	if (!interaction.memberPermissions?.has("Administrator")) {
		await interaction.reply("You need administrator permissions to use this command!")
		return false
	}
	return true
}

Maintenance Mode

You can implement a maintenance mode that prevents commands from being used:

private maintenanceMode = false

public override async preCheck(interaction: CommandInteraction): Promise<true | unknown> {
	if (this.maintenanceMode) {
		await interaction.reply("This command is currently under maintenance. Please try again later.")
		return false
	}
	return true
}

How Prechecks Work

Common Use Cases

Cooldowns

Permission Checks

Maintenance Mode

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