discord.js/packages/builders/src/interactions/slashCommands/Assertions.ts

import { s } from '@sapphire/shapeshift';
import is from '@sindresorhus/is';
import { type APIApplicationCommandOptionChoice, Locale } from 'discord-api-types/v10';
import type { ToAPIApplicationCommandOptions } from './SlashCommandBuilder';
import type { SlashCommandSubcommandBuilder, SlashCommandSubcommandGroupBuilder } from './SlashCommandSubcommands';
import type { ApplicationCommandOptionBase } from './mixins/ApplicationCommandOptionBase';

const namePredicate = s.string
	.lengthGe(1)
	.lengthLe(32)
	.regex(/^[\P{Lu}\p{N}\p{sc=Devanagari}\p{sc=Thai}_-]+$/u);

export function validateName(name: unknown): asserts name is string {
	namePredicate.parse(name);
}

const descriptionPredicate = s.string.lengthGe(1).lengthLe(100);
const localePredicate = s.nativeEnum(Locale);

export function validateDescription(description: unknown): asserts description is string {
	descriptionPredicate.parse(description);
}

const maxArrayLengthPredicate = s.unknown.array.lengthLe(25);
export function validateLocale(locale: unknown) {
	return localePredicate.parse(locale);
}

export function validateMaxOptionsLength(options: unknown): asserts options is ToAPIApplicationCommandOptions[] {
	maxArrayLengthPredicate.parse(options);
}

export function validateRequiredParameters(
	name: string,
	description: string,
	options: ToAPIApplicationCommandOptions[],
) {
	// Assert name matches all conditions
	validateName(name);

	// Assert description conditions
	validateDescription(description);

	// Assert options conditions
	validateMaxOptionsLength(options);
}

const booleanPredicate = s.boolean;

export function validateDefaultPermission(value: unknown): asserts value is boolean {
	booleanPredicate.parse(value);
}

export function validateRequired(required: unknown): asserts required is boolean {
	booleanPredicate.parse(required);
}

const choicesLengthPredicate = s.number.le(25);

export function validateChoicesLength(amountAdding: number, choices?: APIApplicationCommandOptionChoice[]): void {
	choicesLengthPredicate.parse((choices?.length ?? 0) + amountAdding);
}

export function assertReturnOfBuilder<
	T extends ApplicationCommandOptionBase | SlashCommandSubcommandBuilder | SlashCommandSubcommandGroupBuilder,
>(input: unknown, ExpectedInstanceOf: new () => T): asserts input is T {
	const instanceName = ExpectedInstanceOf.name;

	if (is.nullOrUndefined(input)) {
		throw new TypeError(
			`Expected to receive a ${instanceName} builder, got ${input === null ? 'null' : 'undefined'} instead.`,
		);
	}

	if (is.primitive(input)) {
		throw new TypeError(`Expected to receive a ${instanceName} builder, got a primitive (${typeof input}) instead.`);
	}

	if (!(input instanceof ExpectedInstanceOf)) {
		const casted = input as Record<PropertyKey, unknown>;

		const constructorName = is.function_(input) ? input.name : casted.constructor.name;
		const stringTag = Reflect.get(casted, Symbol.toStringTag) as string | undefined;

		const fullResultName = stringTag ? `${constructorName} [${stringTag}]` : constructorName;

		throw new TypeError(`Expected to receive a ${instanceName} builder, got ${fullResultName} instead.`);
	}
}