index.ts

export type OptionDefinitions = {
	name: string;
	type: (t: unknown) => unknown;
	aliases?: string[];
	default?: boolean;
}[];

export interface Result {
	_unknown: {
		_?: string;
		[key: string]: unknown;
	};
	[key: string]: unknown;
}

export function bargs(
	options: OptionDefinitions,
	argv: string[] = process.argv.slice(2),
): Result {
	if (options.filter((i) => i.default).length > 1)
		throw new Error("More than one default option is not allowed");
	const result: Result = { _unknown: {} };
	const aliases: { [alias: string]: string } = {};
	const splitargv = argv
		.join(" ")
		.split(/((--?))(?=\w)/g)
		.filter((i) => !!i && i != "-" && i != "--")
		.map((i) => i.trim());
	for (const index in options) {
		const option = options[index];
		if (!option.name)
			throw new Error("Option name should not be an empty string");
		if (!option.aliases || !option.aliases.length) continue;
		for (const alias of option.aliases as string[]) {
			aliases[alias] = option.name;
		}
	}
	for (const key of splitargv) {
		const split = key.split(" ");
		let name = split.shift() as string;
		if (!argv.includes("-" + name) && !argv.includes("--" + name)) {
			const defaultOption = options.find((option) => option.default);
			if (defaultOption)
				result[defaultOption.name] = defaultOption.type(key);
			else result._unknown._ = key;
		} else {
			if (aliases[name]) name = aliases[name] as string;
			const option = options.find((option) => option.name == name);
			const value = split.join(" ") || true;
			if (!option) result._unknown[name] = value;
			else result[name] = option.type(value);
		}
	}
	return result;
}