export const eq = (a, b) => {
	if (a === b) {
		return true;
	}

	if (a === null || b === null) {
		return false;
	}

	if (typeof a != "object" || typeof b != "object") {
		return false;
	}

	if (Array.isArray(a) !== Array.isArray(b)) {
		return false;
	}

	if (Object.keys(a).length !== Object.keys(b).length) {
		return false;
	}

	for (const k in a) {
		if (!b.hasOwnProperty(k)) {
			return false;
		}
		if (!eq(a[k], b[k])) {
			return false;
		}
	}

	return true;
};

export const keys = (ks, obj) =>
	ks.reduce(
		(ret, k) =>
			obj.hasOwnProperty(k) ?  {...ret, [k]: obj[k]} : ret,
		{},
	);

export const difference = (a, b) => {
	const diff = new Set(a);
	for (const el of b) {
		diff.delete(el);
	}
	return diff;
};

export const assocIn = (obj, path, value) =>
	path.length === 0 ?  obj :
		path.length === 1 ? { ...obj, [path[0]]: value } :
			{
				...obj,
				[path[0]]: assocIn(
					(obj[path[0]] || {}),
					path.slice(1),
					value
				)
			};

export const getIn = (obj, path) =>
	path.length === 0 ? obj :
		getIn(obj?.[path[0]], path.slice(1));

export const first = (arr, fn) => {
	for (const x of arr) {
		const ret = fn(x);
		if (ret) {
			return ret;
		}
	}

	return null;
};

export const promisify = fn => (...args) =>
	new Promise((resolve, reject) =>
		fn(...args, (err, data) => err ? reject(err) : resolve(data)));