[wip] so close; check the ws messages

pkg/shared/kefirs.ts

@@ -0,0 +1,52 @@
+import { merge, Observable } from "kefir";
+import Bus from "kefir-bus";
+
+export type ValueWithin<O extends Observable<any, any>> = Parameters<
+	Parameters<O["map"]>[0]
+>[0];
+
+type Mutation<A, O extends Observable<any, any>> = [
+	O,
+	(prev: A, value: ValueWithin<O>) => A
+];
+
+export const multiScan = <A, M extends Mutation<A, any>[]>(
+	initValue: A,
+	...mutations: M
+): Observable<A, any> =>
+	merge(
+		mutations.map(([source, mutation]) =>
+			source.map((event) => ({ event, mutation }))
+		)
+	).scan((prev, { event, mutation }) => mutation(prev, event), initValue);
+
+export const partition = <
+	C extends readonly [...string[]],
+	T extends { [key: string]: any },
+	E
+>(
+	classes: C,
+	obs: Observable<T, E>
+) => {
+	const classBuses = Object.fromEntries(classes.map((c) => [c, Bus()]));
+	obs.onValue((v) => {
+		for (const _class of classes) {
+			if (_class in v) {
+				classBuses[_class].emit(v);
+				return;
+			}
+		}
+	});
+	return classBuses;
+};
+
+export const isEmpty = (container: { length: number }) => container.length == 0;
+
+export const setDiff = <T>(
+	sets: [Set<T>, s2: Set<T>]
+): { added: T[]; removed: T[] } => ({
+	added: [...sets[1].difference(sets[0])],
+	removed: [...sets[0].difference(sets[1])],
+});
+
+export const set = <T>(arr: T[]) => new Set<T>(arr);