import { PeerId, Primitive, Tid } from "../common.ts";

export class TinyLWW<Shape extends Record<string, Primitive>> {
  values: Partial<Shape> = {};
  lastWriters = new Map<keyof Shape, PeerId>();
  clock = new Map<PeerId, Tid>();

  set<K extends keyof Shape, V extends Shape[K]>(
    key: K,
    value: V,
    from: PeerId,
    at?: Tid,
  ): boolean {
    const lastWriter = this.lastWriters.get(key);
    at ??= lastWriter ? this.clock.get(lastWriter) : undefined;
    at ??= -1;

    if (lastWriter !== undefined && (this.clock.get(lastWriter) ?? -1) >= at) return false;
    if ((this.clock.get(from) ?? -1) >= at) return false;

    this.values[key] = value;
    this.clock.set(from, at);
    this.lastWriters.set(key, from);

    return true;
  }

  get<K extends keyof Shape>(key: K): Shape[K] | undefined {
    return this.values[key];
  }
}