import { ResourceUri } from "@atcute/lexicons";

interface StateObj {
  like?: ResourceUri | false;
  repost?: ResourceUri | false;
  bookmark?: boolean;
}

export type InteractionType = keyof StateObj;

export class InteractionCache {
  #state = new Map<ResourceUri, StateObj>();
  #optimisticState = new Map<ResourceUri, StateObj>();

  get(uri: ResourceUri) {
    return this.#state.get(uri);
  }

  addOptimistic(type: InteractionType, uri: ResourceUri, interaction: ResourceUri | boolean) {
    this.#getAndSet(this.#optimisticState, uri, (val) => {
      val ??= {};
      val[type] = interaction as any;
      return val;
    });
  }

  override(type: InteractionType, uri: ResourceUri, interaction: ResourceUri | boolean) {
    this.#getAndSet(this.#state, uri, (val) => {
      val ??= {};
      val[type] = interaction as any;
      return val;
    });
    this.discard(type, uri);
  }

  commit(type: InteractionType, uri: ResourceUri) {
    if (this.#optimisticState.has(uri)) {
      this.override(type, uri, this.#optimisticState.get(uri)![type]!);
    }
  }

  discard(type: InteractionType, uri: ResourceUri) {
    const newVal = this.#getAndSet(this.#optimisticState, uri, (val) => {
      val ??= {};
      val[type] = undefined;
      return val;
    });

    if (!Object.values(newVal).reduce((a, b) => a || b)) {
      this.#optimisticState.delete(uri);
    }
  }

  #getAndSet<T, U extends object>(map: Map<T, U>, key: T, fun: (val: U | undefined) => U): U {
    const newVal = fun(map.get(key));
    map.set(key, newVal);
    return newVal;
  }
}