boardgame-core/src/utils/entity.ts

import {Signal, signal, SignalOptions} from "@preact/signals-core";
import {create} from 'mutative';

export class Entity<T> extends Signal<T> {
  public constructor(public readonly id: string, t?: T, options?: SignalOptions<T>) {
    super(t, options);
  }
  produce(fn: (draft: T) => void) {
    this.value = create(this.value, fn);
  }
}

export function entity<T = undefined>(id: string, t?: T, options?: SignalOptions<T>) {
  return new Entity<T>(id, t, options);
}

export type EntityCollection<T> = {
  collection: Signal<Record<string, Entity<T>>>;
  remove(...ids: string[]): void;
  add(...entities: (T & {id: string})[]): void;
  get(id: string): Entity<T>;
}

export function createEntityCollection<T>(): EntityCollection<T> {
  const collection = signal({} as Record<string, Entity<T>>);
  const remove = (...ids: string[]) => {
    collection.value = Object.fromEntries(
        Object.entries(collection.value).filter(([id]) => !ids.includes(id)),
    );
  };

  const add = (...entities: (T & {id: string})[]) => {
    collection.value = {
      ...collection.value,
      ...Object.fromEntries(entities.map((e) => [e.id, entity(e.id, e)])),
    };
  };

  const get = (id: string) => collection.value[id];

  return {
    collection,
    remove,
    add,
    get
  }
}