jecs/src/index.d.ts

type Query<T extends unknown[]> = {
  without: (...components: Entity[]) => Query<T>;
} & IterableFunction<LuaTuple<[Entity, ...T]>>;

// Utility Types
export type Entity<T = unknown> = number & { __nominal_type_dont_use: T };
export type EntityType<T> = T extends Entity<infer A> ? A : never;
export type InferComponents<A extends Entity[]> = {
  [K in keyof A]: EntityType<A[K]>;
};
type Nullable<T extends unknown[]> = {
  [K in keyof T]: T[K] | undefined;
};

export class World {
  /**
   * Creates a new World
   */
  constructor();

  /**
   * Creates a new entity
   * @returns Entity
   */
  entity(): Entity;

  /**
   * Creates a new entity located in the first 256 ids.
   * These should be used for static components for fast access.
   * @returns Entity<T>
   */
  component<T = unknown>(): Entity<T>;

  /**
   * Gets the target of a relationship. For example, when a user calls
   * `world.target(id, ChildOf(parent))`, you will obtain the parent entity.
   * @param id Entity
   * @param relation The Relationship
   * @returns The Parent Entity if it exists
   */
  target(id: Entity, relation: Entity): Entity | undefined;

  /**
   * Deletes an entity and all its related components and relationships.
   * @param id Entity to be destroyed
   */
  delete(id: Entity): void;

  /**
   * Adds a component to the entity with no value
   * @param id Target Entity
   * @param component Component
   */
  add<T>(id: Entity, component: Entity<T>): void;

  /**
   * Assigns a value to a component on the given entity
   * @param id Target Entity
   * @param component Target Component
   * @param data Component Data
   */
  set<T>(id: Entity, component: Entity<T>, data: T): void;

  /**
   * Removes a component from the given entity
   * @param id Target Entity
   * @param component Target Component
   */
  remove(id: Entity, component: Entity): void;

  // Manually typed out get since there is a hard limit.

  /**
   * Retrieves the value of one component. This value may be undefined.
   * @param id Target Entity
   * @param component Target Component
   * @returns Data associated with the component if it exists
   */
  get<A>(id: number, component: Entity<A>): A | undefined;

  /**
   * Retrieves the value of two components. This value may be undefined.
   * @param id Target Entity
   * @param component Target Component 1
   * @param component2 Target Component 2
   * @returns Data associated with the components if it exists
   */
  get<A, B>(
    id: number,
    component: Entity<A>,
    component2: Entity<B>
  ): LuaTuple<Nullable<[A, B]>>;

  /**
   * Retrieves the value of three components. This value may be undefined.
   * @param id Target Entity
   * @param component Target Component 1
   * @param component2 Target Component 2
   * @param component3 Target Component 3
   * @returns Data associated with the components if it exists
   */
  get<A, B, C>(
    id: number,
    component: Entity<A>,
    component2: Entity<B>,
    component3: Entity<C>
  ): LuaTuple<Nullable<[A, B, C]>>;

  /**
   * Retrieves the value of four components. This value may be undefined.
   * @param id Target Entity
   * @param component Target Component 1
   * @param component2 Target Component 2
   * @param component3 Target Component 3
   * @param component4 Target Component 4
   * @returns Data associated with the components if it exists
   */
  get<A, B, C, D>(
    id: number,
    component: Entity<A>,
    component2: Entity<B>,
    component3: Entity<C>,
    component4: Entity<D>
  ): LuaTuple<Nullable<[A, B, C, D]>>;

  /**
   * Searches the world for entities that match a given query
   * @param components Queried Components
   * @returns Iterable function
   */
  query<T extends Entity[]>(...components: T): Query<InferComponents<T>>;
}

/**
 * Creates a composite key.
 * @param pred The first entity
 * @param obj The second entity
 * @returns The composite key
 */
export const pair: (pred: Entity, obj: Entity) => Entity;

/**
 * Checks if the entity is a composite key
 * @param e The entity to check
 * @returns If the entity is a pair
 */
export const IS_PAIR: (e: Entity) => boolean;

export const OnAdd: Entity;
export const OnRemove: Entity;
export const OnSet: Entity;
export const Wildcard: Entity;
export const Rest: Entity;