import { Event } from "eventery";
/**
 * A class wrapping an array of entities of a specific type, providing
 * performance-optimized methods for adding, looking up and removing entities, and events
 * for when entities are added or removed.
 */
export declare class Bucket<E> implements Iterable<E> {
    protected _entities: E[];
    protected _version: number;
    /**
     * The current version of the bucket. Increases every time an entity is
     * added or removed.
     */
    get version(): number;
    /**
     * An array of all entities within the bucket. Please note that for iterating
     * over the entities in this bucket, it is recommended that you use the
     * `for (const entity of bucket)` iterator form.
     */
    get entities(): E[];
    [Symbol.iterator](): {
        next: () => {
            value: E;
            done: boolean;
        };
    };
    constructor(_entities?: E[]);
    /**
     * Fired when an entity has been added to the bucket.
     */
    onEntityAdded: Event<[entity: E]>;
    /**
     * Fired when an entity is about to be removed from the bucket.
     */
    onEntityRemoved: Event<[entity: E]>;
    /**
     * A map of entity positions, used for fast lookups.
     */
    private entityPositions;
    /**
     * Returns the total size of the bucket, i.e. the number of entities it contains.
     */
    get size(): number;
    /**
     * Returns the first entity in the bucket, or `undefined` if the bucket is empty.
     */
    get first(): E | undefined;
    /**
     * Returns true if the bucket contains the given entity.
     *
     * @param entity The entity to check for.
     * @returns `true` if the specificed entity is in this bucket, `false` otherwise.
     */
    has(entity: any): entity is E;
    /**
     * Adds the given entity to the bucket. If the entity is already in the bucket, it is
     * not added again.
     *
     * @param entity The entity to add to the bucket.
     * @returns The entity passed into this function (regardless of whether it was added or not).
     */
    add<D extends E>(entity: D): D & E;
    /**
     * Removes the given entity from the bucket. If the entity is not in the bucket, nothing
     * happens.
     *
     * @param entity The entity to remove from the bucket.
     * @returns The entity passed into this function (regardless of whether it was removed or not).
     */
    remove(entity: E): E;
    /**
     * Removes all entities from the bucket. Will cause the `onEntityRemoved` event to be
     * fired for each entity.
     */
    clear(): void;
}