import type { Component, ComponentConstructor } from "./Component";
export declare type EntityID = string | number;
export declare class Entity {
    static readonly isEntity = true;
    id: EntityID;
    private map;
    constructor(id?: EntityID | {
        id: EntityID;
    });
    /**
     * If `klass` is not passed, returns all components on `this`. Otherwise,
     * returns the components of type `C` on `this`.
     */
    get<K extends ComponentConstructor>(klass?: K): ReadonlyArray<InstanceType<K> | undefined>;
    /**
     * Adds `component` to `this`.
     */
    add<K extends ComponentConstructor, C extends InstanceType<K>>(klass: K, component: C): void;
    has<K extends ComponentConstructor>(klass: K): boolean;
    /**
     * If no argument is passed, all components are cleared. If a constructor is
     * passed, all components of that type are cleared. If a specific component
     * is passed, that component is cleared.
     */
    clear<T extends Component | ComponentConstructor>(arg?: T): boolean;
    get components(): Component[];
    toJSON(): {
        id: EntityID;
        components: ReturnType<Component["toJSON"]>[];
        [key: string]: unknown;
    };
    static fromJSON({ components, ...rest }: ReturnType<Entity["toJSON"]>): Entity;
}