/**
 * Minimal typed event emitter used to expose chart events to consumers
 *
 * Dispatch is synchronous: handlers run inside the originating call stack, so a
 * listener can read getConfig() / getData() and observe fully committed state.
 * Note that the sibling sankey library dispatches on a microtask instead, since
 * its internal event bus predates this API.
 */
export type EventListener<TPayload> = (payload: TPayload) => void;
export declare class EventEmitter<TEventMap extends Record<string, unknown>> {
    private listeners;
    /**
     * Register a listener for an event
     * Returns an unsubscribe function, which is idempotent
     */
    on<K extends keyof TEventMap>(event: K, listener: EventListener<TEventMap[K]>): () => void;
    /**
     * Register a listener that is removed after its first invocation
     * Returns an unsubscribe function that cancels it before it fires
     */
    once<K extends keyof TEventMap>(event: K, listener: EventListener<TEventMap[K]>): () => void;
    /**
     * Remove a listener, or every listener for the event when none is given
     */
    off<K extends keyof TEventMap>(event: K, listener?: EventListener<TEventMap[K]>): void;
    /**
     * Dispatch an event synchronously to all listeners
     */
    emit<K extends keyof TEventMap>(event: K, payload: TEventMap[K]): void;
    /**
     * Number of listeners registered for an event
     */
    listenerCount(event: keyof TEventMap): number;
    /**
     * Remove every listener
     */
    clear(): void;
    private addListener;
}
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