import React, { createContext, useCallback, useContext, useMemo, useRef, useState } from 'react';

/**
 * Carries "the user clicked a virtual Layers row -- scroll that array item's
 * card into view" from the Layers panel (left) to the array editors (right).
 *
 * Deliberately a request, not a command: consumers that don't implement
 * scrolling simply ignore it. Selecting the parent node always happens in
 * LayersPanel itself, so a click is useful even with no consumer at all.
 */

export interface LayerFocusRequest {
  nodeId: string;
  prop: string;
  index: number;
  /** Bumped on every request so an identical repeat still re-fires effects. */
  nonce: number;
}

export interface LayerFocusValue {
  focus: LayerFocusRequest | null;
  requestFocus(nodeId: string, prop: string, index: number): void;
}

const LayerFocusContext = createContext<LayerFocusValue>({
  focus: null,
  requestFocus: () => {},
});

export const useLayerFocus = (): LayerFocusValue => useContext(LayerFocusContext);

export const LayerFocusProvider: React.FC<{ children: React.ReactNode }> = ({ children }) => {
  const [focus, setFocus] = useState<LayerFocusRequest | null>(null);
  const nonceRef = useRef(0);

  const requestFocus = useCallback((nodeId: string, prop: string, index: number) => {
    nonceRef.current += 1;
    setFocus({ nodeId, prop, index, nonce: nonceRef.current });
  }, []);

  const value = useMemo(() => ({ focus, requestFocus }), [focus, requestFocus]);

  return <LayerFocusContext.Provider value={value}>{children}</LayerFocusContext.Provider>;
};