import { createContext, useContext, useEffect, useRef, type ReactNode } from "react";
import { WorkerRunner, type Runner } from "@plate-dyn/core";

const RunnerContext = createContext<Runner | null>(null);

/**
 * Provides one numbl runner to a tree of components. By default a WorkerRunner
 * is created lazily; pass `runner` to share or substitute one.
 */
export function RunnerProvider({ children, runner }: { children: ReactNode; runner?: Runner }) {
  const ref = useRef<Runner | null>(null);
  if (!ref.current) ref.current = runner ?? new WorkerRunner();
  useEffect(() => {
    const r = ref.current;
    return () => {
      // Dispose terminates the worker; the runner recreates one on the next run,
      // so React StrictMode's mount-unmount-mount cycle is harmless.
      r?.dispose();
    };
  }, []);
  return <RunnerContext.Provider value={ref.current}>{children}</RunnerContext.Provider>;
}

export function useRunner(): Runner {
  const r = useContext(RunnerContext);
  if (!r) throw new Error("useRunner must be used inside a RunnerProvider");
  return r;
}