import { useCallback, useEffect, useState } from "react";

const PREFIX = "plate-dyn:";

/** React state mirrored into localStorage under `key`. `validate` rejects stale shapes. */
export function usePersistentState<T>(
  key: string,
  initial: () => T,
  validate?: (v: unknown) => v is T,
): [T, (v: T | ((prev: T) => T)) => void, () => void] {
  const full = PREFIX + key;
  const [value, setValue] = useState<T>(() => {
    try {
      const raw = localStorage.getItem(full);
      if (raw !== null) {
        const parsed: unknown = JSON.parse(raw);
        if (!validate || validate(parsed)) return parsed as T;
      }
    } catch {
      /* fall back to the default */
    }
    return initial();
  });
  useEffect(() => {
    try {
      localStorage.setItem(full, JSON.stringify(value));
    } catch {
      /* storage unavailable: state simply does not persist */
    }
  }, [full, value]);
  const reset = useCallback(() => setValue(initial()), [initial]);
  return [value, setValue, reset];
}

/** Forget everything the lab has stored in this browser. */
export function clearPersistentState(): void {
  try {
    const keys: string[] = [];
    for (let i = 0; i < localStorage.length; i++) {
      const k = localStorage.key(i);
      if (k && k.startsWith(PREFIX)) keys.push(k);
    }
    keys.forEach((k) => localStorage.removeItem(k));
  } catch {
    /* ignore */
  }
}