React Hooks 系统

// useCanUseTool: 权限校验 Hook
// 从全局 state 读取 permissions，检查当前工具是否可用
export function useCanUseTool(toolName: string, input?: ToolInput) {
  const permissions = useStore((s) => s.permissions);
  const enabledTools = useStore((s) => s.enabledTools);

  const canUse = useMemo(() => {
    // 1. 检查工具是否在启用列表中
    if (!enabledTools.includes(toolName)) return false;

    // 2. 检查权限策略
    const policy = permissions[toolName];
    if (policy === 'allow') return true;
    if (policy === 'deny') return false;

    // 3. ask 模式下检查用户是否已授权
    return isPreApproved(toolName, input);
  }, [toolName, input, permissions, enabledTools]);

  return { canUse, requestPermission: () => requestToolAccess(toolName) };
}

// useVirtualScroll: 虚拟滚动核心算法
// 只渲染可视区域内的列表项，O(n) → O(viewport)
export function useVirtualScroll<T>(items: T[], itemHeight: number, containerHeight: number) {
  const [scrollTop, setScrollTop] = useState(0);

  // 计算可见范围
  const { startIndex, endIndex, visibleItems, totalHeight } = useMemo(() => {
    const totalHeight = items.length * itemHeight;
    const startIndex = Math.max(0, Math.floor(scrollTop / itemHeight) - BUFFER_SIZE);
    const endIndex = Math.min(
      items.length - 1,
      Math.ceil((scrollTop + containerHeight) / itemHeight) + BUFFER_SIZE
    );
    const visibleItems = items.slice(startIndex, endIndex + 1);
    return { startIndex, endIndex, visibleItems, totalHeight };
  }, [items, scrollTop, itemHeight, containerHeight]);

  const offsetY = startIndex * itemHeight; // 顶部偏移量
  return { visibleItems, totalHeight, offsetY, setScrollTop };
}

const BUFFER_SIZE = 3; // 上下缓冲区大小

// useMemoizedCallbacks: 稳定回调引用
// 通过 ref + useMemo 确保回调集合在依赖不变时返回相同引用
export function useMemoizedCallbacks<T extends Record<string, (...args: any[]) => any>>(
  callbacks: T,
  deps: DependencyList
): T {
  const callbacksRef = useRef(callbacks);
  callbacksRef.current = callbacks;

  const memoized = useMemo(() => {
    return Object.fromEntries(
      Object.entries(callbacks).map(([key, fn]) => [
        key,
        (...args: any[]) => callbacksRef.current[key](...args)
      ])
    ) as T;
    // eslint-disable-next-line react-hooks/exhaustive-deps
  }, deps);

  return memoized;
}