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

/**
 * App-wide toast notifications (issue #130). One provider near the root owns
 * the stack; `useToast()` hands out a fire-and-forget `showToast`. Toasts are
 * announced politely (`aria-live` on the stack container), stack bottom
 * center above the footer, and dismiss themselves — clicking one dismisses
 * it early. The plugin host's `ui.toast` capability feeds the same stack.
 */

export type ToastVariant = 'success' | 'error';

export type ShowToast = (message: string, variant?: ToastVariant) => void;

interface ToastItem {
  id: number;
  message: string;
  variant: ToastVariant;
}

// 6 s statt 2,5 s (issue #170, WCAG 2.2.1): kurzlebige Statusmeldungen
// waren für Screenreader-/Vergrößerungs-Nutzer kaum erfassbar.
const TOAST_DURATION_MS = 6000;

const ToastContext = createContext<ShowToast>(() => {});

export function useToast(): ShowToast {
  return useContext(ToastContext);
}

export function ToastProvider({ children }: { children: React.ReactNode }): React.JSX.Element {
  const [toasts, setToasts] = useState<ToastItem[]>([]);
  const nextId = useRef(0);

  const dismiss = useCallback((id: number): void => {
    setToasts((prev) => prev.filter((toast) => toast.id !== id));
  }, []);

  const showToast = useCallback<ShowToast>(
    (message, variant = 'success') => {
      nextId.current += 1;
      const id = nextId.current;
      setToasts((prev) => [...prev, { id, message, variant }]);
      window.setTimeout(() => dismiss(id), TOAST_DURATION_MS);
    },
    [dismiss],
  );

  return (
    <ToastContext.Provider value={showToast}>
      {children}
      {/* The live region exists permanently, so screen readers pick up
          toasts added to it; individual toasts must not carry their own
          role="status" (a region appearing WITH its content isn't read).
          Deliberately aria-live WITHOUT role="status": the region is
          global and always mounted, and a second status role broke every
          page-scoped getByRole('status') locator (legal.spec, CI). */}
      <div className="toast-stack" aria-live="polite">
        {toasts.map((toast) => (
          <div
            key={toast.id}
            className={`toast toast--${toast.variant}`}
            onClick={() => dismiss(toast.id)}
          >
            {toast.message}
          </div>
        ))}
      </div>
    </ToastContext.Provider>
  );
}