import { useCallback, useEffect, useRef, useState, type ReactNode } from 'react';

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

export interface ToastState {
  id: string;
  message: string;
  variant: ToastVariant;
  title?: string;
  actionLabel?: string;
  onAction?: () => void;
  visual?: ReactNode;
}

export interface ShowToastOptions {
  /** 同じ ID の通知は更新し、重複して積まない。 */
  id?: string;
  title?: string;
  actionLabel?: string;
  onAction?: () => void;
  visual?: ReactNode;
}

let nextToastId = 0;

/**
 * 画面内通知のキュー。既存の `toast` は後方互換のため最新1件を返す。
 * 同じ ID は置き換えるため、ポーリング由来の重複通知を表示しない。
 */
export function useToast(durationMs = 3500) {
  const [toasts, setToasts] = useState<ToastState[]>([]);
  const timers = useRef(new Map<string, ReturnType<typeof setTimeout>>());

  const dismissToast = useCallback((id: string) => {
    const timer = timers.current.get(id);
    if (timer) clearTimeout(timer);
    timers.current.delete(id);
    setToasts(current => current.filter(toast => toast.id !== id));
  }, []);

  const showToast = useCallback((message: string, variant: ToastVariant = 'success', options: ShowToastOptions = {}) => {
    const id = options.id ?? `toast-${++nextToastId}`;
    const timer = timers.current.get(id);
    if (timer) clearTimeout(timer);
    const toast: ToastState = { id, message, variant, title: options.title, actionLabel: options.actionLabel, onAction: options.onAction, visual: options.visual };
    setToasts(current => [...current.filter(item => item.id !== id), toast]);
    timers.current.set(id, setTimeout(() => dismissToast(id), durationMs));
  }, [dismissToast, durationMs]);

  useEffect(() => () => {
    timers.current.forEach(clearTimeout);
    timers.current.clear();
  }, []);

  const latest = toasts.at(-1);
  // Legacy consumers only expect these two properties.
  const toast = latest ? { message: latest.message, variant: latest.variant } : null;
  return { toast, toasts, showToast, dismissToast };
}