import { createContext, useCallback, useContext, useMemo, useState, type ReactNode } from "react";

interface UnreadContextValue {
  hasUnread: boolean; // 推播觸發的提示 或 任一房間有未讀，兩者只要有一個成立即為 true
  markUnread: () => void; // Q-4：收到推播時呼叫
  markRead: () => void; // Q-4：使用者切回聊天分頁時呼叫，只清推播提示，不動各房未讀數
  roomUnreadCounts: Record<string, number>; // T20-P2：各進行中房間的未讀數（來自大廳聚合查詢）
  setRoomUnreadCounts: (counts: Record<string, number>) => void;
  totalRoomUnread: number;
}

const UnreadContext = createContext<UnreadContextValue | null>(null);

// Q-4：聊天分頁的未讀／推播提示紅點狀態，由根佈局的推播接收監聽器寫入，
// 由聊天分頁在取得焦點時清除（見 app/(tabs)/index.tsx 的 useFocusEffect）。
// T20-P2：擴充承接大廳多房未讀——分頁籤紅點現在同時反映「有推播尚未看」與「任一房間有未讀訊息」，
// 兩個來源各自獨立更新，互不覆蓋（推播清除不會把房間未讀數也清空，反之亦然）。
export function UnreadProvider({ children }: { children: ReactNode }) {
  const [pushUnread, setPushUnread] = useState(false);
  const [roomUnreadCounts, setRoomUnreadCounts] = useState<Record<string, number>>({});
  const markUnread = useCallback(() => setPushUnread(true), []);
  const markRead = useCallback(() => setPushUnread(false), []);
  const totalRoomUnread = useMemo(
    () => Object.values(roomUnreadCounts).reduce((sum, count) => sum + count, 0),
    [roomUnreadCounts],
  );
  const hasUnread = pushUnread || totalRoomUnread > 0;

  return (
    <UnreadContext.Provider
      value={{ hasUnread, markUnread, markRead, roomUnreadCounts, setRoomUnreadCounts, totalRoomUnread }}
    >
      {children}
    </UnreadContext.Provider>
  );
}

export function useUnread(): UnreadContextValue {
  const ctx = useContext(UnreadContext);
  if (!ctx) {
    throw new Error("useUnread 必須在 UnreadProvider 底下使用");
  }
  return ctx;
}