import { useCallback, useEffect, useRef, useState } from "react";
import useSWR from "swr";
import type { AgentApiClient } from "../api/client";

export function useAgentMessageInbox(client: AgentApiClient, sessionId: string | null) {
  const inbox = useSWR(sessionId ? ["agent-message-inbox", sessionId] : null,
    ([, id]) => client.listAgentMessages(id), { revalidateOnMount: false, revalidateOnFocus: true, shouldRetryOnError: false });
  const [loadingMore, setLoadingMore] = useState(false);
  const mutate = inbox.mutate;
  const refresh = useCallback(() => { void mutate().catch(() => undefined); }, [mutate]);
  const refreshRef = useRef(refresh);
  useEffect(() => { refreshRef.current = refresh; }, [refresh]);
  useEffect(() => {
    if (!sessionId) return;
    const controller = new AbortController();
    let timer: ReturnType<typeof setTimeout> | undefined;
    let retryDelay = 1500;
    let initialized = false;
    // Prefer the initial stream notification, but do not wait indefinitely for its first frame.
    const initialLoadTimer = setTimeout(() => { initialized = true; refreshRef.current(); }, 1500);
    function subscribe() {
      void client.streamAgentMessages(sessionId!, { signal: controller.signal, onMessage: () => { initialized = true; clearTimeout(initialLoadTimer); retryDelay = 1500; refreshRef.current(); } })
        .catch(() => {
          // A failed subscription must not prevent the initial list from loading.
          if (!initialized && !controller.signal.aborted) { initialized = true; clearTimeout(initialLoadTimer); refreshRef.current(); }
          retryDelay = Math.min(retryDelay * 2, 30_000);
        })
        .finally(() => {
          if (!controller.signal.aborted) timer = setTimeout(subscribe, retryDelay);
        });
    }
    subscribe();
    return () => { controller.abort(); clearTimeout(timer); clearTimeout(initialLoadTimer); };
  }, [client, sessionId]);
  return {
    messages: inbox.data?.items ?? [],
    hasMore: Boolean(inbox.data?.next_cursor),
    loading: Boolean(sessionId) && (inbox.isLoading || (!inbox.data && !inbox.error)),
    error: inbox.error ? "任务消息暂时无法加载" : null,
    refresh,
    loadingMore,
    loadMore: async () => {
      if (!sessionId || !inbox.data?.next_cursor || loadingMore) return;
      setLoadingMore(true);
      try {
        const page = await client.listAgentMessages(sessionId, { cursor: inbox.data.next_cursor });
        await inbox.mutate((current) => current ? { items: [...current.items, ...page.items.filter((item) => !current.items.some((existing) => existing.message_id === item.message_id))], next_cursor: page.next_cursor } : page, { revalidate: false });
      } finally { setLoadingMore(false); }
    }
  };
}