import type { AIMessage, Message } from "@langchain/langgraph-sdk";
import type { ThreadsClient } from "@langchain/langgraph-sdk/client";
import { useStream } from "@langchain/langgraph-sdk/react";
import { useMutation, useQuery, useQueryClient } from "@tanstack/react-query";
import type { QueryClient } from "@tanstack/react-query";
import { useCallback, useEffect, useRef, useState } from "react";
import { useNavigate } from "react-router-dom";
import { toast } from "sonner";

import type { PromptInputMessage } from "@/components/ai-elements/prompt-input";

import { getAPIClient } from "../api";
import { apiFetch } from "../api";
import { getStoredAuth } from "../auth";
import { rememberAskTime } from "../chat-timestamps";
import { getBackendBaseURL, getLangGraphBaseURL } from "../config";
import { useI18n } from "../i18n/hooks";
import type { FileInMessage } from "../messages/utils";
import type { LocalSettings } from "../settings";
import { isThreadRagModeLocked, lockThreadRagMode, useLocalSettings } from "../settings";
import { useUpdateSubtask } from "../tasks/context";
import type { UploadedFileInfo } from "../uploads";
import { promptInputFilePartToFile, uploadFiles } from "../uploads";

import type { AgentThread, AgentThreadState } from "./types";

export type ToolEndEvent = {
  name: string;
  data: unknown;
};

export type ThreadStreamOptions = {
  threadId?: string | null | undefined;
  context: LocalSettings["context"];
  isMock?: boolean;
  assistantId?: string;
  /** 额外写到新建 thread 的 metadata（与 agent_id 合并）。
   *  任务深链用 `{ taskId }` 把对话挂到任务下（1:N），列表按 metadata.taskId 过滤。 */
  threadMetadata?: Record<string, unknown>;
  onStart?: (threadId: string) => void;
  onFinish?: (state: AgentThreadState) => void;
  onToolEnd?: (event: ToolEndEvent) => void;
};

type SendMessageOptions = {
  additionalKwargs?: Record<string, unknown>;
};

function normalizeStoredRunId(runId: string | null): string | null {
  if (!runId) {
    return null;
  }

  const trimmed = runId.trim();
  if (!trimmed) {
    return null;
  }

  const queryIndex = trimmed.indexOf("?");
  if (queryIndex >= 0) {
    const params = new URLSearchParams(trimmed.slice(queryIndex + 1));
    const queryRunId = params.get("run_id")?.trim();
    if (queryRunId) {
      return queryRunId;
    }
  }

  const pathWithoutQueryOrHash = trimmed.split(/[?#]/, 1)[0]?.trim() ?? "";
  if (!pathWithoutQueryOrHash) {
    return null;
  }

  const runsMarker = "/runs/";
  const runsIndex = pathWithoutQueryOrHash.lastIndexOf(runsMarker);
  if (runsIndex >= 0) {
    const runIdAfterMarker = pathWithoutQueryOrHash
      .slice(runsIndex + runsMarker.length)
      .split("/", 1)[0]
      ?.trim();
    if (runIdAfterMarker) {
      return runIdAfterMarker;
    }
    return null;
  }

  const segments = pathWithoutQueryOrHash
    .split("/")
    .map((segment) => segment.trim())
    .filter(Boolean);
  return segments.at(-1) ?? null;
}

function getRunMetadataStorage(): {
  getItem(key: `lg:stream:${string}`): string | null;
  setItem(key: `lg:stream:${string}`, value: string): void;
  removeItem(key: `lg:stream:${string}`): void;
} {
  return {
    getItem(key) {
      const normalized = normalizeStoredRunId(
        window.sessionStorage.getItem(key),
      );
      if (normalized) {
        window.sessionStorage.setItem(key, normalized);
        return normalized;
      }
      window.sessionStorage.removeItem(key);
      return null;
    },
    setItem(key, value) {
      const normalized = normalizeStoredRunId(value);
      if (normalized) {
        window.sessionStorage.setItem(key, normalized);
        return;
      }
      window.sessionStorage.removeItem(key);
    },
    removeItem(key) {
      window.sessionStorage.removeItem(key);
    },
  };
}

/**
 * 显式停止某会话「服务端正在跑」的 run。
 *
 * 注意：useStream / `thread.stop()` 只中断本地 SSE 监听，服务端 run 仍会继续跑。
 * 任务流程要求「开启新对话时老对话要停止」，所以这里读出 SDK 存在 sessionStorage
 * （``lg:stream:{threadId}``）里的 run id，调用 ``runs.cancel`` 真正取消后端 run，
 * 再清掉本地 reconnect 记录。已结束 / 不存在的 run 取消失败时静默忽略。
 */
export async function stopThreadRun(
  threadId: string | null | undefined,
): Promise<void> {
  if (!threadId || typeof window === "undefined") return;
  let runId: string | null = null;
  try {
    runId = normalizeStoredRunId(
      window.sessionStorage.getItem(`lg:stream:${threadId}`),
    );
  } catch {
    runId = null;
  }
  if (!runId) return;
  try {
    await getAPIClient().runs.cancel(threadId, runId);
  } catch {
    /* 已结束 / 不存在 / 网络错误等忽略 */
  }
  try {
    window.sessionStorage.removeItem(`lg:stream:${threadId}`);
  } catch {
    /* noop */
  }
}

function getStreamErrorMessage(error: unknown): string {
  if (typeof error === "string" && error.trim()) {
    return error;
  }
  if (error instanceof Error && error.message.trim()) {
    return error.message;
  }
  if (typeof error === "object" && error !== null) {
    const message = Reflect.get(error, "message");
    if (typeof message === "string" && message.trim()) {
      return message;
    }
    const nestedError = Reflect.get(error, "error");
    if (nestedError instanceof Error && nestedError.message.trim()) {
      return nestedError.message;
    }
    if (typeof nestedError === "string" && nestedError.trim()) {
      return nestedError;
    }
  }
  return "Request failed.";
}

/**
 * Detect "thread not found" / forbidden errors from the LangGraph SDK.
 *
 * Backend returns 404 both when a thread truly doesn't exist and when the
 * currently authenticated user doesn't own it — the SDK surfaces both as
 * ``HTTP 404: {"detail":"Thread <uuid> not found"}``. The most common cause
 * we see in practice is a stale tab whose URL still points at the previous
 * login session's thread. Raw-toasting the 404 just confuses the user, so
 * we re-frame it around the current login identity.
 */
function isThreadNotAccessibleError(message: string): boolean {
  const lowered = message.toLowerCase();
  // Backend now returns "not found" (no row + no checkpoint) and
  // "not accessible" (row owned by another user / stale login session) as
  // distinct details — both mean the current user can't use this thread.
  if (/thread\s+[\w-]{8,}\s+not\s+(found|accessible)/i.test(message)) {
    return true;
  }
  // Fallback: a bare 404/403 from the threads endpoint when the SDK has
  // wrapped the detail differently.
  return (
    (lowered.includes("http 404") || lowered.includes("http 403")) &&
    lowered.includes("thread")
  );
}

/**
 * Detect a "Run <id> not found" 404 from the LangGraph SDK.
 *
 * The SDK persists the in-flight run id under ``lg:stream:{threadId}`` in
 * sessionStorage and, on mount, auto-``joinStream``s it to resume a dropped
 * SSE. After a backend restart the in-memory run registry is gone, so the join
 * 404s — and the SDK only clears that key on reconnect *success*, never on
 * failure. So every switch back into the conversation re-fires the same 404.
 * We detect it here to clear the stale key ourselves and stay silent (the
 * conversation renders from history; there is nothing live to reconnect to).
 */
function isRunNotFoundError(message: string): boolean {
  return /run\s+[\w-]{8,}\s+not\s+found/i.test(message);
}

function buildCurrentUserLabel(): string {
  const auth = getStoredAuth();
  if (!auth) {
    return "未登录";
  }
  const email = auth.email?.trim();
  if (email) {
    return email;
  }
  const userId = auth.user_id?.trim();
  return userId ? userId : "未知用户";
}

export function useThreadStream({
  threadId,
  context,
  isMock,
  assistantId,
  threadMetadata,
  onStart,
  onFinish,
  onToolEnd,
}: ThreadStreamOptions) {
  const { t } = useI18n();
  const [localSettings] = useLocalSettings();
  // Track the thread ID that is currently streaming to handle thread changes during streaming
  const [onStreamThreadId, setOnStreamThreadId] = useState(() => threadId);
  // Ref to track current thread ID across async callbacks without causing re-renders,
  // and to allow access to the current thread id in onUpdateEvent
  const threadIdRef = useRef<string | null>(threadId ?? null);
  const startedRef = useRef(false);

  const listeners = useRef({
    onStart,
    onFinish,
    onToolEnd,
  });

  // Keep listeners ref updated with latest callbacks
  useEffect(() => {
    listeners.current = { onStart, onFinish, onToolEnd };
  }, [onStart, onFinish, onToolEnd]);

  useEffect(() => {
    const normalizedThreadId = threadId ?? null;
    if (!normalizedThreadId) {
      // Reset when the UI moves back to a brand new unsaved thread.
      startedRef.current = false;
      setOnStreamThreadId(normalizedThreadId);
    } else {
      setOnStreamThreadId(normalizedThreadId);
    }
    threadIdRef.current = normalizedThreadId;
  }, [threadId]);

  const _handleOnStart = useCallback((id: string) => {
    if (!startedRef.current) {
      listeners.current.onStart?.(id);
      startedRef.current = true;
    }
  }, []);

  const handleStreamStart = useCallback(
    (_threadId: string) => {
      threadIdRef.current = _threadId;
      _handleOnStart(_threadId);
    },
    [_handleOnStart],
  );

  const queryClient = useQueryClient();
  const updateSubtask = useUpdateSubtask();
  const navigate = useNavigate();
  const runMetadataStorageRef = useRef<
    ReturnType<typeof getRunMetadataStorage> | undefined
  >(undefined);

  if (
    typeof window !== "undefined" &&
    runMetadataStorageRef.current === undefined
  ) {
    runMetadataStorageRef.current = getRunMetadataStorage();
  }

  const thread = useStream<AgentThreadState>({
    client: getAPIClient(isMock),
    assistantId: assistantId ?? "lead_agent",
    threadId: onStreamThreadId,
    reconnectOnMount: runMetadataStorageRef.current
      ? () => runMetadataStorageRef.current!
      : false,
    fetchStateHistory: { limit: 1 },
    onCreated(meta) {
      handleStreamStart(meta.thread_id);
      setOnStreamThreadId(meta.thread_id);
      const metadataAgentId = context.agent_id ?? context.agent_name;
      const extraMetadata =
        threadMetadata && typeof threadMetadata === "object" ? threadMetadata : {};
      const metadata: Record<string, unknown> = {
        ...(metadataAgentId ? { agent_id: metadataAgentId } : {}),
        ...extraMetadata,
      };
      if (Object.keys(metadata).length > 0 && !isMock) {
        void getAPIClient()
          .threads.update(meta.thread_id, { metadata })
          .catch(() => ({}));
      }
    },
    onLangChainEvent(event) {
      if (event.event === "on_tool_end") {
        listeners.current.onToolEnd?.({
          name: event.name,
          data: event.data,
        });
      }
    },
    onUpdateEvent(data) {
      const updates: Array<Partial<AgentThreadState> | null> = Object.values(
        data || {},
      );
      for (const update of updates) {
        if (update && "title" in update && update.title) {
          const nextTitle = update.title;
          updateCachedThreadLists(queryClient, (threads) =>
            threads.map((t) =>
              t.thread_id === threadIdRef.current
                ? {
                    ...t,
                    values: {
                      ...t.values,
                      title: nextTitle,
                    },
                  }
                : t,
            ),
          );
        }
      }
    },
    onCustomEvent(event: unknown) {
      if (
        typeof event === "object" &&
        event !== null &&
        "type" in event &&
        event.type === "task_running"
      ) {
        const e = event as {
          type: "task_running";
          task_id: string;
          message: AIMessage;
        };
        updateSubtask({ id: e.task_id, latestMessage: e.message });
        return;
      }

      if (
        typeof event === "object" &&
        event !== null &&
        "type" in event &&
        event.type === "llm_retry" &&
        "message" in event &&
        typeof event.message === "string" &&
        event.message.trim()
      ) {
        const e = event as { type: "llm_retry"; message: string };
        toast(e.message);
        return;
      }

      // Context compression about to run a (blocking) summarization LLM call —
      // surface a transient hint so the wait before the answer streams isn't a
      // silent dead air. Emitted by DeerFlowSummarizationMiddleware.
      if (
        typeof event === "object" &&
        event !== null &&
        "type" in event &&
        event.type === "context_compacting" &&
        "message" in event &&
        typeof event.message === "string" &&
        event.message.trim()
      ) {
        const e = event as { type: "context_compacting"; message: string };
        toast(e.message);
      }
    },
    onError(error) {
      setOptimisticMessages([]);
      const message = getStreamErrorMessage(error);
      // A stale auto-reconnect ("Run <id> not found") after a backend restart:
      // drop the dirty ``lg:stream:{threadId}`` key so switching back into this
      // conversation stops re-firing the same 404, and render from history
      // silently — there is no live run to rejoin.
      if (isRunNotFoundError(message)) {
        const staleThreadId = threadIdRef.current ?? onStreamThreadId ?? null;
        if (staleThreadId && runMetadataStorageRef.current) {
          runMetadataStorageRef.current.removeItem(
            `lg:stream:${staleThreadId}`,
          );
        }
        return;
      }
      // A "thread not found" 404 almost always means the URL points at a
      // thread from a previous login session — either this tab outlived a
      // logout/re-login or the thread genuinely belongs to a different user.
      // Re-frame the error around the *current* logged-in identity and bounce
      // the user to a fresh chat instead of leaving them stuck on the stale
      // route looking at a raw HTTP 404.
      if (isThreadNotAccessibleError(message)) {
        const userLabel = buildCurrentUserLabel();
        toast.info(
          `当前登录用户为 ${userLabel}，原对话不存在或无权访问，正在为你刷新页面…`,
        );
        // Prefer staying inside an agent chat context when the user is on an
        // agent thread URL — otherwise fall back to the global new chat.
        const hash = typeof window !== "undefined" ? window.location.hash : "";
        const agentMatch = hash.match(/#\/page\/workspace\/agents\/([^/]+)\//);
        const iframeMatch = hash.match(/#\/page\/workspace\/chats_iframe\//);
        const target = agentMatch
          ? `/page/workspace/agents/${agentMatch[1]}/chats/new`
          : iframeMatch
            ? "/page/workspace/chats_iframe/new"
            : "/page/workspace/chats/new";
        // First navigate to a safe URL so the post-reload page lands on a
        // valid route. Then full-reload so TanStack Query cache, context
        // providers and any other state captured under the previous user's
        // identity get rebuilt against the current login.
        if (typeof window !== "undefined") {
          window.location.hash = target;
          window.setTimeout(() => {
            window.location.reload();
          }, 900);
        } else {
          navigate(target, { replace: true });
        }
        return;
      }
      toast.error(message);
    },
    onFinish(state) {
      listeners.current.onFinish?.(state.values);
      void queryClient.invalidateQueries({ queryKey: ["threads", "search"] });
    },
  });

  // Optimistic messages shown before the server stream responds
  const [optimisticMessages, setOptimisticMessages] = useState<Message[]>([]);
  const [isUploading, setIsUploading] = useState(false);
  const sendInFlightRef = useRef(false);
  // Carries the ask time of an in-flight send until the server-assigned human
  // message id shows up, so we can bind the timestamp to the real id (see the
  // reconciliation effect below). ``known`` is the set of human ids that
  // already existed at send time, used to spot the newly-arrived one.
  const pendingAskTimeRef = useRef<{ ts: string; known: Set<string> } | null>(
    null,
  );
  // Track message count before sending so we know when server has responded
  const prevMsgCountRef = useRef(thread.messages.length);

  // Keep a ref to the latest `thread` so the threadId-change effect can stop
  // an in-flight stream without re-running on every render that produces a
  // new `thread` identity.
  const threadStreamRef = useRef(thread);
  threadStreamRef.current = thread;

  // Reset thread-local pending UI state when the caller actually switches AWAY
  // from a thread (threadId becomes nullish). This is the "click 新对话 / open
  // a fresh chat" signal — abort the in-flight SSE and clear optimistic state.
  //
  // We deliberately do NOT reset on every threadId change. During a normal
  // "user just sent the first message on /chats/new" flow, useThreadStream
  // sees threadId transition from undefined (the landing state) to the
  // server-assigned thread id once onCreated fires. Stopping the stream and
  // clearing optimistic messages in that case is exactly what made submitted
  // questions visually disappear — the live run that just started would be
  // aborted by the very effect intended to reset stale state.
  useEffect(() => {
    if (threadId != null) {
      // Forward direction: starting or continuing with a real thread.
      // No reset needed; the upstream useStream will load history for this id.
      return;
    }
    const prevThread = threadStreamRef.current;
    if (prevThread?.isLoading) {
      try {
        prevThread.stop();
      } catch {
        // best-effort; nothing useful to do if the SDK fails to abort
      }
    }
    startedRef.current = false;
    sendInFlightRef.current = false;
    prevMsgCountRef.current = 0;
    setOptimisticMessages([]);
    setIsUploading(false);
  }, [threadId]);

  // Clear optimistic when server messages arrive (count increases)
  useEffect(() => {
    if (
      optimisticMessages.length > 0 &&
      thread.messages.length > prevMsgCountRef.current
    ) {
      setOptimisticMessages([]);
    }
  }, [thread.messages.length, optimisticMessages.length]);

  // Bind a just-sent question's ask time to the server-assigned human message
  // id once it appears. Persists to localStorage so the time shows on every
  // question and survives reloads, independent of the backend echoing it back.
  useEffect(() => {
    const pending = pendingAskTimeRef.current;
    if (!pending) return;
    for (const message of thread.messages) {
      if (
        message.type === "human" &&
        message.id &&
        !message.id.startsWith("opt-") &&
        !pending.known.has(message.id)
      ) {
        rememberAskTime(message.id, pending.ts);
        pendingAskTimeRef.current = null;
        break;
      }
    }
  }, [thread.messages]);

  const sendMessage = useCallback(
    async (
      threadId: string,
      message: PromptInputMessage,
      extraContext?: Record<string, unknown>,
      options?: SendMessageOptions,
    ) => {
      if (sendInFlightRef.current) {
        return;
      }
      sendInFlightRef.current = true;

      const text = message.text.trim();
      // Wall-clock time the question was asked. Stored on the human message so
      // the chat can show "几点提问" and have it survive a reload (it round-trips
      // through the checkpoint inside additional_kwargs, same as `files`).
      const clientTs = new Date().toISOString();
      // Remember which human messages already exist so the reconciliation
      // effect can bind ``clientTs`` to the new one once the server returns it.
      pendingAskTimeRef.current = {
        ts: clientTs,
        known: new Set(
          thread.messages
            .filter((m) => m.type === "human" && m.id)
            .map((m) => m.id as string),
        ),
      };

      // Capture current count before showing optimistic messages
      prevMsgCountRef.current = thread.messages.length;

      // Build optimistic files list with uploading status
      const optimisticFiles: FileInMessage[] = (message.files ?? []).map(
        (f) => ({
          filename: f.filename ?? "",
          size: 0,
          status: "uploading" as const,
        }),
      );

      const hideFromUI = options?.additionalKwargs?.hide_from_ui === true;
      const optimisticAdditionalKwargs = {
        ...options?.additionalKwargs,
        client_ts: clientTs,
        ...(optimisticFiles.length > 0 ? { files: optimisticFiles } : {}),
      };

      const newOptimistic: Message[] = [];
      if (!hideFromUI) {
        newOptimistic.push({
          type: "human",
          id: `opt-human-${Date.now()}`,
          content: text ? [{ type: "text", text }] : "",
          additional_kwargs: optimisticAdditionalKwargs,
        });
      }

      if (optimisticFiles.length > 0 && !hideFromUI) {
        // Mock AI message while files are being uploaded
        newOptimistic.push({
          type: "ai",
          id: `opt-ai-${Date.now()}`,
          content: t.uploads.uploadingFiles,
          additional_kwargs: { element: "task" },
        });
      }
      setOptimisticMessages(newOptimistic);

      // Only fire onStart immediately for an existing persisted thread.
      // Brand-new chats should wait for onCreated(meta.thread_id) so URL sync
      // uses the real server-generated thread id.
      if (threadIdRef.current) {
        _handleOnStart(threadId);
      }

      let uploadedFileInfo: UploadedFileInfo[] = [];

      try {
        // Upload files first if any
        if (message.files && message.files.length > 0) {
          setIsUploading(true);
          try {
            const filePromises = message.files.map((fileUIPart) =>
              promptInputFilePartToFile(fileUIPart),
            );

            const conversionResults = await Promise.all(filePromises);
            const files = conversionResults.filter(
              (file): file is File => file !== null,
            );
            const failedConversions = conversionResults.length - files.length;

            if (failedConversions > 0) {
              throw new Error(
                `Failed to prepare ${failedConversions} attachment(s) for upload. Please retry.`,
              );
            }

            if (!threadId) {
              throw new Error("Thread is not ready for file upload.");
            }

            if (files.length > 0) {
              const uploadResponse = await uploadFiles(threadId, files);
              uploadedFileInfo = uploadResponse.files;

              // Update optimistic human message with uploaded status + paths
              const uploadedFiles: FileInMessage[] = uploadedFileInfo.map(
                (info) => ({
                  filename: info.filename,
                  size: info.size,
                  path: info.virtual_path,
                  status: "uploaded" as const,
                }),
              );
              setOptimisticMessages((messages) => {
                if (messages.length > 1 && messages[0]) {
                  const humanMessage: Message = messages[0];
                  return [
                    {
                      ...humanMessage,
                      additional_kwargs: {
                        ...humanMessage.additional_kwargs,
                        files: uploadedFiles,
                      },
                    },
                    ...messages.slice(1),
                  ];
                }
                return messages;
              });
            }
          } catch (error) {
            const errorMessage =
              error instanceof Error
                ? error.message
                : "Failed to upload files.";
            toast.error(errorMessage);
            setOptimisticMessages([]);
            throw error;
          } finally {
            setIsUploading(false);
          }
        }

        // Build files metadata for submission (included in additional_kwargs)
        const filesForSubmit: FileInMessage[] = uploadedFileInfo.map(
          (info) => ({
            filename: info.filename,
            size: info.size,
            path: info.virtual_path,
            status: "uploaded" as const,
          }),
        );

        const ragModeEnabled =
          localSettings.display.ragModeEnabled || isThreadRagModeLocked(threadId);
        if (ragModeEnabled) {
          lockThreadRagMode(threadId);
        }

        const contextCompressionEnabled =
          localSettings.display.contextCompressionEnabled ?? false;

        const mergedContext = {
          ...context,
          ...extraContext,
        };

        await thread.submit(
          {
            messages: [
              {
                type: "human",
                content: [
                  {
                    type: "text",
                    text,
                  },
                ],
                additional_kwargs: {
                  ...options?.additionalKwargs,
                  client_ts: clientTs,
                  ...(filesForSubmit.length > 0
                    ? { files: filesForSubmit }
                    : {}),
                },
              },
            ],
          },
          {
            threadId: threadId,
            streamSubgraphs: true,
            streamResumable: true,
            config: {
              recursion_limit: 1000,
            },
            context: {
              ...mergedContext,
              thinking_enabled: mergedContext.mode !== "flash",
              is_plan_mode:
                mergedContext.mode === "pro" || mergedContext.mode === "ultra",
              subagent_enabled: mergedContext.mode === "ultra",
              reasoning_effort:
                mergedContext.reasoning_effort ??
                (mergedContext.mode === "ultra"
                  ? "high"
                  : mergedContext.mode === "pro"
                    ? "medium"
                    : mergedContext.mode === "thinking"
                      ? "low"
                      : undefined),
              memory_injection_enabled:
                mergedContext.memory_injection_enabled ?? true,
              rag_mode_enabled: ragModeEnabled,
              summarization_enabled: contextCompressionEnabled,
              thread_id: threadId,
            },
          },
        );
        void queryClient.invalidateQueries({ queryKey: ["threads", "search"] });
      } catch (error) {
        setOptimisticMessages([]);
        setIsUploading(false);
        throw error;
      } finally {
        sendInFlightRef.current = false;
      }
    },
    [thread, _handleOnStart, t.uploads.uploadingFiles, context, localSettings.display.ragModeEnabled, queryClient],
  );

  // Merge thread with optimistic messages for display
  const mergedThread =
    optimisticMessages.length > 0
      ? ({
          ...thread,
          messages: [...thread.messages, ...optimisticMessages],
        } as typeof thread)
      : thread;

  // 第 4 个返回值 `onStreamThreadId` = 底层 useStream 当前实际绑定的线程 id（新建/未保存时为 null）。
  // 调用方据此判断「流是否已切到全新线程」，避免在切换会话的那一帧把消息发进上一个会话
  // （submit 的 threadId 选项仅在 hook 线程为 null/undefined 时才生效）。
  return [mergedThread, sendMessage, isUploading, onStreamThreadId] as const;
}

export function useThreads(
  params: Parameters<ThreadsClient["search"]>[0] = {
    limit: 50,
    sortBy: "updated_at",
    sortOrder: "desc",
    select: ["thread_id", "updated_at", "values", "metadata"],
  },
) {
  const apiClient = getAPIClient();
  return useQuery<AgentThread[]>({
    queryKey: ["threads", "search", params],
    queryFn: async () => {
      const maxResults = params.limit;
      const initialOffset = params.offset ?? 0;
      const DEFAULT_PAGE_SIZE = 50;

      // Preserve prior semantics: if a non-positive limit is explicitly provided,
      // delegate to a single search call with the original parameters.
      if (maxResults !== undefined && maxResults <= 0) {
        const response =
          await apiClient.threads.search<AgentThreadState>(params);
        return response as AgentThread[];
      }

      const pageSize =
        typeof maxResults === "number" && maxResults > 0
          ? Math.min(DEFAULT_PAGE_SIZE, maxResults)
          : DEFAULT_PAGE_SIZE;

      const threads: AgentThread[] = [];
      let offset = initialOffset;

      while (true) {
        if (typeof maxResults === "number" && threads.length >= maxResults) {
          break;
        }

        const currentLimit =
          typeof maxResults === "number"
            ? Math.min(pageSize, maxResults - threads.length)
            : pageSize;

        if (typeof maxResults === "number" && currentLimit <= 0) {
          break;
        }

        const response = (await apiClient.threads.search<AgentThreadState>({
          ...params,
          limit: currentLimit,
          offset,
        })) as AgentThread[];

        threads.push(...response);

        if (response.length < currentLimit) {
          break;
        }

        offset += response.length;
      }

      // Safety net on top of the backend's system-thread exclusion: drop
      // machine-created threads (scheduled tasks, roundtable workers,
      // notebooks) in case an older backend still returns them.
      return threads.filter((t) => {
        const metadata = t.metadata as Record<string, unknown> | null;
        if (metadata?.system) return false;
        const threadType = metadata?.thread_type;
        return (
          threadType !== "notebook" &&
          threadType !== "scheduler" &&
          threadType !== "roundtable"
        );
      });
    },
    refetchOnWindowFocus: false,
  });
}

export interface ThreadsPageResult {
  threads: AgentThread[];
  hasMore: boolean;
}

/**
 * Apply ``transform`` to the thread array inside every cached
 * ``["threads", "search"]`` entry. The sidebar queries cache a plain
 * ``AgentThread[]`` while the paged chats list (`useThreadsPage`) caches a
 * ``ThreadsPageResult`` object under the same key prefix, so fuzzy
 * ``setQueriesData`` updaters must handle both shapes.
 */
function updateCachedThreadLists(
  queryClient: QueryClient,
  transform: (threads: AgentThread[]) => AgentThread[],
) {
  queryClient.setQueriesData<AgentThread[] | ThreadsPageResult | undefined>(
    { queryKey: ["threads", "search"], exact: false },
    (oldData) => {
      if (Array.isArray(oldData)) {
        return transform(oldData);
      }
      if (oldData && Array.isArray(oldData.threads)) {
        return { ...oldData, threads: transform(oldData.threads) };
      }
      return oldData;
    },
  );
}

/**
 * Server-side paginated conversation list for the chats page. Unlike
 * `useThreads` (which loads a bounded recent window for the sidebar), this
 * fetches exactly one page per request so a long history is never pulled in
 * one go. `search` matches thread titles on the backend; one extra row is
 * over-fetched only to detect whether a next page exists. The query key stays
 * under ["threads", "search"] so existing invalidations refresh pages too.
 */
export function useThreadsPage(options: {
  page: number;
  pageSize: number;
  search?: string;
  metadata?: Record<string, unknown>;
}) {
  const { page, pageSize, search, metadata } = options;
  const normalizedSearch = search?.trim() ?? "";
  return useQuery<ThreadsPageResult>({
    queryKey: [
      "threads",
      "search",
      "paged",
      page,
      pageSize,
      normalizedSearch,
      metadata ?? null,
    ],
    queryFn: async () => {
      // Direct fetch instead of the LangGraph SDK: the SDK's threads.search
      // drops fields it doesn't know about, and `query` (title search) is a
      // gateway extension.
      const response = await apiFetch(
        `${getLangGraphBaseURL()}/threads/search`,
        {
          method: "POST",
          headers: { "Content-Type": "application/json" },
          body: JSON.stringify({
            limit: pageSize + 1,
            offset: (page - 1) * pageSize,
            metadata: metadata ?? {},
            query: normalizedSearch || undefined,
          }),
        },
      );
      if (!response.ok) {
        throw new Error("Failed to load conversations");
      }
      const rows = (await response.json()) as AgentThread[];
      return {
        threads: rows.slice(0, pageSize),
        hasMore: rows.length > pageSize,
      };
    },
    placeholderData: (previous) => previous,
    refetchOnWindowFocus: false,
  });
}

/**
 * Total number of conversations matching the same filters as
 * `useThreadsPage`, via the lightweight `/threads/count` endpoint — powers
 * the "共 N 条 / X 页" display without fetching any rows. Depends only on the
 * filters (not the page), so paging doesn't refire it.
 */
export function useThreadsCount(options: {
  search?: string;
  metadata?: Record<string, unknown>;
}) {
  const normalizedSearch = options.search?.trim() ?? "";
  return useQuery<number>({
    queryKey: [
      "threads",
      "search",
      "count",
      normalizedSearch,
      options.metadata ?? null,
    ],
    queryFn: async () => {
      const response = await apiFetch(
        `${getLangGraphBaseURL()}/threads/count`,
        {
          method: "POST",
          headers: { "Content-Type": "application/json" },
          body: JSON.stringify({
            metadata: options.metadata ?? {},
            query: normalizedSearch || undefined,
          }),
        },
      );
      if (!response.ok) {
        throw new Error("Failed to count conversations");
      }
      const data = (await response.json()) as { total: number };
      return data.total;
    },
    refetchOnWindowFocus: false,
  });
}

export function useDeleteThread() {
  const queryClient = useQueryClient();
  const apiClient = getAPIClient();
  return useMutation({
    mutationFn: async ({ threadId }: { threadId: string }) => {
      await apiClient.threads.delete(threadId);

      const response = await apiFetch(
        `${getBackendBaseURL()}/api/threads/${encodeURIComponent(threadId)}`,
        {
          method: "DELETE",
        },
      );

      if (!response.ok) {
        const error = await response
          .json()
          .catch(() => ({ detail: "Failed to delete local thread data." }));
        throw new Error(error.detail ?? "Failed to delete local thread data.");
      }
    },
    onSuccess(_, { threadId }) {
      updateCachedThreadLists(queryClient, (threads) =>
        threads.filter((t) => t.thread_id !== threadId),
      );
    },
    onSettled() {
      void queryClient.invalidateQueries({ queryKey: ["threads", "search"] });
    },
  });
}

/**
 * Delete a conversation turn (a user question together with its answer) from a
 * thread. Hits the Gateway endpoint that removes the question and every
 * following message up to the next question from the latest checkpoint, and
 * returns the ids that were actually removed. The live `useStream` cache is not
 * auto-refreshed by this call — callers hide the returned ids locally (see
 * `MessageList`) so the removal shows immediately; a reload then reads the
 * persisted, already-trimmed state.
 */
export function useDeleteMessage() {
  return useMutation({
    mutationFn: async ({
      threadId,
      messageId,
    }: {
      threadId: string;
      messageId: string;
    }): Promise<string[]> => {
      const response = await apiFetch(
        `${getBackendBaseURL()}/api/threads/${encodeURIComponent(
          threadId,
        )}/messages/${encodeURIComponent(messageId)}`,
        {
          method: "DELETE",
        },
      );

      if (!response.ok) {
        const error = await response
          .json()
          .catch(() => ({ detail: "删除消息失败。" }));
        throw new Error(error.detail ?? "删除消息失败。");
      }

      const body = (await response.json().catch(() => ({}))) as {
        deleted_ids?: string[];
      };
      // Fall back to the requested id so the caller can always hide something.
      return body.deleted_ids?.length ? body.deleted_ids : [messageId];
    },
  });
}

/**
 * Merge metadata into a conversation's record via the Gateway
 * `PATCH /api/threads/{id}` route. Used to persist per-conversation flags such
 * as `is_pinned` (置顶) and `is_favorite` (收藏) — a conversation belongs to a
 * single user, so these live directly on the thread metadata (no join table).
 * Updates the `["threads", "search"]` cache optimistically so the UI reflects
 * the toggle immediately, mirroring `useRenameThread`.
 */
export function useUpdateThreadMetadata() {
  const queryClient = useQueryClient();
  return useMutation({
    mutationFn: async ({
      threadId,
      metadata,
    }: {
      threadId: string;
      metadata: Record<string, unknown>;
    }) => {
      const response = await apiFetch(
        `${getBackendBaseURL()}/api/threads/${encodeURIComponent(threadId)}`,
        {
          method: "PATCH",
          headers: { "Content-Type": "application/json" },
          body: JSON.stringify({ metadata }),
        },
      );
      if (!response.ok) {
        const error = await response
          .json()
          .catch(() => ({ detail: "更新对话失败。" }));
        throw new Error(error.detail ?? "更新对话失败。");
      }
    },
    onSuccess(_, { threadId, metadata }) {
      updateCachedThreadLists(queryClient, (threads) =>
        threads.map((t) =>
          t.thread_id === threadId
            ? {
                ...t,
                metadata: {
                  ...(t.metadata as Record<string, unknown> | null),
                  ...metadata,
                },
              }
            : t,
        ),
      );
    },
  });
}

/** Toggle a conversation's pinned (置顶) flag. */
export function useToggleThreadPin() {
  const { mutate, ...rest } = useUpdateThreadMetadata();
  return {
    ...rest,
    toggle: (threadId: string, pinned: boolean) =>
      mutate({ threadId, metadata: { is_pinned: pinned } }),
  };
}

/** Toggle a conversation's favorite (收藏) flag. */
export function useToggleThreadFavorite() {
  const { mutate, ...rest } = useUpdateThreadMetadata();
  return {
    ...rest,
    toggle: (threadId: string, favorite: boolean) =>
      mutate({ threadId, metadata: { is_favorite: favorite } }),
  };
}

export function useRenameThread() {
  const queryClient = useQueryClient();
  const apiClient = getAPIClient();
  return useMutation({
    mutationFn: async ({
      threadId,
      title,
    }: {
      threadId: string;
      title: string;
    }) => {
      await apiClient.threads.updateState(threadId, {
        values: { title },
      });
    },
    onSuccess(_, { threadId, title }) {
      updateCachedThreadLists(queryClient, (threads) =>
        threads.map((t) =>
          t.thread_id === threadId
            ? {
                ...t,
                values: {
                  ...t.values,
                  title,
                },
              }
            : t,
        ),
      );
    },
  });
}