import { Router } from "express";
import { z } from "zod";

import { type LearningOrchestrator } from "../learning/orchestrator.js";
import { type SessionTranscriptStore } from "../sessions/transcriptStore.js";
import { logger } from "../logger.js";
import { MemoryStore } from "../memory/store.js";
import { type SessionUiStateStore } from "../sessions/uiStateStore.js";
import { type SessionMetadataStore } from "../sessions/metadataStore.js";
import { type ResultReferenceResolver } from "../results/resolver.js";
import { RESULT_REFERENCE_KIND } from "../results/store.js";
import { type OpencodeRuntimeAdapter } from "../runtime/opencode.js";
import { type ChatSessionBridge } from "../chat/sessionBridge.js";
import { type SessionRecord } from "../sessions/metadataStore.js";
import { toActorKey, toProjectKey } from "../utils/fileStore.js";
import {
  buildPromptWithLearningContext,
  extractLatestFrontendTurn,
  generateSessionTitle,
  shouldGenerateSessionTitle,
} from "./chatSession.js";
import {
  collectTextContent,
  streamPromptResponse,
  supportedModels,
  type SupportedModel,
} from "./chatStream.js";

const payloadSchema = z.object({
  message: z.string().min(1).max(10000),
  session_id: z.string().max(128).optional(),
  model: z.enum(supportedModels).optional(),
});

const abortPayloadSchema = z.object({
  session_id: z.string().max(128),
});

const createSessionPayloadSchema = z.object({
  session_id: z.string().max(128).optional(),
  parent_session_id: z.string().max(128).optional(),
});

const forkPayloadSchema = z.object({
  session_id: z.string().max(128).optional(),
  keep_message_count: z.coerce.number().int().min(0),
});

const sessionStateSchema = z.object({
  title: z.string().max(120).optional(),
  is_title_manually_edited: z.boolean().optional(),
  messages: z.array(z.unknown()).default([]),
  branch_groups: z.array(z.unknown()).default([]),
});

type RunStatus = "running" | "completed" | "error" | "aborted";

type StreamSubscriber = {
  write: (event: string, data: Record<string, unknown>) => void;
  close: () => void;
};

type ActiveRun = {
  clientSessionId: string;
  controller: AbortController;
  messages: unknown[];
  status: RunStatus;
  subscribers: Set<StreamSubscriber>;
};

const activeRuns = new Map<string, ActiveRun>();
const lastRunStatuses = new Map<string, RunStatus>();

const toSessionUiStateContext = (sessionRecord: SessionRecord) => ({
  sessionId: sessionRecord.sessionId,
});

const getSessionRunStatus = (sessionId: string) =>
  activeRuns.get(sessionId)?.status ?? lastRunStatuses.get(sessionId);

const isObjectRecord = (value: unknown): value is Record<string, unknown> =>
  typeof value === "object" && value !== null && !Array.isArray(value);

const createFrontendMessageId = () =>
  `msg-${Date.now().toString(36)}-${Math.random().toString(36).slice(2, 8)}`;

const createInitialStreamingMessages = (existingMessages: unknown[], userContent: string) => {
  const userMessage = {
    id: createFrontendMessageId(),
    role: "user",
    content: userContent,
  };
  return [
    ...existingMessages,
    {
      ...userMessage,
      branchRootId: userMessage.id,
    },
    {
      id: createFrontendMessageId(),
      role: "assistant",
      content: "",
      progress: [
        {
          id: "request-received",
          phase: "start",
          status: "running",
          title: "已收到请求，正在启动 Agent 分析",
          detail: "已接收用户消息，正在建立会话并准备进入分析、规划和工具调用阶段。",
          startedAt: Date.now(),
          elapsedMs: 0,
          elapsedSnapshotAt: Date.now(),
        },
      ],
    },
  ];
};

const upsertBackendProgress = (
  progress: unknown,
  payload: Record<string, unknown>,
) => {
  const next = Array.isArray(progress) ? [...progress] : [];
  const id = typeof payload.id === "string" ? payload.id : `progress-${Date.now()}`;
  const index = next.findIndex((item) => isObjectRecord(item) && item.id === id);
  const nextItem = {
    id,
    phase: typeof payload.phase === "string" ? payload.phase : "progress",
    status:
      payload.status === "completed" || payload.status === "error"
        ? payload.status
        : "running",
    title: typeof payload.title === "string" ? payload.title : "正在处理",
    detail: typeof payload.detail === "string" ? payload.detail : undefined,
    startedAt: typeof payload.started_at === "number" ? payload.started_at : undefined,
    endedAt: typeof payload.ended_at === "number" ? payload.ended_at : undefined,
    elapsedMs: typeof payload.elapsed_ms === "number" ? payload.elapsed_ms : undefined,
    elapsedSnapshotAt:
      typeof payload.elapsed_ms === "number" ? Date.now() : undefined,
    durationMs: typeof payload.duration_ms === "number" ? payload.duration_ms : undefined,
  };
  if (index >= 0) {
    next[index] = nextItem;
  } else {
    next.push(nextItem);
  }
  return next;
};

const completeBackendProgress = (progress: unknown) =>
  Array.isArray(progress)
    ? progress.map((item) => {
        if (!isObjectRecord(item) || item.status !== "running") {
          return item;
        }
        const endedAt = Date.now();
        const startedAt = typeof item.startedAt === "number" ? item.startedAt : undefined;
        return {
          ...item,
          status: "completed",
          endedAt,
          elapsedMs: undefined,
          elapsedSnapshotAt: undefined,
          durationMs:
            typeof item.durationMs === "number"
              ? item.durationMs
              : startedAt !== undefined
                ? Math.max(0, endedAt - startedAt)
                : item.elapsedMs,
        };
      })
    : progress;

const updateLastAssistantMessage = (
  messages: unknown[],
  updater: (message: Record<string, unknown>) => Record<string, unknown>,
) => {
  for (let index = messages.length - 1; index >= 0; index -= 1) {
    const message = messages[index];
    if (isObjectRecord(message) && message.role === "assistant") {
      const next = [...messages];
      next[index] = updater(message);
      return next;
    }
  }
  return messages;
};

export const buildChatRouter = (
  sessionBridge: ChatSessionBridge,
  runtime: OpencodeRuntimeAdapter,
  sessionMetadataStore: SessionMetadataStore,
  sessionUiStateStore: SessionUiStateStore,
  memoryStore: MemoryStore,
  sessionTranscriptStore: SessionTranscriptStore,
  learningOrchestrator: LearningOrchestrator,
  resultReferenceResolver: ResultReferenceResolver,
) => {
  const chatRouter = Router();

  chatRouter.post("/session", async (req, res) => {
    const parsed = createSessionPayloadSchema.safeParse(req.body ?? {});
    if (!parsed.success) {
      res.status(400).json({
        message: "invalid request payload",
        detail: parsed.error.flatten(),
      });
      return;
    }

    const projectId = req.header("x-project-id") ?? undefined;
    const userId = req.header("x-user-id") ?? undefined;
    const actorKey = toActorKey(userId);
    const projectKey = toProjectKey(projectId);
    const requestedSessionId = parsed.data.session_id?.trim();
    const sessionId = requestedSessionId || (await runtime.createSession()).id;

    const { record, created } = await sessionMetadataStore.ensure({
      actorKey,
      parentSessionId: parsed.data.parent_session_id,
      projectId,
      projectKey,
      sessionId,
      userId,
    });

    res.status(created ? 201 : 200).json({
      session_id: record.sessionId,
      created_at: record.createdAt,
      updated_at: record.updatedAt,
      status: record.status,
      title: record.title,
      parent_session_id: record.parentSessionId,
    });
  });

  chatRouter.get("/sessions", async (req, res) => {
    const projectId = req.header("x-project-id") ?? undefined;
    const userId = req.header("x-user-id") ?? undefined;
    const actorKey = toActorKey(userId);
    const projectKey = toProjectKey(projectId);
    const records = await sessionMetadataStore.list({
      actorKey,
      projectId,
      projectKey,
      userId,
    });
    res.json({
      sessions: records.map((record) => ({
        id: record.sessionId,
        title: record.title ?? "新对话",
        created_at: record.createdAt,
        updated_at: record.updatedAt,
        status: record.status,
        parent_session_id: record.parentSessionId,
        is_streaming: activeRuns.get(record.sessionId)?.status === "running",
        run_status: getSessionRunStatus(record.sessionId),
      })),
    });
  });

  chatRouter.get("/session/:sessionId", async (req, res) => {
    const sessionId = req.params.sessionId?.trim();
    const projectId = req.header("x-project-id") ?? undefined;
    const userId = req.header("x-user-id") ?? undefined;
    const actorKey = toActorKey(userId);
    const projectKey = toProjectKey(projectId);
    if (!sessionId) {
      res.status(400).json({ message: "session_id is required" });
      return;
    }

    const sessionRecord = await sessionMetadataStore.get(
      {
        actorKey,
        projectId,
        projectKey,
        userId,
      },
      sessionId,
    );
    if (!sessionRecord) {
      res.status(404).json({ message: "session not found" });
      return;
    }

    const state = await sessionUiStateStore.read(
      toSessionUiStateContext(sessionRecord),
    );
    res.json({
      id: sessionRecord.sessionId,
      title: sessionRecord.title ?? "新对话",
      is_title_manually_edited: state?.isTitleManuallyEdited ?? false,
      created_at: sessionRecord.createdAt,
      updated_at: sessionRecord.updatedAt,
      status: sessionRecord.status,
      session_id: sessionRecord.sessionId,
      messages: state?.messages ?? [],
      branch_groups: state?.branchGroups ?? [],
      parent_session_id: sessionRecord.parentSessionId,
      is_streaming: activeRuns.get(sessionRecord.sessionId)?.status === "running",
      run_status: getSessionRunStatus(sessionRecord.sessionId),
    });
  });

  chatRouter.get("/session/:sessionId/stream", async (req, res) => {
    const sessionId = req.params.sessionId?.trim();
    const projectId = req.header("x-project-id") ?? undefined;
    const userId = req.header("x-user-id") ?? undefined;
    const actorKey = toActorKey(userId);
    const projectKey = toProjectKey(projectId);
    if (!sessionId) {
      res.status(400).json({ message: "session_id is required" });
      return;
    }

    const sessionRecord = await sessionMetadataStore.get(
      { actorKey, projectId, projectKey, userId },
      sessionId,
    );
    if (!sessionRecord) {
      res.status(404).json({ message: "session not found" });
      return;
    }

    res.status(200);
    res.setHeader("Content-Type", "text/event-stream; charset=utf-8");
    res.setHeader("Cache-Control", "no-cache");
    res.setHeader("Connection", "keep-alive");
    res.setHeader("X-Accel-Buffering", "no");
    res.flushHeaders?.();

    const run = activeRuns.get(sessionRecord.sessionId);
    const state = await sessionUiStateStore.read(toSessionUiStateContext(sessionRecord));
    res.write(
      toSse("state", {
        session_id: sessionRecord.sessionId,
        messages: state?.messages ?? run?.messages ?? [],
        is_streaming: run?.status === "running",
        run_status: getSessionRunStatus(sessionRecord.sessionId) ?? "completed",
      }),
    );

    if (!run || run.status !== "running") {
      res.end();
      return;
    }

    const subscriber: StreamSubscriber = {
      write: (event, data) => {
        if (!res.writableEnded && !res.destroyed) {
          res.write(toSse(event, data));
        }
      },
      close: () => {
        if (!res.writableEnded && !res.destroyed) {
          res.end();
        }
      },
    };
    run.subscribers.add(subscriber);

    const cleanup = () => {
      run.subscribers.delete(subscriber);
    };
    req.on("close", cleanup);
    res.on("close", cleanup);
  });

  chatRouter.put("/session/:sessionId", async (req, res) => {
    const sessionId = req.params.sessionId?.trim();
    const parsed = sessionStateSchema.safeParse(req.body ?? {});
    if (!parsed.success) {
      res.status(400).json({
        message: "invalid request payload",
        detail: parsed.error.flatten(),
      });
      return;
    }

    const projectId = req.header("x-project-id") ?? undefined;
    const userId = req.header("x-user-id") ?? undefined;
    const actorKey = toActorKey(userId);
    const projectKey = toProjectKey(projectId);
    if (!sessionId) {
      res.status(400).json({ message: "session_id is required" });
      return;
    }

    const { record } = await sessionMetadataStore.ensure({
      actorKey,
      projectId,
      projectKey,
      sessionId,
      userId,
    });
    const nextRecord = await sessionMetadataStore.touch(record, {
      ...(parsed.data.title ? { title: parsed.data.title } : {}),
    });
    await sessionUiStateStore.write(toSessionUiStateContext(nextRecord), {
      sessionId: nextRecord.sessionId,
      isTitleManuallyEdited: parsed.data.is_title_manually_edited,
      messages: parsed.data.messages,
      branchGroups: parsed.data.branch_groups,
    });
    const latestTurn = extractLatestFrontendTurn(parsed.data.messages);
    if (latestTurn) {
      void learningOrchestrator.onTurnCompleted({
        ...latestTurn,
        requestContext: {
          actorKey,
          clientSessionId: nextRecord.sessionId,
          projectId,
          projectKey,
          traceId: req.header("x-trace-id") ?? `save-${nextRecord.sessionId}`,
          userId,
        },
        sessionId: nextRecord.sessionId,
      }).catch((error) => {
        logger.warn(
          { err: error, sessionId: nextRecord.sessionId },
          "post-save learning failed",
        );
      });
    }
    res.json({
      id: nextRecord.sessionId,
      title: nextRecord.title ?? "新对话",
      created_at: nextRecord.createdAt,
      updated_at: nextRecord.updatedAt,
      status: nextRecord.status,
      session_id: nextRecord.sessionId,
    });
  });

  chatRouter.patch("/session/:sessionId/title", async (req, res) => {
    const sessionId = req.params.sessionId?.trim();
    const title =
      typeof req.body?.title === "string" ? req.body.title.trim() : "";
    const isTitleManuallyEdited =
      typeof req.body?.is_title_manually_edited === "boolean"
        ? req.body.is_title_manually_edited
        : undefined;
    const projectId = req.header("x-project-id") ?? undefined;
    const userId = req.header("x-user-id") ?? undefined;
    const actorKey = toActorKey(userId);
    const projectKey = toProjectKey(projectId);
    if (!sessionId || !title) {
      res.status(400).json({ message: "session_id and title are required" });
      return;
    }
    const sessionRecord = await sessionMetadataStore.get(
      { actorKey, projectId, projectKey, userId },
      sessionId,
    );
    if (!sessionRecord) {
      res.status(404).json({ message: "session not found" });
      return;
    }
    const nextSessionRecord = await sessionMetadataStore.touch(sessionRecord, { title });
    const state = await sessionUiStateStore.read(
      toSessionUiStateContext(nextSessionRecord),
    );
    if (state) {
      await sessionUiStateStore.write(
        toSessionUiStateContext(nextSessionRecord),
        {
        ...state,
        isTitleManuallyEdited:
          isTitleManuallyEdited ?? state.isTitleManuallyEdited,
        },
      );
    }
    res.json({
      id: nextSessionRecord.sessionId,
      title: nextSessionRecord.title,
      updated_at: nextSessionRecord.updatedAt,
    });
  });

  chatRouter.delete("/session/:sessionId", async (req, res) => {
    const sessionId = req.params.sessionId?.trim();
    const projectId = req.header("x-project-id") ?? undefined;
    const userId = req.header("x-user-id") ?? undefined;
    const actorKey = toActorKey(userId);
    const projectKey = toProjectKey(projectId);
    if (!sessionId) {
      res.status(400).json({ message: "session_id is required" });
      return;
    }
    const sessionRecord = await sessionMetadataStore.get(
      { actorKey, projectId, projectKey, userId },
      sessionId,
    );
    if (!sessionRecord) {
      res.status(204).end();
      return;
    }
    await sessionUiStateStore.remove(toSessionUiStateContext(sessionRecord));
    await sessionBridge.deleteSession({
      clientSessionId: sessionRecord.sessionId,
      sessionId: sessionRecord.sessionId,
    });
    activeRuns.delete(sessionRecord.sessionId);
    lastRunStatuses.delete(sessionRecord.sessionId);
    await sessionMetadataStore.remove(sessionRecord);
    res.status(204).end();
  });

  chatRouter.get("/render-ref/:renderRef", async (req, res) => {
    const renderRef = req.params.renderRef?.trim();
    const userId = req.header("x-user-id")?.trim();
    const projectId = req.header("x-project-id") ?? undefined;
    const clientSessionId =
      typeof req.query.session_id === "string"
        ? req.query.session_id.trim()
        : undefined;

    if (!userId) {
      res.status(400).json({
        message: "x-user-id is required",
      });
      return;
    }

    if (!renderRef) {
      res.status(400).json({
        message: "render_ref is required",
      });
      return;
    }

    const result = await resultReferenceResolver.getFullAuthorized(
      renderRef,
      {
        actorKey: toActorKey(userId),
        clientSessionId,
        projectId,
      },
      {
        expectedKind: RESULT_REFERENCE_KIND.renderJunctionsPayload,
      },
    );

    if (!result) {
      res.status(404).json({ message: "render_ref not found" });
      return;
    }

    res.json(result);
  });

  chatRouter.post("/abort", async (req, res) => {
    const parsed = abortPayloadSchema.safeParse(req.body);
    if (!parsed.success) {
      res.status(400).json({
        message: "invalid request payload",
        detail: parsed.error.flatten(),
      });
      return;
    }

    try {
      const projectId = req.header("x-project-id") ?? undefined;
      const userId = req.header("x-user-id") ?? undefined;
      const actorKey = toActorKey(userId);
      const projectKey = toProjectKey(projectId);
      const sessionRecord = await sessionMetadataStore.get(
        { actorKey, projectId, projectKey, userId },
        parsed.data.session_id,
      );
      const binding = sessionRecord
        ? await sessionBridge.abort({
            clientSessionId: sessionRecord.sessionId,
            sessionId: sessionRecord.sessionId,
          })
        : null;
      const run = activeRuns.get(parsed.data.session_id);
      if (run && run.status === "running") {
        run.status = "aborted";
        lastRunStatuses.set(parsed.data.session_id, "aborted");
        run.controller.abort();
        run.messages = updateLastAssistantMessage(run.messages, (message) => ({
          ...message,
          content:
            typeof message.content === "string" && message.content.trim()
              ? message.content
              : "⚠️ **请求已中断**",
          isError: true,
          progress: completeBackendProgress(message.progress),
        }));
        if (sessionRecord) {
          const currentState = await sessionUiStateStore.read(
            toSessionUiStateContext(sessionRecord),
          );
          await sessionUiStateStore.write(toSessionUiStateContext(sessionRecord), {
            sessionId: sessionRecord.sessionId,
            isTitleManuallyEdited: currentState?.isTitleManuallyEdited ?? false,
            messages: run.messages,
            branchGroups: currentState?.branchGroups ?? [],
          });
        }
        for (const subscriber of run.subscribers) {
          subscriber.write("error", {
            session_id: parsed.data.session_id,
            message: "请求已中断",
          });
          subscriber.close();
        }
        run.subscribers.clear();
      }

      if (!binding && !run) {
        res.status(204).end();
        return;
      }

      logger.info(
        {
          clientSessionId: parsed.data.session_id,
          sessionId: binding?.sessionId ?? parsed.data.session_id,
        },
        "aborted chat session by client request",
      );
      res.status(202).json({
        session_id: parsed.data.session_id,
        aborted: true,
      });
    } catch (error) {
      const detail = error instanceof Error ? error.message : String(error);
      logger.error({ err: error }, "chat abort failed");
      res.status(500).json({
        message: "chat abort failed",
        detail,
      });
    }
  });

  chatRouter.post("/fork", async (req, res) => {
    const parsed = forkPayloadSchema.safeParse(req.body);
    if (!parsed.success) {
      res.status(400).json({
        message: "invalid request payload",
        detail: parsed.error.flatten(),
      });
      return;
    }

    try {
      const projectId = req.header("x-project-id") ?? undefined;
      const traceId = req.header("x-trace-id") ?? undefined;
      const userId = req.header("x-user-id") ?? undefined;

      const actorKey = toActorKey(userId);
      const projectKey = toProjectKey(projectId);
      const sourceSessionId = parsed.data.session_id?.trim();
      const sourceSessionRecord = sourceSessionId
        ? await sessionMetadataStore.get(
            {
              actorKey,
              projectId,
              projectKey,
              userId,
            },
            sourceSessionId,
          )
        : null;
      const forkSession = await runtime.createSession();
      const { record: targetSessionRecord } = await sessionMetadataStore.ensure({
        actorKey,
        parentSessionId: sourceSessionId,
        projectId,
        projectKey,
        sessionId: forkSession.id,
        userId,
      });
      const nextSessionId = targetSessionRecord.sessionId;

      if (sourceSessionId && parsed.data.keep_message_count > 0) {
        await sessionTranscriptStore.cloneThread(
          {
            actorKey,
            clientSessionId: sourceSessionId,
            projectKey,
            sessionId: sourceSessionId,
          },
          {
            actorKey,
            clientSessionId: nextSessionId,
            projectKey,
            sessionId: nextSessionId,
          },
          parsed.data.keep_message_count,
        );
        if (sourceSessionRecord?.title) {
          await sessionMetadataStore.touch(targetSessionRecord, {
            title: sourceSessionRecord.title,
          });
        }
      }

      logger.info(
        {
          sourceSessionId: parsed.data.session_id,
          sessionId: nextSessionId,
          traceId,
          projectId,
          keepMessageCount: parsed.data.keep_message_count,
        },
        "forked chat session",
      );

      res.status(200).json({
        session_id: nextSessionId,
      });
    } catch (error) {
      const detail = error instanceof Error ? error.message : String(error);
      logger.error({ err: error }, "chat fork failed");
      res.status(500).json({
        message: "chat fork failed",
        detail,
      });
    }
  });

  chatRouter.post("/stream", async (req, res) => {
    const parsed = payloadSchema.safeParse(req.body);
    if (!parsed.success) {
      res.status(400).json({
        message: "invalid request payload",
        detail: parsed.error.flatten(),
      });
      return;
    }

    try {
      const authHeader = req.header("authorization");
      const accessToken = authHeader?.startsWith("Bearer ")
        ? authHeader.slice("Bearer ".length)
        : authHeader;
      const projectId = req.header("x-project-id") ?? undefined;
      const traceId = req.header("x-trace-id") ?? undefined;
      const userId = req.header("x-user-id") ?? undefined;
      const actorKey = toActorKey(userId);
      const projectKey = toProjectKey(projectId);
      const requestedSessionId = parsed.data.session_id?.trim();
      const existingSessionRecord = requestedSessionId
        ? await sessionMetadataStore.get(
            { actorKey, projectId, projectKey, userId },
            requestedSessionId,
          )
        : null;
      const hadExistingRuntimeSession = Boolean(existingSessionRecord);

      const { binding, requestContext, created } = await sessionBridge.resolve({
        sessionId: requestedSessionId,
        accessToken,
        projectId,
        traceId,
        userId,
      });
      const { record: ensuredSessionRecord, created: sessionCreated } =
        await sessionMetadataStore.ensure({
          actorKey,
          projectId,
          projectKey,
          sessionId: binding.sessionId,
          userId,
        });
      const activeSessionRecord = await sessionMetadataStore.touch(ensuredSessionRecord);
      const historyContext = {
        actorKey: requestContext.actorKey,
        clientSessionId: requestContext.clientSessionId,
        projectKey: requestContext.projectKey,
        sessionId: requestContext.clientSessionId,
      };
      const recentTurns = await sessionTranscriptStore.getRecentTurns(historyContext, 8);
      const initialSessionState = await sessionUiStateStore.read(
        toSessionUiStateContext(activeSessionRecord),
      );
      if (activeRuns.get(activeSessionRecord.sessionId)?.status === "running") {
        res.status(409).json({
          message: "session is already streaming",
          session_id: activeSessionRecord.sessionId,
        });
        return;
      }

      logger.info(
        {
          clientSessionId: requestContext.clientSessionId,
          sessionId: binding.sessionId,
          created: created || sessionCreated,
          model: parsed.data.model,
          traceId: requestContext.traceId,
          projectId: requestContext.projectId,
        },
        "processing chat request",
      );

      res.status(200);
      res.setHeader("Content-Type", "text/event-stream; charset=utf-8");
      res.setHeader("Cache-Control", "no-cache");
      res.setHeader("Connection", "keep-alive");
      res.setHeader("X-Accel-Buffering", "no");
      res.flushHeaders?.();

      const clientSessionId = requestContext.clientSessionId;
      let streamClosed = false;
      const abortController = new AbortController();
      sessionBridge.registerAbortController(clientSessionId, abortController);
      const initialMessages = createInitialStreamingMessages(
        initialSessionState?.messages ?? [],
        parsed.data.message,
      );
      const branchGroups = initialSessionState?.branchGroups ?? [];
      const activeRun: ActiveRun = {
        clientSessionId,
        controller: abortController,
        messages: initialMessages,
        status: "running",
        subscribers: new Set(),
      };
      activeRuns.set(clientSessionId, activeRun);
      lastRunStatuses.set(clientSessionId, "running");
      const sessionUiStateContext = toSessionUiStateContext(activeSessionRecord);
      let persistQueue = sessionUiStateStore.write(sessionUiStateContext, {
        sessionId: activeSessionRecord.sessionId,
        isTitleManuallyEdited: initialSessionState?.isTitleManuallyEdited ?? false,
        messages: initialMessages,
        branchGroups,
      });
      const queueSessionUiStatePersist = () => {
        const snapshot = {
          sessionId: activeSessionRecord.sessionId,
          isTitleManuallyEdited: initialSessionState?.isTitleManuallyEdited ?? false,
          messages: activeRun.messages,
          branchGroups,
        };
        persistQueue = persistQueue
          .catch((error) => {
            logger.warn(
              { err: error, sessionId: clientSessionId },
              "failed to persist previous chat stream state",
            );
          })
          .then(() => sessionUiStateStore.write(sessionUiStateContext, snapshot));
        return persistQueue;
      };
      const primarySubscriber: StreamSubscriber = {
        write: (event, data) => {
          if (!streamClosed && !res.writableEnded && !res.destroyed) {
            res.write(toSse(event, data));
          }
        },
        close: () => {
          if (!res.writableEnded && !res.destroyed) {
            res.end();
          }
        },
      };
      activeRun.subscribers.add(primarySubscriber);
      const handleClientClose = () => {
        streamClosed = true;
        activeRun.subscribers.delete(primarySubscriber);
      };

      req.on("close", handleClientClose);
      res.on("close", handleClientClose);

      const publish = (event: string, data: Record<string, unknown>) => {
        if (event === "token") {
          activeRun.messages = updateLastAssistantMessage(activeRun.messages, (message) => ({
            ...message,
            content: `${typeof message.content === "string" ? message.content : ""}${typeof data.content === "string" ? data.content : ""}`,
            isError: false,
          }));
        } else if (event === "progress") {
          activeRun.messages = updateLastAssistantMessage(activeRun.messages, (message) => ({
            ...message,
            progress: upsertBackendProgress(message.progress, data),
          }));
        } else if (event === "done") {
          activeRun.status = "completed";
          lastRunStatuses.set(clientSessionId, "completed");
          activeRun.messages = updateLastAssistantMessage(activeRun.messages, (message) => ({
            ...message,
            content:
              typeof message.content === "string" && message.content.trim()
                ? message.content
                : "Agent 已完成处理，但没有生成文本回答。请查看过程记录，或换个更具体的问题重试。",
            progress: completeBackendProgress(message.progress),
          }));
        } else if (event === "error") {
          activeRun.status = activeRun.status === "aborted" ? "aborted" : "error";
          lastRunStatuses.set(clientSessionId, activeRun.status);
          activeRun.messages = updateLastAssistantMessage(activeRun.messages, (message) => ({
            ...message,
            content:
              typeof message.content === "string" && message.content.trim()
                ? message.content
                : `⚠️ **错误：** ${typeof data.message === "string" ? data.message : "unknown error"}`,
            isError: true,
            progress: completeBackendProgress(message.progress),
          }));
        }

        for (const subscriber of activeRun.subscribers) {
          subscriber.write(event, data);
        }
        void queueSessionUiStatePersist().catch((error) => {
          logger.warn({ err: error, sessionId: clientSessionId }, "failed to persist chat stream state");
        });
      };

      try {
        const preparedMessage = await buildPromptWithLearningContext(
          memoryStore,
          requestContext.actorKey,
          requestContext.projectKey,
          {
            recentTurns,
            persistedMessages: initialSessionState?.messages,
            message: parsed.data.message,
            restoreConversation: !hadExistingRuntimeSession,
          },
        );
        const streamResult = await streamPromptResponse({
          runtime,
          sessionId: binding.sessionId,
          clientSessionId,
          message: preparedMessage,
          model: parsed.data.model,
          traceId: requestContext.traceId,
          projectId: requestContext.projectId,
          signal: abortController.signal,
          write: (event, data) => {
            publish(event, data);
          },
        });
        await persistQueue.catch((error) => {
          logger.warn({ err: error, sessionId: clientSessionId }, "failed to persist chat stream state");
        });

        if (!streamResult.aborted && !streamResult.failed) {
          const messages = await runtime.messages(binding.sessionId, 60);
          const assistantMessage = [...messages]
            .reverse()
            .find((message) => message.info.role === "assistant");
          const assistantText = collectTextContent(assistantMessage?.parts ?? []);
          const latestSessionRecord =
            (await sessionMetadataStore.get(
              { actorKey, projectId, projectKey, userId },
              activeSessionRecord.sessionId,
            )) ?? activeSessionRecord;
          const latestSessionState = await sessionUiStateStore.read(
            toSessionUiStateContext(latestSessionRecord),
          );
          const existingSessionTitle = latestSessionRecord.title;
          let sessionTitle = existingSessionTitle;
          const shouldGenerateTitle = shouldGenerateSessionTitle({
            recentTurnCount: recentTurns.length,
            isTitleManuallyEdited:
              latestSessionState?.isTitleManuallyEdited ?? false,
          });
          if (shouldGenerateTitle) {
            sessionTitle = await generateSessionTitle(runtime, {
              sessionId: binding.sessionId,
              latestAssistantMessage: assistantText,
              latestUserMessage: parsed.data.message,
              fallbackTitle: existingSessionTitle,
            });
          }
          const nextSessionRecord = await sessionMetadataStore.touch(latestSessionRecord, {
            ...(sessionTitle && sessionTitle !== existingSessionTitle
              ? { title: sessionTitle }
              : {}),
          });
          if (
            shouldGenerateTitle &&
            sessionTitle &&
            sessionTitle !== existingSessionTitle
          ) {
            publish("session_title", {
              session_id: clientSessionId,
              title: sessionTitle,
            });
            await persistQueue.catch((error) => {
              logger.warn({ err: error, sessionId: clientSessionId }, "failed to persist chat stream state");
            });
          }
        }
      } finally {
        await persistQueue.catch((error) => {
          logger.warn({ err: error, sessionId: clientSessionId }, "failed to persist chat stream state");
        });
        sessionBridge.finalizeRequest(clientSessionId);
        activeRun.status = abortController.signal.aborted
          ? activeRun.status === "aborted"
            ? "aborted"
            : "aborted"
          : activeRun.status === "running"
            ? "completed"
            : activeRun.status;
        lastRunStatuses.set(clientSessionId, activeRun.status);
        for (const subscriber of activeRun.subscribers) {
          subscriber.close();
        }
        activeRun.subscribers.clear();
        activeRuns.delete(clientSessionId);
        streamClosed = true;
        req.off("close", handleClientClose);
        res.off("close", handleClientClose);
      }

      if (!res.writableEnded && !res.destroyed) {
        res.end();
      }
    } catch (error) {
      const detail = error instanceof Error ? error.message : String(error);
      logger.error({ err: error }, "chat stream failed");
      res.status(500).json({
        message: "chat stream failed",
        detail,
      });
    }
  });

  return chatRouter;
};

const toSse = (event: string, data: Record<string, unknown>) =>
  `event: ${event}\ndata: ${JSON.stringify(data)}\n\n`;