const { logger } = require('@librechat/data-schemas');
const { Constants } = require('librechat-data-provider');
const {
  sendEvent,
  GenerationJobManager,
  sanitizeFileForTransmit,
  sanitizeMessageForTransmit,
} = require('@librechat/api');
const { handleAbortError } = require('~/server/middleware');
const { disposeClient, clientRegistry, requestDataMap } = require('~/server/cleanup');
const { saveMessage } = require('~/models');

function createCloseHandler(abortController) {
  return function (manual) {
    if (!manual) {
      logger.debug('[AgentController] Request closed');
    }
    if (!abortController) {
      return;
    } else if (abortController.signal.aborted) {
      return;
    } else if (abortController.requestCompleted) {
      return;
    }

    abortController.abort();
    logger.debug('[AgentController] Request aborted on close');
  };
}

/**
 * Resumable Agent Controller - Generation runs independently of HTTP connection.
 * Returns streamId immediately, client subscribes separately via SSE.
 */
const ResumableAgentController = async (req, res, next, initializeClient, addTitle) => {
  const {
    text,
    isRegenerate,
    endpointOption,
    conversationId: reqConversationId,
    isContinued = false,
    editedContent = null,
    parentMessageId = null,
    overrideParentMessageId = null,
    responseMessageId: editedResponseMessageId = null,
  } = req.body;

  const userId = req.user.id;

  // Generate conversationId upfront if not provided - streamId === conversationId always
  const conversationId = reqConversationId || crypto.randomUUID();
  const streamId = conversationId;

  let client = null;

  try {
    const prelimAbortController = new AbortController();
    res.on('close', () => {
      if (!prelimAbortController.signal.aborted) {
        prelimAbortController.abort();
      }
    });

    const job = await GenerationJobManager.createJob(streamId, userId, conversationId);
    req._resumableStreamId = streamId;

    // Track if partial response was already saved to avoid duplicates
    let partialResponseSaved = false;

    /**
     * Listen for all subscribers leaving to save partial response.
     * This ensures the response is saved to DB even if all clients disconnect
     * while generation continues.
     *
     * Note: The messageId used here falls back to `${userMessage.messageId}_` if the
     * actual response messageId isn't available yet. The final response save will
     * overwrite this with the complete response using the same messageId pattern.
     */
    job.emitter.on('allSubscribersLeft', async (aggregatedContent) => {
      if (partialResponseSaved || !aggregatedContent || aggregatedContent.length === 0) {
        return;
      }

      const resumeState = await GenerationJobManager.getResumeState(streamId);
      if (!resumeState?.userMessage) {
        logger.debug('[ResumableAgentController] No user message to save partial response for');
        return;
      }

      partialResponseSaved = true;
      const responseConversationId = resumeState.conversationId || conversationId;

      try {
        const partialMessage = {
          messageId: resumeState.responseMessageId || `${resumeState.userMessage.messageId}_`,
          conversationId: responseConversationId,
          parentMessageId: resumeState.userMessage.messageId,
          sender: client?.sender ?? 'AI',
          content: aggregatedContent,
          unfinished: true,
          error: false,
          isCreatedByUser: false,
          user: userId,
          endpoint: endpointOption.endpoint,
          model: endpointOption.modelOptions?.model || endpointOption.model_parameters?.model,
        };

        if (req.body?.agent_id) {
          partialMessage.agent_id = req.body.agent_id;
        }

        await saveMessage(req, partialMessage, {
          context: 'api/server/controllers/agents/request.js - partial response on disconnect',
        });

        logger.debug(
          `[ResumableAgentController] Saved partial response for ${streamId}, content parts: ${aggregatedContent.length}`,
        );
      } catch (error) {
        logger.error('[ResumableAgentController] Error saving partial response:', error);
        // Reset flag so we can try again if subscribers reconnect and leave again
        partialResponseSaved = false;
      }
    });

    /** @type {{ client: TAgentClient; userMCPAuthMap?: Record<string, Record<string, string>> }} */
    const result = await initializeClient({
      req,
      res,
      endpointOption,
      signal: prelimAbortController.signal,
    });

    if (prelimAbortController.signal.aborted) {
      GenerationJobManager.completeJob(streamId, 'Request aborted during initialization');
      return res.status(400).json({ error: 'Request aborted during initialization' });
    }

    client = result.client;

    if (client?.sender) {
      GenerationJobManager.updateMetadata(streamId, { sender: client.sender });
    }

    // Store reference to client's contentParts - graph will be set when run is created
    if (client?.contentParts) {
      GenerationJobManager.setContentParts(streamId, client.contentParts);
    }

    res.json({ streamId, conversationId, status: 'started' });

    let userMessage;

    const getReqData = (data = {}) => {
      if (data.userMessage) {
        userMessage = data.userMessage;
      }
      // conversationId is pre-generated, no need to update from callback
    };

    // Start background generation - wait for subscriber with timeout fallback
    const startGeneration = async () => {
      try {
        await Promise.race([job.readyPromise, new Promise((resolve) => setTimeout(resolve, 3500))]);
      } catch (waitError) {
        logger.warn(
          `[ResumableAgentController] Error waiting for subscriber: ${waitError.message}`,
        );
      }

      try {
        const onStart = (userMsg, respMsgId, _isNewConvo) => {
          userMessage = userMsg;

          // Store userMessage and responseMessageId upfront for resume capability
          GenerationJobManager.updateMetadata(streamId, {
            responseMessageId: respMsgId,
            userMessage: {
              messageId: userMsg.messageId,
              parentMessageId: userMsg.parentMessageId,
              conversationId: userMsg.conversationId,
              text: userMsg.text,
            },
          });

          GenerationJobManager.emitChunk(streamId, {
            created: true,
            message: userMessage,
            streamId,
          });
        };

        const messageOptions = {
          user: userId,
          onStart,
          getReqData,
          isContinued,
          isRegenerate,
          editedContent,
          conversationId,
          parentMessageId,
          abortController: job.abortController,
          overrideParentMessageId,
          isEdited: !!editedContent,
          userMCPAuthMap: result.userMCPAuthMap,
          responseMessageId: editedResponseMessageId,
          progressOptions: {
            res: {
              write: () => true,
              end: () => {},
              headersSent: false,
              writableEnded: false,
            },
          },
        };

        const response = await client.sendMessage(text, messageOptions);

        const messageId = response.messageId;
        const endpoint = endpointOption.endpoint;
        response.endpoint = endpoint;

        const databasePromise = response.databasePromise;
        delete response.databasePromise;

        const { conversation: convoData = {} } = await databasePromise;
        const conversation = { ...convoData };
        conversation.title =
          conversation && !conversation.title ? null : conversation?.title || 'New Chat';

        if (req.body.files && client.options?.attachments) {
          userMessage.files = [];
          const messageFiles = new Set(req.body.files.map((file) => file.file_id));
          for (const attachment of client.options.attachments) {
            if (messageFiles.has(attachment.file_id)) {
              userMessage.files.push(sanitizeFileForTransmit(attachment));
            }
          }
          delete userMessage.image_urls;
        }

        if (!job.abortController.signal.aborted) {
          const finalEvent = {
            final: true,
            conversation,
            title: conversation.title,
            requestMessage: sanitizeMessageForTransmit(userMessage),
            responseMessage: { ...response },
          };

          GenerationJobManager.emitDone(streamId, finalEvent);
          GenerationJobManager.completeJob(streamId);

          if (client.savedMessageIds && !client.savedMessageIds.has(messageId)) {
            await saveMessage(
              req,
              { ...response, user: userId },
              { context: 'api/server/controllers/agents/request.js - resumable response end' },
            );
          }
        } else {
          const finalEvent = {
            final: true,
            conversation,
            title: conversation.title,
            requestMessage: sanitizeMessageForTransmit(userMessage),
            responseMessage: { ...response, error: true },
            error: { message: 'Request was aborted' },
          };
          GenerationJobManager.emitDone(streamId, finalEvent);
          GenerationJobManager.completeJob(streamId, 'Request aborted');
        }

        if (!client.skipSaveUserMessage && userMessage) {
          await saveMessage(req, userMessage, {
            context: 'api/server/controllers/agents/request.js - resumable user message',
          });
        }

        // Skip title generation if job was aborted
        const newConvo = !reqConversationId;
        const shouldGenerateTitle =
          addTitle &&
          parentMessageId === Constants.NO_PARENT &&
          newConvo &&
          !job.abortController.signal.aborted;

        if (shouldGenerateTitle) {
          addTitle(req, {
            text,
            response: { ...response },
            client,
          })
            .catch((err) => {
              logger.error('[ResumableAgentController] Error in title generation', err);
            })
            .finally(() => {
              if (client) {
                disposeClient(client);
              }
            });
        } else {
          if (client) {
            disposeClient(client);
          }
        }
      } catch (error) {
        // Check if this was an abort (not a real error)
        const wasAborted = job.abortController.signal.aborted || error.message?.includes('abort');

        if (wasAborted) {
          logger.debug(`[ResumableAgentController] Generation aborted for ${streamId}`);
          // abortJob already handled emitDone and completeJob
        } else {
          logger.error(`[ResumableAgentController] Generation error for ${streamId}:`, error);
          GenerationJobManager.emitError(streamId, error.message || 'Generation failed');
          GenerationJobManager.completeJob(streamId, error.message);
        }

        if (client) {
          disposeClient(client);
        }

        // Don't continue to title generation after error/abort
        return;
      }
    };

    // Start generation and handle any unhandled errors
    startGeneration().catch((err) => {
      logger.error(
        `[ResumableAgentController] Unhandled error in background generation: ${err.message}`,
      );
      GenerationJobManager.completeJob(streamId, err.message);
    });
  } catch (error) {
    logger.error('[ResumableAgentController] Initialization error:', error);
    if (!res.headersSent) {
      res.status(500).json({ error: error.message || 'Failed to start generation' });
    }
    GenerationJobManager.completeJob(streamId, error.message);
    if (client) {
      disposeClient(client);
    }
  }
};

/**
 * Non-resumable Agent Controller - Uses GenerationJobManager for abort handling.
 * Response is streamed directly to client via res, but abort state is managed centrally.
 */
const AgentController = async (req, res, next, initializeClient, addTitle) => {
  const isResumable = req.query.resumable === 'true';
  if (isResumable) {
    return ResumableAgentController(req, res, next, initializeClient, addTitle);
  }

  const {
    text,
    isRegenerate,
    endpointOption,
    conversationId: reqConversationId,
    isContinued = false,
    editedContent = null,
    parentMessageId = null,
    overrideParentMessageId = null,
    responseMessageId: editedResponseMessageId = null,
  } = req.body;

  // Generate conversationId upfront if not provided - streamId === conversationId always
  const conversationId = reqConversationId || crypto.randomUUID();
  const streamId = conversationId;

  let userMessage;
  let userMessageId;
  let responseMessageId;
  let client = null;
  let cleanupHandlers = [];

  const newConvo = !reqConversationId;
  const userId = req.user.id;

  // Create handler to avoid capturing the entire parent scope
  let getReqData = (data = {}) => {
    for (let key in data) {
      if (key === 'userMessage') {
        userMessage = data[key];
        userMessageId = data[key].messageId;
      } else if (key === 'responseMessageId') {
        responseMessageId = data[key];
      } else if (key === 'promptTokens') {
        // Update job metadata with prompt tokens for abort handling
        GenerationJobManager.updateMetadata(streamId, { promptTokens: data[key] });
      } else if (key === 'sender') {
        GenerationJobManager.updateMetadata(streamId, { sender: data[key] });
      }
      // conversationId is pre-generated, no need to update from callback
    }
  };

  // Create a function to handle final cleanup
  const performCleanup = async () => {
    logger.debug('[AgentController] Performing cleanup');
    if (Array.isArray(cleanupHandlers)) {
      for (const handler of cleanupHandlers) {
        try {
          if (typeof handler === 'function') {
            handler();
          }
        } catch (e) {
          logger.error('[AgentController] Error in cleanup handler', e);
        }
      }
    }

    // Complete the job in GenerationJobManager
    if (streamId) {
      logger.debug('[AgentController] Completing job in GenerationJobManager');
      await GenerationJobManager.completeJob(streamId);
    }

    // Dispose client properly
    if (client) {
      disposeClient(client);
    }

    // Clear all references
    client = null;
    getReqData = null;
    userMessage = null;
    cleanupHandlers = null;

    // Clear request data map
    if (requestDataMap.has(req)) {
      requestDataMap.delete(req);
    }
    logger.debug('[AgentController] Cleanup completed');
  };

  try {
    let prelimAbortController = new AbortController();
    const prelimCloseHandler = createCloseHandler(prelimAbortController);
    res.on('close', prelimCloseHandler);
    const removePrelimHandler = (manual) => {
      try {
        prelimCloseHandler(manual);
        res.removeListener('close', prelimCloseHandler);
      } catch (e) {
        logger.error('[AgentController] Error removing close listener', e);
      }
    };
    cleanupHandlers.push(removePrelimHandler);

    /** @type {{ client: TAgentClient; userMCPAuthMap?: Record<string, Record<string, string>> }} */
    const result = await initializeClient({
      req,
      res,
      endpointOption,
      signal: prelimAbortController.signal,
    });

    if (prelimAbortController.signal?.aborted) {
      prelimAbortController = null;
      throw new Error('Request was aborted before initialization could complete');
    } else {
      prelimAbortController = null;
      removePrelimHandler(true);
      cleanupHandlers.pop();
    }
    client = result.client;

    // Register client with finalization registry if available
    if (clientRegistry) {
      clientRegistry.register(client, { userId }, client);
    }

    // Store request data in WeakMap keyed by req object
    requestDataMap.set(req, { client });

    // Create job in GenerationJobManager for abort handling
    // streamId === conversationId (pre-generated above)
    const job = await GenerationJobManager.createJob(streamId, userId, conversationId);

    // Store endpoint metadata for abort handling
    GenerationJobManager.updateMetadata(streamId, {
      endpoint: endpointOption.endpoint,
      iconURL: endpointOption.iconURL,
      model: endpointOption.modelOptions?.model || endpointOption.model_parameters?.model,
      sender: client?.sender,
    });

    // Store content parts reference for abort
    if (client?.contentParts) {
      GenerationJobManager.setContentParts(streamId, client.contentParts);
    }

    const closeHandler = createCloseHandler(job.abortController);
    res.on('close', closeHandler);
    cleanupHandlers.push(() => {
      try {
        res.removeListener('close', closeHandler);
      } catch (e) {
        logger.error('[AgentController] Error removing close listener', e);
      }
    });

    /**
     * onStart callback - stores user message and response ID for abort handling
     */
    const onStart = (userMsg, respMsgId, _isNewConvo) => {
      sendEvent(res, { message: userMsg, created: true });
      userMessage = userMsg;
      userMessageId = userMsg.messageId;
      responseMessageId = respMsgId;

      // Store metadata for abort handling (conversationId is pre-generated)
      GenerationJobManager.updateMetadata(streamId, {
        responseMessageId: respMsgId,
        userMessage: {
          messageId: userMsg.messageId,
          parentMessageId: userMsg.parentMessageId,
          conversationId,
          text: userMsg.text,
        },
      });
    };

    const messageOptions = {
      user: userId,
      onStart,
      getReqData,
      isContinued,
      isRegenerate,
      editedContent,
      conversationId,
      parentMessageId,
      abortController: job.abortController,
      overrideParentMessageId,
      isEdited: !!editedContent,
      userMCPAuthMap: result.userMCPAuthMap,
      responseMessageId: editedResponseMessageId,
      progressOptions: {
        res,
      },
    };

    let response = await client.sendMessage(text, messageOptions);

    // Extract what we need and immediately break reference
    const messageId = response.messageId;
    const endpoint = endpointOption.endpoint;
    response.endpoint = endpoint;

    // Store database promise locally
    const databasePromise = response.databasePromise;
    delete response.databasePromise;

    // Resolve database-related data
    const { conversation: convoData = {} } = await databasePromise;
    const conversation = { ...convoData };
    conversation.title =
      conversation && !conversation.title ? null : conversation?.title || 'New Chat';

    // Process files if needed (sanitize to remove large text fields before transmission)
    if (req.body.files && client.options?.attachments) {
      userMessage.files = [];
      const messageFiles = new Set(req.body.files.map((file) => file.file_id));
      for (const attachment of client.options.attachments) {
        if (messageFiles.has(attachment.file_id)) {
          userMessage.files.push(sanitizeFileForTransmit(attachment));
        }
      }
      delete userMessage.image_urls;
    }

    // Only send if not aborted
    if (!job.abortController.signal.aborted) {
      // Create a new response object with minimal copies
      const finalResponse = { ...response };

      sendEvent(res, {
        final: true,
        conversation,
        title: conversation.title,
        requestMessage: sanitizeMessageForTransmit(userMessage),
        responseMessage: finalResponse,
      });
      res.end();

      // Save the message if needed
      if (client.savedMessageIds && !client.savedMessageIds.has(messageId)) {
        await saveMessage(
          req,
          { ...finalResponse, user: userId },
          { context: 'api/server/controllers/agents/request.js - response end' },
        );
      }
    }
    // Edge case: sendMessage completed but abort happened during sendCompletion
    // We need to ensure a final event is sent
    else if (!res.headersSent && !res.finished) {
      logger.debug(
        '[AgentController] Handling edge case: `sendMessage` completed but aborted during `sendCompletion`',
      );

      const finalResponse = { ...response };
      finalResponse.error = true;

      sendEvent(res, {
        final: true,
        conversation,
        title: conversation.title,
        requestMessage: sanitizeMessageForTransmit(userMessage),
        responseMessage: finalResponse,
        error: { message: 'Request was aborted during completion' },
      });
      res.end();
    }

    // Save user message if needed
    if (!client.skipSaveUserMessage) {
      await saveMessage(req, userMessage, {
        context: "api/server/controllers/agents/request.js - don't skip saving user message",
      });
    }

    // Add title if needed - extract minimal data
    if (addTitle && parentMessageId === Constants.NO_PARENT && newConvo) {
      addTitle(req, {
        text,
        response: { ...response },
        client,
      })
        .then(() => {
          logger.debug('[AgentController] Title generation started');
        })
        .catch((err) => {
          logger.error('[AgentController] Error in title generation', err);
        })
        .finally(() => {
          logger.debug('[AgentController] Title generation completed');
          performCleanup();
        });
    } else {
      performCleanup();
    }
  } catch (error) {
    // Handle error without capturing much scope
    handleAbortError(res, req, error, {
      conversationId,
      sender: client?.sender,
      messageId: responseMessageId,
      parentMessageId: overrideParentMessageId ?? userMessageId ?? parentMessageId,
      userMessageId,
    })
      .catch((err) => {
        logger.error('[api/server/controllers/agents/request] Error in `handleAbortError`', err);
      })
      .finally(() => {
        performCleanup();
      });
  }
};

module.exports = AgentController;