const { nanoid } = require('nanoid');
const { logger } = require('@librechat/data-schemas');
const { Callback, ToolEndHandler, formatAgentMessages } = require('@librechat/agents');
const {
  EModelEndpoint,
  ResourceType,
  PermissionBits,
  hasPermissions,
  AgentCapabilities,
} = require('librechat-data-provider');
const {
  writeSSE,
  createRun,
  createChunk,
  buildToolSet,
  loadSkillStates,
  sendFinalChunk,
  createSafeUser,
  validateRequest,
  initializeAgent,
  getBalanceConfig,
  injectSkillPrimes,
  extractManualSkills,
  createErrorResponse,
  recordCollectedUsage,
  createSubagentUsageSink,
  getTransactionsConfig,
  resolveRecursionLimit,
  findPiiMatchInMessages,
  discoverConnectedAgents,
  getRemoteAgentPermissions,
  createToolExecuteHandler,
  buildNonStreamingResponse,
  createOpenAIStreamTracker,
  resolveAgentScopedSkillIds,
  createOpenAIContentAggregator,
  isChatCompletionValidationFailure,
} = require('@librechat/api');
const {
  buildSummarizationHandlers,
  markSummarizationUsage,
  createToolEndCallback,
  agentLogHandlerObj,
} = require('~/server/controllers/agents/callbacks');
const { loadAgentTools, loadToolsForExecution } = require('~/server/services/ToolService');
const {
  findAccessibleResources,
  getEffectivePermissions,
} = require('~/server/services/PermissionService');
const {
  getSkillToolDeps,
  getSkillDbMethods,
  canAuthorSkillFiles,
  withDeploymentSkillIds,
  buildAgentToolContext,
  enrichLoadedToolsWithAgentContext,
} = require('~/server/services/Endpoints/agents/skillDeps');
const { getModelsConfig } = require('~/server/controllers/ModelController');
const { logViolation } = require('~/cache');
const db = require('~/models');

/**
 * Creates a tool loader function for the agent.
 * @param {AbortSignal} signal - The abort signal
 * @param {boolean} [definitionsOnly=true] - When true, returns only serializable
 *   tool definitions without creating full tool instances (for event-driven mode)
 */
function createToolLoader(signal, definitionsOnly = true) {
  return async function loadTools({
    req,
    res,
    tools,
    model,
    agentId,
    provider,
    tool_options,
    tool_resources,
  }) {
    const agent = { id: agentId, tools, provider, model, tool_options };
    try {
      return await loadAgentTools({
        req,
        res,
        agent,
        signal,
        tool_resources,
        definitionsOnly,
        streamId: null, // No resumable stream for OpenAI compat
      });
    } catch (error) {
      logger.error('Error loading tools for agent ' + agentId, error);
    }
  };
}

/**
 * Convert content part to internal format
 * @param {Object} part - Content part
 * @returns {Object} Converted part
 */
function convertContentPart(part) {
  if (part.type === 'text') {
    return { type: 'text', text: part.text };
  }
  if (part.type === 'image_url') {
    return { type: 'image_url', image_url: part.image_url };
  }
  return part;
}

/**
 * Convert OpenAI messages to internal format
 * @param {Array} messages - OpenAI format messages
 * @returns {Array} Internal format messages
 */
function convertMessages(messages) {
  return messages.map((msg) => {
    let content;
    if (typeof msg.content === 'string') {
      content = msg.content;
    } else if (msg.content) {
      content = msg.content.map(convertContentPart);
    } else {
      content = '';
    }

    return {
      role: msg.role,
      content,
      ...(msg.name && { name: msg.name }),
      ...(msg.tool_calls && { tool_calls: msg.tool_calls }),
      ...(msg.tool_call_id && { tool_call_id: msg.tool_call_id }),
    };
  });
}

/**
 * Send an error response in OpenAI format
 */
function sendErrorResponse(res, statusCode, message, type = 'invalid_request_error', code = null) {
  res.status(statusCode).json(createErrorResponse(message, type, code));
}

/**
 * OpenAI-compatible chat completions controller for agents.
 *
 * POST /v1/chat/completions
 *
 * Request format:
 * {
 *   "model": "agent_id_here",
 *   "messages": [{"role": "user", "content": "Hello!"}],
 *   "stream": true,
 *   "conversation_id": "optional",
 *   "parent_message_id": "optional"
 * }
 */
const OpenAIChatCompletionController = async (req, res) => {
  const appConfig = req.config;
  const requestStartTime = Date.now();

  const validation = validateRequest(req.body);
  if (isChatCompletionValidationFailure(validation)) {
    return sendErrorResponse(res, 400, validation.error);
  }

  const request = validation.request;
  const agentId = request.model;

  // Look up the agent
  const agent = await db.getAgent({ id: agentId });
  if (!agent) {
    return sendErrorResponse(
      res,
      404,
      `Agent not found: ${agentId}`,
      'invalid_request_error',
      'model_not_found',
    );
  }

  const piiHit = findPiiMatchInMessages(request.messages, appConfig?.messageFilter?.pii);
  if (piiHit != null) {
    return sendErrorResponse(
      res,
      400,
      `Message contains a ${piiHit.label}. Remove it and try again.`,
      'invalid_request_error',
      'message_filter_pii_block',
    );
  }

  const responseId = `chatcmpl-${nanoid()}`;
  const created = Math.floor(Date.now() / 1000);

  /** @type {import('@librechat/api').OpenAIResponseContext} — key must be `requestId` to match the type used by createChunk/buildNonStreamingResponse */
  const context = {
    created,
    requestId: responseId,
    model: agentId,
  };

  logger.debug(
    `[OpenAI API] Response ${responseId} started for agent ${agentId}, stream: ${request.stream}`,
  );

  // Set up abort controller
  const abortController = new AbortController();

  // Handle client disconnect
  req.on('close', () => {
    if (!abortController.signal.aborted) {
      abortController.abort();
      logger.debug('[OpenAI API] Client disconnected, aborting');
    }
  });

  try {
    if (request.conversation_id != null) {
      if (typeof request.conversation_id !== 'string') {
        return sendErrorResponse(
          res,
          400,
          'conversation_id must be a string',
          'invalid_request_error',
        );
      }
      if (!(await db.getConvo(req.user?.id, request.conversation_id))) {
        return sendErrorResponse(res, 404, 'Conversation not found', 'invalid_request_error');
      }
    }

    const conversationId = request.conversation_id ?? nanoid();
    const parentMessageId = request.parent_message_id ?? null;

    const agentsEConfig = appConfig?.endpoints?.[EModelEndpoint.agents];
    const allowedProviders = new Set(agentsEConfig?.allowedProviders);

    // Create tool loader
    const loadTools = createToolLoader(abortController.signal);

    // Initialize the agent first to check for disableStreaming
    const endpointOption = {
      endpoint: agent.provider,
      model_parameters: agent.model_parameters ?? {},
    };
    const skillDbMethods = getSkillDbMethods();

    // `filterFilesByAgentAccess` is intentionally omitted: it calls
    // `checkPermission` with `resourceType: AGENT`, but this route
    // authorizes callers through `REMOTE_AGENT` (via
    // `getRemoteAgentPermissions`), so including it would silently drop
    // owner-attached context files for any remote user who has
    // `REMOTE_AGENT_VIEWER` but not direct `AGENT_VIEW`.
    const dbMethods = {
      getConvoFiles: db.getConvoFiles,
      getFiles: db.getFiles,
      getUserKey: db.getUserKey,
      getMessages: db.getMessages,
      updateFilesUsage: db.updateFilesUsage,
      getUserKeyValues: db.getUserKeyValues,
      getUserCodeFiles: db.getUserCodeFiles,
      getToolFilesByIds: db.getToolFilesByIds,
      getCodeGeneratedFiles: db.getCodeGeneratedFiles,
      listSkillsByAccess: skillDbMethods.listSkillsByAccess,
      listAlwaysApplySkills: skillDbMethods.listAlwaysApplySkills,
      getSkillByName: skillDbMethods.getSkillByName,
    };

    const enabledCapabilities = new Set(agentsEConfig?.capabilities);
    const skillsCapabilityEnabled = enabledCapabilities.has(AgentCapabilities.skills);
    const ephemeralSkillsToggle = req.body?.ephemeralAgent?.skills === true;
    const accessibleSkillIds = skillsCapabilityEnabled
      ? withDeploymentSkillIds(
          await findAccessibleResources({
            userId: req.user.id,
            role: req.user.role,
            resourceType: ResourceType.SKILL,
            requiredPermissions: PermissionBits.VIEW,
          }),
        )
      : [];
    const editableSkillIds = skillsCapabilityEnabled
      ? await findAccessibleResources({
          userId: req.user.id,
          role: req.user.role,
          resourceType: ResourceType.SKILL,
          requiredPermissions: PermissionBits.EDIT,
        })
      : [];
    const skillCreateAllowed = skillsCapabilityEnabled
      ? await getSkillToolDeps().canCreateSkill({ req })
      : false;

    const { skillStates, defaultActiveOnShare } = await loadSkillStates({
      userId: req.user.id,
      appConfig,
      getUserById: db.getUserById,
      accessibleSkillIds,
    });

    const manualSkills = extractManualSkills(req.body);

    const primaryScopedSkillIds = resolveAgentScopedSkillIds({
      agent,
      accessibleSkillIds,
      skillsCapabilityEnabled,
      ephemeralSkillsToggle,
    });
    const primaryScopedEditableSkillIds = resolveAgentScopedSkillIds({
      agent,
      accessibleSkillIds: editableSkillIds,
      skillsCapabilityEnabled,
      ephemeralSkillsToggle,
    });

    const primaryConfig = await initializeAgent(
      {
        req,
        res,
        loadTools,
        requestFiles: [],
        conversationId,
        parentMessageId,
        agent,
        endpointOption,
        allowedProviders,
        isInitialAgent: true,
        accessibleSkillIds: primaryScopedSkillIds,
        skillAuthoringAvailable: canAuthorSkillFiles({
          agent,
          scopedEditableSkillIds: primaryScopedEditableSkillIds,
          skillCreateAllowed,
          skillsCapabilityEnabled,
          ephemeralSkillsToggle,
        }),
        codeEnvAvailable: enabledCapabilities.has(AgentCapabilities.execute_code),
        skillStates,
        defaultActiveOnShare,
        manualSkills,
      },
      dbMethods,
    );

    /**
     * Per-agent tool-execution context map, keyed by agentId.
     * Needed so the ON_TOOL_EXECUTE callback routes each sub-agent's tool calls
     * to the correct toolRegistry / userMCPAuthMap / tool_resources.
     * @type {Map<string, {
     *   agent: object,
     *   toolRegistry?: import('@librechat/agents').LCToolRegistry,
     *   requestScopedConnections?: import('@librechat/api').RequestScopedMCPConnectionStore,
     *   userMCPAuthMap?: Record<string, Record<string, string>>,
     *   tool_resources?: object,
     *   actionsEnabled?: boolean,
     * }>}
     */
    const agentToolContexts = new Map();
    agentToolContexts.set(
      primaryConfig.id,
      buildAgentToolContext({ agent, config: primaryConfig }),
    );

    // Only run BFS discovery (and pay `getModelsConfig` upfront) when the
    // primary has edges to follow — the common API case is single-agent.
    let handoffAgentConfigs = new Map();
    let discoveredEdges = [];
    let discoveredMCPAuthMap;
    if (primaryConfig.edges?.length) {
      const modelsConfig = await getModelsConfig(req);
      ({
        agentConfigs: handoffAgentConfigs,
        edges: discoveredEdges,
        userMCPAuthMap: discoveredMCPAuthMap,
      } = await discoverConnectedAgents(
        {
          req,
          res,
          primaryConfig,
          endpointOption,
          allowedProviders,
          modelsConfig,
          loadTools,
          requestFiles: [],
          conversationId,
          parentMessageId,
          // The route enforces REMOTE_AGENT on the primary; every discovered
          // sub-agent must clear the same sharing boundary, not the looser
          // in-app AGENT one.
          resourceType: ResourceType.REMOTE_AGENT,
          computeAccessibleSkillIds: (handoffAgent) =>
            resolveAgentScopedSkillIds({
              agent: handoffAgent,
              accessibleSkillIds,
              skillsCapabilityEnabled,
              ephemeralSkillsToggle,
            }),
          computeSkillAuthoringAvailable: (handoffAgent) =>
            canAuthorSkillFiles({
              agent: handoffAgent,
              scopedEditableSkillIds: resolveAgentScopedSkillIds({
                agent: handoffAgent,
                accessibleSkillIds: editableSkillIds,
                skillsCapabilityEnabled,
                ephemeralSkillsToggle,
              }),
              skillCreateAllowed,
              skillsCapabilityEnabled,
              ephemeralSkillsToggle,
            }),
          skillStates,
          defaultActiveOnShare,
          /** @see DiscoverConnectedAgentsParams.codeEnvAvailable */
          codeEnvAvailable: enabledCapabilities.has(AgentCapabilities.execute_code),
        },
        {
          getAgent: db.getAgent,
          // Use `getRemoteAgentPermissions` so sub-agent authorization
          // matches what the route's `createCheckRemoteAgentAccess`
          // middleware does for the primary: AGENT owners with the SHARE
          // bit are treated as remotely authorized even without an
          // explicit REMOTE_AGENT grant.
          checkPermission: async ({ userId, role, resourceId, requiredPermission }) => {
            const permissions = await getRemoteAgentPermissions(
              { getEffectivePermissions },
              userId,
              role,
              resourceId,
            );
            return hasPermissions(permissions, requiredPermission);
          },
          logViolation,
          db: dbMethods,
          onAgentInitialized: (agentId, handoffAgent, config) => {
            agentToolContexts.set(agentId, buildAgentToolContext({ agent: handoffAgent, config }));
          },
          initializeAgent,
        },
      ));
    }

    primaryConfig.edges = discoveredEdges;

    // Determine if streaming is enabled (check both request and agent config)
    const streamingDisabled = !!primaryConfig.model_parameters?.disableStreaming;
    const isStreaming = request.stream === true && !streamingDisabled;

    // Create tracker for streaming or aggregator for non-streaming
    const tracker = isStreaming ? createOpenAIStreamTracker() : null;
    const aggregator = isStreaming ? null : createOpenAIContentAggregator();

    // Set up response for streaming
    if (isStreaming) {
      res.setHeader('Content-Type', 'text/event-stream');
      res.setHeader('Cache-Control', 'no-cache');
      res.setHeader('Connection', 'keep-alive');
      res.setHeader('X-Accel-Buffering', 'no');
      res.flushHeaders();

      // Send initial chunk with role
      const initialChunk = createChunk(context, { role: 'assistant' });
      writeSSE(res, initialChunk);
    }

    // Create handler config for OpenAI streaming (only used when streaming)
    const handlerConfig = isStreaming
      ? {
          res,
          context,
          tracker,
        }
      : null;

    const collectedUsage = [];
    /** @type {Promise<import('librechat-data-provider').TAttachment | null>[]} */
    const artifactPromises = [];

    const toolEndCallback = createToolEndCallback({ req, res, artifactPromises, streamId: null });

    /* Stable for the turn: the primary prime list is fixed once
       `initializeAgent` resolves and is used as the fallback when a
       specific agent context is unavailable. `codeEnvAvailable` is read
       per-agent from the stored tool context (admin cap AND that
       agent's `tools` list includes `execute_code`) — a skills-only
       agent never gains sandbox access even if the admin enabled the
       capability globally. */
    const toolExecuteOptions = {
      loadTools: async (toolNames, agentId) => {
        const ctx = agentToolContexts.get(agentId) ?? agentToolContexts.get(primaryConfig.id) ?? {};
        const result = await loadToolsForExecution({
          req,
          res,
          toolNames,
          agent: ctx.agent ?? agent,
          signal: abortController.signal,
          toolRegistry: ctx.toolRegistry,
          mcpAvailableTools: ctx.mcpAvailableTools,
          requestScopedConnections: ctx.requestScopedConnections,
          userMCPAuthMap: ctx.userMCPAuthMap,
          tool_resources: ctx.tool_resources,
          actionsEnabled: ctx.actionsEnabled,
        });
        return enrichLoadedToolsWithAgentContext({
          result,
          req,
          ctx,
        });
      },
      toolEndCallback,
      ...getSkillToolDeps(),
    };

    const summarizationConfig = appConfig?.summarization;

    const openaiMessages = convertMessages(request.messages);

    const toolSet = buildToolSet(primaryConfig);
    const formatted = formatAgentMessages(openaiMessages, {}, toolSet);
    const formattedMessages = formatted.messages;
    const initialSummary = formatted.summary;
    let indexTokenCountMap = formatted.indexTokenCountMap;

    /**
     * Inject manual + always-apply skill primes so the model sees SKILL.md
     * bodies for this turn — parity with AgentClient's chat path. OpenAI-
     * compatible streaming uses its own tracker/aggregator shape, so the
     * LibreChat-style card SSE events don't apply here; only the
     * message-context part carries over.
     */
    const manualSkillPrimes = primaryConfig.manualSkillPrimes;
    const alwaysApplySkillPrimes = primaryConfig.alwaysApplySkillPrimes;
    if (
      (manualSkillPrimes && manualSkillPrimes.length > 0) ||
      (alwaysApplySkillPrimes && alwaysApplySkillPrimes.length > 0)
    ) {
      const primeResult = injectSkillPrimes({
        initialMessages: formattedMessages,
        indexTokenCountMap,
        manualSkillPrimes,
        alwaysApplySkillPrimes,
      });
      indexTokenCountMap = primeResult.indexTokenCountMap;
      /* Surface the cap-driven always-apply truncation at the controller
         layer too — `injectSkillPrimes` already logs internally, but the
         controller-level warn includes endpoint context so operators can
         tell at a glance which path hit the cap. Mirrors AgentClient's
         warn in `client.js`. */
      if (primeResult.alwaysApplyDropped > 0) {
        logger.warn(
          `[OpenAI API] Dropped ${primeResult.alwaysApplyDropped} always-apply prime(s) to stay within MAX_PRIMED_SKILLS_PER_TURN.`,
        );
      }
    }

    /**
     * Create a simple handler that processes data
     */
    const createHandler = (processor) => ({
      handle: (_event, data) => {
        if (processor) {
          processor(data);
        }
      },
    });

    /**
     * Stream text content in OpenAI format
     */
    const streamText = (text) => {
      if (!text) {
        return;
      }
      if (isStreaming) {
        tracker.addText();
        writeSSE(res, createChunk(context, { content: text }));
      } else {
        aggregator.addText(text);
      }
    };

    /**
     * Stream reasoning content in OpenAI format (OpenRouter convention)
     */
    const streamReasoning = (text) => {
      if (!text) {
        return;
      }
      if (isStreaming) {
        tracker.addReasoning();
        writeSSE(res, createChunk(context, { reasoning: text }));
      } else {
        aggregator.addReasoning(text);
      }
    };

    // Event handlers for OpenAI-compatible streaming
    const handlers = {
      // Text content streaming
      on_message_delta: createHandler((data) => {
        const content = data?.delta?.content;
        if (Array.isArray(content)) {
          for (const part of content) {
            if (part.type === 'text' && part.text) {
              streamText(part.text);
            }
          }
        }
      }),

      // Reasoning/thinking content streaming
      on_reasoning_delta: createHandler((data) => {
        const content = data?.delta?.content;
        if (Array.isArray(content)) {
          for (const part of content) {
            const text = part.think || part.text;
            if (text) {
              streamReasoning(text);
            }
          }
        }
      }),

      // Tool call initiation - streams id and name (from on_run_step)
      on_run_step: createHandler((data) => {
        const stepDetails = data?.stepDetails;
        if (stepDetails?.type === 'tool_calls' && stepDetails.tool_calls) {
          for (const tc of stepDetails.tool_calls) {
            const toolIndex = data.index ?? 0;
            const toolId = tc.id ?? '';
            const toolName = tc.name ?? '';
            const toolCall = {
              id: toolId,
              type: 'function',
              function: { name: toolName, arguments: '' },
            };

            // Track tool call in tracker or aggregator
            if (isStreaming) {
              if (!tracker.toolCalls.has(toolIndex)) {
                tracker.toolCalls.set(toolIndex, toolCall);
              }
              // Stream initial tool call chunk (like OpenAI does)
              writeSSE(
                res,
                createChunk(context, {
                  tool_calls: [{ index: toolIndex, ...toolCall }],
                }),
              );
            } else {
              if (!aggregator.toolCalls.has(toolIndex)) {
                aggregator.toolCalls.set(toolIndex, toolCall);
              }
            }
          }
        }
      }),

      // Tool call argument streaming (from on_run_step_delta)
      on_run_step_delta: createHandler((data) => {
        const delta = data?.delta;
        if (delta?.type === 'tool_calls' && delta.tool_calls) {
          for (const tc of delta.tool_calls) {
            const args = tc.args ?? '';
            if (!args) {
              continue;
            }

            const toolIndex = tc.index ?? 0;

            // Update tool call arguments
            const targetMap = isStreaming ? tracker.toolCalls : aggregator.toolCalls;
            const tracked = targetMap.get(toolIndex);
            if (tracked) {
              tracked.function.arguments += args;
            }

            // Stream argument delta (only for streaming)
            if (isStreaming) {
              writeSSE(
                res,
                createChunk(context, {
                  tool_calls: [
                    {
                      index: toolIndex,
                      function: { arguments: args },
                    },
                  ],
                }),
              );
            }
          }
        }
      }),

      // Usage tracking
      on_chat_model_end: {
        handle: (_event, data, metadata) => {
          const usage = data?.output?.usage_metadata;
          if (usage) {
            const taggedUsage = markSummarizationUsage(usage, metadata);
            collectedUsage.push(taggedUsage);
            const target = isStreaming ? tracker : aggregator;
            target.usage.promptTokens += taggedUsage.input_tokens ?? 0;
            target.usage.completionTokens += taggedUsage.output_tokens ?? 0;
          }
        },
      },
      on_run_step_completed: createHandler(),
      // Use proper ToolEndHandler for processing artifacts (images, file citations, code output)
      on_tool_end: new ToolEndHandler(toolEndCallback, logger),
      on_chain_stream: createHandler(),
      on_chain_end: createHandler(),
      on_agent_update: createHandler(),
      on_agent_log: agentLogHandlerObj,
      on_custom_event: createHandler(),
      on_tool_execute: createToolExecuteHandler(toolExecuteOptions),
      ...(summarizationConfig?.enabled !== false
        ? buildSummarizationHandlers({ isStreaming, res })
        : {}),
    };

    // Create and run the agent
    const userId = req.user?.id ?? 'api-user';

    // Extract merged userMCPAuthMap (needed for MCP tool connections across
    // the primary and any discovered handoff sub-agents)
    const userMCPAuthMap = discoveredMCPAuthMap ?? primaryConfig.userMCPAuthMap;

    const runAgents = [primaryConfig, ...handoffAgentConfigs.values()];

    const run = await createRun({
      agents: runAgents,
      messages: formattedMessages,
      indexTokenCountMap,
      initialSummary,
      runId: responseId,
      summarizationConfig,
      appConfig,
      signal: abortController.signal,
      customHandlers: handlers,
      requestBody: {
        messageId: responseId,
        conversationId,
      },
      user: { id: userId },
      tenantId: req.user?.tenantId,
      /** Bills subagent child-run model calls (reported outside the
       *  streamEvents loop) into the same collectedUsage array. */
      subagentUsageSink: createSubagentUsageSink(collectedUsage),
    });

    if (!run) {
      throw new Error('Failed to create agent run');
    }

    const config = {
      runName: 'AgentRun',
      configurable: {
        thread_id: conversationId,
        user_id: userId,
        user: createSafeUser(req.user),
        requestBody: {
          messageId: responseId,
          conversationId,
        },
        ...(userMCPAuthMap != null && { userMCPAuthMap }),
      },
      recursionLimit: resolveRecursionLimit(agentsEConfig, agent),
      signal: abortController.signal,
      streamMode: 'values',
      version: 'v2',
    };

    await run.processStream({ messages: formattedMessages }, config, {
      callbacks: {
        [Callback.TOOL_ERROR]: (graph, error, toolId) => {
          logger.error(`[OpenAI API] Tool Error "${toolId}"`, error);
        },
      },
    });

    // Record token usage against balance
    const balanceConfig = getBalanceConfig(appConfig);
    const transactionsConfig = getTransactionsConfig(appConfig);
    recordCollectedUsage(
      {
        spendTokens: db.spendTokens,
        spendStructuredTokens: db.spendStructuredTokens,
        pricing: { getMultiplier: db.getMultiplier, getCacheMultiplier: db.getCacheMultiplier },
        bulkWriteOps: { insertMany: db.bulkInsertTransactions, updateBalance: db.updateBalance },
      },
      {
        user: userId,
        conversationId,
        collectedUsage,
        context: 'message',
        messageId: responseId,
        balance: balanceConfig,
        transactions: transactionsConfig,
        model: primaryConfig.model || agent.model_parameters?.model,
      },
    ).catch((err) => {
      logger.error('[OpenAI API] Error recording usage:', err);
    });

    // Finalize response
    const duration = Date.now() - requestStartTime;
    if (isStreaming) {
      sendFinalChunk(handlerConfig);
      res.end();
      logger.debug(`[OpenAI API] Response ${responseId} completed in ${duration}ms (streaming)`);

      // Wait for artifact processing after response ends (non-blocking)
      if (artifactPromises.length > 0) {
        Promise.all(artifactPromises).catch((artifactError) => {
          logger.warn('[OpenAI API] Error processing artifacts:', artifactError);
        });
      }
    } else {
      // For non-streaming, wait for artifacts before sending response
      if (artifactPromises.length > 0) {
        try {
          await Promise.all(artifactPromises);
        } catch (artifactError) {
          logger.warn('[OpenAI API] Error processing artifacts:', artifactError);
        }
      }

      // Build usage from aggregated data
      const usage = {
        prompt_tokens: aggregator.usage.promptTokens,
        completion_tokens: aggregator.usage.completionTokens,
        total_tokens: aggregator.usage.promptTokens + aggregator.usage.completionTokens,
      };

      if (aggregator.usage.reasoningTokens > 0) {
        usage.completion_tokens_details = {
          reasoning_tokens: aggregator.usage.reasoningTokens,
        };
      }

      const response = buildNonStreamingResponse(
        context,
        aggregator.getText(),
        aggregator.getReasoning(),
        aggregator.toolCalls,
        usage,
      );
      res.json(response);
      logger.debug(
        `[OpenAI API] Response ${responseId} completed in ${duration}ms (non-streaming)`,
      );
    }
  } catch (error) {
    const errorMessage = error instanceof Error ? error.message : 'An error occurred';
    logger.error('[OpenAI API] Error:', error);

    // Check if we already started streaming (headers sent)
    if (res.headersSent) {
      // Headers already sent, send error in stream
      const errorChunk = createChunk(context, { content: `\n\nError: ${errorMessage}` }, 'stop');
      writeSSE(res, errorChunk);
      writeSSE(res, '[DONE]');
      res.end();
    } else {
      // Forward upstream provider status codes (e.g., Anthropic 400s) instead of masking as 500
      const statusCode =
        typeof error?.status === 'number' && error.status >= 400 && error.status < 600
          ? error.status
          : 500;
      const errorType =
        statusCode >= 400 && statusCode < 500 ? 'invalid_request_error' : 'server_error';
      sendErrorResponse(res, statusCode, errorMessage, errorType);
    }
  }
};

/**
 * List available agents as models (filtered by remote access permissions)
 *
 * GET /v1/models
 */
const ListModelsController = async (req, res) => {
  try {
    const userId = req.user?.id;
    const userRole = req.user?.role;

    if (!userId) {
      return sendErrorResponse(res, 401, 'Authentication required', 'auth_error');
    }

    // Find agents the user has remote access to (VIEW permission on REMOTE_AGENT)
    const accessibleAgentIds = await findAccessibleResources({
      userId,
      role: userRole,
      resourceType: ResourceType.REMOTE_AGENT,
      requiredPermissions: PermissionBits.VIEW,
    });

    // Get the accessible agents
    let agents = [];
    if (accessibleAgentIds.length > 0) {
      agents = await db.getAgents({ _id: { $in: accessibleAgentIds } });
    }

    const models = agents.map((agent) => ({
      id: agent.id,
      object: 'model',
      created: Math.floor(new Date(agent.createdAt || Date.now()).getTime() / 1000),
      owned_by: 'librechat',
      permission: [],
      root: agent.id,
      parent: null,
      // LibreChat extensions
      name: agent.name,
      description: agent.description,
      provider: agent.provider,
    }));

    res.json({
      object: 'list',
      data: models,
    });
  } catch (error) {
    const errorMessage = error instanceof Error ? error.message : 'Failed to list models';
    logger.error('[OpenAI API] Error listing models:', error);
    sendErrorResponse(res, 500, errorMessage, 'server_error');
  }
};

/**
 * Get a specific model/agent (with remote access permission check)
 *
 * GET /v1/models/:model
 */
const GetModelController = async (req, res) => {
  try {
    const { model } = req.params;
    const userId = req.user?.id;
    const userRole = req.user?.role;

    if (!userId) {
      return sendErrorResponse(res, 401, 'Authentication required', 'auth_error');
    }

    const agent = await db.getAgent({ id: model });

    if (!agent) {
      return sendErrorResponse(
        res,
        404,
        `Model not found: ${model}`,
        'invalid_request_error',
        'model_not_found',
      );
    }

    // Check if user has remote access to this agent
    const accessibleAgentIds = await findAccessibleResources({
      userId,
      role: userRole,
      resourceType: ResourceType.REMOTE_AGENT,
      requiredPermissions: PermissionBits.VIEW,
    });

    const hasAccess = accessibleAgentIds.some((id) => id.toString() === agent._id.toString());

    if (!hasAccess) {
      return sendErrorResponse(
        res,
        403,
        `No remote access to model: ${model}`,
        'permission_error',
        'access_denied',
      );
    }

    res.json({
      id: agent.id,
      object: 'model',
      created: Math.floor(new Date(agent.createdAt || Date.now()).getTime() / 1000),
      owned_by: 'librechat',
      permission: [],
      root: agent.id,
      parent: null,
      // LibreChat extensions
      name: agent.name,
      description: agent.description,
      provider: agent.provider,
    });
  } catch (error) {
    const errorMessage = error instanceof Error ? error.message : 'Failed to get model';
    logger.error('[OpenAI API] Error getting model:', error);
    sendErrorResponse(res, 500, errorMessage, 'server_error');
  }
};

module.exports = {
  OpenAIChatCompletionController,
  ListModelsController,
  GetModelController,
};