const { tool } = require('@librechat/agents/langchain/tools');
const { logger, getTenantId } = require('@librechat/data-schemas');
const { Providers, Constants: AgentConstants } = require('@librechat/agents');
const {
  sendEvent,
  PENDING_STALE_MS,
  MCPOAuthHandler,
  isMCPDomainAllowed,
  splitMCPToolKey,
  normalizeServerName,
  normalizeMCPToolKey,
  buildServerNameAliases,
  findShadowedServerNames,
  resolveMCPServerContext,
  normalizeJsonSchema,
  GenerationJobManager,
  resolveJsonSchemaRefs,
  sanitizeGeminiSchema,
  buildMCPAuthStepId,
  buildMCPAuthToolCall,
  processMCPEnv,
  buildMCPAuthRunStepEvent,
  buildMCPAuthRunStepDeltaEvent,
  buildMCPAuthRunStepEndDeltaEvent,
  isUserSourced,
  checkAccessWithRequestCache,
  getServerCustomUserVars,
  requiresEphemeralUserConnection,
  containsGraphTokenPlaceholder,
} = require('@librechat/api');
const {
  Time,
  CacheKeys,
  Constants,
  Permissions,
  PermissionTypes,
  isAssistantsEndpoint,
} = require('librechat-data-provider');
const {
  getOAuthReconnectionManager,
  getMCPServersRegistry,
  getFlowStateManager,
  getMCPManager,
} = require('~/config');
const db = require('~/models');
const { findToken, createToken, updateToken, deleteTokens } = db;
const { getGraphApiToken } = require('./GraphTokenService');
const { exchangeOboToken } = require('./OboTokenService');
const { createOboTrustChecker } = require('./OboPolicyService');
const { reinitMCPServer } = require('./Tools/mcp');
const { getAppConfig } = require('./Config');
const { getLogStores } = require('~/cache');

const MAX_CACHE_SIZE = 1000;
const lastReconnectAttempts = new Map();
const RECONNECT_THROTTLE_MS = 10_000;

const missingToolCache = new Map();
const MISSING_TOOL_TTL_MS = 10_000;

async function userCanUseMCPServers(user, req) {
  if (!user?.id || !user?.role) {
    return false;
  }

  try {
    return await checkAccessWithRequestCache({
      req,
      user,
      permissionType: PermissionTypes.MCP_SERVERS,
      permissions: [Permissions.USE],
      getRoleByName: db.getRoleByName,
    });
  } catch (error) {
    logger.error(`[MCP][User: ${user.id}] Failed MCP permission check`, error);
    return false;
  }
}

function createMCPPermissionContext(req) {
  return {
    canUseServers: (user = req?.user) => userCanUseMCPServers(user, req),
  };
}

function evictStale(map, ttl) {
  if (map.size <= MAX_CACHE_SIZE) {
    return;
  }
  const now = Date.now();
  for (const [key, timestamp] of map) {
    if (now - timestamp >= ttl) {
      map.delete(key);
    }
    if (map.size <= MAX_CACHE_SIZE) {
      return;
    }
  }
}

const unavailableMsg =
  "This tool's MCP server is temporarily unavailable. Please try again shortly.";

function getOAuthFlowId(userId, serverName, tenantId = getTenantId()) {
  if (!tenantId) {
    return MCPOAuthHandler.generateFlowId(userId, serverName);
  }
  return MCPOAuthHandler.generateFlowId(userId, serverName, tenantId);
}

async function getAppConfigForRequest(req) {
  const user = req?.user;
  return await getAppConfigForUser(user?.id, user);
}

async function getAppConfigForUser(userId, user) {
  return await getAppConfig({ role: user?.role, tenantId: getTenantId(), userId });
}

/**
 * Resolves config-source MCP servers from admin Config overrides for the current
 * request context. Returns the parsed configs keyed by server name.
 * @param {import('express').Request} req - Express request with user context
 * @returns {Promise<Record<string, import('@librechat/api').ParsedServerConfig>>}
 */
async function resolveConfigServers(req) {
  try {
    const registry = getMCPServersRegistry();
    const appConfig = await getAppConfigForRequest(req);
    return await registry.ensureConfigServers(appConfig?.mcpConfig || {});
  } catch (error) {
    logger.warn(
      '[resolveConfigServers] Failed to resolve config servers, degrading to empty:',
      error,
    );
    return {};
  }
}

/**
 * Resolves operator-managed MCP server names from admin Config overrides for the current request.
 * Returns a request-time snapshot for DB server creation, not a cross-process lock.
 * @throws Propagates app config lookup errors to keep DB server creation fail-closed.
 * @param {import('express').Request} req - Express request with user context
 * @returns {Promise<string[]>}
 */
async function resolveMcpConfigNames(req) {
  const appConfig = await getAppConfigForRequest(req);
  return Object.keys(appConfig?.mcpConfig || {});
}

/**
 * All configured server names in the normalized form tool keys are built with.
 * Unlike `resolveConfigServers`, this keeps unmodified YAML servers, which
 * `ensureConfigServers` skips - those are exactly the ones that must still
 * resolve the tool-key boundary.
 * @param {import('express').Request} req
 * @returns {Promise<string[]>}
 */
async function resolveMcpServerNames(req) {
  try {
    const names = await resolveMcpConfigNames(req);
    return names.map(normalizeServerName);
  } catch (error) {
    logger.warn(
      '[resolveMcpServerNames] Failed to resolve server names, degrading to empty:',
      error,
    );
    return [];
  }
}

/**
 * Config-source servers and all configured names from a single app-config read,
 * so the tool-loading path does not pay two lookups for the same principal.
 * Degrades to empty like `resolveConfigServers` rather than aborting tool loading.
 * @param {import('express').Request} req
 * @returns {Promise<{ configServers: Record<string, import('@librechat/api').ParsedServerConfig>, serverNames: string[] }>}
 */
async function resolveMcpServerContext(req) {
  try {
    const appConfig = await getAppConfigForRequest(req);
    return await resolveMCPServerContext({
      mcpConfig: appConfig?.mcpConfig || {},
      ensureConfigServers: (mcpConfig) => getMCPServersRegistry().ensureConfigServers(mcpConfig),
    });
  } catch (error) {
    logger.warn(
      '[resolveMcpServerContext] Failed to resolve MCP servers, degrading to empty:',
      error,
    );
    return { configServers: {}, serverNames: [], rawServerNames: [] };
  }
}

/**
 * Resolves config-source servers and merges all server configs (YAML + config + user DB)
 * for the given user context. Shared helper for controllers needing the full merged config.
 * @param {string} userId
 * @param {{ id?: string, role?: string }} [user]
 * @returns {Promise<Record<string, import('@librechat/api').ParsedServerConfig>>}
 */
/**
 * Names of every MCP server the user can reach (operator config + user DB),
 * for the legacy-key heal's collision detection in `initializeAgent`. Only
 * consulted when a configured server name needs normalization.
 * @param {string} [userId]
 * @param {string} [role]
 * @returns {Promise<string[]>}
 */
async function getAccessibleMcpServerNames(userId, role) {
  const configs = await resolveAllMcpConfigs(
    userId,
    role != null ? { id: userId, role } : { id: userId },
  );
  return Object.keys(configs ?? {});
}

/**
 * Heals legacy raw-keyed MCP tool names in an assistant payload to the
 * current normalized cache keys. Cached tool definitions are keyed
 * `${toolName}${mcp_delimiter}${normalizeServerName(server)}`, while an
 * assistant saved before that convention resubmits the raw-suffixed string
 * on every edit — the controllers' exact-only lookup would then silently
 * drop the tool from the assistant. SHADOWED raw names (normalized slot
 * claimed by another configured server) stay raw and fail closed, mirroring
 * the runtime heal, with the shadow set built from the FULL accessible
 * audit (cross-tier collisions included) and healing skipped outright when
 * that audit cannot complete. Config names are read only when a
 * delimiter-bearing name actually misses the cache; config-read failures
 * propagate (write path) rather than silently dropping the tool. Healed
 * string entries dedupe order-preserving so a payload carrying both
 * spellings can't submit duplicate function names.
 * @param {object} params
 * @param {ServerRequest} params.req
 * @param {Array<string | object>} [params.tools]
 * @param {Record<string, unknown>} params.toolDefinitions
 * @returns {Promise<Array<string | object>>}
 */
async function healMcpToolNames({ req, tools, toolDefinitions }) {
  const list = tools ?? [];
  const needsHeal = list.some(
    (tool) =>
      typeof tool === 'string' &&
      tool.includes(Constants.mcp_delimiter) &&
      toolDefinitions[tool] == null,
  );
  if (!needsHeal) {
    return list;
  }
  const rawServerNames = await resolveMcpConfigNames(req);
  /** Cross-tier shadowing (DB `foo` vs operator `foo!`) is invisible to
   *  operator names alone — the shadow set must come from the FULL
   *  accessible audit. Every rewrite candidate here is normalization-
   *  sensitive by construction, so an incomplete audit skips healing
   *  entirely (the raw key stays raw and fails closed). */
  const audit = await resolveCollisionAuditNames({
    rawServerNames,
    userId: req.user?.id,
    role: req.user?.role,
  });
  if (!audit.complete) {
    return list;
  }
  const shadowed = findShadowedServerNames(audit.names);
  const seen = new Set();
  const healedList = [];
  for (const tool of list) {
    let healedTool = tool;
    if (
      typeof tool === 'string' &&
      tool.includes(Constants.mcp_delimiter) &&
      toolDefinitions[tool] == null
    ) {
      const [, parsedServerName] = splitMCPToolKey(tool, rawServerNames);
      if (
        parsedServerName != null &&
        rawServerNames.includes(parsedServerName) &&
        !shadowed.has(parsedServerName)
      ) {
        const healed = normalizeMCPToolKey(tool, rawServerNames);
        if (toolDefinitions[healed] != null) {
          healedTool = healed;
        }
      }
    }
    /** A payload carrying both spellings collapses to one entry after the
     *  heal — duplicate function names make providers reject the save. */
    if (typeof healedTool === 'string') {
      if (seen.has(healedTool)) {
        continue;
      }
      seen.add(healedTool);
    }
    healedList.push(healedTool);
  }
  return healedList;
}

/**
 * Resolves the name set MCP collision guards audit against. Prefers the
 * caller-threaded accessible set; self-fetches only when a configured name
 * needs normalization (safe-name deployments never pay the lookup); reports
 * `complete: false` when the full set was needed but unavailable — callers
 * must then fail closed for normalization-sensitive references instead of
 * auditing against operator names alone.
 * @param {object} params
 * @param {readonly string[]} params.rawServerNames
 * @param {readonly string[]} [params.accessibleServerNames]
 * @param {string} [params.userId]
 * @param {string} [params.role]
 * @returns {Promise<{ names: readonly string[], complete: boolean }>}
 */
async function resolveCollisionAuditNames({ rawServerNames, accessibleServerNames, userId, role }) {
  if (accessibleServerNames?.length) {
    return { names: accessibleServerNames, complete: true };
  }
  const needsFullAudit = rawServerNames.some((name) => normalizeServerName(name) !== name);
  if (!needsFullAudit) {
    return { names: rawServerNames, complete: true };
  }
  try {
    const names = await getAccessibleMcpServerNames(userId, role);
    /** `resolveAllMcpConfigs` tolerates `ensureConfigServers` failures, so
     *  the merged read can silently omit config-only servers. The caller's
     *  raw config names come from the app-config snapshot (registry-
     *  independent), so the union keeps `complete: true` honest. */
    return { names: [...new Set([...names, ...rawServerNames])], complete: true };
  } catch (error) {
    logger.warn(
      '[MCP] Collision audit unavailable; normalization-sensitive references fail closed:',
      error,
    );
    return { names: rawServerNames, complete: false };
  }
}

async function resolveAllMcpConfigs(userId, user) {
  const registry = getMCPServersRegistry();
  const appConfig = await getAppConfigForUser(userId, user);
  let configServers = {};
  try {
    configServers = await registry.ensureConfigServers(appConfig?.mcpConfig || {});
  } catch (error) {
    logger.warn(
      '[resolveAllMcpConfigs] Config server resolution failed, continuing without:',
      error,
    );
  }
  if (user?.role) {
    return await registry.getAllServerConfigs(userId, configServers, user.role);
  }

  return await registry.getAllServerConfigs(userId, configServers);
}

/**
 * Best-effort early gate; the authoritative check is
 * `assertResolvedRuntimeConfigAllowed` in `@librechat/api`, whose resolution
 * this must mirror. Graph placeholders resolve later (async), so a URL still
 * carrying one defers to the authoritative check instead of rejecting here.
 */
async function isEarlyDomainAllowed({
  serverConfig,
  user,
  requestBody,
  userMCPAuthMap,
  serverName,
  allowedDomains,
  allowedAddresses,
}) {
  const validationConfig = processMCPEnv({
    user,
    body: requestBody,
    dbSourced: isUserSourced(serverConfig),
    options: serverConfig,
    customUserVars: getServerCustomUserVars(userMCPAuthMap, serverName),
  });
  if (
    typeof validationConfig?.url === 'string' &&
    containsGraphTokenPlaceholder(validationConfig.url)
  ) {
    return true;
  }
  return await isMCPDomainAllowed(validationConfig, allowedDomains, allowedAddresses);
}

/**
 * @param {string} toolName
 * @param {string} serverName
 */
function createUnavailableToolStub(toolName, serverName) {
  const normalizedToolKey = `${toolName}${Constants.mcp_delimiter}${normalizeServerName(serverName)}`;
  const _call = async () => [unavailableMsg, null];
  const toolInstance = tool(_call, {
    schema: {
      type: 'object',
      properties: {
        input: { type: 'string', description: 'Input for the tool' },
      },
      required: [],
    },
    name: normalizedToolKey,
    description: unavailableMsg,
    responseFormat: AgentConstants.CONTENT_AND_ARTIFACT,
  });
  toolInstance.mcp = true;
  toolInstance.mcpRawServerName = serverName;
  return toolInstance;
}

function isEmptyObjectSchema(jsonSchema) {
  return (
    jsonSchema != null &&
    typeof jsonSchema === 'object' &&
    jsonSchema.type === 'object' &&
    (jsonSchema.properties == null || Object.keys(jsonSchema.properties).length === 0) &&
    !jsonSchema.additionalProperties
  );
}

/**
 * @param {object} params
 * @param {ServerResponse} params.res - The Express response object for sending events.
 * @param {string} params.stepId - The ID of the step in the flow.
 * @param {ToolCallChunk} params.toolCall - The tool call object containing tool information.
 * @param {string | null} [params.streamId] - The stream ID for resumable mode.
 * @param {number} [params.jobCreatedAt] - The generation epoch that owns emitted events.
 */
function createRunStepDeltaEmitter({ res, stepId, toolCall, streamId = null, jobCreatedAt }) {
  /**
   * @param {string} authURL - The URL to redirect the user for OAuth authentication.
   * @param {{ expiresAt?: number }} [options]
   * @returns {Promise<void>}
   */
  return async function (authURL, options) {
    const eventData = buildMCPAuthRunStepDeltaEvent({ authURL, stepId, toolCall, options });
    if (streamId) {
      await GenerationJobManager.emitChunk(streamId, eventData, {
        expectedCreatedAt: jobCreatedAt,
      });
    } else {
      sendEvent(res, eventData);
    }
  };
}

/**
 * @param {object} params
 * @param {ServerResponse} params.res - The Express response object for sending events.
 * @param {string} params.runId - The Run ID, i.e. message ID
 * @param {string} params.stepId - The ID of the step in the flow.
 * @param {ToolCallChunk} params.toolCall - The tool call object containing tool information.
 * @param {number} [params.index]
 * @param {string | null} [params.streamId] - The stream ID for resumable mode.
 * @param {number} [params.jobCreatedAt] - The generation epoch that owns emitted events.
 * @returns {() => Promise<void>}
 */
function createRunStepEmitter({
  res,
  runId,
  stepId,
  toolCall,
  index,
  streamId = null,
  jobCreatedAt,
}) {
  return async function () {
    const eventData = buildMCPAuthRunStepEvent({ runId, stepId, toolCall, index });
    if (streamId) {
      await GenerationJobManager.emitChunk(streamId, eventData, {
        expectedCreatedAt: jobCreatedAt,
      });
    } else {
      sendEvent(res, eventData);
    }
  };
}

/**
 * Creates a function used to ensure the flow handler is only invoked once
 * @param {object} params
 * @param {string} params.flowId - The ID of the login flow.
 * @param {FlowStateManager<any>} params.flowManager - The flow manager instance.
 * @param {(authURL: string, options?: { expiresAt?: number }) => void | Promise<void>} [params.callback]
 */
function createOAuthStart({ flowId, flowManager, callback }) {
  /**
   * Creates a function to handle OAuth login requests.
   * @param {string} authURL - The URL to redirect the user for OAuth authentication.
   * @param {{ expiresAt?: number }} [options]
   * @returns {Promise<boolean>} Returns true to indicate the event was sent successfully.
   */
  return async function (authURL, options) {
    let emitted = false;
    const emitOAuthStart = async (message) => {
      if (options) {
        await callback?.(authURL, options);
      } else {
        await callback?.(authURL);
      }
      emitted = true;
      logger.debug(message);
    };

    const existingFlow = await flowManager.getFlowState(flowId, 'oauth_login');
    if (existingFlow) {
      await emitOAuthStart('Re-sent OAuth login request to client');
      return true;
    }

    await flowManager.createFlowWithHandler(flowId, 'oauth_login', async () => {
      await emitOAuthStart('Sent OAuth login request to client');
      return true;
    });

    if (!emitted) {
      await emitOAuthStart('Re-sent OAuth login request to client');
    }

    return true;
  };
}

/**
 * @param {object} params
 * @param {ServerResponse} params.res - The Express response object for sending events.
 * @param {string} params.stepId - The ID of the step in the flow.
 * @param {ToolCallChunk} params.toolCall - The tool call object containing tool information.
 * @param {string | null} [params.streamId] - The stream ID for resumable mode.
 * @param {number} [params.jobCreatedAt] - The generation epoch that owns emitted events.
 */
function createOAuthEnd({ res, stepId, toolCall, streamId = null, jobCreatedAt }) {
  return async function () {
    const eventData = buildMCPAuthRunStepEndDeltaEvent({ stepId, toolCall });
    if (streamId) {
      await GenerationJobManager.emitChunk(streamId, eventData, {
        expectedCreatedAt: jobCreatedAt,
      });
    } else {
      sendEvent(res, eventData);
    }
    logger.debug('Sent OAuth login success to client');
  };
}

/**
 * @param {object} params
 * @param {string} params.userId - The ID of the user.
 * @param {string} params.serverName - The name of the server.
 * @param {string} params.toolName - The name of the tool.
 * @param {string} [params.tenantId] - The tenant ID for the current request.
 * @param {FlowStateManager<any>} params.flowManager - The flow manager instance.
 */
function createAbortHandler({ userId, serverName, toolName, tenantId, flowManager }) {
  return function () {
    logger.info(`[MCP][User: ${userId}][${serverName}][${toolName}] Tool call aborted`);
    const flowId = getOAuthFlowId(userId, serverName, tenantId);
    // Clean up both mcp_oauth and mcp_get_tokens flows
    flowManager.failFlow(flowId, 'mcp_oauth', new Error('Tool call aborted'));
    flowManager.failFlow(flowId, 'mcp_get_tokens', new Error('Tool call aborted'));
  };
}

/**
 * @param {Object} params
 * @param {() => Promise<void>} params.runStepEmitter
 * @param {(authURL: string, options?: { expiresAt?: number }) => Promise<void>} params.runStepDeltaEmitter
 * @returns {(authURL: string, options?: { expiresAt?: number }) => Promise<void>}
 */
function createOAuthCallback({ runStepEmitter, runStepDeltaEmitter }) {
  return async function (authURL, options) {
    await runStepEmitter();
    await runStepDeltaEmitter(authURL, options);
  };
}

/**
 * @param {Object} params
 * @param {ServerResponse} params.res - The Express response object for sending events.
 * @param {IUser} params.user - The user from the request object.
 * @param {string} params.serverName
 * @param {AbortSignal} params.signal
 * @param {string} params.model
 * @param {number} [params.index]
 * @param {string | null} [params.streamId] - The stream ID for resumable mode.
 * @param {number} [params.jobCreatedAt] - The generation epoch that owns emitted events.
 * @param {Record<string, Record<string, string>>} [params.userMCPAuthMap]
 * @param {import('@librechat/api').RequestScopedMCPConnectionStore} [params.requestScopedConnections]
 * @param {import('@librechat/api').ParsedServerConfig} [params.serverConfig] - Used to bypass reconnect throttling for request-scoped servers.
 * @returns { Promise<Array<typeof tool | { _call: (toolInput: Object | string) => unknown}>> } An object with `_call` method to execute the tool input.
 */
async function reconnectServer({
  res,
  user,
  index,
  signal,
  serverName,
  serverConfig,
  configServers,
  userMCPAuthMap,
  requestBody,
  requestScopedConnections,
  streamId = null,
  jobCreatedAt,
}) {
  logger.debug(
    `[MCP][reconnectServer] serverName: ${serverName}, user: ${user?.id}, hasUserMCPAuthMap: ${!!userMCPAuthMap}`,
  );

  // Request-scoped servers reconnect on every message by design; throttling them
  // would stub out healthy tools for messages sent within the throttle window.
  const requestScoped = serverConfig ? requiresEphemeralUserConnection(serverConfig) : false;
  if (!requestScoped) {
    const throttleKey = `${user.id}:${serverName}`;
    const now = Date.now();
    const lastAttempt = lastReconnectAttempts.get(throttleKey) ?? 0;
    if (now - lastAttempt < RECONNECT_THROTTLE_MS) {
      logger.debug(`[MCP][reconnectServer] Throttled reconnect for ${serverName}`);
      return null;
    }
    lastReconnectAttempts.set(throttleKey, now);
    evictStale(lastReconnectAttempts, RECONNECT_THROTTLE_MS);
  }

  const runId = Constants.USE_PRELIM_RESPONSE_MESSAGE_ID;
  const flowId = `${user.id}:${serverName}:${Date.now()}`;
  const flowManager = getFlowStateManager(getLogStores(CacheKeys.FLOWS));
  const stepId = buildMCPAuthStepId(serverName);
  const toolCall = buildMCPAuthToolCall({
    id: flowId,
    serverName,
  });

  // Set up abort handler to clean up OAuth flows if request is aborted
  const tenantId = user?.tenantId ?? getTenantId();
  const oauthFlowId = getOAuthFlowId(user.id, serverName, tenantId);
  const abortHandler = () => {
    logger.info(
      `[MCP][User: ${user.id}][${serverName}] Tool loading aborted, cleaning up OAuth flows`,
    );
    // Clean up both mcp_oauth and mcp_get_tokens flows
    flowManager.failFlow(oauthFlowId, 'mcp_oauth', new Error('Tool loading aborted'));
    flowManager.failFlow(oauthFlowId, 'mcp_get_tokens', new Error('Tool loading aborted'));
  };

  if (signal) {
    signal.addEventListener('abort', abortHandler, { once: true });
  }

  try {
    const runStepEmitter = createRunStepEmitter({
      res,
      index,
      runId,
      stepId,
      toolCall,
      streamId,
      jobCreatedAt,
    });
    const runStepDeltaEmitter = createRunStepDeltaEmitter({
      res,
      stepId,
      toolCall,
      streamId,
      jobCreatedAt,
    });
    const callback = createOAuthCallback({ runStepEmitter, runStepDeltaEmitter });
    const oauthStart = createOAuthStart({
      res,
      flowId,
      callback,
      flowManager,
    });
    return await reinitMCPServer({
      user,
      signal,
      serverName,
      configServers,
      oauthStart,
      flowManager,
      userMCPAuthMap,
      requestBody,
      requestScopedConnections,
      forceNew: true,
      returnOnOAuth: false,
      connectionTimeout: Time.THIRTY_SECONDS,
    });
  } finally {
    // Clean up abort handler to prevent memory leaks
    if (signal) {
      signal.removeEventListener('abort', abortHandler);
    }
  }
}

/**
 * Creates all tools from the specified MCP Server via `toolKey`.
 *
 * This function assumes tools could not be aggregated from the cache of tool definitions,
 * i.e. `availableTools`, and will reinitialize the MCP server to ensure all tools are generated.
 *
 * @param {Object} params
 * @param {ServerResponse} params.res - The Express response object for sending events.
 * @param {{ canUseServers: (user?: IUser) => Promise<boolean> }} [params.mcpPermissionContext] - Request-scoped MCP permission context.
 * @param {IUser} params.user - The user from the request object.
 * @param {string} params.serverName
 * @param {string} params.model
 * @param {Providers | EModelEndpoint} params.provider - The provider for the tool.
 * @param {number} [params.index]
 * @param {AbortSignal} [params.signal]
 * @param {string | null} [params.streamId] - The stream ID for resumable mode.
 * @param {number} [params.jobCreatedAt] - The generation epoch that owns emitted events.
 * @param {import('@librechat/api').ParsedServerConfig} [params.config]
 * @param {import('@librechat/api').RequestBody} [params.requestBody]
 * @param {import('@librechat/api').RequestScopedMCPConnectionStore} [params.requestScopedConnections]
 * @param {Record<string, Record<string, string>>} [params.userMCPAuthMap]
 * @returns { Promise<Array<typeof tool | { _call: (toolInput: Object | string) => unknown}>> } An object with `_call` method to execute the tool input.
 */
async function createMCPTools({
  res,
  mcpPermissionContext,
  user,
  index,
  signal,
  config,
  provider,
  serverName,
  configServers,
  userMCPAuthMap,
  requestBody,
  requestScopedConnections,
  streamId = null,
  jobCreatedAt,
}) {
  const serverConfig =
    config ?? (await getMCPServersRegistry().getServerConfig(serverName, user?.id, configServers));

  if (serverConfig?.url) {
    const appConfig = await getAppConfig({
      role: user?.role,
      tenantId: user?.tenantId,
      userId: user?.id,
    });
    const allowedDomains = appConfig?.mcpSettings?.allowedDomains;
    const allowedAddresses = appConfig?.mcpSettings?.allowedAddresses;
    const isDomainAllowed = await isEarlyDomainAllowed({
      serverConfig,
      user,
      requestBody,
      userMCPAuthMap,
      serverName,
      allowedDomains,
      allowedAddresses,
    });
    if (!isDomainAllowed) {
      logger.warn(`[MCP][${serverName}] Domain not allowed, skipping all tools`);
      return [];
    }
  }

  const result = await reconnectServer({
    res,
    user,
    index,
    signal,
    serverName,
    serverConfig,
    configServers,
    userMCPAuthMap,
    requestBody,
    requestScopedConnections,
    streamId,
    jobCreatedAt,
  });
  if (result === null) {
    logger.debug(`[MCP][${serverName}] Reconnect throttled, skipping tool creation.`);
    return [];
  }
  if (!result || !result.tools) {
    logger.warn(`[MCP][${serverName}] Failed to reinitialize MCP server.`);
    return [];
  }

  const serverTools = [];
  for (const tool of result.tools) {
    const toolInstance = await createMCPTool({
      res,
      mcpPermissionContext,
      user,
      provider,
      userMCPAuthMap,
      configServers,
      streamId,
      jobCreatedAt,
      availableTools: result.availableTools,
      serverName,
      /** Model-facing key: matches the normalized `availableTools` keys and
       *  the instance name `createToolInstance` will assign. */
      toolKey: `${tool.name}${Constants.mcp_delimiter}${normalizeServerName(serverName)}`,
      requestBody,
      requestScopedConnections,
      config: serverConfig,
    });
    if (toolInstance) {
      serverTools.push(toolInstance);
    }
  }

  return serverTools;
}

/**
 * Creates a single tool from the specified MCP Server via `toolKey`.
 * @param {Object} params
 * @param {ServerResponse} params.res - The Express response object for sending events.
 * @param {{ canUseServers: (user?: IUser) => Promise<boolean> }} [params.mcpPermissionContext] - Request-scoped MCP permission context.
 * @param {IUser} params.user - The user from the request object.
 * @param {string} params.toolKey - The toolKey for the tool.
 * @param {string} params.model - The model for the tool.
 * @param {number} [params.index]
 * @param {AbortSignal} [params.signal]
 * @param {string | null} [params.streamId] - The stream ID for resumable mode.
 * @param {Providers | EModelEndpoint} params.provider - The provider for the tool.
 * @param {LCAvailableTools} [params.availableTools]
 * @param {import('@librechat/api').RequestBody} [params.requestBody]
 * @param {import('@librechat/api').RequestScopedMCPConnectionStore} [params.requestScopedConnections]
 * @param {Record<string, Record<string, string>>} [params.userMCPAuthMap]
 * @param {import('@librechat/api').ParsedServerConfig} [params.config]
 * @param {(availableTools: LCAvailableTools) => void} [params.onAvailableTools]
 * @param {number} [params.jobCreatedAt] - The generation epoch that owns emitted events.
 * @returns { Promise<typeof tool | { _call: (toolInput: Object | string) => unknown}> } An object with `_call` method to execute the tool input.
 */
async function createMCPTool({
  res,
  mcpPermissionContext,
  user,
  index,
  signal,
  toolKey,
  provider,
  userMCPAuthMap,
  availableTools,
  requestBody,
  requestScopedConnections,
  config,
  configServers,
  serverName: resolvedServerName,
  onAvailableTools,
  streamId = null,
  jobCreatedAt,
}) {
  /** `loadTools` already resolved the server for this key; parsing is the fallback. */
  const [parsedToolName, parsedServerName] = splitMCPToolKey(
    toolKey,
    /** Current keys embed the NORMALIZED server name, legacy persisted keys
     *  the RAW one — the candidate list needs both spellings or a raw name
     *  that contains the delimiter mis-splits under the generic fallback. */
    resolvedServerName
      ? [resolvedServerName, normalizeServerName(resolvedServerName)]
      : Object.keys(configServers ?? {}).flatMap((name) => [name, normalizeServerName(name)]),
  );
  let serverName = resolvedServerName ?? parsedServerName;
  const toolName = parsedToolName;

  let serverConfig =
    config ?? (await getMCPServersRegistry().getServerConfig(serverName, user?.id, configServers));
  /** DIRECT-FIRST alias fallback: only when the parsed name resolves to no
   *  server is it treated as the normalized spelling of a raw config name —
   *  a user-DB server named like an operator server's normalized form must
   *  keep its own identity. */
  if (!serverConfig && resolvedServerName == null && parsedServerName != null) {
    const aliasedName = buildServerNameAliases(Object.keys(configServers ?? {})).get(
      parsedServerName,
    );
    if (aliasedName != null && aliasedName !== parsedServerName) {
      serverConfig = await getMCPServersRegistry().getServerConfig(
        aliasedName,
        user?.id,
        configServers,
      );
      if (serverConfig) {
        serverName = aliasedName;
      }
    }
  }
  const requestScopedTools = serverConfig ? requiresEphemeralUserConnection(serverConfig) : false;
  const useMissingToolCache = !requestScopedTools;

  if (serverConfig?.url) {
    const appConfig = await getAppConfig({
      role: user?.role,
      tenantId: user?.tenantId,
      userId: user?.id,
    });
    const allowedDomains = appConfig?.mcpSettings?.allowedDomains;
    const allowedAddresses = appConfig?.mcpSettings?.allowedAddresses;
    const isDomainAllowed = await isEarlyDomainAllowed({
      serverConfig,
      user,
      requestBody,
      userMCPAuthMap,
      serverName,
      allowedDomains,
      allowedAddresses,
    });
    if (!isDomainAllowed) {
      logger.warn(`[MCP][${serverName}] Domain no longer allowed, skipping tool: ${toolName}`);
      return undefined;
    }
  }

  /** Legacy keys persisted pre-normalization (assistants, direct tool
   *  calls) carry the RAW server name, while `availableTools` is keyed by
   *  the canonical normalized key — look up both spellings. */
  const canonicalToolKey =
    serverName != null
      ? `${toolName}${Constants.mcp_delimiter}${normalizeServerName(serverName)}`
      : toolKey;
  const findToolDefinition = (tools) =>
    tools?.[toolKey]?.function ??
    (canonicalToolKey !== toolKey ? tools?.[canonicalToolKey]?.function : undefined);

  /** @type {LCTool | undefined} */
  let toolDefinition = findToolDefinition(availableTools);
  if (!toolDefinition) {
    const cachedAt = useMissingToolCache ? missingToolCache.get(toolKey) : undefined;
    if (cachedAt && Date.now() - cachedAt < MISSING_TOOL_TTL_MS) {
      logger.debug(
        `[MCP][${serverName}][${toolName}] Tool in negative cache, returning unavailable stub.`,
      );
      return createUnavailableToolStub(toolName, serverName);
    }

    logger.warn(
      `[MCP][${serverName}][${toolName}] Requested tool not found in available tools, re-initializing MCP server.`,
    );
    const result = await reconnectServer({
      res,
      user,
      index,
      signal,
      serverName,
      serverConfig,
      configServers,
      userMCPAuthMap,
      requestBody,
      requestScopedConnections,
      streamId,
      jobCreatedAt,
    });
    if (result?.availableTools) {
      onAvailableTools?.(result.availableTools);
    }
    toolDefinition = findToolDefinition(result?.availableTools);

    if (!toolDefinition && useMissingToolCache) {
      missingToolCache.set(toolKey, Date.now());
      evictStale(missingToolCache, MISSING_TOOL_TTL_MS);
    }
  }

  if (!toolDefinition) {
    logger.warn(
      `[MCP][${serverName}][${toolName}] Tool definition not found, returning unavailable stub.`,
    );
    return createUnavailableToolStub(toolName, serverName);
  }

  return createToolInstance({
    res,
    mcpPermissionContext,
    user,
    requestBody,
    requestScopedConnections,
    provider,
    toolName,
    serverName,
    serverConfig,
    toolDefinition,
    streamId,
    jobCreatedAt,
  });
}

function createToolInstance({
  res,
  mcpPermissionContext,
  user: capturedUser = null,
  requestBody: capturedRequestBody,
  requestScopedConnections: capturedRequestScopedConnections,
  toolName,
  serverName,
  serverConfig: capturedServerConfig,
  toolDefinition,
  provider: capturedProvider,
  streamId = null,
  jobCreatedAt,
}) {
  /** @type {LCTool} */
  const { description, parameters } = toolDefinition;
  const isGoogle = capturedProvider === Providers.VERTEXAI || capturedProvider === Providers.GOOGLE;

  let schema = parameters ? normalizeJsonSchema(resolveJsonSchemaRefs(parameters)) : null;

  if (schema && isGoogle) {
    // Gemini/Vertex AI accept only a subset of JSON Schema; sanitize so MCP tools with
    // unions, non-string enums, etc. don't 400 (they work as-is on OpenAI/Claude).
    schema = sanitizeGeminiSchema(schema);
  }

  if (!schema || (isGoogle && isEmptyObjectSchema(schema))) {
    schema = {
      type: 'object',
      properties: {
        input: { type: 'string', description: 'Input for the tool' },
      },
      required: [],
    };
  }

  const normalizedToolKey = `${toolName}${Constants.mcp_delimiter}${normalizeServerName(serverName)}`;

  /** @type {(toolArguments: Object | string, config?: GraphRunnableConfig) => Promise<unknown>} */
  const _call = async (toolArguments, config) => {
    const effectiveUser = config?.configurable?.user ?? capturedUser;
    const permissionUser = effectiveUser;
    const userId = effectiveUser?.id || config?.configurable?.user_id || capturedUser?.id;
    /** @type {ReturnType<typeof createAbortHandler>} */
    let abortHandler = null;
    /** @type {AbortSignal} */
    let derivedSignal = null;

    try {
      const provider = (config?.metadata?.provider || capturedProvider)?.toLowerCase();
      const canUseMCP = mcpPermissionContext
        ? await mcpPermissionContext.canUseServers(permissionUser)
        : await userCanUseMCPServers(permissionUser);
      if (!canUseMCP) {
        throw new Error('Forbidden: Insufficient MCP server permissions');
      }
      const flowsCache = getLogStores(CacheKeys.FLOWS);
      const flowManager = getFlowStateManager(flowsCache);
      derivedSignal = config?.signal ? AbortSignal.any([config.signal]) : undefined;
      const mcpManager = getMCPManager(userId);

      const { args: _args, stepId, ...toolCall } = config.toolCall ?? {};
      const flowId = `${serverName}:oauth_login:${config.metadata.thread_id}:${config.metadata.run_id}`;
      const runStepDeltaEmitter = createRunStepDeltaEmitter({
        res,
        stepId,
        toolCall,
        streamId,
        jobCreatedAt,
      });
      const oauthStart = createOAuthStart({
        flowId,
        flowManager,
        callback: runStepDeltaEmitter,
      });
      const oauthEnd = createOAuthEnd({
        res,
        stepId,
        toolCall,
        streamId,
        jobCreatedAt,
      });

      if (derivedSignal) {
        const tenantId = config?.configurable?.user?.tenantId ?? getTenantId();
        abortHandler = createAbortHandler({ userId, serverName, toolName, tenantId, flowManager });
        derivedSignal.addEventListener('abort', abortHandler, { once: true });
      }

      const customUserVars =
        config?.configurable?.userMCPAuthMap?.[`${Constants.mcp_prefix}${serverName}`];

      const result = await mcpManager.callTool({
        serverName,
        serverConfig: capturedServerConfig,
        toolName,
        provider,
        toolArguments,
        options: {
          signal: derivedSignal,
        },
        user: effectiveUser,
        requestBody: config?.configurable?.requestBody ?? capturedRequestBody,
        requestScopedConnections:
          config?.configurable?.requestScopedConnections ?? capturedRequestScopedConnections,
        customUserVars,
        flowManager,
        tokenMethods: {
          findToken,
          createToken,
          updateToken,
          deleteTokens,
        },
        oauthStart,
        oauthEnd,
        graphTokenResolver: getGraphApiToken,
        oboTokenResolver: exchangeOboToken,
        oboTrustChecker: createOboTrustChecker(),
      });

      if (isAssistantsEndpoint(provider) && Array.isArray(result)) {
        return result[0];
      }
      return result;
    } catch (error) {
      logger.error(
        `[MCP][${serverName}][${toolName}][User: ${userId}] Error calling MCP tool:`,
        error,
      );

      /** OAuth error, provide a helpful message */
      const isOAuthError =
        error.message?.includes('401') ||
        error.message?.includes('OAuth') ||
        error.message?.includes('authentication') ||
        error.message?.includes('Non-200 status code (401)');

      if (isOAuthError) {
        throw new Error(
          `[MCP][${serverName}][${toolName}] OAuth authentication required. Please check the server logs for the authentication URL.`,
        );
      }

      throw new Error(
        `[MCP][${serverName}][${toolName}] tool call failed${error?.message ? `: ${error?.message}` : '.'}`,
      );
    } finally {
      // Clean up abort handler to prevent memory leaks
      if (abortHandler && derivedSignal) {
        derivedSignal.removeEventListener('abort', abortHandler);
      }
    }
  };

  const toolInstance = tool(_call, {
    schema,
    name: normalizedToolKey,
    description: description || '',
    responseFormat: AgentConstants.CONTENT_AND_ARTIFACT,
  });
  toolInstance.mcp = true;
  toolInstance.mcpRawServerName = serverName;
  // Ephemeral request-scoped servers (runtime body placeholders) tear their
  // connection down at request end, so they must never be backgrounded. A
  // missing/stale config means the server's lifetime is unknowable, so fail
  // closed (foreground) rather than risk a detached call against a torn-down
  // connection.
  toolInstance.mcpRequiresEphemeralConnection = capturedServerConfig
    ? requiresEphemeralUserConnection(capturedServerConfig)
    : true;
  // On Google/Vertex, propagate the union-flattened schema so definitions extracted
  // from this instance don't reach the Gemini converter with unsupported unions.
  toolInstance.mcpJsonSchema = isGoogle ? schema : parameters;
  return toolInstance;
}

/**
 * Get MCP setup data including config, connections, and OAuth servers.
 * Resolves config-source servers from admin Config overrides when tenant context is available.
 * @param {string} userId - The user ID
 * @param {{ role?: string, tenantId?: string }} [options] - Optional role/tenant context
 * @returns {Object} Object containing mcpConfig, appConnections, userConnections, and oauthServers
 */
async function getMCPSetupData(userId, options = {}) {
  const registry = getMCPServersRegistry();
  const { role, tenantId } = options;

  const appConfig = await getAppConfig({ role, tenantId, userId });
  const configServers = await registry.ensureConfigServers(appConfig?.mcpConfig || {});
  const mcpConfig = role
    ? await registry.getAllServerConfigs(userId, configServers, role)
    : await registry.getAllServerConfigs(userId, configServers);
  const mcpManager = getMCPManager(userId);
  /** @type {Map<string, import('@librechat/api').MCPConnection>} */
  let appConnections = new Map();
  try {
    // Use getLoaded() instead of getAll() to avoid forcing connection creation.
    // getAll() creates connections for all servers, which is problematic for servers
    // that require user context (e.g., those with {{LIBRECHAT_USER_ID}} placeholders).
    appConnections = (await mcpManager.appConnections?.getLoaded()) || new Map();
  } catch (error) {
    logger.error(`[MCP][User: ${userId}] Error getting app connections:`, error);
  }
  const userConnections = mcpManager.getUserConnections(userId) || new Map();
  const oauthServers = new Set(
    Object.entries(mcpConfig)
      .filter(([, config]) => config.requiresOAuth)
      .map(([name]) => name),
  );

  return {
    mcpConfig,
    oauthServers,
    appConnections,
    userConnections,
  };
}

/**
 * Check OAuth flow status for a user and server
 * @param {string} userId - The user ID
 * @param {string} serverName - The server name
 * @param {string} [tenantId] - The tenant ID for the current request.
 * @returns {Object} Object containing hasActiveFlow and hasFailedFlow flags
 */
async function checkOAuthFlowStatus(userId, serverName, tenantId = getTenantId()) {
  const flowsCache = getLogStores(CacheKeys.FLOWS);
  const flowManager = getFlowStateManager(flowsCache);
  const flowId = getOAuthFlowId(userId, serverName, tenantId);

  try {
    const flowState = await flowManager.getFlowState(flowId, 'mcp_oauth');
    if (!flowState) {
      return { hasActiveFlow: false, hasFailedFlow: false };
    }

    const flowAge = Date.now() - flowState.createdAt;
    // Report active only while the flow is still usable (the handling/reuse window),
    // not for the full Keyv retention TTL — otherwise the UI shows "connecting" for a
    // flow the initiate/callback paths already reject, hiding the connect button.
    const flowTTL = flowState.ttl || PENDING_STALE_MS;

    if (flowState.status === 'FAILED' || flowAge > flowTTL) {
      const wasCancelled = flowState.error && flowState.error.includes('cancelled');

      if (wasCancelled) {
        logger.debug(`[MCP Connection Status] Found cancelled OAuth flow for ${serverName}`, {
          flowId,
          status: flowState.status,
          error: flowState.error,
        });
        return { hasActiveFlow: false, hasFailedFlow: false };
      } else {
        logger.debug(`[MCP Connection Status] Found failed OAuth flow for ${serverName}`, {
          flowId,
          status: flowState.status,
          flowAge,
          flowTTL,
          timedOut: flowAge > flowTTL,
          error: flowState.error,
        });
        return { hasActiveFlow: false, hasFailedFlow: true };
      }
    }

    if (flowState.status === 'PENDING') {
      logger.debug(`[MCP Connection Status] Found active OAuth flow for ${serverName}`, {
        flowId,
        flowAge,
        flowTTL,
      });
      return { hasActiveFlow: true, hasFailedFlow: false };
    }

    return { hasActiveFlow: false, hasFailedFlow: false };
  } catch (error) {
    logger.error(`[MCP Connection Status] Error checking OAuth flows for ${serverName}:`, error);
    return { hasActiveFlow: false, hasFailedFlow: false };
  }
}

/**
 * Get connection status for a specific MCP server
 * @param {string} userId - The user ID
 * @param {string} serverName - The server name
 * @param {import('@librechat/api').ParsedServerConfig} config - The server configuration
 * @param {Map<string, import('@librechat/api').MCPConnection>} appConnections - App-level connections
 * @param {Map<string, import('@librechat/api').MCPConnection>} userConnections - User-level connections
 * @param {Set} oauthServers - Set of OAuth servers
 * @returns {Object} Object containing requiresOAuth and connectionState
 */
async function getServerConnectionStatus(
  userId,
  serverName,
  config,
  appConnections,
  userConnections,
  oauthServers,
) {
  const connection = appConnections.get(serverName) || userConnections.get(serverName);
  const isStaleOrDoNotExist = connection ? connection?.isStale(config.updatedAt) : true;

  const baseConnectionState = isStaleOrDoNotExist
    ? 'disconnected'
    : connection?.connectionState || 'disconnected';
  let finalConnectionState = baseConnectionState;

  // connection state overrides specific to OAuth servers
  if (baseConnectionState === 'disconnected' && oauthServers.has(serverName)) {
    // check if server is actively being reconnected
    const oauthReconnectionManager = getOAuthReconnectionManager();
    if (oauthReconnectionManager.isReconnecting(userId, serverName)) {
      finalConnectionState = 'connecting';
    } else {
      const { hasActiveFlow, hasFailedFlow } = await checkOAuthFlowStatus(userId, serverName);

      if (hasFailedFlow) {
        finalConnectionState = 'error';
      } else if (hasActiveFlow) {
        finalConnectionState = 'connecting';
      }
    }
  }

  return {
    requiresOAuth: oauthServers.has(serverName),
    connectionState: finalConnectionState,
  };
}

module.exports = {
  createMCPTool,
  createMCPTools,
  createMCPPermissionContext,
  userCanUseMCPServers,
  getMCPSetupData,
  resolveConfigServers,
  resolveMcpServerNames,
  resolveMcpServerContext,
  getAccessibleMcpServerNames,
  healMcpToolNames,
  resolveCollisionAuditNames,
  resolveMcpConfigNames,
  resolveAllMcpConfigs,
  createOAuthStart,
  checkOAuthFlowStatus,
  getServerConnectionStatus,
  createUnavailableToolStub,
};