import { logger } from '@librechat/data-schemas';
import { ErrorCode, McpError } from '@modelcontextprotocol/sdk/types.js';
import { MCPConnectionFactory } from '~/mcp/MCPConnectionFactory';
import { MCPServersRegistry } from '~/mcp/registry/MCPServersRegistry';
import { MCPConnection } from './connection';
import type * as t from './types';
import { ConnectionsRepository } from '~/mcp/ConnectionsRepository';
import { mcpConfig } from './mcpConfig';

/**
 * Abstract base class for managing user-specific MCP connections with lifecycle management.
 * Only meant to be extended by MCPManager.
 * Much of the logic was move here from the old MCPManager to make it more manageable.
 * User connections will soon be ephemeral and not cached anymore:
 * https://github.com/danny-avila/LibreChat/discussions/8790
 */
export abstract class UserConnectionManager {
  // Connections shared by all users.
  public appConnections: ConnectionsRepository | null = null;
  // Connections per userId -> serverName -> connection
  protected userConnections: Map<string, Map<string, MCPConnection>> = new Map();
  /** Last activity timestamp for users (not per server) */
  protected userLastActivity: Map<string, number> = new Map();

  /** Updates the last activity timestamp for a user */
  protected updateUserLastActivity(userId: string): void {
    const now = Date.now();
    this.userLastActivity.set(userId, now);
    logger.debug(
      `[MCP][User: ${userId}] Updated last activity timestamp: ${new Date(now).toISOString()}`,
    );
  }

  /** Gets or creates a connection for a specific user */
  public async getUserConnection({
    serverName,
    forceNew,
    user,
    flowManager,
    customUserVars,
    requestBody,
    tokenMethods,
    oauthStart,
    oauthEnd,
    signal,
    returnOnOAuth = false,
    connectionTimeout,
  }: {
    serverName: string;
    forceNew?: boolean;
  } & Omit<t.OAuthConnectionOptions, 'useOAuth'>): Promise<MCPConnection> {
    const userId = user.id;
    if (!userId) {
      throw new McpError(ErrorCode.InvalidRequest, `[MCP] User object missing id property`);
    }

    if (await this.appConnections!.has(serverName)) {
      throw new McpError(
        ErrorCode.InvalidRequest,
        `[MCP][User: ${userId}] Trying to create user-specific connection for app-level server "${serverName}"`,
      );
    }

    const config = await MCPServersRegistry.getInstance().getServerConfig(serverName, userId);

    const userServerMap = this.userConnections.get(userId);
    let connection = forceNew ? undefined : userServerMap?.get(serverName);
    const now = Date.now();

    // Check if user is idle
    const lastActivity = this.userLastActivity.get(userId);
    if (lastActivity && now - lastActivity > mcpConfig.USER_CONNECTION_IDLE_TIMEOUT) {
      logger.info(`[MCP][User: ${userId}] User idle for too long. Disconnecting all connections.`);
      // Disconnect all user connections
      try {
        await this.disconnectUserConnections(userId);
      } catch (err) {
        logger.error(`[MCP][User: ${userId}] Error disconnecting idle connections:`, err);
      }
      connection = undefined; // Force creation of a new connection
    } else if (connection) {
      if (!config || (config.lastUpdatedAt && connection.isStale(config.lastUpdatedAt))) {
        if (config) {
          logger.info(
            `[MCP][User: ${userId}][${serverName}] Config was updated, disconnecting stale connection`,
          );
        }
        await this.disconnectUserConnection(userId, serverName);
        connection = undefined;
      } else if (await connection.isConnected()) {
        logger.debug(`[MCP][User: ${userId}][${serverName}] Reusing active connection`);
        this.updateUserLastActivity(userId);
        return connection;
      } else {
        // Connection exists but is not connected, attempt to remove potentially stale entry
        logger.warn(
          `[MCP][User: ${userId}][${serverName}] Found existing but disconnected connection object. Cleaning up.`,
        );
        this.removeUserConnection(userId, serverName); // Clean up maps
        connection = undefined;
      }
    }

    // Now check if config exists for new connection creation
    if (!config) {
      throw new McpError(
        ErrorCode.InvalidRequest,
        `[MCP][User: ${userId}] Configuration for server "${serverName}" not found.`,
      );
    }

    // If no valid connection exists, create a new one
    logger.info(`[MCP][User: ${userId}][${serverName}] Establishing new connection`);

    try {
      connection = await MCPConnectionFactory.create(
        {
          serverName: serverName,
          serverConfig: config,
        },
        {
          useOAuth: true,
          user: user,
          customUserVars: customUserVars,
          flowManager: flowManager,
          tokenMethods: tokenMethods,
          signal: signal,
          oauthStart: oauthStart,
          oauthEnd: oauthEnd,
          returnOnOAuth: returnOnOAuth,
          requestBody: requestBody,
          connectionTimeout: connectionTimeout,
        },
      );

      if (!(await connection?.isConnected())) {
        throw new Error('Failed to establish connection after initialization attempt.');
      }

      if (!this.userConnections.has(userId)) {
        this.userConnections.set(userId, new Map());
      }
      this.userConnections.get(userId)?.set(serverName, connection);

      logger.info(`[MCP][User: ${userId}][${serverName}] Connection successfully established`);
      // Update timestamp on creation
      this.updateUserLastActivity(userId);
      return connection;
    } catch (error) {
      logger.error(`[MCP][User: ${userId}][${serverName}] Failed to establish connection`, error);
      // Ensure partial connection state is cleaned up if initialization fails
      await connection?.disconnect().catch((disconnectError) => {
        logger.error(
          `[MCP][User: ${userId}][${serverName}] Error during cleanup after failed connection`,
          disconnectError,
        );
      });
      // Ensure cleanup even if connection attempt fails
      this.removeUserConnection(userId, serverName);
      throw error; // Re-throw the error to the caller
    }
  }

  /** Returns all connections for a specific user */
  public getUserConnections(userId: string) {
    return this.userConnections.get(userId);
  }

  /** Removes a specific user connection entry */
  protected removeUserConnection(userId: string, serverName: string): void {
    const userMap = this.userConnections.get(userId);
    if (userMap) {
      userMap.delete(serverName);
      if (userMap.size === 0) {
        this.userConnections.delete(userId);
        // Only remove user activity timestamp if all connections are gone
        this.userLastActivity.delete(userId);
      }
    }

    logger.debug(`[MCP][User: ${userId}][${serverName}] Removed connection entry.`);
  }

  /** Disconnects and removes a specific user connection */
  public async disconnectUserConnection(userId: string, serverName: string): Promise<void> {
    const userMap = this.userConnections.get(userId);
    const connection = userMap?.get(serverName);
    if (connection) {
      logger.info(`[MCP][User: ${userId}][${serverName}] Disconnecting...`);
      await connection.disconnect();
      this.removeUserConnection(userId, serverName);
    }
  }

  /** Disconnects and removes all connections for a specific user */
  public async disconnectUserConnections(userId: string): Promise<void> {
    const userMap = this.userConnections.get(userId);
    const disconnectPromises: Promise<void>[] = [];
    if (userMap) {
      logger.info(`[MCP][User: ${userId}] Disconnecting all servers...`);
      const userServers = Array.from(userMap.keys());
      for (const serverName of userServers) {
        disconnectPromises.push(
          this.disconnectUserConnection(userId, serverName).catch((error) => {
            logger.error(
              `[MCP][User: ${userId}][${serverName}] Error during disconnection:`,
              error,
            );
          }),
        );
      }
      await Promise.allSettled(disconnectPromises);
      // Ensure user activity timestamp is removed
      this.userLastActivity.delete(userId);
      logger.info(`[MCP][User: ${userId}] All connections processed for disconnection.`);
    }
  }

  /** Check for and disconnect idle connections */
  protected checkIdleConnections(currentUserId?: string): void {
    const now = Date.now();

    // Iterate through all users to check for idle ones
    for (const [userId, lastActivity] of this.userLastActivity.entries()) {
      if (currentUserId && currentUserId === userId) {
        continue;
      }
      if (now - lastActivity > mcpConfig.USER_CONNECTION_IDLE_TIMEOUT) {
        logger.info(
          `[MCP][User: ${userId}] User idle for too long. Disconnecting all connections...`,
        );
        // Disconnect all user connections asynchronously (fire and forget)
        this.disconnectUserConnections(userId).catch((err) =>
          logger.error(`[MCP][User: ${userId}] Error disconnecting idle connections:`, err),
        );
      }
    }
  }
}