index.ts

#!/usr/bin/env node

import { Server } from "@modelcontextprotocol/sdk/server/index.js";
import { StreamableHTTPServerTransport } from "@modelcontextprotocol/sdk/server/streamableHttp.js";
import {
  CallToolRequestSchema,
  ListToolsRequestSchema,
  Tool,
  InitializeRequestSchema,
} from "@modelcontextprotocol/sdk/types.js";
// Fixed chalk import for ESM
import chalk from 'chalk';
import express, { Request, Response, NextFunction } from 'express';
import path from 'path';
import { fileURLToPath } from 'url';
import { randomUUID } from 'node:crypto';
import { SequentialThinkingServer, ThoughtData } from './src/SequentialThinkingServer.js';

interface SessionState {
  server: SequentialThinkingServer;
  lastAccessed: number;
}

const SEQUENTIAL_THINKING_TOOL: Tool = {
  name: "sequentialthinking",
  description: `A detailed tool for dynamic and reflective problem-solving through thoughts.
This tool helps analyze problems through a flexible thinking process that can adapt and evolve.
Each thought can build on, question, or revise previous insights as understanding deepens.

When to use this tool:
- Breaking down complex problems into steps
- Planning and design with room for revision
- Analysis that might need course correction
- Problems where the full scope might not be clear initially
- Problems that require a multi-step solution
- Tasks that need to maintain context over multiple steps
- Situations where irrelevant information needs to be filtered out

Key features:
- You can adjust total_thoughts up or down as you progress
- You can question or revise previous thoughts
- You can add more thoughts even after reaching what seemed like the end
- You can express uncertainty and explore alternative approaches
- Not every thought needs to build linearly - you can branch or backtrack
- Generates a solution hypothesis
- Verifies the hypothesis based on the Chain of Thought steps
- Repeats the process until satisfied
- Provides a correct answer

Parameters explained:
- thought: Your current thinking step, which can include:
* Regular analytical steps
* Revisions of previous thoughts
* Questions about previous decisions
* Realizations about needing more analysis
* Changes in approach
* Hypothesis generation
* Hypothesis verification
- next_thought_needed: True if you need more thinking, even if at what seemed like the end
- thought_number: Current number in sequence (can go beyond initial total if needed)
- total_thoughts: Current estimate of thoughts needed (can be adjusted up/down)
- is_revision: A boolean indicating if this thought revises previous thinking
- revises_thought: If is_revision is true, which thought number is being reconsidered
- branch_from_thought: If branching, which thought number is the branching point
- branch_id: Identifier for the current branch (if any)
- needs_more_thoughts: If reaching end but realizing more thoughts needed

You should:
1. Start with an initial estimate of needed thoughts, but be ready to adjust
2. Feel free to question or revise previous thoughts
3. Don't hesitate to add more thoughts if needed, even at the "end"
4. Express uncertainty when present
5. Mark thoughts that revise previous thinking or branch into new paths
6. Ignore information that is irrelevant to the current step
7. Generate a solution hypothesis when appropriate
8. Verify the hypothesis based on the Chain of Thought steps
9. Repeat the process until satisfied with the solution
10. Provide a single, ideally correct answer as the final output
11. Only set next_thought_needed to false when truly done and a satisfactory answer is reached`,
  inputSchema: {
    type: "object",
    properties: {
      thought: {
        type: "string",
        description: "Your current thinking step"
      },
      nextThoughtNeeded: {
        type: "boolean",
        description: "Whether another thought step is needed"
      },
      thoughtNumber: {
        type: "integer",
        description: "Current thought number",
        minimum: 1
      },
      totalThoughts: {
        type: "integer",
        description: "Estimated total thoughts needed",
        minimum: 1
      },
      isRevision: {
        type: "boolean",
        description: "Whether this revises previous thinking"
      },
      revisesThought: {
        type: "integer",
        description: "Which thought is being reconsidered",
        minimum: 1
      },
      branchFromThought: {
        type: "integer",
        description: "Branching point thought number",
        minimum: 1
      },
      branchId: {
        type: "string",
        description: "Branch identifier"
      },
      needsMoreThoughts: {
        type: "boolean",
        description: "If more thoughts are needed"
      }
    },
    required: ["thought", "nextThoughtNeeded", "thoughtNumber", "totalThoughts"]
  }
};

// Get __dirname equivalent in ESM
const __filename = fileURLToPath(import.meta.url);
const __dirname = path.dirname(__filename);

async function runServer() {
  const app = express();
  const port = parseInt(process.env.PORT || '3000', 10);
  // Use 0.0.0.0 when running in Docker, otherwise use 127.0.0.1 for security
  const host = process.env.DOCKER === 'true' ? '0.0.0.0' : '127.0.0.1';
  
  // Parse allowed origins from environment variable
  const allowedOrigins = process.env.ALLOWED_ORIGINS 
    ? process.env.ALLOWED_ORIGINS.split(',').map(origin => origin.trim())
    : ['http://localhost:3000', 'http://127.0.0.1:3000']; // Default for development

  // Enable CORS
  const corsMiddleware = (req: Request, res: Response, next: NextFunction): void => {
    const origin = req.headers.origin;
    
    // If origin is present and in allowed list, set specific origin
    if (origin && allowedOrigins.includes(origin)) {
      res.header('Access-Control-Allow-Origin', origin);
      res.header('Access-Control-Allow-Credentials', 'true');
    } else if (!origin && process.env.NODE_ENV === 'development') {
      // Allow no-origin requests in development (e.g., direct API calls)
      res.header('Access-Control-Allow-Origin', '*');
    } else if (origin) {
      // Reject requests from unauthorized origins
      console.error(`Rejected connection from unauthorized origin: ${origin}`);
      console.error(`Allowed origins: ${allowedOrigins.join(', ')}`);
      res.status(403).json({ error: 'Origin not allowed' });
      return;
    }
    
    res.header('Access-Control-Allow-Methods', 'GET, POST, DELETE, OPTIONS');
    res.header('Access-Control-Allow-Headers', 'Content-Type, mcp-session-id');

    if (req.method === 'OPTIONS') {
      res.sendStatus(200);
      return;
    }
    next();
  };

  app.use(corsMiddleware);
  app.use(express.json());

  // Map to store transports by session ID
  const transports: { [sessionId: string]: StreamableHTTPServerTransport } = {};
  // Map to store session-specific thinking servers
  const sessionStates: { [sessionId: string]: SessionState } = {};

  // Create a single, centralized MCP Server
  const server = new Server(
    {
      name: "sequential-thinking-server",
      version: "0.2.0",
    },
    {
      capabilities: {
        tools: {},
      },
    }
  );

  // Centralized request handlers
  server.setRequestHandler(ListToolsRequestSchema, async () => ({
    tools: [SEQUENTIAL_THINKING_TOOL],
  }));

  server.setRequestHandler(CallToolRequestSchema, async (request, transport) => {
    const sessionId = (transport as unknown as StreamableHTTPServerTransport).sessionId;
    if (!sessionId || !sessionStates[sessionId]) {
      return {
        content: [{ type: "text", text: "Session not found for tool call" }],
        isError: true,
      };
    }

    // Update last accessed time on tool call
    sessionStates[sessionId].lastAccessed = Date.now();

    const thinkingServer = sessionStates[sessionId].server;

    if (request.params.name === "sequentialthinking") {
      return thinkingServer.processThought(request.params.arguments);
    }

    return {
      content: [{
        type: "text",
        text: `Unknown tool: ${request.params.name}`
      }],
      isError: true
    };
  });

  // Serve the web interface
  app.get('/', (req: Request, res: Response): void => {
    res.sendFile(path.join(__dirname, '..', 'web', 'index.html'));
  });

  app.post('/mcp', async (req: Request, res: Response) => {
    // Check for existing session ID
    const sessionId = req.headers['mcp-session-id'] as string | undefined;
    let transport: StreamableHTTPServerTransport;

    if (sessionId && transports[sessionId]) {
      // Reuse existing transport
      transport = transports[sessionId];
    } else if (!sessionId && req.body?.method === 'initialize') {
      // New initialization request
      transport = new StreamableHTTPServerTransport({
        sessionIdGenerator: () => randomUUID(),
        onsessioninitialized: (newSessionId: string) => {
          // Store the transport and create a new session state
          transports[newSessionId] = transport;
          sessionStates[newSessionId] = {
            server: new SequentialThinkingServer(),
            lastAccessed: Date.now(),
          };
          console.error(`New session initialized: ${newSessionId}`);
        }
      });

      // Clean up transport and session state when closed
      transport.onclose = () => {
        if (transport.sessionId) {
          delete transports[transport.sessionId];
          delete sessionStates[transport.sessionId];
          console.error(`Session closed: ${transport.sessionId}`);
        }
      };

      // Connect the transport to the central server
      await server.connect(transport);
    } else {
      // Invalid request
      res.status(400).json({
        jsonrpc: '2.0',
        error: {
          code: -32000,
          message: 'Bad Request: No valid session ID provided',
        },
        id: null,
      });
      return;
    }

    // Handle the request
    await transport.handleRequest(req, res, req.body);
  });

  // Reusable handler for GET and DELETE requests
  const handleSessionRequest = async (req: Request, res: Response) => {
    // Check header first, then query parameter (for EventSource compatibility)
    const sessionId = req.headers['mcp-session-id'] as string | undefined || req.query.sessionId as string | undefined;
    if (!sessionId || !transports[sessionId]) {
      res.status(400).send('Invalid or missing session ID');
      return;
    }

    // Update last accessed time for GET requests (SSE stream)
    if (req.method === 'GET' && sessionStates[sessionId]) {
      sessionStates[sessionId].lastAccessed = Date.now();
    }

    const transport = transports[sessionId];
    await transport.handleRequest(req, res);
  };

  // Handle GET requests for server-to-client notifications via SSE
  app.get('/mcp', handleSessionRequest);

  // Handle DELETE requests for session termination
  app.delete('/mcp', handleSessionRequest);

  // Health check endpoint
  app.get('/health', (req: Request, res: Response): void => {
    const sessionCount = Object.keys(transports).length;
    res.json({
      status: 'ok',
      transport: 'streamable-http',
      activeSessions: sessionCount
    });
  });

  const SESSION_TIMEOUT_MS = 60 * 60 * 1000; // 1 hour
  const SESSION_CLEANUP_INTERVAL_MS = 5 * 60 * 1000; // 5 minutes

  setInterval(() => {
    const now = Date.now();
    const sessionCount = Object.keys(sessionStates).length;
    if (sessionCount > 0) {
      console.error(`Running session cleanup. Currently ${sessionCount} active sessions.`);
      for (const sessionId in sessionStates) {
        if (now - sessionStates[sessionId].lastAccessed > SESSION_TIMEOUT_MS) {
          console.error(`Session ${sessionId} timed out. Cleaning up.`);
          const transport = transports[sessionId];
          if (transport) {
            // The transport's close method should trigger the onclose event,
            // which handles the cleanup of both transports and sessionStates.
            transport.close();
          } else {
            // If transport is somehow already gone, clean up state directly.
            delete sessionStates[sessionId];
          }
        }
      }
    }
  }, SESSION_CLEANUP_INTERVAL_MS);

  // Start server on configured host
  app.listen(port, host, () => {
    console.error(`Sequential Thinking MCP Server (Streamable HTTP) running on http://${host}:${port}`);
    console.error(`MCP endpoint: http://${host}:${port}/mcp`);
    console.error(`Test interface: http://${host}:${port}/`);
    if (process.env.DOCKER === 'true') {
      console.error('Running in Docker mode - accessible from outside the container');
    }
    console.error(`Allowed origins: ${allowedOrigins.join(', ')}`);
  });
}

runServer().catch((error) => {
  console.error("Fatal error running server:", error);
  process.exit(1);
});