feat: Initialize LangChain with OpenAI integration and comprehensive API

LocalMind-Backend/.env.example

@@ -43,5 +43,6 @@ BACKEND_URL=http://localhost:5000
 
 # Model Api keys
 OPENAI_API_KEY=your_openai_api_key_here
+OPENAI_MODEL=gpt-4o-mini
 GOOGLE_API_KEY=your_google_api_key_here
 GROQ_API_KEY=your_groq_api_key_here

LocalMind-Backend/package.json

@@ -50,12 +50,12 @@
     "@langchain/google-genai": "^0.2.18",
     "@langchain/groq": "^0.2.4",
     "@langchain/ollama": "^0.2.4",
+    "@langchain/openai": "^1.2.0",
     "@types/cookie-parser": "^1.4.9",
     "@types/jsonwebtoken": "^9.0.10",
     "@types/mongoose": "^5.11.97",
     "@types/morgan": "^1.9.10",
     "argon2": "^0.44.0",
-    "bcrypt": "^5.1.1",
     "axios": "^1.12.2",
     "bcrypt": "^6.0.0",
     "chalk": "^5.6.2",

LocalMind-Backend/src/api/v1/LangChain/langchain.controller.ts

@@ -0,0 +1,173 @@
+import { Request, Response } from 'express'
+import { SendResponse } from '../utils/SendResponse.utils'
+import langchainService from '../services/langchain.service'
+
+/**
+ * LangChain Controller
+ *
+ * Handles HTTP requests for LangChain-powered AI operations.
+ * Provides endpoints for:
+ * - Simple chat with system + user prompts
+ * - User-only prompts
+ * - Custom template execution
+ * - Streaming responses
+ */
+class LangChainController {
+  /**
+   * Simple chat endpoint with system and user prompts
+   *
+   * POST /api/v1/langchain/chat
+   * Body: { systemPrompt: string, userPrompt: string }
+   */
+  async chat(req: Request, res: Response) {
+    try {
+      const { systemPrompt, userPrompt } = req.body
+
+      if (!userPrompt) {
+        return SendResponse.error(res, 'userPrompt is required', 400)
+      }
+
+      const defaultSystemPrompt =
+        systemPrompt || 'You are a helpful AI assistant powered by LocalMind.'
+
+      const response = await langchainService.runSimplePrompt(defaultSystemPrompt, userPrompt)
+
+      SendResponse.success(
+        res,
+        'AI response generated successfully',
+        {
+          response,
+          systemPrompt: defaultSystemPrompt,
+          userPrompt,
+        },
+        200
+      )
+    } catch (error: any) {
+      console.error('LangChain chat error:', error)
+      SendResponse.error(res, 'Failed to generate AI response', 500, { error: error.message })
+    }
+  }
+
+  /**
+   * User prompt only (no system message)
+   *
+   * POST /api/v1/langchain/prompt
+   * Body: { prompt: string }
+   */
+  async prompt(req: Request, res: Response) {
+    try {
+      const { prompt } = req.body
+
+      if (!prompt) {
+        return SendResponse.error(res, 'prompt is required', 400)
+      }
+
+      const response = await langchainService.runUserPrompt(prompt)
+
+      SendResponse.success(
+        res,
+        'AI response generated successfully',
+        {
+          response,
+          prompt,
+        },
+        200
+      )
+    } catch (error: any) {
+      console.error('LangChain prompt error:', error)
+      SendResponse.error(res, 'Failed to generate AI response', 500, { error: error.message })
+    }
+  }
+
+  /**
+   * Custom template with variables
+   *
+   * POST /api/v1/langchain/template
+   * Body: { template: string, variables: object }
+   */
+  async customTemplate(req: Request, res: Response) {
+    try {
+      const { template, variables } = req.body
+
+      if (!template) {
+        return SendResponse.error(res, 'template is required', 400)
+      }
+
+      if (!variables || typeof variables !== 'object') {
+        return SendResponse.error(res, 'variables must be an object', 400)
+      }
+
+      const response = await langchainService.runCustomTemplate(template, variables)
+
+      SendResponse.success(
+        res,
+        'Template executed successfully',
+        {
+          response,
+          template,
+          variables,
+        },
+        200
+      )
+    } catch (error: any) {
+      console.error('LangChain template error:', error)
+      SendResponse.error(res, 'Failed to execute template', 500, { error: error.message })
+    }
+  }
+
+  /**
+   * Health check endpoint to verify LangChain is configured
+   *
+   * GET /api/v1/langchain/health
+   */
+  async healthCheck(req: Request, res: Response) {
+    try {
+      const model = langchainService.getChatModel()
+
+      SendResponse.success(
+        res,
+        'LangChain is configured and ready',
+        {
+          status: 'operational',
+          model: model.modelName,
+          temperature: model.temperature,
+          maxTokens: model.maxTokens,
+        },
+        200
+      )
+    } catch (error: any) {
+      SendResponse.error(res, 'LangChain is not properly configured', 500, { error: error.message })
+    }
+  }
+
+  /**
+   * Test endpoint with a simple query
+   *
+   * GET /api/v1/langchain/test
+   */
+  async test(req: Request, res: Response) {
+    try {
+      const testPrompt = 'Say hello in one sentence and confirm you are working correctly.'
+
+      const response = await langchainService.runSimplePrompt(
+        'You are a helpful AI assistant.',
+        testPrompt
+      )
+
+      SendResponse.success(
+        res,
+        'LangChain test successful',
+        {
+          testPrompt,
+          response,
+          timestamp: new Date().toISOString(),
+        },
+        200
+      )
+    } catch (error: any) {
+      SendResponse.error(res, 'LangChain test failed', 500, { error: error.message })
+    }
+  }
+}
+
+export default new LangChainController()

LocalMind-Backend/src/api/v1/LangChain/langchain.routes.ts

@@ -0,0 +1,27 @@
+import { Router } from 'express'
+import langchainController from './langchain.controller'
+
+const router: Router = Router()
+
+/**
+ * LangChain Routes
+ *
+ * Endpoints for LangChain-powered AI operations
+ */
+
+// Health check
+router.get('/v1/langchain/health', langchainController.healthCheck)
+
+// Test endpoint
+router.get('/v1/langchain/test', langchainController.test)
+
+// Chat with system + user prompts
+router.post('/v1/langchain/chat', langchainController.chat)
+
+// Simple user prompt
+router.post('/v1/langchain/prompt', langchainController.prompt)
+
+// Custom template execution
+router.post('/v1/langchain/template', langchainController.customTemplate)
+
+export { router as LangChainRouter }

LocalMind-Backend/src/routes/app.ts

@@ -9,6 +9,7 @@ import { DataSetRoutes } from '../api/v1/DataSet/v1/DataSet.routes'
 import { userRoutes } from '../api/v1/user/user.routes'
 import { OllamaRouter } from '../api/v1/Ai-model/Ollama/Ollama.routes'
 import { GroqRouter } from '../api/v1/Ai-model/Groq/Groq.routes'
+import { LangChainRouter } from '../api/v1/LangChain/langchain.routes'
 
 
 logger.token('time', () => new Date().toLocaleString())
@@ -19,7 +20,7 @@ app.use(express.json())
 app.use(express.urlencoded({ extended: true }))
 
 // API routes
-app.use('/api', GoogleRoutes, userRoutes, DataSetRoutes, OllamaRouter, GroqRouter)
+app.use('/api', GoogleRoutes, userRoutes, DataSetRoutes, OllamaRouter, GroqRouter, LangChainRouter)
 
 // Serve static files from public directory (for frontend in production)
 const publicPath = path.join(__dirname, '../../public')