refactor: migrate from Vercel AI SDK to LangChain + LangGraph

package.json

@@ -14,6 +14,10 @@
     "@11labs/react": "^0.1.4",
     "@ai-sdk/google": "^1.1.17",
     "@deepgram/sdk": "^3.11.1",
+    "@langchain/community": "^0.3.51",
+    "@langchain/core": "^0.3.71",
+    "@langchain/google-genai": "^0.2.16",
+    "@langchain/langgraph": "^0.4.5",
     "@lottiefiles/dotlottie-react": "^0.12.2",
     "@mediapipe/face_mesh": "^0.4.1633559619",
     "@monaco-editor/react": "^4.6.0",
@@ -38,10 +42,11 @@
     "framer-motion": "^12.0.5",
     "jspdf": "^3.0.1",
     "jspdf-autotable": "^5.0.2",
+    "langchain": "^0.3.30",
     "lucide-react": "^0.473.0",
     "next": "^14.2.24",
     "next-themes": "^0.4.4",
-    "puppeteer": "^24.3.1",
+    "pdf-parse": "1.1.1",
     "react": "^18.3.1",
     "react-dom": "^18.3.1",
     "react-markdown": "^10.1.0",
@@ -50,7 +55,8 @@
     "styled-components": "^6.1.14",
     "tailwind-merge": "^2.6.0",
     "tailwindcss-animate": "^1.0.7",
-    "zod": "^3.24.2",
+    "zod": "^3.23.8",
+    "zod4": "npm:zod@^4.0.17",
     "zustand": "^5.0.3"
   },
   "devDependencies": {
@@ -64,5 +70,11 @@
     "prisma": "^6.7.0",
     "tailwindcss": "^3.4.1",
     "typescript": "^5"
+  },
+  "resolutions": {
+    "zod": "^4.0.17"
+  },
+  "overrides": {
+    "@tensorflow-models/universal-sentence-encoder": "0.0.0"
   }
 }

src/app/api/interview/helpers/speech.ts

@@ -43,3 +43,21 @@ const getAudioBuffer = async (response: any) => {
 
   return Buffer.from(dataArray.buffer);
 };
+
+
+export const getText = async (audioFile: ArrayBuffer) => {
+  try {
+    const { result, error } = await deepgram.listen.prerecorded.transcribeFile(
+      Buffer.from(audioFile),
+      {
+        model: "nova-3",
+        smart_format: true,
+      }
+    );
+    if (error) throw error;
+    return result.results.channels[0].alternatives[0].transcript;
+  } catch (error) {
+    console.error("Error in getText:", error);
+    throw error;
+  }
+}

src/app/api/interview/route.ts

@@ -1,56 +1,61 @@
-import { getChatHistory, saveToDbModel, saveToDbUser } from "@/db/dbFunctions";
-import { aiGenerator } from "@/lib/helpers/aiGenerator";
-import { getAudio } from "./helpers/speech";
+import { graph } from "@/lib/ai/conversation/graph";
+import { initialState } from "@/lib/ai/conversation/state";
 import fs from "fs";
 
 export async function POST(req: Request) {
   try {
     const formData = await req.formData();
+
     const file = formData.get("file") as File;
     const arrayBuffer = file ? await file.arrayBuffer() : null;
     const interviewId = formData.get("interviewId") as string;
     const timeLeft = formData.get("timeLeft") as string;
     const text = formData.get("text") as string;
     const round = formData.get("round") as string;
+
     if (!interviewId || !timeLeft || !round) {
-      return new Response("Missing parameters", { status: 500 });
+      return new Response("Missing parameters", { status: 400 });
     }
-    const history = await getChatHistory(interviewId);
-    const textGen = await aiGenerator(
-      round,
-      text,
-      history,
-      arrayBuffer,
-      timeLeft
-    );
-    if (!textGen?.reply || !textGen?.speechToText) {
-      return new Response("Error in reponse", { status: 500 });
+
+    const initiateState = {
+      ...initialState,
+      interviewId: interviewId,
+      round: round,
+      timeLeft: timeLeft,
+      userInput: text || "",
+      audioFile: arrayBuffer,
     }
-    const audio = await getAudio(textGen.reply);
-    if (!audio) throw "Not Found!";
-    await saveToDbUser(textGen.speechToText, interviewId);
-    await saveToDbModel(textGen.reply, interviewId);
-    const audioBase64 = audio.toString("base64");
+
+    const result = await graph.invoke(initiateState);
+
     const response = {
-      audio: audioBase64,
-      dsaQuestion: textGen.dsaQuestion,
-      codeHelp: textGen.codeHelp,
-      reply: textGen.reply,
+      audio: result.audioResponse,
+      dsaQuestion: result.dsaQuestion,
+      codeHelp: result.codeHelp,
+      reply: result.reply,
     };
+
     return new Response(JSON.stringify(response), {
       status: 200,
+      headers: { 'Content-Type': 'application/json' }
     });
-  } catch {
+
+  } catch (error) {
+    console.error("Error in interview conversation:", error);
+
     const audioBuffer = fs.readFileSync("/sound/error.wav");
     const audioBase64 = audioBuffer.toString("base64");
     const response = {
       audio: audioBase64,
       dsaQuestion: null,
       codeHelp: null,
-      reply: null,
+      reply: "Sorry, I encountered an error. Please try again.",
     };
+
     return new Response(JSON.stringify(response), {
       status: 500,
+      headers: { 'Content-Type': 'application/json' }
     });
+
   }
-}
+}

src/app/api/resume/route.ts

@@ -1,12 +1,6 @@
-import { generateObject } from "ai";
-import { z } from "zod";
-import { GEMINI_1_5_FLASH } from "@/lib/utils/ai";
-import { getPrompts } from "@/db/dbFunctions";
+import { graph } from "@/lib/ai/resume/graph";
+import { initialState } from "@/lib/ai/resume/state";
 
-const schema = z.object({
-  rating: z.number().int().min(0).max(100),
-  detailedReview: z.string(),
-});
 
 export async function POST(req: Request) {
   try {
@@ -19,48 +13,15 @@ export async function POST(req: Request) {
         { status: 400 },
       );
     }
-    const fileBase64 = await file.arrayBuffer();
-    const fileBuffer = Buffer.from(fileBase64);
-    const systemInstruction = await getPrompts("resume-review");
-    if (!systemInstruction) {
-      return Response.json(
-        { error: "System instruction not found" },
-        { status: 500 },
-      );
+    const initiateState = {
+      ...initialState,
+      resume: file,
+      country: country,
     }
-
-    const result = await generateObject({
-      model: GEMINI_1_5_FLASH,
-      messages: [
-        {
-          role: "user",
-          content: file
-            ? [
-                {
-                  type: "text",
-                  text: `Country: ${country}`,
-                },
-                {
-                  type: "file",
-                  mimeType: "application/pdf",
-                  data: fileBuffer,
-                },
-              ]
-            : [
-                {
-                  type: "text",
-                  text: `Country: ${country}`,
-                },
-              ],
-        },
-      ],
-      system: systemInstruction,
-      schema,
-    });
-
-    return Response.json(result.object);
-  } catch (error) {
-    console.error(error);
+    const response = await graph.invoke(initiateState)
+    if (response.country === "Not Found") throw new Error("Country not found");
+    return Response.json(response);
+  } catch {
     return Response.json(
       { error: "Failed to process resume" },
       { status: 500 },