server.ts

import express from "express";
import path from "path";
import { createServer as createViteServer } from "vite";
import { GoogleGenAI, Type } from "@google/genai";

const ai = new GoogleGenAI({
  apiKey: process.env.GEMINI_API_KEY,
  httpOptions: {
    headers: {
      "User-Agent": "aistudio-build",
    },
  },
});

async function startServer() {
  const app = express();
  const PORT = 3000;

  app.use(express.json());

  app.post("/api/analyze", async (req, res) => {
    try {
      const { code, output, error } = req.body;
      
      const prompt = `You are an expert Python tutor. 
Analyze the following Python code written by a student, and its execution result.

Student's Code:
\`\`\`python
${code}
\`\`\`

Execution Output (stdout):
\`\`\`
${output}
\`\`\`

Execution Error (stderr):
\`\`\`
${error || "None"}
\`\`\`

Determine if the code is correct or wrong. 
Explain any syntax or logic errors clearly and constructively to the student.
If the code is correct but can be improved, provide a tip.`;

      const response = await ai.models.generateContent({
        model: "gemini-3.5-flash",
        contents: prompt,
        config: {
          responseMimeType: "application/json",
          responseSchema: {
            type: Type.OBJECT,
            properties: {
              status: {
                type: Type.STRING,
                description: "Either 'Correct', 'Incorrect', or 'Error'",
              },
              feedback: {
                type: Type.STRING,
                description: "Markdown formatted feedback explaining the logic and syntax, telling the student why it is correct or wrong.",
              },
              tip: {
                type: Type.STRING,
                description: "Optional tip for improvement if the code is correct, or empty string.",
              }
            },
            required: ["status", "feedback", "tip"],
          },
        },
      });

      res.json(JSON.parse(response.text || "{}"));
    } catch (err: any) {
      console.error(err);
      res.status(500).json({ error: "Failed to analyze code." });
    }
  });

  if (process.env.NODE_ENV !== "production") {
    const vite = await createViteServer({
      server: { middlewareMode: true },
      appType: "spa",
    });
    app.use(vite.middlewares);
  } else {
    const distPath = path.join(process.cwd(), "dist");
    app.use(express.static(distPath));
    app.get("*", (req, res) => {
      res.sendFile(path.join(distPath, "index.html"));
    });
  }

  app.listen(PORT, "0.0.0.0", () => {
    console.log(`Server running on http://localhost:${PORT}`);
  });
}

startServer();