Edu_helper/backend/src/routes/chat.ts

import { Router, Response } from "express";
import prisma from "../lib/prisma";
import { getDeepSeekClient } from "../lib/deepseek";
import type { AuthRequest } from "../middleware/auth";

const router = Router();

router.get("/history", async (req: AuthRequest, res: Response) => {
  const studentId = req.studentId!;
  const messages = await prisma.chatMessage.findMany({
    where: { studentId },
    orderBy: { createdAt: "asc" },
    take: 100,
  });
  res.json(messages);
});

router.post("/", async (req: AuthRequest, res: Response) => {
  const { message } = req.body;
  const studentId = req.studentId!;

  if (!message || typeof message !== "string") {
    res.status(400).json({ error: "Message is required" });
    return;
  }

  await prisma.chatMessage.create({
    data: { role: "user", content: message, studentId },
  });

  const history = await prisma.chatMessage.findMany({
    where: { studentId },
    orderBy: { createdAt: "asc" },
    take: 50,
  });

  const client = await getDeepSeekClient();

  const messages = history.map((m: { role: string; content: string }) => ({
    role: m.role as "user" | "assistant",
    content: m.content,
  }));

  res.setHeader("Content-Type", "text/event-stream");
  res.setHeader("Cache-Control", "no-cache");
  res.setHeader("Connection", "keep-alive");

  try {
    const stream = await client.chat.completions.create({
      model: "deepseek-chat",
      messages,
      stream: true,
    });

    let fullResponse = "";

    for await (const chunk of stream) {
      const content = chunk.choices[0]?.delta?.content || "";
      if (content) {
        fullResponse += content;
        res.write(`data: ${JSON.stringify({ content })}\n\n`);
      }
    }

    await prisma.chatMessage.create({
      data: { role: "assistant", content: fullResponse, studentId },
    });

    res.write(`data: [DONE]\n\n`);
    res.end();
  } catch (err: any) {
    res.write(`data: ${JSON.stringify({ error: err.message })}\n\n`);
    res.end();
  }
});

router.delete("/history", async (req: AuthRequest, res: Response) => {
  const studentId = req.studentId!;
  await prisma.chatMessage.deleteMany({ where: { studentId } });
  res.json({ success: true });
});

export default router;