server.ts

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

dotenv.config();

const app = express();
const PORT = 3000;

app.use(express.json({ limit: "10mb" }));

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

// API Routes
// 1. Text to Speech API (using gemini-3.1-flash-tts-preview)
app.post("/api/tts", async (req, res) => {
  try {
    const { text, voice = "Kore", promptPrefix } = req.body;

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

    if (!process.env.GEMINI_API_KEY) {
      return res.status(500).json({ error: "GEMINI_API_KEY is missing on server" });
    }

    // Standard instruction for clear nursing terminology reading
    let finalPrompt = text;
    if (promptPrefix) {
      finalPrompt = `${promptPrefix}: ${text}`;
    }

    const response = await ai.models.generateContent({
      model: "gemini-3.1-flash-tts-preview",
      contents: [{ parts: [{ text: finalPrompt }] }],
      config: {
        responseModalities: [Modality.AUDIO],
        speechConfig: {
          voiceConfig: {
            prebuiltVoiceConfig: { voiceName: voice },
          },
        },
      },
    });

    const candidate = response.candidates?.[0];
    const audioPart = candidate?.content?.parts?.find((p: any) => p.inlineData?.data);
    const base64Audio = audioPart?.inlineData?.data;

    if (!base64Audio) {
      return res.status(500).json({ error: "Failed to generate audio from Gemini TTS" });
    }

    return res.json({
      audio: base64Audio,
      mimeType: audioPart?.inlineData?.mimeType || "audio/pcm",
    });
  } catch (error: any) {
    console.error("TTS API Error:", error);
    return res.status(500).json({
      error: error.message || "Failed to call Gemini TTS API",
    });
  }
});

// 2. AI Nursing Care Tutor API (using gemini-3.6-flash)
app.post("/api/tutor", async (req, res) => {
  try {
    const { prompt, conversationHistory = [] } = req.body;

    if (!prompt) {
      return res.status(400).json({ error: "Prompt is required" });
    }

    if (!process.env.GEMINI_API_KEY) {
      return res.status(500).json({ error: "GEMINI_API_KEY is missing on server" });
    }

    const systemInstruction = `Anda adalah 'Kaigo Sensei' (Tutor AI Ujian Keperawatan 特定技能1号 Tokutei Ginou Kaigo 2024 Ver 4.0).
Tugas Anda adalah membantu calon pekerja migran Indonesia memahami materi keperawatan Jepang (Kaigo Text Ver 4.0).
Gunakan bahasa Indonesia yang jelas, ramah, dan komunikatif, disertai istilah bahasa Jepang (Kanji, Hiragana, Romaji) beserta artinya.
Berikan penjelasan ringkas, contoh kasus di panti jompo/fasilitas lansia (Kaigo Shisetsu), dan petunjuk tips lulus ujian CBT Kaigo.`;

    const contents = [
      ...conversationHistory.map((msg: any) => ({
        role: msg.role === "user" ? "user" : "model",
        parts: [{ text: msg.content }],
      })),
      { role: "user", parts: [{ text: prompt }] },
    ];

    const response = await ai.models.generateContent({
      model: "gemini-3.6-flash",
      contents,
      config: {
        systemInstruction,
        temperature: 0.7,
      },
    });

    return res.json({
      reply: response.text,
    });
  } catch (error: any) {
    console.error("AI Tutor Error:", error);
    return res.status(500).json({
      error: error.message || "Failed to call Gemini Tutor API",
    });
  }
});

async function startServer() {
  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();