server.ts

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

dotenv.config();

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

  // 1-hour cache to prevent quota exhaustion
const tipsCache = new Map<string, { tips: string[], expiry: number }>();

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

  app.use(express.json());

  // API Route for Gemini Financial Tips
  app.post('/api/tips', async (req, res) => {
    console.log('[API_TIPS]: Received request');
    try {
      const { budgetSpent, totalBalance, budgetLimits, userId } = req.body;
      
      // Use userId for caching if available, otherwise fallback to balance bucket
      const cacheKey = userId || `bal_${Math.floor((totalBalance || 0) / 1000)}`;
      
      // Check cache (valid for 1 hour)
      const cached = tipsCache.get(cacheKey);
      if (cached && cached.expiry > Date.now()) {
        console.log('[API_TIPS]: Serving from 1-hour cache');
        return res.json({ tips: cached.tips });
      }

      const apiKey = process.env.GEMINI_API_KEY;
      if (!apiKey) {
        console.error('[API_TIPS]: Missing GEMINI_API_KEY');
        return res.status(500).json({ error: 'GEMINI_API_KEY is not configured' });
      }

      console.log('[API_TIPS]: Payload received', { totalBalance, userId });

      const prompt = `
        You are an AI Financial Advisor for an app called Pocket Pay (UPI Simulator).
        Based on the following budget data, give 3 short, actionable financial tips.
        
        Account Balance: ₹${totalBalance || 0}
        Budget Spent: ${JSON.stringify(budgetSpent || {})}
        Budget Limits: ${JSON.stringify(budgetLimits || {})}
        
        Keep each tip under 12 words. Focus on overspending or smart savings.
        Return as a raw JSON array of strings. Do not include markdown blocks.
      `;

      console.log('[API_TIPS]: Calling Gemini...');
      let tips: string[] = ["Track your small daily spends.", "Save at least 20% of your income.", "Plan your major expenses."];

      try {
        const response = await ai.models.generateContent({
          model: 'gemini-2.0-flash',
          contents: prompt,
        });

        const responseText = response.text || '';
        console.log('[API_TIPS]: Gemini responded');
        
        const jsonMatch = responseText.match(/\[.*\]/s);
        if (jsonMatch) {
          tips = JSON.parse(jsonMatch[0]);
          // Cache the successful response for 1 hour
          tipsCache.set(cacheKey, { tips, expiry: Date.now() + 60 * 60 * 1000 });
        }
      } catch (geminiError: any) {
        // Handle 429 quota errors silently to avoid cluttering logs
        const isQuota = geminiError?.message?.includes('429') || geminiError?.status === 429;
        if (!isQuota) {
          console.error('[API_TIPS]: Gemini call failed', geminiError);
        } else {
          console.warn('[API_TIPS]: Quota hit, using fallbacks');
        }
      }

      res.json({ tips });
    } catch (error) {
      console.error('[API_TIPS_CRITICAL]:', error);
      res.status(500).json({ 
        error: 'Failed to generate tips',
        details: error instanceof Error ? error.message : String(error)
      });
    }
  });

  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 at http://localhost:${PORT}`);
  });
}

startServer();