wondersheets/server/index.js

import express from 'express';
import cors from 'cors';
import dotenv from 'dotenv';
import fs from 'fs';
import path from 'path';
import { fileURLToPath } from 'url';
import { GoogleGenerativeAI } from '@google/generative-ai';
import { getPromptForActivity } from './prompts.js';

dotenv.config();

const __filename = fileURLToPath(import.meta.url);
const __dirname = path.dirname(__filename);

const app = express();
const port = 3001;

app.use(cors());
app.use(express.json());

// Initialize Gemini API
const genAI = new GoogleGenerativeAI(process.env.GEMINI_API_KEY || '');

// ============================================
// GALLERY STORAGE - Recent 6 generations
// ============================================
const GALLERY_FILE = path.join(__dirname, 'gallery.json');
const MAX_GALLERY_SIZE = 6;

// Load gallery from file
function loadGallery() {
    try {
        if (fs.existsSync(GALLERY_FILE)) {
            const data = fs.readFileSync(GALLERY_FILE, 'utf8');
            return JSON.parse(data);
        }
    } catch (error) {
        console.error('Error loading gallery:', error);
    }
    return [];
}

// Save gallery to file
function saveGallery(gallery) {
    try {
        fs.writeFileSync(GALLERY_FILE, JSON.stringify(gallery, null, 2));
    } catch (error) {
        console.error('Error saving gallery:', error);
    }
}

// Add item to gallery (keeps only recent 6)
function addToGallery(item) {
    const gallery = loadGallery();

    // Add new item at the beginning
    gallery.unshift({
        ...item,
        id: Date.now(),
        createdAt: new Date().toISOString()
    });

    // Keep only the most recent 6
    while (gallery.length > MAX_GALLERY_SIZE) {
        gallery.pop();
    }

    saveGallery(gallery);
    return gallery;
}

// ============================================
// API ENDPOINTS
// ============================================

// Get recent gallery items
app.get('/api/gallery', (req, res) => {
    try {
        const gallery = loadGallery();
        res.json(gallery);
    } catch (error) {
        console.error('Gallery fetch error:', error);
        res.status(500).json({ error: 'Failed to fetch gallery' });
    }
});

app.post('/api/surprise', async (req, res) => {
    try {
        if (!process.env.GEMINI_API_KEY) {
            return res.status(500).json({ error: 'Missing API Key' });
        }
        const model = genAI.getGenerativeModel({ model: "gemini-2.5-pro" });
        const prompt = `
        Generate ONE creative, fun, specific theme for a children's worksheet (e.g. "Space-Rex Coding", "Underwater Hamster Tea Party").
        Pick a random age between 3 and 7.
        Pick a random activity type from: coloring, numbers, writing, find-way, counting.

        Return JSON ONLY:
        {
            "theme": "string",
            "age": number,
            "section": "string"
        }
        `;

        const result = await model.generateContent(prompt);
        const text = result.response.text();
        const jsonStr = text.replace(/```json/g, '').replace(/```/g, '').trim();
        res.json(JSON.parse(jsonStr));
    } catch (error) {
        console.error('Surprise error:', error);
        res.status(500).json({ error: 'Failed' });
    }
});

app.post('/api/generate', async (req, res) => {
    try {
        const { theme, age, sections } = req.body;
        console.log('Received generation request:', { theme, age, sections });

        if (!process.env.GEMINI_API_KEY) {
            console.warn('Missing GEMINI_API_KEY');
            return res.status(500).json({ error: 'Server configuration error: Missing API Key' });
        }

        const model = genAI.getGenerativeModel({ model: "gemini-2.5-pro" });

        // Get the activity-specific prompt for the first section
        const activityType = sections[0] || 'coloring';
        const prompt = getPromptForActivity(activityType, theme, age);

        console.log(`Using specialized prompt for activity: ${activityType}`);

        const result = await model.generateContent(prompt);
        const response = await result.response;
        const text = response.text();

        // Cleanup markdown code blocks if present
        const jsonStr = text.replace(/```json/g, '').replace(/```/g, '').trim();
        const data = JSON.parse(jsonStr);

        if (!data.title || !data.sections || !Array.isArray(data.sections)) {
            throw new Error('Invalid generation format');
        }

        // Save to gallery
        const galleryItem = {
            ...data,
            age,
            activityType
        };
        addToGallery(galleryItem);
        console.log('Added to gallery, current size:', loadGallery().length);

        res.json(data);
    } catch (error) {
        console.error('Generation error:', error);
        res.status(500).json({ error: 'Failed to generate content' });
    }
});

app.listen(port, () => {
    console.log(`Server running at http://localhost:${port}`);
});