const express = require('express');
const cors = require('cors');
const fs = require('fs');
const path = require('path');

const app = express();
const PORT = process.env.PORT || 3000;
const TASKS_FILE = path.join(__dirname, 'tasks.json');

// Middleware
app.use(cors());
app.use(express.json());
app.use(express.static('public'));

// Lade Aufgaben
function loadTasks() {
  try {
    const data = fs.readFileSync(TASKS_FILE, 'utf8');
    return JSON.parse(data);
  } catch (error) {
    console.error('Fehler beim Laden der Aufgaben:', error);
    return [];
  }
}

// Speichere Aufgaben
function saveTasks(tasks) {
  fs.writeFileSync(TASKS_FILE, JSON.stringify(tasks, null, 2));
}

// API: Hole alle Aufgaben
app.get('/api/tasks', (req, res) => {
  const tasks = loadTasks();
  res.json({ tasks });
});


// API: Prüfe Antwort
app.post('/api/check-answer', (req, res) => {
  const { taskId, answer } = req.body;
  
  if (!taskId || answer === undefined) {
    return res.status(400).json({ error: 'taskId und answer sind erforderlich' });
  }
  
  const tasks = loadTasks();
  const taskIndex = tasks.findIndex(t => t.id === taskId);
  
  if (taskIndex === -1) {
    return res.status(404).json({ error: 'Aufgabe nicht gefunden' });
  }
  
  const task = tasks[taskIndex];
  const userAnswer = parseInt(answer);
  const correctAnswer = parseInt(task.answer);
  const isCorrect = userAnswer === correctAnswer;
  
  // Initialisiere attempts Counter falls nicht vorhanden
  if (tasks[taskIndex].attempts === undefined) {
    tasks[taskIndex].attempts = 0;
  }
  
  // Erhöhe Versuchszähler bei jeder Antwortprüfung
  tasks[taskIndex].attempts += 1;
  
  // Speichere Antwort, isCorrect und Timestamp in der Task
  tasks[taskIndex].userAnswer = userAnswer;
  tasks[taskIndex].isCorrect = isCorrect;
  tasks[taskIndex].answerTimestamp = new Date().toISOString();
  saveTasks(tasks);
  
  res.json({
    correct: isCorrect,
    correctAnswer: correctAnswer,
    points: isCorrect ? task.points : 0
  });
});


// Starte Server
app.listen(PORT, () => {
  console.log(`MathQuest Server läuft auf http://localhost:${PORT}`);
});