const express = require('express');
const sqlite3 = require('sqlite3').verbose();
const path = require('path');
const fs = require('fs');

const app = express();
const PORT = process.env.PORT || 3000;

// Shared option lists (used in multiple views)
const ART_OPTIONS = [
  'E-Mail', 'Online-Portal', 'Indeed', 'StepStone',
  'Firmenwebsite', 'Post', 'Initiativbewerbung',
  'Arbeitsagentur', 'Sonstiges'
];
const STATUS_OPTIONS = [
  'Gesendet', 'Eingangsbestätigung', 'Vorstellungsgespräch',
  'Absage', 'Einstellung', 'Keine Rückmeldung'
];

// Middleware
app.use(express.json());
app.use(express.urlencoded({ extended: true }));
app.use(express.static(path.join(__dirname, 'public')));

// Set EJS as template engine
app.set('view engine', 'ejs');
app.set('views', path.join(__dirname, 'views'));

// Ensure data directory exists
const dataDir = path.join(__dirname, 'data');
if (!fs.existsSync(dataDir)) {
  fs.mkdirSync(dataDir, { recursive: true });
}

// Database setup
const dbPath = path.join(dataDir, 'bewerbungen.db');
const db = new sqlite3.Database(dbPath);

// Sanitize input to prevent XSS
function sanitizeInput(input) {
  if (typeof input !== 'string') return input;
  return input
    .replace(/</g, '&lt;')
    .replace(/>/g, '&gt;')
    .replace(/"/g, '&quot;')
    .replace(/'/g, '&#39;');
}

// Promise wrapper for db operations
function dbGet(sql, params = []) {
  return new Promise((resolve, reject) => {
    db.get(sql, params, (err, result) => {
      if (err) reject(err);
      else resolve(result);
    });
  });
}

function dbAll(sql, params = []) {
  return new Promise((resolve, reject) => {
    db.all(sql, params, (err, results) => {
      if (err) reject(err);
      else resolve(results);
    });
  });
}

function dbRun(sql, params = []) {
  return new Promise((resolve, reject) => {
    db.run(sql, params, function(err) {
      if (err) reject(err);
      else resolve({ lastID: this.lastID, changes: this.changes });
    });
  });
}

// Recompute an application's current status from its latest timeline entry
async function syncCurrentStatus(bewerbungId) {
  const latest = await dbGet(
    'SELECT status FROM status_verlauf WHERE bewerbung_id = ? ORDER BY date(datum) DESC, id DESC LIMIT 1',
    [bewerbungId]
  );
  await dbRun(
    'UPDATE bewerbungen SET status = ?, updated_at = CURRENT_TIMESTAMP WHERE id = ?',
    [latest ? latest.status : '', bewerbungId]
  );
}

// Attach the status timeline to each application (single query, grouped in JS)
async function attachVerlauf(applications) {
  if (!applications.length) return applications;
  const all = await dbAll('SELECT * FROM status_verlauf ORDER BY date(datum) ASC, id ASC');
  const byApp = {};
  all.forEach((v) => { (byApp[v.bewerbung_id] = byApp[v.bewerbung_id] || []).push(v); });
  applications.forEach((a) => { a.verlauf = byApp[a.id] || []; });
  return applications;
}

// Initialize database - create tables and default settings in one operation
function initializeDatabase() {
  return new Promise((resolve, reject) => {
    db.serialize(() => {
      db.run('PRAGMA foreign_keys = ON');

      // Create tables
      db.run(`
        CREATE TABLE IF NOT EXISTS bewerbungen (
          id INTEGER PRIMARY KEY AUTOINCREMENT,
          datum DATE NOT NULL,
          firma TEXT NOT NULL,
          stelle TEXT NOT NULL,
          art TEXT,
          status TEXT,
          notizen TEXT,
          interne_notizen TEXT,
          created_at DATETIME DEFAULT CURRENT_TIMESTAMP,
          updated_at DATETIME DEFAULT CURRENT_TIMESTAMP
        )
      `, (err) => {
        if (err) return reject(err);

        // Migration: add interne_notizen to pre-existing databases (ignore "duplicate column")
        db.run('ALTER TABLE bewerbungen ADD COLUMN interne_notizen TEXT', () => {

        // Chronological status changes, each with an optional comment
        db.run(`
          CREATE TABLE IF NOT EXISTS status_verlauf (
            id INTEGER PRIMARY KEY AUTOINCREMENT,
            bewerbung_id INTEGER NOT NULL,
            datum DATE NOT NULL,
            status TEXT NOT NULL,
            kommentar TEXT,
            created_at DATETIME DEFAULT CURRENT_TIMESTAMP,
            FOREIGN KEY (bewerbung_id) REFERENCES bewerbungen(id) ON DELETE CASCADE
          )
        `, (err) => {
          if (err) return reject(err);

          db.run(`
            CREATE TABLE IF NOT EXISTS settings (
              id INTEGER PRIMARY KEY CHECK (id = 1),
              name TEXT,
              adresse TEXT,
              kundennummer TEXT
            )
          `, (err) => {
            if (err) return reject(err);

            // Insert default settings if not exists
            db.get('SELECT COUNT(*) as count FROM settings WHERE id = 1', (err, result) => {
              if (err) return reject(err);

              if (result && result.count === 0) {
                db.run(
                  'INSERT INTO settings (id, name, adresse, kundennummer) VALUES (1, ?, ?, ?)',
                  ['Max Mustermann', 'Musterstraße 1, 12345 Musterstadt', ''],
                  (err) => {
                    if (err) return reject(err);
                    resolve();
                  }
                );
              } else {
                resolve();
              }
            });
          });
        });
        });
      });
    });
  });
}

// Initialize and start server
initializeDatabase().then(() => {
  console.log('Database initialized successfully');
  
  // Routes
  app.get('/', async (req, res) => {
    try {
      const { month, year } = req.query;
      
      let query = 'SELECT * FROM bewerbungen ORDER BY datum DESC, created_at DESC';
      const params = [];
      
      if (month && year) {
        query = 'SELECT * FROM bewerbungen WHERE strftime("%m", datum) = ? AND strftime("%Y", datum) = ? ORDER BY datum DESC, created_at DESC';
        params.push(month.padStart(2, '0'), year);
      } else if (year) {
        query = 'SELECT * FROM bewerbungen WHERE strftime("%Y", datum) = ? ORDER BY datum DESC, created_at DESC';
        params.push(year);
      }
      
      const applications = await dbAll(query, params);
      await attachVerlauf(applications);
      const settings = await dbGet('SELECT * FROM settings WHERE id = 1');

      // Get statistics
      const totalCount = await dbGet('SELECT COUNT(*) as count FROM bewerbungen');
      const byArt = await dbAll(`
        SELECT art, COUNT(*) as count FROM bewerbungen 
        WHERE art IS NOT NULL AND art != ''
        GROUP BY art ORDER BY count DESC
      `);
      const byStatus = await dbAll(`
        SELECT status, COUNT(*) as count FROM bewerbungen 
        WHERE status IS NOT NULL AND status != ''
        GROUP BY status ORDER BY count DESC
      `);
      
      // Get available months/years for filter
      const availableMonths = await dbAll(`
        SELECT DISTINCT strftime("%Y-%m", datum) as yearmonth, 
               strftime("%m", datum) as month, 
               strftime("%Y", datum) as year
        FROM bewerbungen ORDER BY datum DESC
      `);
      
      res.render('index', {
        applications,
        settings,
        statistics: {
          total: totalCount ? totalCount.count : 0,
          byArt,
          byStatus
        },
        availableMonths,
        currentFilter: { month, year },
        artOptions: ART_OPTIONS,
        statusOptions: STATUS_OPTIONS
      });
    } catch (error) {
      console.error('Error:', error);
      res.status(500).send('Serverfehler');
    }
  });

  // Get single application
  app.get('/api/bewerbungen/:id', async (req, res) => {
    try {
      const { id } = req.params;
      const application = await dbGet('SELECT * FROM bewerbungen WHERE id = ?', [id]);
      
      if (!application) {
        return res.status(404).json({ error: 'Bewerbung nicht gefunden' });
      }
      
      res.json(application);
    } catch (error) {
      console.error('Error getting application:', error);
      res.status(500).json({ error: 'Serverfehler' });
    }
  });

  // Get settings
  app.get('/api/settings', async (req, res) => {
    try {
      const settings = await dbGet('SELECT * FROM settings WHERE id = 1');
      res.json(settings);
    } catch (error) {
      console.error('Error getting settings:', error);
      res.status(500).json({ error: 'Serverfehler' });
    }
  });

  // Save settings
  app.post('/api/settings', async (req, res) => {
    try {
      const { name, adresse, kundennummer } = req.body;
      
      await dbRun(
        'UPDATE settings SET name = ?, adresse = ?, kundennummer = ? WHERE id = 1',
        [sanitizeInput(name), sanitizeInput(adresse), sanitizeInput(kundennummer)]
      );
      
      res.json({ success: true });
    } catch (error) {
      console.error('Error saving settings:', error);
      res.status(500).json({ error: 'Serverfehler' });
    }
  });

  // Create application
  app.post('/api/bewerbungen', async (req, res) => {
    try {
      const { datum, firma, stelle, art, status, notizen, interne_notizen, kommentar } = req.body;

      const result = await dbRun(
        'INSERT INTO bewerbungen (datum, firma, stelle, art, status, notizen, interne_notizen) VALUES (?, ?, ?, ?, ?, ?, ?)',
        [datum, sanitizeInput(firma), sanitizeInput(stelle),
         sanitizeInput(art), sanitizeInput(status), sanitizeInput(notizen), sanitizeInput(interne_notizen)]
      );

      // Record the initial status as the first timeline entry
      if (status && status.trim()) {
        await dbRun(
          'INSERT INTO status_verlauf (bewerbung_id, datum, status, kommentar) VALUES (?, ?, ?, ?)',
          [result.lastID, datum, sanitizeInput(status), sanitizeInput(kommentar || '')]
        );
      }

      const newApplication = await dbGet('SELECT * FROM bewerbungen WHERE id = ?', [result.lastID]);

      res.json({ success: true, application: newApplication });
    } catch (error) {
      console.error('Error creating application:', error);
      res.status(500).json({ error: 'Serverfehler' });
    }
  });

  // Update application
  app.put('/api/bewerbungen/:id', async (req, res) => {
    try {
      const { id } = req.params;
      const { datum, firma, stelle, art, status, notizen } = req.body;
      
      await dbRun(
        'UPDATE bewerbungen SET datum = ?, firma = ?, stelle = ?, art = ?, status = ?, notizen = ?, updated_at = CURRENT_TIMESTAMP WHERE id = ?',
        [datum, sanitizeInput(firma), sanitizeInput(stelle), 
         sanitizeInput(art), sanitizeInput(status), sanitizeInput(notizen), id]
      );
      
      const updatedApplication = await dbGet('SELECT * FROM bewerbungen WHERE id = ?', [id]);
      
      res.json({ success: true, application: updatedApplication });
    } catch (error) {
      console.error('Error updating application:', error);
      res.status(500).json({ error: 'Serverfehler' });
    }
  });

  // Delete application
  app.delete('/api/bewerbungen/:id', async (req, res) => {
    try {
      const { id } = req.params;
      await dbRun('DELETE FROM status_verlauf WHERE bewerbung_id = ?', [id]);
      await dbRun('DELETE FROM bewerbungen WHERE id = ?', [id]);

      res.json({ success: true });
    } catch (error) {
      console.error('Error deleting application:', error);
      res.status(500).json({ error: 'Serverfehler' });
    }
  });

  // Applications for PDF export (optionally filtered), including the status timeline
  app.get('/api/export', async (req, res) => {
    try {
      const { month, year } = req.query;

      let query = 'SELECT * FROM bewerbungen ORDER BY datum DESC';
      const params = [];

      if (month && year) {
        query = 'SELECT * FROM bewerbungen WHERE strftime("%m", datum) = ? AND strftime("%Y", datum) = ? ORDER BY datum DESC';
        params.push(month.padStart(2, '0'), year);
      } else if (year) {
        query = 'SELECT * FROM bewerbungen WHERE strftime("%Y", datum) = ? ORDER BY datum DESC';
        params.push(year);
      }

      const applications = await dbAll(query, params);
      await attachVerlauf(applications);
      // Internal notes must never reach the PDF/export
      applications.forEach((a) => { delete a.interne_notizen; });

      res.json(applications);
    } catch (error) {
      console.error('Error exporting applications:', error);
      res.status(500).json({ error: 'Serverfehler' });
    }
  });

  // ----- Dedicated edit page + status-timeline management -----

  // Edit page for a single application
  app.get('/bewerbung/:id', async (req, res) => {
    try {
      const { id } = req.params;
      const application = await dbGet('SELECT * FROM bewerbungen WHERE id = ?', [id]);
      if (!application) return res.status(404).send('Bewerbung nicht gefunden');

      const verlauf = await dbAll(
        'SELECT * FROM status_verlauf WHERE bewerbung_id = ? ORDER BY date(datum) ASC, id ASC',
        [id]
      );

      res.render('bewerbung', {
        application,
        verlauf,
        artOptions: ART_OPTIONS,
        statusOptions: STATUS_OPTIONS,
        hideSettings: true
      });
    } catch (error) {
      console.error('Error loading edit page:', error);
      res.status(500).send('Serverfehler');
    }
  });

  // Update application core data (status is managed via the timeline)
  app.post('/bewerbung/:id', async (req, res) => {
    try {
      const { id } = req.params;
      const { datum, firma, stelle, art, notizen, interne_notizen } = req.body;

      await dbRun(
        'UPDATE bewerbungen SET datum = ?, firma = ?, stelle = ?, art = ?, notizen = ?, interne_notizen = ?, updated_at = CURRENT_TIMESTAMP WHERE id = ?',
        [datum, sanitizeInput(firma), sanitizeInput(stelle), sanitizeInput(art), sanitizeInput(notizen), sanitizeInput(interne_notizen), id]
      );

      res.redirect('/bewerbung/' + id);
    } catch (error) {
      console.error('Error updating application:', error);
      res.status(500).send('Serverfehler');
    }
  });

  // Add a timeline entry (status change with date + comment)
  app.post('/bewerbung/:id/verlauf', async (req, res) => {
    try {
      const { id } = req.params;
      const { datum, status, kommentar } = req.body;

      if (datum && status && status.trim()) {
        await dbRun(
          'INSERT INTO status_verlauf (bewerbung_id, datum, status, kommentar) VALUES (?, ?, ?, ?)',
          [id, datum, sanitizeInput(status), sanitizeInput(kommentar || '')]
        );
        await syncCurrentStatus(id);
      }

      res.redirect('/bewerbung/' + id);
    } catch (error) {
      console.error('Error adding timeline entry:', error);
      res.status(500).send('Serverfehler');
    }
  });

  // Update a timeline entry
  app.post('/bewerbung/:id/verlauf/:eintragId', async (req, res) => {
    try {
      const { id, eintragId } = req.params;
      const { datum, status, kommentar } = req.body;

      if (datum && status && status.trim()) {
        await dbRun(
          'UPDATE status_verlauf SET datum = ?, status = ?, kommentar = ? WHERE id = ? AND bewerbung_id = ?',
          [datum, sanitizeInput(status), sanitizeInput(kommentar || ''), eintragId, id]
        );
        await syncCurrentStatus(id);
      }

      res.redirect('/bewerbung/' + id);
    } catch (error) {
      console.error('Error updating timeline entry:', error);
      res.status(500).send('Serverfehler');
    }
  });

  // Delete a timeline entry
  app.post('/bewerbung/:id/verlauf/:eintragId/delete', async (req, res) => {
    try {
      const { id, eintragId } = req.params;
      await dbRun('DELETE FROM status_verlauf WHERE id = ? AND bewerbung_id = ?', [eintragId, id]);
      await syncCurrentStatus(id);
      res.redirect('/bewerbung/' + id);
    } catch (error) {
      console.error('Error deleting timeline entry:', error);
      res.status(500).send('Serverfehler');
    }
  });

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

  // Handle 404
  app.use((req, res) => {
    res.status(404).send('Seite nicht gefunden');
  });
}).catch((err) => {
  console.error('Failed to initialize database:', err);
  process.exit(1);
});

// Close database on exit
process.on('SIGINT', () => {
  db.close();
  process.exit();
});

process.on('SIGTERM', () => {
  db.close();
  process.exit();
});