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

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

// Initialize SQLite database
const db = new sqlite3.Database('./products.db', (err) => {
  if (err) console.error(err.message);
  console.log('Connected to products database.');
});

// Create products table
db.run(`CREATE TABLE IF NOT EXISTS products (
  id INTEGER PRIMARY KEY AUTOINCREMENT,
  mpn TEXT NOT NULL,
  sn TEXT NOT NULL,
  createdAt DATETIME DEFAULT CURRENT_TIMESTAMP,
  createdBy TEXT NOT NULL
)`);

// API Routes

// Create products (batch insert)
app.post('/api/product/create', (req, res) => {
  const products = req.body;
  
  if (!Array.isArray(products) || products.length === 0) {
    return res.status(400).json({ error: 'Expected an array of products' });
  }

  const stmt = db.prepare('INSERT INTO products (mpn, sn, createdBy) VALUES (?, ?, ?)');
  let inserted = 0;
  let errors = [];

  products.forEach((product, index) => {
    if (!product.mpn || !product.sn || !product.createdBy) {
      errors.push(`Product at index ${index} is missing required fields`);
      return;
    }

    stmt.run(product.mpn, product.sn, product.createdBy, (err) => {
      if (err) errors.push(`Error inserting product at index ${index}: ${err.message}`);
      else inserted++;
    });
  });

  stmt.finalize(() => {
    res.json({ 
      success: true, 
      inserted,
      errors: errors.length > 0 ? errors : undefined
    });
  });
});

// Get products with pagination, search, and sort
app.get('/api/product/get', (req, res) => {
  const page = parseInt(req.query.page) || 1;
  const limit = parseInt(req.query.limit) || 50;
  const search = req.query.search || '';
  const sortBy = req.query.sortBy || 'id';
  const sortOrder = req.query.sortOrder || 'DESC';
  const offset = (page - 1) * limit;

  // Validate sortBy to prevent SQL injection
  const validColumns = ['id', 'mpn', 'sn', 'createdAt', 'createdBy'];
  const column = validColumns.includes(sortBy) ? sortBy : 'id';
  const order = sortOrder.toUpperCase() === 'ASC' ? 'ASC' : 'DESC';

  let query = 'SELECT * FROM products';
  let countQuery = 'SELECT COUNT(*) as total FROM products';
  let params = [];

  if (search) {
    const searchCondition = ` WHERE mpn LIKE ? OR sn LIKE ? OR createdBy LIKE ? OR id LIKE ?`;
    query += searchCondition;
    countQuery += searchCondition;
    const searchParam = `%${search}%`;
    params = [searchParam, searchParam, searchParam, searchParam];
  }

  query += ` ORDER BY ${column} ${order} LIMIT ? OFFSET ?`;
  params.push(limit, offset);

  db.get(countQuery, search ? params.slice(0, 4) : [], (err, countRow) => {
    if (err) {
      return res.status(500).json({ error: err.message });
    }

    db.all(query, params, (err, rows) => {
      if (err) {
        return res.status(500).json({ error: err.message });
      }

      res.json({
        products: rows,
        total: countRow.total,
        page,
        limit,
        totalPages: Math.ceil(countRow.total / limit)
      });
    });
  });
});

// Delete product
app.delete('/api/product/delete/:id', (req, res) => {
  const id = req.params.id;

  db.run('DELETE FROM products WHERE id = ?', id, function(err) {
    if (err) {
      return res.status(500).json({ error: err.message });
    }

    if (this.changes === 0) {
      return res.status(404).json({ error: 'Product not found' });
    }

    res.json({ success: true, deleted: this.changes });
  });
});

// Serve HTML UI
app.get('/', (req, res) => {
  res.sendFile(path.join(__dirname, 'public', 'index.html'));
});

const PORT = process.env.PORT || 4444;
app.listen(PORT, () => {
  console.log(`Server is running on http://localhost:${PORT}`);
});