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'));

// CORS middleware
app.use((req, res, next) => {
  res.header('Access-Control-Allow-Origin', '*');
  res.header('Access-Control-Allow-Methods', 'GET, POST, PUT, DELETE, OPTIONS');
  res.header('Access-Control-Allow-Headers', 'Content-Type');
  if (req.method === 'OPTIONS') {
    return res.sendStatus(200);
  }
  next();
});

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

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

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

async function initializeDatabase() {
  await runInitAsync(`CREATE TABLE IF NOT EXISTS batches (
    id INTEGER PRIMARY KEY AUTOINCREMENT,
    batch_name TEXT NOT NULL UNIQUE,
    createdAt DATETIME DEFAULT CURRENT_TIMESTAMP,
    status INTEGER NOT NULL DEFAULT 0
  )`);

  // Migration for existing databases: add status column if missing
  const columns = await allInitAsync(`PRAGMA table_info(batches)`);
  const hasStatusColumn = columns.some((col) => col.name === 'status');
  if (!hasStatusColumn) {
    await runInitAsync(`ALTER TABLE batches ADD COLUMN status INTEGER NOT NULL DEFAULT 0`);
    console.log('Added status column to batches table.');
  }

  await runInitAsync(`CREATE TABLE IF NOT EXISTS items (
    id INTEGER PRIMARY KEY AUTOINCREMENT,
    batch_id INTEGER NOT NULL,
    brand TEXT,
    mpn TEXT NOT NULL,
    mpn_custom TEXT,
    sn TEXT NOT NULL,
    createdAt DATETIME DEFAULT CURRENT_TIMESTAMP,
    FOREIGN KEY (batch_id) REFERENCES batches(id) ON DELETE CASCADE
  )`);

  await runInitAsync(`CREATE TABLE IF NOT EXISTS items_mix (
    id INTEGER PRIMARY KEY AUTOINCREMENT,
    batch_id INTEGER NOT NULL,
    brand TEXT,
    mpn TEXT NOT NULL,
    mpn_custom TEXT,
    sn TEXT NOT NULL,
    createdAt DATETIME DEFAULT CURRENT_TIMESTAMP,
    FOREIGN KEY (batch_id) REFERENCES batches(id) ON DELETE CASCADE
  )`);

  // Create indexes for better performance
  await runInitAsync(`CREATE INDEX IF NOT EXISTS idx_items_batch_id ON items(batch_id)`);
  await runInitAsync(`CREATE INDEX IF NOT EXISTS idx_items_mix_batch_id ON items_mix(batch_id)`);
  await runInitAsync(`CREATE INDEX IF NOT EXISTS idx_batches_status ON batches(status)`);
  await runInitAsync(`CREATE INDEX IF NOT EXISTS idx_items_mpn ON items(mpn)`);
  await runInitAsync(`CREATE INDEX IF NOT EXISTS idx_items_sn ON items(sn)`);
  await runInitAsync(`CREATE INDEX IF NOT EXISTS idx_items_brand ON items(brand)`);
  await runInitAsync(`CREATE INDEX IF NOT EXISTS idx_items_mix_brand ON items_mix(brand)`);
}

// ==================== BATCH API ROUTES ====================

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

function prepareRunAsync(stmt, params = []) {
  return new Promise((resolve, reject) => {
    stmt.run(params, function (err) {
      if (err) reject(err);
      else resolve();
    });
  });
}

function finalizeAsync(stmt) {
  return new Promise((resolve, reject) => {
    stmt.finalize((err) => (err ? reject(err) : resolve()));
  });
}

// Save batch with items and items_mix
app.post('/api/batch/save', async (req, res) => {
  const { batch_name, items, items_mix } = req.body;

  if (!batch_name) {
    return res.status(400).json({ error: 'batch_name is required' });
  }

  if (!Array.isArray(items) || items.length === 0) {
    return res.status(400).json({ error: 'items array is required and must not be empty' });
  }

  let insertedItems = 0;
  let insertedMixItems = 0;
  let errors = [];

  try {
    // BEGIN
    await runAsync(db, 'BEGIN TRANSACTION');

    // Insert batch
    const batchResult = await runAsync(
      db,
      'INSERT INTO batches (batch_name) VALUES (?)',
      [batch_name]
    );

    const batchId = batchResult.lastID;

    // ===== Insert items =====
    const itemStmt = db.prepare(
      'INSERT INTO items (batch_id, brand, mpn, mpn_custom, sn) VALUES (?, ?, ?, ?, ?)'
    );

    for (let i = 0; i < items.length; i++) {
      const item = items[i];

      if (!item.mpn || !item.sn) {
        errors.push(`Item at index ${i} is missing mpn or sn`);
        continue;
      }

      try {
        await prepareRunAsync(itemStmt, [
          batchId,
          item.brand || null,
          item.mpn,
          item.mpn_custom || null,
          item.sn
        ]);
        insertedItems++;
      } catch (err) {
        errors.push(`Error inserting item at index ${i}: ${err.message}`);
      }
    }

    await finalizeAsync(itemStmt);

    // ===== Insert items_mix (optional) =====
    if (Array.isArray(items_mix) && items_mix.length > 0) {
      const mixStmt = db.prepare(
        'INSERT INTO items_mix (batch_id, brand, mpn, mpn_custom, sn) VALUES (?, ?, ?, ?, ?)'
      );

      for (let i = 0; i < items_mix.length; i++) {
        const item = items_mix[i];

        if (!item.mpn || !item.sn) {
          errors.push(`Mixed item at index ${i} is missing mpn or sn`);
          continue;
        }

        try {
          await prepareRunAsync(mixStmt, [
            batchId,
            item.brand || null,
            item.mpn,
            item.mpn_custom || null,
            item.sn
          ]);
          insertedMixItems++;
        } catch (err) {
          errors.push(`Error inserting mixed item at index ${i}: ${err.message}`);
        }
      }

      await finalizeAsync(mixStmt);
    }

    // COMMIT
    await runAsync(db, 'COMMIT');

    return res.json({
      success: true,
      batch_id: batchId,
      batch_name,
      inserted_items: insertedItems,
      inserted_mix_items: insertedMixItems,
      errors: errors.length ? errors : undefined
    });

  } catch (err) {
    // ROLLBACK nếu có lỗi nghiêm trọng
    try {
      await runAsync(db, 'ROLLBACK');
    } catch (_) { }

    return res.status(500).json({
      error: err.message
    });
  }
});


// Get all batches with their items and items_mix
app.get('/api/batch/get-all', (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
  const validColumns = ['id', 'batch_name', 'createdAt'];
  const column = validColumns.includes(sortBy) ? sortBy : 'id';
  const order = sortOrder.toUpperCase() === 'ASC' ? 'ASC' : 'DESC';

  const whereConditions = ['status = 0'];
  let searchParams = [];

  if (search) {
    const searchCondition = `
      (
        batch_name LIKE ?
        OR id LIKE ?
        OR EXISTS (
          SELECT 1 FROM items 
          WHERE items.batch_id = batches.id 
          AND sn LIKE ?
        )
        OR EXISTS (
          SELECT 1 FROM items_mix 
          WHERE items_mix.batch_id = batches.id 
          AND sn LIKE ?
        )
      )
    `;
    whereConditions.push(searchCondition);

    const searchParam = `%${search}%`;
    searchParams = [searchParam, searchParam, searchParam, searchParam];
  }

  const whereClause = ` WHERE ${whereConditions.join(' AND ')}`;
  const countQuery = `SELECT COUNT(*) as total FROM batches${whereClause}`;
  const query = `SELECT * FROM batches${whereClause} ORDER BY ${column} ${order} LIMIT ? OFFSET ?`;
  const countParams = [...searchParams];
  const queryParams = [...searchParams, limit, offset];

  db.get(countQuery, countParams, (err, countRow) => {
    if (err) {
      return res.status(500).json({ error: err.message });
    }

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

      if (batches.length === 0) {
        return res.json({
          batches: [],
          total: 0,
          page,
          limit,
          totalPages: 0
        });
      }

      // Get items for each batch
      let processed = 0;
      const batchesWithItems = [];

      batches.forEach(batch => {
        // Get items
        db.all('SELECT brand, mpn, mpn_custom, sn, createdAt FROM items WHERE batch_id = ?', [batch.id], (err, items) => {
          if (err) {
            console.error('Error fetching items:', err);
            items = [];
          }

          // Get items_mix
          db.all('SELECT brand, mpn, mpn_custom, sn, createdAt FROM items_mix WHERE batch_id = ?', [batch.id], (err, items_mix) => {
            if (err) {
              console.error('Error fetching items_mix:', err);
              items_mix = [];
            }

            batchesWithItems.push({
              id: batch.id,
              batch_name: batch.batch_name,
              createdAt: batch.createdAt,
              items: items || [],
              items_mix: items_mix || []
            });

            processed++;

            if (processed === batches.length) {
              res.json({
                batches: batchesWithItems,
                total: countRow.total,
                page,
                limit,
                totalPages: Math.ceil(countRow.total / limit)
              });
            }
          });
        });
      });
    });
  });
});

// Get single batch by ID
app.get('/api/batch/get/:id', (req, res) => {
  const id = req.params.id;

  db.get('SELECT * FROM batches WHERE id = ? AND status = 0', [id], (err, batch) => {
    if (err) {
      return res.status(500).json({ error: err.message });
    }

    if (!batch) {
      return res.status(404).json({ error: 'Batch not found' });
    }

    // Get items
    db.all('SELECT brand, mpn, mpn_custom, sn, createdAt FROM items WHERE batch_id = ?', [id], (err, items) => {
      if (err) {
        return res.status(500).json({ error: err.message });
      }

      // Get items_mix
      db.all('SELECT brand, mpn, mpn_custom, sn, createdAt FROM items_mix WHERE batch_id = ?', [id], (err, items_mix) => {
        if (err) {
          return res.status(500).json({ error: err.message });
        }

        res.json({
          id: batch.id,
          batch_name: batch.batch_name,
          createdAt: batch.createdAt,
          items: items || [],
          items_mix: items_mix || []
        });
      });
    });
  });
});

// Soft delete batch (update status from 0 to 1)
app.delete('/api/batch/delete/:id', (req, res) => {
  const id = req.params.id;

  db.run('UPDATE batches SET status = 1 WHERE id = ? AND status = 0', [id], function (err) {
    if (err) {
      return res.status(500).json({ error: err.message });
    }

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

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

// Search items across all batches
app.get('/api/items/search', (req, res) => {
  const search = req.query.q || '';

  if (!search) {
    return res.status(400).json({ error: 'Search query is required' });
  }

  const searchParam = `%${search}%`;

  const query = `
    SELECT 
      b.id as batch_id,
      b.batch_name,
      i.brand,
      i.mpn,
      i.mpn_custom,
      i.sn,
      i.createdAt,
      'items' as type
    FROM items i
    JOIN batches b ON i.batch_id = b.id
    WHERE i.mpn LIKE ? OR i.sn LIKE ? OR i.brand LIKE ? OR i.mpn_custom LIKE ?
    UNION ALL
    SELECT 
      b.id as batch_id,
      b.batch_name,
      im.brand,
      im.mpn,
      im.mpn_custom,
      im.sn,
      im.createdAt,
      'items_mix' as type
    FROM items_mix im
    JOIN batches b ON im.batch_id = b.id
    WHERE im.mpn LIKE ? OR im.sn LIKE ? OR im.brand LIKE ? OR im.mpn_custom LIKE ?
    ORDER BY createdAt DESC
    LIMIT 100
  `;

  db.all(query, [
    searchParam, searchParam, searchParam, searchParam,
    searchParam, searchParam, searchParam, searchParam
  ], (err, results) => {
    if (err) {
      return res.status(500).json({ error: err.message });
    }

    res.json({ results });
  });
});

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

const PORT = process.env.PORT || 4444;
initializeDatabase()
  .then(() => {
    app.listen(PORT, () => {
      console.log(`Server is running on http://localhost:${PORT}`);
    });
  })
  .catch((err) => {
    console.error('Database initialization failed:', err.message);
    process.exit(1);
  });