import express from 'express';
import mysql from 'mysql2/promise';
import cors from 'cors';
import dotenv from 'dotenv';
import fs from 'fs';

dotenv.config();

const app = express();
app.use(cors());
app.use(express.json({ limit: '50mb' }));

// MySQL Pool Configuration
const pool = mysql.createPool({
  host: process.env.DB_HOST,
  user: process.env.DB_USER,
  password: process.env.DB_PASS,
  database: process.env.DB_NAME,
  port: parseInt(process.env.DB_PORT || '3306'),
  waitForConnections: true,
  connectionLimit: 10,
  queueLimit: 0
});

// Error Handler
const handleError = (res, err, label) => {
  console.error(`❌ [${label}] Error:`, err);
  res.status(500).json({ error: err.message });
};

// --- API Endpoints ---

// 1. Generic Batch Save (Dynamic Table Detection)
app.post('/api/:table/batch', async (req, res) => {
  const { table } = req.params;
  const data = req.body;
  if (!Array.isArray(data)) return res.status(400).json({ error: 'Data must be an array' });

  let connection;
  try {
    connection = await pool.getConnection();
    await connection.beginTransaction();

    // 1. Get Table Schema
    const [columns] = await connection.query(`DESCRIBE ${table}`);
    const validFields = columns.map(c => c.Field);

    // 2. Clear Existing Data (Optional - depending on strategy)
    // For now, we use REPLACE INTO or similar. But user requested batch save as sync.
    await connection.query(`DELETE FROM ${table}`);

    // 3. Insert New Data
    if (data.length > 0) {
        const placeholders = validFields.map(() => '?').join(', ');
        const sql = `INSERT INTO ${table} (${validFields.join(', ')}) VALUES (${placeholders})`;
        
        for (const item of data) {
            const values = validFields.map(field => {
                const val = item[field];
                return val === undefined ? null : val;
            });
            await connection.query(sql, values);
        }
    }

    await connection.commit();
    console.log(`✅ [BATCH SAVE] Table: ${table}, Count: ${data.length}`);
    res.json({ success: true, count: data.length });
  } catch (err) {
    if (connection) await connection.rollback();
    handleError(res, err, 'BATCH SAVE');
  } finally {
    if (connection) connection.release();
  }
});

// 2. Get All Assets (Integrated Master Data)
app.get('/api/assets/master', async (req, res) => {
  try {
    const connection = await pool.getConnection();
    const tables = {
      pc: 'asset_pc',
      server: 'asset_server',
      storage: 'asset_storage',
      network: 'asset_network',
      equipment: 'asset_equipment',
      officeSupplies: 'asset_office_supplies',
      survey: 'asset_survey',
      vip: 'asset_vip',
      swInternal: 'sw_internal',
      swExternal: 'sw_external',
      cloud: 'asset_cloud',
      users: 'user_master',
      swUsers: 'sw_assignment',
      logs: 'asset_history'
    };

    const masterData = {};
    for (const [key, tableName] of Object.entries(tables)) {
      try {
        const [rows] = await connection.query(`SELECT * FROM ${tableName}`);
        masterData[key] = rows;
      } catch (err) {
        console.warn(`[MASTER DATA] Skipping ${tableName}: ${err.message}`);
        masterData[key] = [];
      }
    }

    connection.release();
    res.json(masterData);
  } catch (err) {
    handleError(res, err, 'MASTER DATA');
  }
});

// 3. Single Asset Save (Update or Insert)
app.post('/api/asset/:category/save', async (req, res) => {
  const { category } = req.params;
  const asset = req.body;
  const tableMap = {
    pc: 'asset_pc',
    server: 'asset_server',
    storage: 'asset_storage',
    network: 'asset_network',
    equipment: 'asset_equipment',
    officeSupplies: 'asset_office_supplies',
    survey: 'asset_survey',
    vip: 'asset_vip',
    swInternal: 'sw_internal',
    swExternal: 'sw_external',
    cloud: 'asset_cloud'
  };
  const table = tableMap[category];

  if (!table) return res.status(400).json({ error: 'Invalid category' });

  try {
    const connection = await pool.getConnection();
    const [columns] = await connection.query(`DESCRIBE ${table}`);
    const validFields = columns.map(c => c.Field);

    const dataObj = {};
    validFields.forEach(f => { if (asset[f] !== undefined) dataObj[f] = asset[f]; });

    const keys = Object.keys(dataObj);
    const values = Object.values(dataObj);
    const placeholders = keys.map(() => '?').join(', ');
    const updates = keys.map(k => `${k} = VALUES(${k})`).join(', ');

    const sql = `INSERT INTO ${table} (${keys.join(', ')}) VALUES (${placeholders}) ON DUPLICATE KEY UPDATE ${updates}`;
    
    await connection.query(sql, values);
    connection.release();
    console.log(`💾 [ASSET SAVE] Category: ${category}, ID: ${asset.id}`);
    res.json({ success: true });
  } catch (err) {
    handleError(res, err, 'ASSET SAVE');
  }
});

// 4. Asset Delete
app.delete('/api/asset/:category/:id', async (req, res) => {
  const { category, id } = req.params;
  const tableMap = {
    pc: 'asset_pc', server: 'asset_server', storage: 'asset_storage', network: 'asset_network',
    equipment: 'asset_equipment', officeSupplies: 'asset_office_supplies', survey: 'asset_survey', 
    vip: 'asset_vip', swInternal: 'sw_internal', swExternal: 'sw_external', cloud: 'asset_cloud'
  };
  const table = tableMap[category];
  if (!table) return res.status(400).json({ error: 'Invalid category' });

  try {
    const connection = await pool.getConnection();
    await connection.query(`DELETE FROM ${table} WHERE id = ?`, [id]);
    connection.release();
    console.log(`🗑️ [ASSET DELETE] Category: ${category}, ID: ${id}`);
    res.json({ success: true });
  } catch (err) {
    handleError(res, err, 'ASSET DELETE');
  }
});

// 5. Generate Next Asset Code
app.get('/api/generate-asset-code', async (req, res) => {
  const { prefix, purchaseDate } = req.query;
  if (!prefix) return res.status(400).json({ error: 'Prefix is required' });

  try {
    const connection = await pool.getConnection();
    const tables = [
      'asset_pc', 'asset_server', 'asset_storage', 'asset_network', 
      'asset_equipment', 'asset_office_supplies', 'asset_survey', 'asset_vip'
    ];
    
    // Extract YYYYMM from purchaseDate (format: YYYY-MM-DD)
    const datePart = purchaseDate ? purchaseDate.toString().replace(/-/g, '').substring(0, 6) : '';
    const searchPattern = datePart ? `${prefix}-${datePart}-%` : `${prefix}-%`;

    let maxNum = 0;

    for (const table of tables) {
        try {
          const [rows] = await connection.query(
            `SELECT asset_code FROM ${table} WHERE asset_code LIKE ?`, 
            [searchPattern]
          );
          
          rows.forEach(row => {
            const parts = row.asset_code.split('-');
            const seqPart = parts[parts.length - 1]; // Last part is sequence
            const num = parseInt(seqPart);
            if (!isNaN(num) && num > maxNum) maxNum = num;
          });
        } catch (err) {
          // Table might not exist or column missing
        }
    }
    
    const nextNum = maxNum + 1;
    const nextCode = datePart 
        ? `${prefix}-${datePart}-${String(nextNum).padStart(4, '0')}`
        : `${prefix}-${String(nextNum).padStart(4, '0')}`; // Fallback if no date
    
    connection.release();
    console.log(`🆕 [GENERATE CODE] Prefix: ${prefix}, Date: ${datePart}, Next: ${nextCode}`);
    res.json({ nextCode });
  } catch (err) { 
    handleError(res, err, 'GENERATE CODE'); 
  }
});

// 6. Map Config API (Real-time Save)
app.get('/api/maps', (req, res) => {
  try {
    if (!fs.existsSync('map_config.json')) {
      return res.json({});
    }
    const data = fs.readFileSync('map_config.json', 'utf8');
    res.json(JSON.parse(data || '{}'));
  } catch (err) {
    handleError(res, err, 'GET MAPS');
  }
});

app.post('/api/maps/save', (req, res) => {
  try {
    const { path, boxes } = req.body;
    if (!path) return res.status(400).json({ error: 'Path is required' });

    let config = {};
    if (fs.existsSync('map_config.json')) {
      config = JSON.parse(fs.readFileSync('map_config.json', 'utf8') || '{}');
    }

    config[path] = boxes;
    fs.writeFileSync('map_config.json', JSON.stringify(config, null, 2));
    console.log(`💾 [MAP SAVE] Updated config for: ${path}`);
    res.json({ success: true });
  } catch (err) {
    handleError(res, err, 'SAVE MAPS');
  }
});

app.listen(3000, '0.0.0.0', () => {
  console.log('📡 ITAM BACKEND SERVER RUNNING ON PORT 3000 (Multi-Table Optimized)');
});