require('dotenv').config();
const mysql = require('mysql2/promise');
const config = require('./index');

// Create a connection pool
const pool = mysql.createPool({
  host: process.env.DB_HOST,
  user: process.env.DB_USER,
  password: process.env.DB_PASSWORD,
  database: process.env.DB_NAME,
  waitForConnections: true,
  connectionLimit: 10,
  queueLimit: 0,
  enableKeepAlive: true,
  keepAliveInitialDelay: 0,
  namedPlaceholders: true,
  connectTimeout: 10000,
  idleTimeout: 60000,
  maxIdle: 10
});

// Test the connection
pool.getConnection()
  .then(connection => {
    console.log('Database connected successfully');
    connection.release();
  })
  .catch(err => {
    console.error('Error connecting to the database:', err);
    process.exit(1);
  });

// Handle pool errors
pool.on('error', (err) => {
  console.error('Unexpected error on idle connection', err);
  process.exit(-1);
});

// Query with retry logic
const queryWithRetry = async (sql, params, maxRetries = 3) => {
    let lastError;
    for (let i = 0; i < maxRetries; i++) {
        try {
            const [results] = await pool.query(sql, params);
            return results;
        } catch (error) {
            lastError = error;
            console.error(`Database query error (attempt ${i + 1}/${maxRetries}):`, error);
            if (error.code === 'PROTOCOL_CONNECTION_LOST' || 
                error.code === 'ECONNRESET' || 
                error.code === 'PROTOCOL_ENQUEUE_AFTER_FATAL_ERROR') {
                console.log(`Database connection lost. Retry attempt ${i + 1} of ${maxRetries}`);
                await new Promise(resolve => setTimeout(resolve, 1000 * (i + 1)));
                continue;
            }
            throw error;
        }
    }
    throw lastError;
};

// Health check function
const checkDatabaseConnection = async () => {
    try {
        await pool.query('SELECT 1');
        return true;
    } catch (error) {
        console.error('Database health check failed:', error);
        return false;
    }
};

// Graceful shutdown
const closePool = async () => {
    try {
        await pool.end();
        console.log('Database pool closed successfully');
    } catch (error) {
        console.error('Error closing database pool:', error);
        throw error;
    }
};

module.exports = {
    query: queryWithRetry,
    checkConnection: checkDatabaseConnection,
    closePool
};