using System;
using MySqlConnector;
using Serilog;

namespace SyncEngine.MySql
{
    public sealed class MySqlConnectionHolder : IDisposable
    {
        private readonly MySqlConnectionFactory _factory;
        private readonly ILogger _logger;
        private MySqlConnection _connection;
        private bool _connectionLost;

        public MySqlConnectionHolder(MySqlConnectionFactory factory, ILogger logger)
        {
            _factory = factory;
            _logger = logger;
        }

        public MySqlConnection Connection
        {
            get
            {
                if (_connection == null)
                {
                    throw new InvalidOperationException("MySQL connection is not open.");
                }

                return _connection;
            }
        }

        public void EnsureConnected()
        {
            if (_connection != null && _connection.State == System.Data.ConnectionState.Open)
            {
                return;
            }

            OpenConnection(logRegained: _connectionLost);
        }

        public void Reconnect()
        {
            _logger.Warning("MySQL connection lost; reconnecting...");
            _connectionLost = true;
            OpenConnection(logRegained: true);
        }

        public void Dispose()
        {
            DisposeConnection();
        }

        private void OpenConnection(bool logRegained)
        {
            DisposeConnection();
            var conn = _factory.Create();
            try
            {
                conn.Open();
                _connection = conn;
                if (logRegained)
                {
                    _logger.Information("MySQL connection regained");
                    _connectionLost = false;
                }
            }
            catch
            {
                conn.Dispose();
                throw;
            }
        }

        private void DisposeConnection()
        {
            if (_connection == null)
            {
                return;
            }

            _connection.Dispose();
            _connection = null;
        }
    }
}