using System;
using System.Collections;
using System.Collections.Generic;
using System.Data;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Transactions;


using MySqlConnector;


using ServerCore; using ServerBase;


namespace ServerBase;

public partial class MySqlDbConnector : IDisposable
{
    // MySql 접속 재시도 간격 시간 밀리초) 
    private Int32 MYSQL_CONNECT_RETRY_INTERVAL_MSEC = 3000;
    // MySql 접속 재시도 간격 활성화 조건 실패 횟수
    private Int32 MYSQL_CONNECT_RETRY_INTERVAL_ENABLE_CONDITION_FAILED_COUNT = 3;
    // private Int16 m_curr_retry_connect_count = 0;

    private string m_connection_string = string.Empty;

    private MySqlConnection? m_connection;
    private ConnectionState m_last_connection_state = ConnectionState.Closed;

    private delegate int MyDelegate(int a, int b);

    public MySqlDbConnector()
    {
    }


    public async Task<ServerErrorCode> initMySql(string connectionString)
    {
        var err_msg = string.Empty;

        var error_code = createConnection(connectionString);
        if (error_code.isFail())
        {
            return error_code;
        }

        error_code = await openMySql();
        if (error_code.isFail())
        {
            Log.getLogger().error($"Failed to initMySql() !!! : errorCode:{error_code} - connectString:{m_connection_string}");

            return error_code;
        }

        return ServerErrorCode.Success;
    }

    public ServerErrorCode createConnection(string connectionString)
    {
        try
        {
            if(null != m_connection)
            {
                Dispose();
            }

            m_connection_string = connectionString;
            m_connection = new MySqlConnection(connectionString);

            // 연결 상태 변경에 대한 이벤트를 받기 위해 등록 한다. - kangms
            m_connection.StateChange += new StateChangeEventHandler(onStateChange);
        }
        catch (Exception e)
        {
            Log.getLogger().error($"Exception !!!, new MySqlConnection() !!! : message:{e}, connectString:{m_connection_string}");
            return ServerErrorCode.MySqlConnectionCreateFailed;
        }

        return ServerErrorCode.Success;
    }

    public async Task<ServerErrorCode> openMySql()
    {
        if (m_connection == null)
        {
            return ServerErrorCode.MySqlConnectionCreateFailed;
        }

        try
        {
            await m_connection.OpenAsync();
        }
        catch (Exception e)
        {
            Log.getLogger().error($"Exception to open MySqlConnection !!! : errDesc:{e.Message} - connectString:{m_connection_string}");
            return ServerErrorCode.MySqlConnectionOpenFailed;
        }

        return ServerErrorCode.Success;
    }

    public void Dispose()
    {
        // 객체 소멸시점 MySqlConnection 이 ConnectionPool 에 반환될 수 있도록
        // MySqlConnection.Dispose() 를 반드시 호출해 주어야 한다. - kangms
        if (m_connection != null)
        {
            m_connection.Dispose();
            m_connection = null;
        }
    }

    public void disposeMySql()
    {
        Dispose();
    }

    //=========================================================================================
    // MySqlDbConnector.onStateChange() 함수가 호출되는 시점은
    // 1. Self Disconnect : MySqlConnection.Dispose() 이 호출되는 시점 (Using 으로 생성후 Using 범위를 벗어나는 순간, 즉 GC 호출 시점)
    // 2. Other Disconnect : 실제로 MySql 서버와 끊어진 경우
    // 3. 기타 : 비정상적인 상황
    //=========================================================================================
    private void onStateChange(object sender, StateChangeEventArgs e)
    {
        if (m_connection == null)
        {
            Log.getLogger().error($"Failed to onStateChange(), Connection is null or CurrentState is null !!! - connectString:{m_connection_string}");
            return;
        }

        switch (e.CurrentState)
        {
            case ConnectionState.Closed:
                Log.getLogger().debug($"Closed MySqlConnector !!! - connectString:{m_connection_string}");
                break;

            case ConnectionState.Open:
                Log.getLogger().debug($"Opened MySqlConnector !!! - connectString:{m_connection_string}");
                break;
        }

        m_last_connection_state = e.CurrentState;
    }

    public async Task<ServerErrorCode> retryOpenMySql()
    {
        Log.getLogger().info($"Retry db connect start !!! - connectString:{m_connection_string}");

        var error_code = ServerErrorCode.Success;

        for (var i = 0; i < MYSQL_CONNECT_RETRY_INTERVAL_ENABLE_CONDITION_FAILED_COUNT; i++)
        {
            await Task.Delay(MYSQL_CONNECT_RETRY_INTERVAL_MSEC);

            error_code = createConnection(m_connection_string);
            if (error_code.isFail())
            {
                Log.getLogger().error($"Failed to createConnection() when retryOpenMySql() !!! : errorCode:{error_code}, retryCount:{i} - connectString:{m_connection_string}");
                continue;
            }

            error_code = await openMySql();
            if (error_code.isFail())
            {
                Log.getLogger().error($"Failed to openMySql() when retryOpenMySql() !!! : errorCode:{error_code}, retryCount:{i} - connectString:{m_connection_string}");
            }
            else
            {
                Log.getLogger().info($"Success Retry db connect !!! : retryCount:{i} - connectString:{m_connection_string}");
                return ServerErrorCode.Success;
            }
        }

        return error_code;
    }

    public async Task<ServerErrorCode> querySQL(string queryString, Func<MySqlDataReader, ServerErrorCode> dataReader)
    {
        var error_code = ServerErrorCode.Success;

        try
        {
            using (var cmd = new MySqlCommand(queryString, m_connection))
            using (var reader = await cmd.ExecuteReaderAsync())
            {
                if (true == await reader.ReadAsync())
                {
                    if (null != dataReader)
                    {
                        error_code = dataReader.Invoke(reader);
                        if (error_code.isFail())
                        {
                            Log.getLogger().error($"Failed to dataReader.Invoke() when querySQL() !!! : errorCode:{error_code}, queryString:{queryString} - connectString:{m_connection_string}");
                            return error_code;
                        }
                    }
                }
            }
        }
        catch(Exception e)
        {
            error_code = ServerErrorCode.MySqlDbQueryException;
            var err_msg = $"Exception !!!, Failed to query for Read when querySQL() !!! : errorCode:{error_code}, exception:{e}, queryString:{queryString} - connectString:{m_connection_string}";
            Log.getLogger().fatal(err_msg);
            return error_code;
        }

        return error_code;
    }
}