using MySql.Data.MySqlClient;
using ServiceShared.Database.Migrations;
using ServiceShared.Models.Database;
using System.Reflection;

namespace ServiceShared.Database
{
    public class DbContext
    {
        /// <summary>
        /// Current Application Version
        /// </summary>
        private static string _currentVersion = null;

        /// <summary>
        /// ConnectionString to the mysql server
        /// </summary>
        private readonly string _connectionString = null;
        
        /// <summary>
        /// Constructor of DbContext
        /// </summary>
        /// <param name="connectionString">ConnectionString to the mysql server</param>
        public DbContext(string connectionString)
        {
            this._connectionString = connectionString;
        }

        /// <summary>
        /// Runs a migration
        /// </summary>
        /// <param name="migration">Migration that should be run</param>
        /// <param name="currentVersion">Application version</param>
        /// <returns>returns true if migration was succssfully</returns>
        public bool RunMigration(Migration migration, string currentVersion)
        {
            _currentVersion = currentVersion + (migration != null ? "_" + migration.Version.ToString() : "");
            return migration.Run(this);
        }

        /// <summary>
        /// Sets application version
        /// </summary>
        /// <param name="currentVersion"></param>

        public static void setApplicationVersion(string currentVersion)
        {
            _currentVersion = currentVersion;
        }

        /// <summary>
        /// Checks if database exists
        /// </summary>
        /// <returns>returns true if database exists</returns>
        public bool DatabaseExists()
        {
            bool result = false;

            try
            {
                MySqlConnection dbConnection = this.CreateConnection();

                using (MySqlConnection client = this.CreateConnectionWithoutSelectedDatabase())
                {
                    client.Open();

                    MySqlCommand cmd = client.CreateCommand();

                    cmd.CommandText = "show databases like '" + dbConnection.Database + "'";

                    MySqlDataReader reader = cmd.ExecuteReader();

                    if (reader.HasRows)
                    {
                        result = true;
                        client.Close();
                    }
                }
            }
            catch(Exception ex)
            {
                Log.Critical(ex, "ServiceShared.Database.DbContext", "DatabaseExists");
                
                if(ex.InnerException != null)
                {
                    Log.Critical(ex.InnerException, "ServiceShared.Database.DbContext", "DatabaseExists");
                }

                result = false;
            }

            return result;
        }

        /// <summary>
        /// Creates a database if not exists
        /// </summary>
        /// <returns>returns true if the creation of database was successfully</returns>
        public bool DatabaseCreate()
        {
            bool result = false;

            try
            {
                MySqlConnection dbConnection = this.CreateConnection();

                using (MySqlConnection client = this.CreateConnectionWithoutSelectedDatabase())
                {
                    client.Open();
                    MySqlCommand cmd = client.CreateCommand();
                    cmd.CommandText = "create database if not exists " + dbConnection.Database + " character set utf8mb4 collate utf8mb4_general_ci";
                    cmd.ExecuteNonQuery();
                    client.Close();
                    result = true;
                }
            }
            catch (Exception ex)
            {
                Log.Error(ex, "ServiceOutside.Database.DbContext", "DatabaseCreate");
            }

            return result;
        }

        /// <summary>
        /// Maintenance flag
        /// </summary>
        /// <returns>returns true if Maintenance state has been activated</returns>
        public bool GetMaintenance()
        {
            bool result = false;

            try
            {
                using (MySqlConnection client = this.CreateConnection())
                {
                    client.Open();

                    MySqlCommand cmd = client.CreateCommand();
                    cmd.CommandText = @"select maintenance from config limit 1";

                    MySqlDataReader reader = cmd.ExecuteReader();

                    if (reader != null && reader.HasRows)
                    {
                        while (reader.Read())
                        {
                            result = (reader["maintenance"] != null && reader["maintenance"] != DBNull.Value && Convert.ToInt32(reader["maintenance"].ToString()) == 1);
                        }
                    }

                    client.Close();
                }
            }
            catch (Exception ex)
            {
                Log.Error(ex, "ServiceOutside.Database.DbContext", "Maintenance");
            }

            return result;
        }

        /// <summary>
        /// Returns a new MySqlConnection
        /// </summary>
        /// <returns>MySqlConnection</returns>
        public MySqlConnection CreateConnection()
        {
            return new MySqlConnection(this._connectionString);
        }

        /// <summary>
        /// Returns a new MySqlConnection without selected database
        /// </summary>
        /// <returns>MySqlConnection</returns>
        public MySqlConnection CreateConnectionWithoutSelectedDatabase()
        {
            string connectionString = null;

            if (!string.IsNullOrEmpty(this._connectionString))
            {
                string[] parts = this._connectionString.Split(';');

                if (parts.Length > 0)
                {
                    connectionString = "";

                    foreach (string part in parts)
                    {
                        string[] values = part.Split('=');

                        if (values.Length > 0)
                        {
                            if (values[0].ToLower().Replace(" ", "") != "database")
                            {
                                connectionString += part + ";";
                            }
                        }
                    }

                    connectionString = connectionString.TrimEnd(';');
                }
            }

            return new MySqlConnection(connectionString);
        }

        /// <summary>
        /// Retursn current migration of app
        /// </summary>
        /// <returns>Migration object</returns>
        public static string GetCurrentVersion()
        {
            return _currentVersion;
        }
    }
}