using Microsoft.SqlServer.Management.Common;
using Microsoft.SqlServer.Management.Smo;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using Tango.Core.DB;

namespace Tango.Web.SMO
{
    public class SmoManager : IDisposable
    {
        private ServerConnection _connection;
        private Server _server;
        private static Random random = new Random();

        public SmoManager()
        {
            _connection = new ServerConnection(WebConfig.DB_ADDRESS, WebConfig.DB_USER_NAME, WebConfig.DB_PASSWORD);
            _server = new Server(_connection);
        }

        public DbCredentials CreateRandomLoginAndUser()
        {
            var database = _server.Databases.OfType<Database>().SingleOrDefault(x => x.Name == WebConfig.DB_CATALOG);

            String userName = GetRandomString(36);
            String password = System.Web.Security.Membership.GeneratePassword(16, 2);

            Login login = new Login(_server, userName);
            login.LoginType = LoginType.SqlLogin;
            login.DefaultDatabase = WebConfig.DB_CATALOG;
            login.PasswordPolicyEnforced = false;
            login.Create(password);

            User user = new User(database, userName);
            user.Login = userName;
            user.Create();
            user.AddToRole("db_datareader");

            // Have to add this permission so user can view column definitions (default values etc..) !!!
            DatabasePermissionSet dbPermSet = new DatabasePermissionSet();
            dbPermSet.Add(DatabasePermission.ViewDefinition);

            database.Grant(dbPermSet, user.Name);

            return new DbCredentials() { UserName = userName, Password = password };
        }

        public void DeleteLoginAndUser(String userName)
        {
            var database = _server.Databases.OfType<Database>().SingleOrDefault(x => x.Name == WebConfig.DB_CATALOG);

            var user = database.Users.OfType<User>().SingleOrDefault(x => x.Name == userName);

            if (user != null)
            {
                user.Drop();
            }

            Login login = _server.Logins.OfType<Login>().SingleOrDefault(x => x.Name == userName);
            if (login != null)
            {
                login.Drop();
            }
        }

        public string GetRandomString(int length)
        {
            const string chars = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
            return "TEMP_" + new string(Enumerable.Repeat(chars, length).Select(s => s[random.Next(s.Length)]).ToArray());
        }

        public void Dispose()
        {
            _connection.Disconnect();
        }
    }
}