using DatabaseCore.Models.Security;
using ModelTools.Enums;
using ModelTools.Interfaces;
using ModelTools.Models;
using SecurityBusinessLogic.BusinessLogics;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Security.Cryptography;
using System.Text;
using System.Threading.Tasks;

namespace DatabaseCore
{
	public class SecurityManager : ISecurityManager
	{
		private readonly int _countDayToBanned = 3;

		private readonly int _countMaxAttempt = 3;

		private static SecurityManager _securityManager;

		private static readonly object _lockObject = new();

		private SecurityManager() { }

		/// <summary>
		/// Singleton для класса
		/// </summary>
		public static SecurityManager GetInstance
		{
			get
			{
				if (_securityManager == null)
				{
					lock (_lockObject)
					{
						_securityManager = new SecurityManager();
					}
				}
				return _securityManager;
			}
		}

		public Guid? User { get; set; }

		public List<Guid> Roles { get; set; }

		public string ErrorMessage { get; set; }

		public bool IsAuth => User != null;

		public bool CheckAccess(SecurityManagerCheckAccessModel model)
		{
			using var context = DatabaseManager.GetContext;
			Access access = null;
			if (model != null)
			{
				// простой просмотр возможен
				if (model.Model.SkipCheck && model.Type == AccessType.SimpleView)
				{
					return true;
				}
				// если не указан идентификатор пользователя, то смотрим, может он авторизован
				if (!model.Model.UserId.HasValue && User.HasValue)
				{
					model.Model.UserId = User.Value;
				}

				var roles = context.UserRoles.Where(x => x.UserId == model.Model.UserId).Select(x => x.Role).OrderByDescending(x => x.RolePriority).ToList();
				if (roles == null)
				{
					ErrorMessage = $"Не верный пользователь";
					return false;
				}
				access = context.Accesses.FirstOrDefault(a => a.AccessOperation == model.Operation && roles.Contains(a.Role));
			}
			else if (Roles != null)
			{
				access = context.Accesses.FirstOrDefault(a => a.AccessOperation == model.Operation && Roles.Contains(a.RoleId));
			}
			if (access != null)
			{
				if (access.AccessType >= model.Type) return true;
			}
			switch (model.Type)
			{
				case AccessType.FullView:
					ErrorMessage = $"Нет доступа на чтение данных по сущности '{model.Entity}'";
					return false;
				case AccessType.Change:
					ErrorMessage = $"Нет доступа на изменение данных по сущности '{model.Entity}'";
					return false;
				case AccessType.Delete:
					ErrorMessage = $"Нет доступа на удаление данных по сущности '{model.Entity}'";
					return false;
				default:
					ErrorMessage = $"Нет доступа по сущности '{model.Entity}'";
					return false;
			}
		}

		public void CheckStartDataSource()
		{
			using var context = DatabaseManager.GetContext;
			using var transaction = context.Database.BeginTransaction();
			var role = context.Roles.FirstOrDefault(x => x.RoleName == "Администратор");
			if (role == null)
			{
				role = new Role
				{
					RoleName = "Администратор",
					RolePriority = 100
				};
				context.Roles.Add(role);
				context.SaveChanges();
			}

			var accesses = context.Accesses.Where(x => x.RoleId == role.Id);
			foreach (AccessOperation operation in Enum.GetValues(typeof(AccessOperation)))
			{
				if (!accesses.Any(x => x.AccessOperation == operation && x.AccessType == AccessType.Delete))
				{
					context.Accesses.Add(new Access
					{
						AccessOperation = operation,
						AccessType = AccessType.Delete,
						RoleId = role.Id
					});
				}
			}
			context.SaveChanges();

			var md5 = new MD5CryptoServiceProvider();
			var user = context.Users.FirstOrDefault(x => x.UserName == "admin");
			if (user == null)
			{
				user = new User
				{
					UserName = "admin",
					PasswordHash = Encoding.ASCII.GetString(md5.ComputeHash(Encoding.ASCII.GetBytes("qwerty"))),
					CountAttempt = 0
				};
				context.Users.Add(user);
				context.SaveChanges();
			}
			var link = context.UserRoles.FirstOrDefault(x => x.RoleId == role.Id && x.UserId == user.Id);
			if (link == null)
			{
				context.UserRoles.Add(new UserRole
				{
					RoleId = role.Id,
					UserId = user.Id
				});
				context.SaveChanges();
			}

			transaction.Commit();
		}

		public async Task LoginAsync(string login, string password)
		{
			var passwordHash = GetPasswordHash(password);
			using var context = DatabaseManager.GetContext;
			var user = context.Users.FirstOrDefault(x => x.UserName == login && x.PasswordHash == passwordHash);
			await CheckUserAsync(login, user, context);
			user.DateLastVisit = DateTime.Now;
			user.CountAttempt = 0;
			await context.SaveChangesAsync();

			User = user.Id;
			Roles = context.UserRoles.Where(x => x.UserId == user.Id).Select(x => x.RoleId).ToList();
		}

		public async Task LogoutAsync()
		{
			await Task.Run(() =>
			{
				User = null;
				Roles = null;
			});
		}

		public async Task ChangePassword(string login, string oldPassword, string newPassword)
		{
			using var context = DatabaseManager.GetContext;
			var user = context.Users.FirstOrDefault(x => x.UserName == login && x.PasswordHash == GetPasswordHash(oldPassword));
			await CheckUserAsync(login, user, context);
			user.PasswordHash = GetPasswordHash(newPassword);
			await context.SaveChangesAsync();
		}

		/// <summary>
		/// Получение хеша пароля
		/// </summary>
		/// <param name="password"></param>
		/// <returns></returns>
		private static string GetPasswordHash(string password) => Encoding.ASCII.GetString((new MD5CryptoServiceProvider()).ComputeHash(Encoding.ASCII.GetBytes(password)));

		/// <summary>
		/// Проверка пользователя при авторизации и при смене пароля
		/// </summary>
		/// <param name="login"></param>
		/// <param name="user"></param>
		/// <param name="context"></param>
		/// <returns></returns>
		private async Task CheckUserAsync(string login, User user, DatabaseContext context)
		{
			if (user == null)
			{
				user = context.Users.FirstOrDefault(x => x.UserName == login);
				if (user != null)
				{
					user.CountAttempt++;
					if (user.CountAttempt > _countMaxAttempt)
					{
						user.IsBanned = true;
						user.DateBanned = DateTime.Now;
						await context.SaveChangesAsync();

						throw new Exception($"Введен неверный логин/пароль? учетная запись заблоикрована на {_countDayToBanned} дней(я)");
					}
				}

				throw new Exception("Введен неверный логин/пароль");
			}
			if (user.IsBanned)
			{
				if (user.DateBanned.Value.AddDays(_countDayToBanned) > DateTime.Now)
				{
					user.IsBanned = false;
					await context.SaveChangesAsync();
				}
				else
				{
					throw new Exception("Пользователь заблокирован");
				}
			}
		}
	}
}