using data.RemoteData.RemoteDataBase.DAO;
using Microsoft.EntityFrameworkCore;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using data.RemoteData.RemoteDataBase;

namespace data.Repository
{
    public class SQLGroupRepositoryImpl : IGroupRepository
    {
        private readonly RemoteDatabaseContext _context;

        public SQLGroupRepositoryImpl(RemoteDatabaseContext context)
        {
            _context = context;
        }
        
        public GroupDAO AddGroup(string groupName)
        {
            if (_context.Groups.AnyAsync(g => g.Name == groupName)!=null)
                throw new ArgumentException($"Группа '{groupName}' уже существует");

            var newGroup = new GroupDAO { Name = groupName };
            _context.Groups.AddAsync(newGroup);
            _context.SaveChangesAsync();
            return newGroup;
        }

        public async Task RemoveAllStudentsFromGroup(int groupId)
        {
            using var transaction = _context.Database.BeginTransactionAsync();
            
            try
            {
                var users = await _context.Users
                    .Where(u => u.GroupId == groupId)
                    .ToListAsync();

                _context.Users.RemoveRange(users);
                await _context.SaveChangesAsync();
            }
            catch (Exception ex)
            {
                throw;
            }
        }

        public async Task AddStudentToGroupAsync(int groupId, UserDAO student)
        {
            var groupExists = await _context.Groups.AnyAsync(g => g.Id == groupId);
            if (!groupExists) throw new ArgumentException("Группа не найдена");

            var studentExists = await _context.Users.AnyAsync(u => u.UserId == student.UserId);
            if (studentExists) throw new ArgumentException("Студент уже существует");

            student.GroupId = groupId;
            await _context.Users.AddAsync(student);
            await _context.SaveChangesAsync();
        }
        
        public GroupDAO GetGroupById(int groupId)
        {
            return _context.Groups
                .AsNoTracking()
                .Include(g => g.Users)
                .Select(g => new GroupDAO
                {
                    Id = g.Id,
                    Name = g.Name,
                    Users = g.Users.Select(u => new UserDAO 
                    { 
                        UserId = u.UserId, 
                        FIO = u.FIO 
                    }).ToList()
                })
                .FirstOrDefault(g => g.Id == groupId)
                ?? throw new AggregateException("Группа не найдена");
        }

        public async Task<List<GroupDAO>> GetAllGroupsAsync()
        {
            return await _context.Groups
                .AsNoTracking()
                .Select(g => new GroupDAO
                {
                    Id = g.Id,
                    Name = g.Name
                })
                .ToListAsync();
        }

        public async Task UpdateGroupAsync(int groupId, string newName)
        {
            var group = await _context.Groups
                .FirstOrDefaultAsync(g => g.Id == groupId)
                ?? throw new ArgumentException("Группа не найдена");

            group.Name = newName;
            await _context.SaveChangesAsync();
        }

        public async Task DeleteGroupAsync(int groupId)
        {
            await using var transaction = await _context.Database.BeginTransactionAsync();
            
            try
            {
                // Каскадное удаление пользователей
                await _context.Users
                    .Where(u => u.GroupId == groupId)
                    .ExecuteDeleteAsync();

                await _context.Groups
                    .Where(g => g.Id == groupId)
                    .ExecuteDeleteAsync();

                await transaction.CommitAsync();
            }
            catch
            {
                await transaction.RollbackAsync();
                throw;
            }
        }

        public List<GroupDAO> GetAllGroups()
        {
            return _context.Groups.ToList();
        }
    }
}