using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using Terminal.Gui;
using YamlDotNet.Serialization;

namespace Akari.Provider.WaveshareUART.Users
{
    public class UsersManager
    {
        public const int RangeStart = 1;
        public const int RangeLength = 20;
        public const string UsersFilePath = "users.yaml";

        public int Count => _users.Count;
        public IReadOnlyList<User> Users => _users.AsReadOnly();

        private readonly List<User> _users;
        private readonly IDeserializer _deserializer;
        private readonly ISerializer _serializer;

        public UsersManager()
        {
            _serializer = new SerializerBuilder().Build();
            _deserializer = new DeserializerBuilder().Build();

            try
            {
                if (!File.Exists(UsersFilePath))
                {
                    _users = new List<User>();
                }
                else
                {
                    _users = _deserializer.Deserialize<List<User>>(File.ReadAllText(UsersFilePath));
                }
            }
            catch (Exception e)
            {
                Console.WriteLine($"Can't load users: {e.Message}");
                Console.WriteLine(e.StackTrace);
            }
        }

        public User this[string name] => _users.FirstOrDefault(u => u.Name.Equals(name, StringComparison.OrdinalIgnoreCase));
        public User this[ushort start] => _users.FirstOrDefault(u => u.Start == start);

        public User Add(string name, string token)
        {
            // Find first available position
            var usedStarts = _users.Select(u => u.Start).ToHashSet();
            int start;

            for (start = RangeStart; start < ushort.MaxValue; start += RangeLength)
            {
                if (!usedStarts.Contains((ushort)start))
                {
                    break;
                }
            }

            // Add user
            var user = new User(name, token, (ushort)start);

            _users.Add(user);

            Save();

            return user;
        }

        public bool Remove(User user)
        {
            if (_users.Remove(user))
            {
                Save();

                return true;
            }

            return false;
        }

        public bool Remove(IEnumerable<User> users)
        {
            foreach (var user in users)
            {
                if (!Remove(user))
                {
                    return false;
                }
            }

            return true;
        }

        public bool Clear()
        {
            _users.Clear();

            Save();

            return true;
        }

        public void Save()
        {
            try
            {
                File.WriteAllText(UsersFilePath, _serializer.Serialize(_users));
            }
            catch (Exception e)
            {
                Console.WriteLine($"Can't save users: {e.Message}");
                Console.WriteLine(e.StackTrace);

                MessageBox.ErrorQuery("Users", $"Can't save users: {e.Message}");
            }
        }
    }
}