using model;
using System.Collections.ObjectModel;
using System.Diagnostics;

namespace Snake.Model;

public class SnakeLevel : IDisposable{
    public static readonly TimeSpan TickTimeSpan = TimeSpan.FromMilliseconds(500);
    public int Size {get; }

    public enum LevelBlock{
        Empty,
        Obstacle,
        Egg,
        Snake,
        SnakeHead,
        OutOfBounds
    }

    public enum SnakeDirection{
        Up,
        Down,
        Left,
        Right
    }

    public enum GameState{
        Running,
        Paused,
        Dead
    }

    private readonly List<Point> _obstacles;
    public ReadOnlyCollection<Point> Obstacles => _obstacles.AsReadOnly();
    public Point SnakeHead {get; private set;}
    private readonly List<Point> _snake;
    // Head is not in snake
    // First is closest to the head
    public ReadOnlyCollection<Point> Snake => _snake.AsReadOnly();
    public int SnakeLength => Snake.Count + 1;
    private readonly List<Point> _eggs;
    public ReadOnlyCollection<Point> Eggs => _eggs.AsReadOnly();
    public int NewEggRound { get; }
    public int EggLimit { get; }
    private int _round;
    private ITimer timer;
    public int Score { get; private set; }

    public event EventHandler? GameUpdate;
    public event EventHandler<GameState>? GameStateUpdate;
    private GameState _state;
    public GameState State
    {
        get => _state;
        private set
        {
            _state = value;
            GameStateUpdate?.Invoke(this, _state);
            if(_state == GameState.Dead)
            {
                timer.Change(Timeout.InfiniteTimeSpan, TickTimeSpan);
            }
        }
    }


    private SnakeDirection LastDirection = SnakeDirection.Down;
    private SnakeDirection _SnakeHeadDirection;
    private bool disposedValue;

    public SnakeDirection SnakeHeadDirection
    {
        get => _SnakeHeadDirection;
        set
        {
            switch (value, LastDirection)
            {
                case { value: SnakeDirection.Up or SnakeDirection.Down, LastDirection: SnakeDirection.Left or SnakeDirection.Right}:
                case { value: SnakeDirection.Left or SnakeDirection.Right, LastDirection: SnakeDirection.Up or SnakeDirection.Down }:
                    _SnakeHeadDirection = value;
                    break;
            }
        }
    }

    public SnakeLevel(int size, IEnumerable<Point> obstacles, int snake_start_length, int new_egg_round, int egg_limit, TimeProvider time_provider){
        this.Size = size;
        this.NewEggRound = new_egg_round;
        this._round = NewEggRound;
        this.EggLimit = egg_limit;

        _obstacles = new List<Point>(obstacles);
        _eggs = [];
        _snake = [];
        
        SnakeHead = (size / 2, snake_start_length-1);
        for(int i= snake_start_length - 2; i>=0; i--){
            _snake.Add((size / 2, i));
        }

        _SnakeHeadDirection = SnakeDirection.Down;
        LastDirection = SnakeDirection.Down;

        timer = time_provider.CreateTimer(new TimerCallback(_timer_Tick), null, Timeout.InfiniteTimeSpan, TickTimeSpan);

        _state = GameState.Paused;
    }

    private void _timer_Tick(object? sender)
    {
        Tick();
        GameUpdate?.Invoke(this, EventArgs.Empty);
    }

    public SnakeLevel(int size, IEnumerable<Point> obstacles, int snake_start_length, int new_egg_round, int egg_limit) : this(size, obstacles, snake_start_length, new_egg_round, egg_limit, TimeProvider.System)
    {
    }

    public LevelBlock this[Point p]{
        get{
            if(_obstacles.Contains(p)){
                return LevelBlock.Obstacle;
            }else if(p == SnakeHead){
                return LevelBlock.SnakeHead;
            }else if(_snake.Contains(p)){
                return LevelBlock.Snake;
            }else if(_eggs.Contains(p)){
                return LevelBlock.Egg;
            }else if(p.X < 0 || p.Y < 0 || p.X>=Size || p.Y >= Size){
                return LevelBlock.OutOfBounds;
            }

            return LevelBlock.Empty;
        }
    }

    public void Tick(){
        Point new_snake_head = (0,0);
        switch(SnakeHeadDirection){
            case SnakeDirection.Up:
                new_snake_head = (SnakeHead.X, SnakeHead.Y - 1);
                break;
            case SnakeDirection.Down:
                new_snake_head = (SnakeHead.X, SnakeHead.Y + 1);
                break;
            case SnakeDirection.Left:
                new_snake_head = (SnakeHead.X - 1, SnakeHead.Y);
                break;
            case SnakeDirection.Right:
                new_snake_head = (SnakeHead.X + 1, SnakeHead.Y);
                break;
        }

        if(this[new_snake_head] is LevelBlock.Obstacle or LevelBlock.Snake or LevelBlock.OutOfBounds){
            State = GameState.Dead;
            return;
        }

        Point last = _snake.Last();

        for (int i = Snake.Count - 1; i > 0; i--)
        {
            _snake[i] = _snake[i - 1];
        }
        _snake[0] = SnakeHead;

        if(this[new_snake_head] is LevelBlock.Egg){
            _snake.Add(last);
            _eggs.Remove(new_snake_head);
            Score++;
        }

        SnakeHead = new_snake_head;

        if (Eggs.Count < EggLimit && --_round == 0)
        {
            _round = NewEggRound;
            int avail_pos = Size * Size - Eggs.Count - Obstacles.Count - SnakeLength;
            if (avail_pos > 0)
            {
                int pos = Random.Shared.Next(0, avail_pos);
                Point p = (0, 0);
                for (int i = 0; i < pos; i++)
                {
                    do
                    {
                        p = (p.X + 1, p.Y);
                        if (p.X >= Size)
                        {
                            p = (0, p.Y + 1);
                        }
                    } while (this[p] is not LevelBlock.Empty);
                }
                _eggs.Add(p);
            }
        }

        LastDirection = SnakeHeadDirection;
    }

    public void Start()
    {
        if(State == GameState.Paused)
        {
            State = GameState.Running;
            timer.Change(TickTimeSpan, TickTimeSpan);
        }
        else
        {
            throw new Exception("Game is not paused");
        }
    }

    public void Pause()
    {
        if(State == GameState.Running)
        {
            State = GameState.Paused;
            timer.Change(Timeout.InfiniteTimeSpan, TickTimeSpan);
        }
        else
        {
            throw new Exception("Game is not running");
        }
    }

    protected virtual void Dispose(bool disposing)
    {
        if (!disposedValue)
        {
            if (disposing)
            {
                // TODO: dispose managed state (managed objects)
                timer.Dispose();
            }

            // TODO: free unmanaged resources (unmanaged objects) and override finalizer
            // TODO: set large fields to null
            disposedValue = true;
        }
    }

    // // TODO: override finalizer only if 'Dispose(bool disposing)' has code to free unmanaged resources
    // ~SnakeLevel()
    // {
    //     // Do not change this code. Put cleanup code in 'Dispose(bool disposing)' method
    //     Dispose(disposing: false);
    // }

    public void Dispose()
    {
        // Do not change this code. Put cleanup code in 'Dispose(bool disposing)' method
        Dispose(disposing: true);
        GC.SuppressFinalize(this);
    }
}