namespace Snake.Core;

public sealed class Food
{
    private readonly Random _random;

    public Food(Board board, IEnumerable<Position> occupiedPositions, Random? random = null)
    {
        _random = random ?? Random.Shared;
        Board = board;
        Respawn(occupiedPositions);
    }

    public Board Board { get; }

    public Position Position { get; private set; }

    public void Respawn(IEnumerable<Position> occupiedPositions)
    {
        var occupied = occupiedPositions.ToHashSet();
        var freeCells = new List<Position>();

        for (var y = 0; y < Board.Height; y++)
        {
            for (var x = 0; x < Board.Width; x++)
            {
                var position = new Position(x, y);
                if (!occupied.Contains(position))
                    freeCells.Add(position);
            }
        }

        if (freeCells.Count == 0)
            throw new InvalidOperationException("No free cells available for food.");

        Position = freeCells[_random.Next(freeCells.Count)];
    }
}