Chessistics/chessistics-engine/Model/BoardState.cs

using Chessistics.Engine.Events;

namespace Chessistics.Engine.Model;

public class BoardState
{
    public int Width { get; }
    public int Height { get; }
    public CellType[,] Grid { get; }
    public Dictionary<Coords, ProductionDef> Productions { get; }
    public Dictionary<Coords, DemandState> Demands { get; }
    public List<PieceState> Pieces { get; }
    public List<PieceState> DestroyedPieces { get; } = new();
    public Dictionary<Coords, int> ProductionBuffers { get; }
    public SimPhase Phase { get; set; }
    public int TurnNumber { get; set; }
    public int NextPieceId { get; set; }
    public Dictionary<PieceKind, int> RemainingStock { get; }
    public int MaxDeadline { get; }

    // Tracks all cells ever occupied by a piece (for metrics)
    public HashSet<Coords> OccupiedCells { get; }

    private readonly LevelDef _levelDef;
    private bool _isApplyingCommand;

    private BoardState(LevelDef level)
    {
        _levelDef = level;
        Width = level.Width;
        Height = level.Height;
        MaxDeadline = level.MaxDeadline;

        Grid = new CellType[Width, Height];
        Productions = new Dictionary<Coords, ProductionDef>();
        Demands = new Dictionary<Coords, DemandState>();
        Pieces = new List<PieceState>();
        ProductionBuffers = new Dictionary<Coords, int>();
        RemainingStock = new Dictionary<PieceKind, int>();
        OccupiedCells = new HashSet<Coords>();

        Phase = SimPhase.Edit;
        TurnNumber = 0;
        NextPieceId = 1;

        // Initialize grid as empty
        for (int c = 0; c < Width; c++)
            for (int r = 0; r < Height; r++)
                Grid[c, r] = CellType.Empty;

        // Place walls
        foreach (var wall in level.Walls)
            Grid[wall.Col, wall.Row] = CellType.Wall;

        // Place productions
        foreach (var prod in level.Productions)
        {
            Grid[prod.Position.Col, prod.Position.Row] = CellType.Production;
            Productions[prod.Position] = prod;
            ProductionBuffers[prod.Position] = 0;
        }

        // Place demands
        foreach (var demand in level.Demands)
        {
            Grid[demand.Position.Col, demand.Position.Row] = CellType.Demand;
            Demands[demand.Position] = new DemandState(demand);
        }

        // Initialize stock
        foreach (var stock in level.Stock)
            RemainingStock[stock.Kind] = stock.Count;
    }

    public static BoardState FromLevel(LevelDef level) => new(level);

    public CellType GetCell(Coords coords) => Grid[coords.Col, coords.Row];

    public bool IsOnBoard(Coords coords) => coords.IsOnBoard(Width, Height);

    /// <summary>
    /// Returns all cells currently occupied by any piece (both start and end during Edit, CurrentCell during sim).
    /// </summary>
    public HashSet<Coords> GetOccupiedCells()
    {
        var occupied = new HashSet<Coords>();
        foreach (var piece in Pieces)
        {
            if (Phase == SimPhase.Edit)
            {
                occupied.Add(piece.StartCell);
                occupied.Add(piece.EndCell);
            }
            else
            {
                occupied.Add(piece.CurrentCell);
            }
        }
        return occupied;
    }

    public PieceState? GetPieceById(int pieceId) => Pieces.Find(p => p.Id == pieceId);

    public void ApplyCommand(Action<BoardState, List<IWorldEvent>> apply, List<IWorldEvent> changeList)
    {
        if (_isApplyingCommand)
            throw new InvalidOperationException("Nested command not allowed.");

        _isApplyingCommand = true;
        try
        {
            apply(this, changeList);
        }
        finally
        {
            _isApplyingCommand = false;
        }
    }

    public void ResetFromLevel()
    {
        Pieces.Clear();
        DestroyedPieces.Clear();
        Productions.Clear();
        Demands.Clear();
        ProductionBuffers.Clear();
        RemainingStock.Clear();
        OccupiedCells.Clear();

        Phase = SimPhase.Edit;
        TurnNumber = 0;
        NextPieceId = 1;

        for (int c = 0; c < Width; c++)
            for (int r = 0; r < Height; r++)
                Grid[c, r] = CellType.Empty;

        foreach (var wall in _levelDef.Walls)
            Grid[wall.Col, wall.Row] = CellType.Wall;

        foreach (var prod in _levelDef.Productions)
        {
            Grid[prod.Position.Col, prod.Position.Row] = CellType.Production;
            Productions[prod.Position] = prod;
            ProductionBuffers[prod.Position] = 0;
        }

        foreach (var demand in _levelDef.Demands)
        {
            Grid[demand.Position.Col, demand.Position.Row] = CellType.Demand;
            Demands[demand.Position] = new DemandState(demand);
        }

        foreach (var stock in _levelDef.Stock)
            RemainingStock[stock.Kind] = stock.Count;
    }
}