using System.Collections.Generic;
using System.Diagnostics;

namespace ProjectGrid.Models
{
  /// <summary>
  /// Holds data for a TicTacTocBoard
  /// 0: empty field, > 0 players
  /// </summary>
  public class TicTacTocBoard
  {
    private List<int> _field;
    public List<int> Field => _field;

    private int _lastSetValue;
    public int LastSetValue => _lastSetValue;

    public bool Full => !!!_field.Contains(0);

    private int PosToIdx(int x, int y)
    {
      Debug.Assert(x >= 0 && x <= 3
                && y >= 0 && y <= 3,
                   $"{x}:{y} outside of playarea!");
      return x + y * 3;
    }

    private int GetField(int x, int y) => _field[PosToIdx(x, y)];
    private void SetField(int value, int x, int y)
    {
      _field[PosToIdx(x, y)] = value;
      _lastSetValue = value;
    }
    private void SetField(int value, int idx)
    {
      _field[idx] = value;
      _lastSetValue = value;
    }

    // 0 1 2
    // 3 4 5
    // 6 7 8
    public static readonly int[,] _winning = new int[,] {
      { 0, 1, 2 },
      { 3, 4, 5 },
      { 6, 7 ,8 },
      { 0, 3 ,6 },
      { 1, 4 ,7 },
      { 2, 5 ,8 },
      { 0, 4 ,8 },
      { 2, 4 ,6 },
    };

    public TicTacTocBoard()
    {
      _field = new List<int>(new int[9] {
        0, 0, 0,
        0, 0, 0,
        0, 0, 0,
      });

      _lastSetValue = 0;
    }

    //public bool SetFieldValue(int value, int x, int y, bool force = false)
    public bool SetFieldValue(int value, int idx, bool force = false)
    {
      int field = _field[idx];
      if (0 == field || force)
      {
        SetField(value, idx);
        return true;
      }
      return false;
    }

    public List<int> ValueWon(int value)
    {
      Debug.Assert(value > 0, "ValueWon called for Empty field 0");

      int x = 0;
      for (; x < _winning.GetLength(0); x++)
      {
        bool won = true;
        for (int y = 0; y < _winning.GetLength(1); y++)
        {
          if (_field[_winning[x, y]] != value)
          {
            won = false;
            break;
          }
        }

        if (won)
        {
          return new List<int>() { _winning[x, 0], _winning[x, 1], _winning[x, 2] };
        }
      }

      return null;
    }
  }
}