85 lines
2.4 KiB
C#
85 lines
2.4 KiB
C#
using OECS;
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namespace TicTacToe;
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/// <summary>
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/// After each move, checks whether the game has been won or drawn.
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/// Updates the GameState singleton accordingly.
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/// </summary>
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public class WinCheckSystem : ISystem
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{
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public void Run(World world)
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{
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// Check game status before doing any work. Use ReadSingleton
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// to avoid auto-marking GameState as modified when we bail early.
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if (world.ReadSingleton<GameState>().Status != GameStatus.Playing)
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return;
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ref var state = ref world.GetSingleton<GameState>();
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// Build a 3×3 grid of marks using the iterator API.
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var grid = new Player[3, 3];
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using var iter = world.Select<Cell, Mark>();
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while (iter.MoveNext())
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{
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grid[iter.Current1.Row, iter.Current1.Col] = iter.Current2.Player;
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}
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// Check rows.
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for (int r = 0; r < 3; r++)
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{
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if (TryGetWinner(grid[r, 0], grid[r, 1], grid[r, 2], out var winner))
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{
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SetWinner(world, ref state, winner);
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return;
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}
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}
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// Check columns.
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for (int c = 0; c < 3; c++)
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{
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if (TryGetWinner(grid[0, c], grid[1, c], grid[2, c], out var winner))
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{
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SetWinner(world, ref state, winner);
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return;
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}
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}
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// Check diagonals.
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if (TryGetWinner(grid[0, 0], grid[1, 1], grid[2, 2], out var diag1))
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{
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SetWinner(world, ref state, diag1);
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return;
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}
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if (TryGetWinner(grid[0, 2], grid[1, 1], grid[2, 0], out var diag2))
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{
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SetWinner(world, ref state, diag2);
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return;
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}
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// Check draw.
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if (state.MoveCount >= 9)
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{
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state.Status = GameStatus.Draw;
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world.MarkModified<GameState>(World.SingletonEntity);
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}
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}
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private static bool TryGetWinner(Player a, Player b, Player c, out Player winner)
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{
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if (a != Player.None && a == b && b == c)
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{
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winner = a;
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return true;
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}
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winner = Player.None;
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return false;
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}
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private static void SetWinner(World world, ref GameState state, Player winner)
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{
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state.Status = winner == Player.X ? GameStatus.XWon : GameStatus.OWon;
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world.MarkModified<GameState>(World.SingletonEntity);
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}
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} |