add custom chess engine

JoshHeaps.Net/Services/Interfaces/IChessEngine.cs

@@ -0,0 +1,19 @@
+namespace JoshHeaps.Net.Services.Interfaces;
+
+/// <summary>
+/// An AI move-selection engine (e.g. Stockfish or the custom native engine).
+/// Selects a move for a position; it does not enforce rules or broadcast updates.
+/// Implementations own unmanaged resources, hence <see cref="IAsyncDisposable"/>.
+/// </summary>
+public interface IChessEngine : IAsyncDisposable
+{
+    /// <summary>The engine's playing strength / search depth.</summary>
+    int Skill { get; }
+
+    /// <summary>
+    /// Returns the engine's chosen move in UCI long-algebraic form (e.g. "e2e4", "e7e8q").
+    /// </summary>
+    /// <param name="fen">The current position as a FEN string.</param>
+    /// <returns>The selected move as a UCI string.</returns>
+    Task<string> GetBestMoveAsync(string fen);
+}

JoshHeaps.Net/Services/Interfaces/IChessEngineFactory.cs

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+namespace JoshHeaps.Net.Services.Interfaces;
+
+/// <summary>
+/// Creates <see cref="IChessEngine"/> instances, choosing the implementation from configuration.
+/// </summary>
+public interface IChessEngineFactory
+{
+    /// <summary>
+    /// Creates a new engine instance for a single game. The caller owns and disposes it.
+    /// </summary>
+    /// <param name="skill">The desired playing strength / search depth.</param>
+    /// <returns>A new, owned <see cref="IChessEngine"/>.</returns>
+    IChessEngine Create(int skill);
+}

JoshHeaps.Net/Services/Interfaces/IComputerMoveOrchestrator.cs

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+using JoshHeaps.Net.Models;
+
+namespace JoshHeaps.Net.Services.Interfaces;
+
+/// <summary>
+/// Drives a computer move: asks the engine for a move, applies it through the rules
+/// service, and broadcasts the result to the game's clients.
+/// </summary>
+public interface IComputerMoveOrchestrator
+{
+    /// <summary>
+    /// Has the engine pick a move for the current position, applies it, and broadcasts it.
+    /// </summary>
+    /// <param name="state">The game to play a move in.</param>
+    /// <param name="engine">The engine that selects the move.</param>
+    /// <returns>The applied move and its result.</returns>
+    Task<(MoveDto move, MoveResultDto result)> PlayAsync(GameState state, IChessEngine engine);
+}