oecs-sharp/Game.CardWars/Systems/PlayPhaseSystem.cs

using OECS;

namespace Game.CardWars;

/// <summary>
/// Manages the play phase: players take turns. If a PendingChoice exists,
/// blocks advancement until the player resolves it.
/// </summary>
public class PlayPhaseSystem : ISystem
{
    public void Run(World world)
    {
        ref var state = ref world.GetSingleton<GameState>();
        if (state.Phase != GamePhase.PlayPhase) return;

        // Block if a pending choice exists.
        if (PendingChoice.Any(world))
            return;

        // If the current player has skipped, move to the next player.
        if (state.PlayPhaseEnded)
        {
            state.PlayPhaseEnded = false;
            AdvanceTurn(world, ref state);
            return;
        }
    }

    private static void AdvanceTurn(World world, ref GameState state)
    {
        int next = (state.CurrentPlayerIndex + 1) % state.PlayerCount;

        // Duelist: if the next player is the one who played duelist, end the phase.
        if (world.HasSingleton<PendingDuelist>())
        {
            var duelist = world.ReadSingleton<PendingDuelist>();
            if (next == duelist.PlayerIndex)
            {
                world.RemoveSingleton<PendingDuelist>();
                state.Phase = GamePhase.FlipPhase;
                state.CurrentPlayerIndex = state.StartingPlayerIndex;
                world.MarkModified<GameState>(World.SingletonEntity);
                return;
            }
        }

        state.CurrentPlayerIndex = next;

        // If we've come back to the starting player, everyone has skipped.
        if (state.CurrentPlayerIndex == state.StartingPlayerIndex)
        {
            state.Phase = GamePhase.FlipPhase;
            world.RemoveSingleton<PendingDuelist>(); // Clean up in case duelist was never triggered.
        }

        world.MarkModified<GameState>(World.SingletonEntity);
    }
}