oecs-sharp/Game.CardWars/CardEffectRegistry.cs

using OECS;

namespace Game.CardWars;

/// <summary>
/// A card effect that can be registered with the effect dispatcher.
/// </summary>
public interface ICardEffect
{
    CardEffect Effect { get; }

    /// <summary>
    /// Called when the card is played face-up or flipped face-up.
    /// Return true if fully resolved. Return false if a pending component
    /// was set and the effect needs a player command to continue.
    /// </summary>
    bool Resolve(World world, Entity card, Entity player, Entity owner);

    /// <summary>
    /// Called when the player provides a choice to continue a pending effect.
    /// The effect handler is responsible for reading the correct pending
    /// component type from the singleton and removing it when done.
    /// </summary>
    bool ResolveChoice(World world, Entity target);
}

/// <summary>
/// Registry of card effects, ordered by registration.
/// </summary>
public static class CardEffectRegistry
{
    private static readonly List<ICardEffect> _effects = new();
    private static bool _frozen;

    public static void Add<TEffect>() where TEffect : ICardEffect, new()
    {
        if (_frozen)
            throw new InvalidOperationException("Cannot add effects after the registry is frozen.");
        _effects.Add(new TEffect());
    }

    public static void Freeze() => _frozen = true;

    /// <summary>
    /// Resolve a card effect. Returns true if fully resolved.
    /// </summary>
    public static bool Dispatch(World world, CardEffect effect, Entity card, Entity player, Entity owner)
    {
        foreach (var e in _effects)
        {
            if (e.Effect == effect)
                return e.Resolve(world, card, player, owner);
        }
        return true;
    }

    /// <summary>
    /// Look up the handler for the currently pending effect and resolve it.
    /// </summary>
    public static bool DispatchChoice(World world, Entity target)
    {
        // Find which pending component is active and dispatch to the matching handler.
        if (world.HasSingleton<PendingMercenary>())
            return DispatchByEffect(world, CardEffect.Mercenary, target);
        if (world.HasSingleton<PendingDancer>())
            return DispatchByEffect(world, CardEffect.Dancer, target);
        if (world.HasSingleton<PendingPaladin>())
            return DispatchByEffect(world, CardEffect.Paladin, target);
        if (world.HasSingleton<PendingNun>())
            return DispatchByEffect(world, CardEffect.Nun, target);
        if (world.HasSingleton<PendingScout>())
            return DispatchByEffect(world, CardEffect.Scout, target);
        if (world.HasSingleton<PendingPegasus>())
            return DispatchByEffect(world, CardEffect.Pegasus, target);
        if (world.HasSingleton<PendingCurseMaster>())
            return DispatchByEffect(world, CardEffect.CurseMaster, target);

        return true;
    }

    private static bool DispatchByEffect(World world, CardEffect effect, Entity target)
    {
        foreach (var e in _effects)
        {
            if (e.Effect == effect)
                return e.ResolveChoice(world, target);
        }
        return true;
    }

    public static void ClearForTests()
    {
        _effects.Clear();
        _frozen = false;
    }
}