#nullable enable
using System;
using Cysharp.Threading.Tasks;
using ShrinkContext;
using ShrinkEventBus;

namespace ShrinkContext.EventBusAdapter
{
    /// <summary>
    /// 把 ShrinkEventBus 的订阅/注册包装为可逆效应：
    /// <c>IShrinkEventSubscription.Dispose</c> 天然就是订阅的逆操作——
    /// 组件在 apply 里订阅，停用时随上下文自动退订，无需手写卸载路径。
    /// </summary>
    public static class ShrinkEventBusEffects
    {
        /// <summary>订阅事件即效应：ctx 卸载或手动 Dispose 句柄时自动退订。</summary>
        public static ShrinkEffectHandle EffectSubscribe<TEvent>(
            this ShrinkCtx ctx,
            Action<TEvent> handler,
            EventPriority priority = EventPriority.NORMAL,
            bool receiveCanceled = false)
            where TEvent : EventBase
        {
            if (ctx == null)
                throw new ArgumentNullException(nameof(ctx));
            if (handler == null)
                throw new ArgumentNullException(nameof(handler));

            var subscription = EventBus.SubscribeEvent(handler, priority, receiveCanceled);
            return ctx.EffectInverse(() =>
            {
                subscription.Dispose();
                return UniTask.CompletedTask;
            });
        }

        /// <summary>
        /// 实例对象整体注册即效应：扫描对象上的 [EventSubscribe] 方法（含未织入的非 MonoBehaviour 类），
        /// 逆操作为 Unregister。
        /// </summary>
        public static ShrinkEffectHandle EffectRegister(this ShrinkCtx ctx, object target)
        {
            if (ctx == null)
                throw new ArgumentNullException(nameof(ctx));
            if (target == null)
                throw new ArgumentNullException(nameof(target));

            EventBus.Register(target);
            return ctx.EffectInverse(() =>
            {
                EventBus.Unregister(target);
                return UniTask.CompletedTask;
            });
        }
    }
}