#nullable enable

using System;
using Cysharp.Threading.Tasks;
using UnityEngine;

namespace ShrinkApp
{
    public static class ShrinkApp
    {
        public static ShrinkAppHost? Host { get; private set; }
        public static ShrinkAppContext? Context { get; private set; }
        public static ShrinkAppSettings Settings => ShrinkAppSettings.Instance;
        public static ShrinkAppServices Services => Context?.Services ?? throw new System.InvalidOperationException("ShrinkApp is not initialized.");
        public static bool IsRunning => (Host != null && Host.IsRunning) || _externalHostRunning;

        private static bool _externalHostRunning;

        [RuntimeInitializeOnLoadMethod(RuntimeInitializeLoadType.SubsystemRegistration)]
        private static void ResetStaticState()
        {
            Host = null;
            Context = null;
            _externalHostRunning = false;
            ShrinkAppSettings.ResetCachedInstance();
        }

        [RuntimeInitializeOnLoadMethod(RuntimeInitializeLoadType.BeforeSceneLoad)]
        private static void Bootstrap()
        {
            if (Host != null)
                return;

            var settings = ShrinkAppSettings.Instance;
            if (settings.hostingMode == ShrinkAppHostingMode.ContextLoader)
            {
                // 阶段 2 过渡：经典宿主让位，由 ShrinkContext 加载器宿主（ShrinkContext.AppAdapter）接管启动
                return;
            }

            var hostGameObject = new GameObject("ShrinkAppHost");
            var host = hostGameObject.AddComponent<ShrinkAppHost>();
            if (settings.dontDestroyOnLoad)
                UnityEngine.Object.DontDestroyOnLoad(hostGameObject);

            var services = new ShrinkAppServices();
            var context = new ShrinkAppContext(host, settings, services);
            host.Configure(context);

            Host = host;
            Context = context;
            host.StartAppAsync().Forget(ex =>
            {
                Debug.LogException(ex);
                Debug.LogError("[ShrinkApp] 启动失败: " + ex.Message);
            });
        }

        /// <summary>
        /// 阶段 2 过渡：由外部宿主（如 ShrinkContext 加载器宿主）提供已初始化的服务容器。
        /// Host 保持 null——外部宿主不经过 ShrinkAppHost 生命周期，IsRunning 以外部宿主为准。
        /// </summary>
        public static void InitializeForExternalHost(ShrinkAppServices services, ShrinkAppSettings? settings = null)
        {
            if (services == null)
                throw new ArgumentNullException(nameof(services));

            Context = new ShrinkAppContext(null!, settings ?? Settings, services);
            _externalHostRunning = false;
        }

        /// <summary>
        /// Lets a non-<see cref="ShrinkAppHost"/> orchestrator expose its lifecycle through
        /// the legacy static facade while the migration is in progress.
        /// </summary>
        public static void SetExternalHostRunning(bool running)
        {
            _externalHostRunning = running;
        }
    }
}