#nullable enable
using System;
using System.Threading;
using Cysharp.Threading.Tasks;
using ShrinkApp;
using ShrinkEventBus;
using UnityEngine;

namespace ShrinkContext.AppAdapter
{
    /// <summary>
    /// ShrinkApp 加载器宿主的自动引导：
    /// hostingMode == ContextLoader 时在 BeforeSceneLoad 创建常驻 GameObject 并启动 ShrinkAppLoaderHost，
    /// 同时把服务容器接回 ShrinkApp 静态入口（InitializeForExternalHost），保证场景脚本照常访问 ShrinkApp.Services。
    /// ClassicHost 模式下完全不动——经典路径零行为变化。
    /// </summary>
    public sealed class ShrinkAppLoaderBootstrapper : MonoBehaviour
    {
        private static ShrinkAppLoaderBootstrapper? _instance;
        private static UniTaskCompletionSource _startupCompletion = new();

        /// <summary>
        /// Starter/组合包在 SubsystemRegistration 阶段设置的默认装配表。
        /// AppAdapter 保持不依赖具体业务模块，组合根负责注册原生组件；若兼容 installer 已被发现则覆盖同 id。
        /// </summary>
        public static System.Action<ShrinkAppLoaderHost>? DefaultComposition { get; set; }

        public static ShrinkAppLoaderBootstrapper? Instance => _instance;
        public static Exception? StartError { get; private set; }

        public ShrinkAppLoaderHost Host { get; private set; } = null!;

        /// <summary>
        /// 等待 ContextLoader 宿主完成启动。支持多个并发等待者；宿主失败时以原始异常结束。
        /// </summary>
        public static async UniTask WaitUntilStartedAsync(CancellationToken cancellationToken = default)
        {
            if (_instance?.Host?.IsRunning == true)
                return;
            if (StartError != null)
                throw StartError;
            if (ShrinkAppSettings.Instance.hostingMode != ShrinkAppHostingMode.ContextLoader)
            {
                throw new InvalidOperationException(
                    "ShrinkAppLoaderBootstrapper requires ShrinkAppHostingMode.ContextLoader.");
            }

            var task = _startupCompletion.Task;
            if (cancellationToken.CanBeCanceled)
                await task.AttachExternalCancellation(cancellationToken);
            else
                await task;

            if (StartError != null)
                throw StartError;
        }

        [RuntimeInitializeOnLoadMethod(RuntimeInitializeLoadType.SubsystemRegistration)]
        private static void ResetStaticState()
        {
            _instance = null;
            StartError = null;
            _startupCompletion = new UniTaskCompletionSource();
        }

        [RuntimeInitializeOnLoadMethod(RuntimeInitializeLoadType.BeforeSceneLoad)]
        private static void AutoBootstrap()
        {
            if (ShrinkAppSettings.Instance.hostingMode != ShrinkAppHostingMode.ContextLoader)
                return;

            var gameObject = new GameObject("ShrinkAppLoaderHost");
            DontDestroyOnLoad(gameObject);
            gameObject.AddComponent<ShrinkAppLoaderBootstrapper>();
        }

        private void Awake()
        {
            if (_instance != null && _instance != this)
            {
                Destroy(gameObject);
                return;
            }

            _instance = this;
            StartHostAsync().Forget();
        }

        private async UniTask StartHostAsync()
        {
            try
            {
                Host = new ShrinkAppLoaderHost();
                DefaultComposition?.Invoke(Host);
                var profile = ShrinkAppCompositionProfile.LoadDefault();
                if (profile != null)
                    Host.ApplyComposition(profile.ResolveDocument());
                global::ShrinkApp.ShrinkApp.InitializeForExternalHost(Host.Services);
                await Host.StartAsync();
                CompleteStartup(null);
            }
            catch (Exception ex)
            {
                CompleteStartup(ex);
                EventBus.Post(new ShrinkAppStartFailedEvent
                {
                    ErrorMessage = ex.Message,
                    FailedModuleId = string.Empty
                });
                Debug.LogException(ex);
                Debug.LogError("[ShrinkApp.LoaderHost] 启动失败: " + ex.Message);
            }
        }

        private static void CompleteStartup(Exception? error)
        {
            StartError = error;
            _startupCompletion.TrySetResult();
        }

        private void OnDestroy()
        {
            if (_instance == this)
                _instance = null;
        }
    }
}