using System;
using System.IO;
using System.Reflection;
using UnityEngine;
using XWorld.Framework;

namespace XGame.MiniGame
{
    // 从代码 AB（manifest.CodeAb）取出 Core/Client 热更 DLL 字节并加载，反射出 IGameClient 入口工厂
    public sealed class MiniGameAssemblyLoader
    {
        public Func<IGameClient> CreateClient { get; private set; }
        public string Error { get; private set; }

        // localDir: MiniGameDownloader.LocalDir；manifest: 解析好的 game.json
        public bool Load(string localDir, MiniGameManifest manifest)
        {
            string abPath = localDir + manifest.CodeAb;
            if (!File.Exists(abPath))
            { Error = $"缺少代码 AB: {abPath}（需要 codeAb 统一 AB 格式，旧 .bytes 包不再支持）"; return false; }

            AssetBundle ab = null;
            try
            {
                ab = MiniGamePlatform.LoadAssetBundle(abPath);
                if (ab == null) { Error = "代码 AB 打开失败: " + abPath; return false; }

                byte[] coreBytes = LoadDllBytes(ab, manifest.CoreDll);
                byte[] clientBytes = LoadDllBytes(ab, manifest.ClientDll);
                if (coreBytes == null || clientBytes == null)
                {
                    Error = $"代码 AB 内缺少 {manifest.CoreDll}/{manifest.ClientDll} 的 .bytes（AB 内资产: {string.Join(", ", ab.GetAllAssetNames())}）";
                    return false;
                }

                // Core 先于 Client 加载（Client 依赖 Core）
                Assembly.Load(coreBytes);
                Assembly clientAsm = Assembly.Load(clientBytes);

                Type entry = clientAsm.GetType(manifest.ClientEntryType);
                if (entry == null) { Error = "找不到入口类型 " + manifest.ClientEntryType; return false; }
                if (!typeof(IGameClient).IsAssignableFrom(entry))
                { Error = manifest.ClientEntryType + " 未实现 IGameClient"; return false; }

                CreateClient = () => (IGameClient)Activator.CreateInstance(entry);
                return true;
            }
            catch (Exception e)
            {
                Error = "加载小游戏程序集失败: " + e;
                Debug.LogError("[MiniGameAssemblyLoader] " + Error);
                return false;
            }
            finally
            {
                // DLL 字节已复制进托管内存，AB 本体可卸；false=不销毁已取出的对象
                if (ab != null) ab.Unload(false);
            }
        }

        // "X.dll.bytes" 导入后资产名为 "X.dll"（Unity 剥最后一个扩展名）；两种写法都试
        private static byte[] LoadDllBytes(AssetBundle ab, string dllName)
        {
            TextAsset ta = ab.LoadAsset<TextAsset>(dllName) ?? ab.LoadAsset<TextAsset>(dllName + ".bytes");
            return ta != null ? ta.bytes : null;
        }
    }
}