using System;
using System.IO;
using System.Runtime.CompilerServices;
using Xunit;
using XWorld.Server.Host;

namespace XWorld.Server.Host.Tests
{
    // 同 (gameId,version) 磁盘内容变化（覆盖重发）→ Registry 自动失效重载；
    // 旧房间打完旧代码（退役条目引用归零即卸载），新房间用新代码。
    public class RegistryContentInvalidationTests : IDisposable
    {
        private string _root;

        private string CopyRps1ToTempRoot()
        {
            string root = Path.Combine(Path.GetTempPath(), "games_" + Guid.NewGuid().ToString("N"));
            string dst = Path.Combine(root, "rps", "1");
            Directory.CreateDirectory(dst);
            string src = Path.Combine(TestGames.Root, "rps", "1");
            foreach (var f in Directory.GetFiles(src))
                File.Copy(f, Path.Combine(dst, Path.GetFileName(f)));
            _root = root;
            return root;
        }

        public void Dispose()
        {
            if (_root != null)
            {
                try { Directory.Delete(_root, true); } catch { }
            }
        }

        // 改变内容指纹（game.json 在指纹范围内；追加空白不影响 JSON 解析）
        private static void TouchContent(string root)
        {
            string gameJson = Path.Combine(root, "rps", "1", "game.json");
            File.AppendAllText(gameJson, " ");
        }

        [Fact]
        public void SameContent_ReturnsCachedInstance()
        {
            string root = CopyRps1ToTempRoot();
            var reg = new GameModuleRegistry(new GameModuleLoader(), root);
            var a = reg.Acquire("rps", 1);
            var b = reg.Acquire("rps", 1);
            Assert.Same(a, b);
            Assert.Equal(2, reg.RefCount("rps", 1));
        }

        [Fact]
        public void ContentChange_AfterRefZero_ReloadsNewInstance()
        {
            string root = CopyRps1ToTempRoot();
            var reg = new GameModuleRegistry(new GameModuleLoader(), root);
            var a = reg.Acquire("rps", 1);
            reg.Release(a);                       // 引用归零，未淘汰 → 保留缓存
            TouchContent(root);
            var b = reg.Acquire("rps", 1);
            Assert.NotSame(a, b);                 // 内容变了 → 新模块实例
            Assert.Equal(1, reg.RefCount("rps", 1));
            Assert.True(reg.IsLoaded("rps", 1));
        }

        [Fact]
        public void ContentChange_WhileOldActive_OldAndNewCoexist_ReleaseBothCorrect()
        {
            string root = CopyRps1ToTempRoot();
            var reg = new GameModuleRegistry(new GameModuleLoader(), root);
            var oldM = reg.Acquire("rps", 1);     // 旧房间在打
            TouchContent(root);
            var newM = reg.Acquire("rps", 1);     // 新房间 → 新内容
            Assert.NotSame(oldM, newM);
            Assert.Equal(1, reg.RefCount("rps", 1)); // RefCount 只统计当前条目

            reg.Release(oldM);                    // 旧房间结束：退役条目按实例识别释放，不抛
            reg.Release(newM);
            Assert.Equal(0, reg.RefCount("rps", 1));
            Assert.True(reg.IsLoaded("rps", 1)); // 当前条目未被淘汰 → 保留复用
        }

        [Fact]
        public void ContentChange_RetiredModule_UnloadsAndReclaims()
        {
            string root = CopyRps1ToTempRoot();
            var weak = AcquireChangeReleaseOld(root);
            for (int i = 0; i < 12 && weak.IsAlive; i++)
            {
                GC.Collect();
                GC.WaitForPendingFinalizers();
            }
            Assert.False(weak.IsAlive, "退役模块未被回收 —— 存在泄漏引用");
        }

        // 独立方法确保局部强引用随返回消失（同 AlcUnloadTests 套路）
        [MethodImpl(MethodImplOptions.NoInlining)]
        private static WeakReference AcquireChangeReleaseOld(string root)
        {
            var reg = new GameModuleRegistry(new GameModuleLoader(), root);
            var oldM = reg.Acquire("rps", 1);
            TouchContent(root);
            var newM = reg.Acquire("rps", 1);     // oldM 退役
            var weak = new WeakReference(oldM);
            reg.Release(oldM);                    // 退役 + 归零 → 卸载
            reg.Release(newM);
            return weak;
        }

        [Fact]
        public void MissingDir_ServesCachedEntry()
        {
            string root = CopyRps1ToTempRoot();
            var reg = new GameModuleRegistry(new GameModuleLoader(), root);
            var a = reg.Acquire("rps", 1);
            string dir = Path.Combine(root, "rps", "1");
            string away = dir + ".away";
            Directory.Move(dir, away);            // 模拟覆盖交换的瞬间窗口
            try
            {
                var b = reg.Acquire("rps", 1);   // 指纹算不出 → 用缓存兜底
                Assert.Same(a, b);
            }
            finally { Directory.Move(away, dir); }
        }
    }
}