using System;
using System.Diagnostics;
using System.IO;
using System.Runtime.InteropServices;
using System.Security.Cryptography;

namespace TfsExcelImporter
{
    /// <summary>
    /// TFS Client OM 除托管程序集外还依赖两个纯 win32 DLL
    /// （Microsoft.WITDataStore32/64.dll）。托管程序集由 Costura 内嵌并从内存加载，
    /// native DLL 只能落盘后 LoadLibrary，所以单文件分发时：
    ///   启动阶段把内嵌的 native DLL 释放到 %TEMP%\TfsExcelImporter\native\{内容hash}，
    ///   再 LoadLibrary 预加载 —— 之后 TFS 内部的 DllImport 会直接命中已加载模块。
    /// 目录名带 DLL 内容 hash，升级后不会残留旧版本。
    /// exe 同目录存在同名 DLL（开发机 bin 目录、绿色解压版）时不做任何处理。
    /// </summary>
    internal static class NativeLibraryLoader
    {
        [DllImport("kernel32", SetLastError = true, CharSet = CharSet.Unicode, EntryPoint = "LoadLibraryW")]
        private static extern IntPtr LoadLibrary(string path);

        public static void EnsureLoaded()
        {
            var fileName = Environment.Is64BitProcess
                ? "Microsoft.WITDataStore64.dll"
                : "Microsoft.WITDataStore32.dll";

            if (File.Exists(Path.Combine(AppDomain.CurrentDomain.BaseDirectory, fileName)))
                return;

            try
            {
                var asm = typeof(NativeLibraryLoader).Assembly;
                var resourceName = "native." + fileName;
                using (var stream = asm.GetManifestResourceStream(resourceName))
                {
                    if (stream == null)
                    {
                        Debug.WriteLine("未找到内嵌 native 资源: " + resourceName);
                        return;
                    }

                    byte[] bytes;
                    using (var buffer = new MemoryStream())
                    {
                        stream.CopyTo(buffer);
                        bytes = buffer.ToArray();
                    }

                    var target = Path.Combine(NativeDir(bytes), fileName);
                    Directory.CreateDirectory(Path.GetDirectoryName(target));
                    if (!File.Exists(target))
                    {
                        try { File.WriteAllBytes(target, bytes); }
                        catch (IOException)
                        {
                            // 同 hash 目录已被另一实例写住，内容等价，直接用
                            if (!File.Exists(target)) throw;
                        }
                    }

                    if (LoadLibrary(target) == IntPtr.Zero)
                        Debug.WriteLine("LoadLibrary 失败(" + Marshal.GetLastWin32Error() + "): " + target);
                }
            }
            catch (Exception ex)
            {
                // 释放失败不阻断启动：TFS 连接时会自行报 DllNotFound，提示仍是可读的
                Debug.WriteLine("释放 native DLL 失败: " + ex.Message);
            }
        }

        private static string NativeDir(byte[] bytes)
        {
            byte[] hash;
            using (var sha = SHA256.Create())
                hash = sha.ComputeHash(bytes);
            var stamp = BitConverter.ToString(hash, 0, 4).Replace("-", "");
            return Path.Combine(Path.GetTempPath(), "TfsExcelImporter", "native", stamp);
        }
    }
}