//
// Author:   Jonathan Blow
// Version:  1
// Date:     31 August, 2018
//
// This code is released under the MIT license, which you can find at
//
//          https://opensource.org/licenses/MIT
//
//
//
// See the comments for how to use this library just below the includes.
//

//
// NOTE(Kalinovcic): I have translated the original implementation to C,
// and made a preprocessor define that enables people to include it without
// the implementation, just as a header.
//
// I also fixed two bugs:
//   - If COM initialization for VS2017 fails, we actually properly continue
//     searching for earlier versions in the registry.
//   - For earlier versions, the code now returns the "bin\amd64" VS directory.
//     Previously it was returning the "bin" directory, which is for x86 stuff.
//
// To include the implementation, before including microsoft_craziness.h,
// define:
//
//   #define MICROSOFT_CRAZINESS_IMPLEMENTATION
//   #include "microsoft_craziness.h"
//

#ifdef __cplusplus
extern "C" {
#endif

#ifndef MICROSOFT_CRAZINESS_HEADER_GUARD
#define MICROSOFT_CRAZINESS_HEADER_GUARD

#ifdef _WIN32

#include <string.h>

typedef struct {
  int windows_sdk_version; // Zero if no Windows SDK found.

  wchar_t *windows_sdk_root;
  wchar_t *windows_sdk_um_library_path;
  wchar_t *windows_sdk_ucrt_library_path;

  wchar_t *vs_exe_path;
  wchar_t *vs_library_path;
} Find_Result;

Find_Result *find_visual_studio_and_windows_sdk();
void free_resources(Find_Result *result);

// Emily: wide_string_to_narrow_string_facepalm
char *wide_string_to_narrow_temp(wchar_t *);

#endif

#endif // MICROSOFT_CRAZINESS_HEADER_GUARD

//
// HOW TO USE THIS CODE
//
// The purpose of this file is to find the folders that contain libraries
// you may need to link against, on Windows, if you are linking with any
// compiled C or C++ code. This will be necessary for many non-C++ programming
// language environments that want to provide compatibility.
//
// We find the place where the Visual Studio libraries live (for example,
// libvcruntime.lib), where the linker and compiler executables live
// (for example, link.exe), and where the Windows SDK libraries reside
// (kernel32.lib, libucrt.lib).
//
// We all wish you didn't have to worry about so many weird dependencies,
// but we don't really have a choice about this, sadly.
//
// I don't claim that this is the absolute best way to solve this problem,
// and so far we punt on things (if you have multiple versions of Visual Studio
// installed, we return the first one, rather than the newest). But it
// will solve the basic problem for you as simply as I know how to do it,
// and because there isn't too much code here, it's easy to modify and expand.
//
//
// Here is the API you need to know about:
//

//
// Call find_visual_studio_and_windows_sdk, look at the resulting
// paths, then call free_resources on the result.
//
// Everything else in this file is implementation details that you
// don't need to care about.
//

//
// This file was about 400 lines before we started adding these comments.
// You might think that's way too much code to do something as simple
// as finding a few library and executable paths. I agree. However,
// Microsoft's own solution to this problem, called "vswhere", is a
// mere EIGHT THOUSAND LINE PROGRAM, spread across 70 files,
// that they posted to github *unironically*.
//
// I am not making this up: https://github.com/Microsoft/vswhere
//
// Several people have therefore found the need to solve this problem
// themselves. We referred to some of these other solutions when
// figuring out what to do, most prominently ziglang's version,
// by Ryan Saunderson.
//
// I hate this kind of code. The fact that we have to do this at all
// is stupid, and the actual maneuvers we need to go through
// are just painful. If programming were like this all the time,
// I would quit.
//
// Because this is such an absurd waste of time, I felt it would be
// useful to package the code in an easily-reusable way, in the
// style of the stb libraries. We haven't gone as all-out as some
// of the stb libraries do (which compile in C with no includes, often).
// For this version you need C++ and the headers at the top of the file.
//
// We return the strings as Windows wide character strings. Aesthetically
// I don't like that (I think most sane programs are UTF-8 internally),
// but apparently, not all valid Windows file paths can even be converted
// correctly to UTF-8. So have fun with that. It felt safest and simplest
// to stay with wchar_t since all of this code is fully ensconced in
// Windows crazy-land.
//
// One other shortcut I took is that this is hardcoded to return the
// folders for x64 libraries. If you want x86 or arm, you can make
// slight edits to the code below, or, if enough people want this,
// I can work it in here.
//

#ifdef MICROSOFT_CRAZINESS_IMPLEMENTATION
#ifndef MICROSOFT_CRAZINESS_IMPLEMENTATION_GUARD
#define MICROSOFT_CRAZINESS_IMPLEMENTATION_GUARD

#ifdef _WIN32

#include <io.h> // For _get_osfhandle
#include <stdbool.h>
#include <stdint.h>
#include <stdio.h>
#include <windows.h>

void free_resources(Find_Result *result) {
  free(result->windows_sdk_root);
  free(result->windows_sdk_um_library_path);
  free(result->windows_sdk_ucrt_library_path);
  free(result->vs_exe_path);
  free(result->vs_library_path);
}

// COM objects for the ridiculous Microsoft craziness.

#undef INTERFACE
#define INTERFACE ISetupInstance
DECLARE_INTERFACE_(ISetupInstance, IUnknown) {
  BEGIN_INTERFACE

  // IUnknown methods
  STDMETHOD(QueryInterface)(THIS_ REFIID, void **) PURE;
  STDMETHOD_(ULONG, AddRef)(THIS) PURE;
  STDMETHOD_(ULONG, Release)(THIS) PURE;

  // ISetupInstance methods
  STDMETHOD(GetInstanceId)(THIS_ _Out_ BSTR * pbstrInstanceId) PURE;
  STDMETHOD(GetInstallDate)(THIS_ _Out_ LPFILETIME pInstallDate) PURE;
  STDMETHOD(GetInstallationName)(THIS_ _Out_ BSTR * pbstrInstallationName) PURE;
  STDMETHOD(GetInstallationPath)(THIS_ _Out_ BSTR * pbstrInstallationPath) PURE;
  STDMETHOD(GetInstallationVersion)
  (THIS_ _Out_ BSTR * pbstrInstallationVersion) PURE;
  STDMETHOD(GetDisplayName)
  (THIS_ _In_ LCID lcid, _Out_ BSTR * pbstrDisplayName) PURE;
  STDMETHOD(GetDescription)
  (THIS_ _In_ LCID lcid, _Out_ BSTR * pbstrDescription) PURE;
  STDMETHOD(ResolvePath)
  (THIS_ _In_opt_z_ LPCOLESTR pwszRelativePath, _Out_ BSTR * pbstrAbsolutePath)
      PURE;

  END_INTERFACE
};

#undef INTERFACE
#define INTERFACE IEnumSetupInstances
DECLARE_INTERFACE_(IEnumSetupInstances, IUnknown) {
  BEGIN_INTERFACE

  // IUnknown methods
  STDMETHOD(QueryInterface)(THIS_ REFIID, void **) PURE;
  STDMETHOD_(ULONG, AddRef)(THIS) PURE;
  STDMETHOD_(ULONG, Release)(THIS) PURE;

  // IEnumSetupInstances methods
  STDMETHOD(Next)
  (THIS_ _In_ ULONG celt,
   _Out_writes_to_(celt, *pceltFetched) ISetupInstance * *rgelt,
   _Out_opt_ _Deref_out_range_(0, celt) ULONG * pceltFetched) PURE;
  STDMETHOD(Skip)(THIS_ _In_ ULONG celt) PURE;
  STDMETHOD(Reset)(THIS) PURE;
  STDMETHOD(Clone)(THIS_ IEnumSetupInstances * *ppenum) PURE;

  END_INTERFACE
};

#undef INTERFACE
#define INTERFACE ISetupConfiguration
DECLARE_INTERFACE_(ISetupConfiguration, IUnknown) {
  BEGIN_INTERFACE

  // IUnknown methods
  STDMETHOD(QueryInterface)(THIS_ REFIID, void **) PURE;
  STDMETHOD_(ULONG, AddRef)(THIS) PURE;
  STDMETHOD_(ULONG, Release)(THIS) PURE;

  // ISetupConfiguration methods
  STDMETHOD(EnumInstances)
  (THIS_ _Out_ IEnumSetupInstances * *ppEnumInstances) PURE;
  STDMETHOD(GetInstanceForCurrentProcess)
  (THIS_ _Out_ ISetupInstance * *ppInstance) PURE;
  STDMETHOD(GetInstanceForPath)
  (THIS_ _In_z_ LPCWSTR wzPath, _Out_ ISetupInstance * *ppInstance) PURE;

  END_INTERFACE
};

#ifdef __cplusplus
#define CALL_STDMETHOD(object, method, ...) object->method(__VA_ARGS__)
#define CALL_STDMETHOD_(object, method) object->method()
#else
#define CALL_STDMETHOD(object, method, ...)                                    \
  object->lpVtbl->method(object, __VA_ARGS__)
#define CALL_STDMETHOD_(object, method) object->lpVtbl->method(object)
#endif

// The beginning of the actual code that does things.

typedef struct {
  int32_t best_version[4]; // For Windows 8 versions, only two of these numbers
                           // are used.
  wchar_t *best_name;
} Version_Data;

bool os_file_exists(wchar_t *name) {
  // @Robustness: What flags do we really want to check here?

  auto attrib = GetFileAttributesW(name);
  if (attrib == INVALID_FILE_ATTRIBUTES)
    return false;
  if (attrib & FILE_ATTRIBUTE_DIRECTORY)
    return false;

  return true;
}

#define concat2(a, b) concat(a, b, NULL, NULL)
#define concat3(a, b, c) concat(a, b, c, NULL)
#define concat4(a, b, c, d) concat(a, b, c, d)
wchar_t *concat(wchar_t *a, wchar_t *b, wchar_t *c, wchar_t *d) {
  // Concatenate up to 4 wide strings together. Allocated with malloc.
  // If you don't like that, use a programming language that actually
  // helps you with using custom allocators. Or just edit the code.

  auto len_a = wcslen(a);
  auto len_b = wcslen(b);

  auto len_c = 0;
  if (c)
    len_c = wcslen(c);

  auto len_d = 0;
  if (d)
    len_d = wcslen(d);

  wchar_t *result = (wchar_t *)malloc((len_a + len_b + len_c + len_d + 1) * 2);
  memcpy(result, a, len_a * 2);
  memcpy(result + len_a, b, len_b * 2);

  if (c)
    memcpy(result + len_a + len_b, c, len_c * 2);
  if (d)
    memcpy(result + len_a + len_b + len_c, d, len_d * 2);

  result[len_a + len_b + len_c + len_d] = 0;

  return result;
}

typedef void (*Visit_Proc_W)(wchar_t *short_name, wchar_t *full_name,
                             Version_Data *data);
bool visit_files_w(wchar_t *dir_name, Version_Data *data, Visit_Proc_W proc) {

  // Visit everything in one folder (non-recursively). If it's a directory
  // that doesn't start with ".", call the visit proc on it. The visit proc
  // will see if the filename conforms to the expected versioning pattern.

  WIN32_FIND_DATAW find_data;

  wchar_t *wildcard_name = concat2(dir_name, L"\\*");
  HANDLE handle = FindFirstFileW(wildcard_name, &find_data);
  free(wildcard_name);

  if (handle == INVALID_HANDLE_VALUE)
    return false;

  while (true) {
    if ((find_data.dwFileAttributes & FILE_ATTRIBUTE_DIRECTORY) &&
        (find_data.cFileName[0] != '.')) {
      wchar_t *full_name = concat3(dir_name, L"\\", find_data.cFileName);
      proc(find_data.cFileName, full_name, data);
      free(full_name);
    }

    BOOL success = FindNextFileW(handle, &find_data);
    if (!success)
      break;
  }

  FindClose(handle);

  return true;
}

wchar_t *find_windows_kit_root_with_key(HKEY key, wchar_t *version) {
  // Given a key to an already opened registry entry,
  // get the value stored under the 'version' subkey.
  // If that's not the right terminology, hey, I never do registry stuff.

  DWORD required_length;
  auto rc = RegQueryValueExW(key, version, NULL, NULL, NULL, &required_length);
  if (rc != 0)
    return NULL;

  DWORD length =
      required_length + 2; // The +2 is for the maybe optional zero later on.
                           // Probably we are over-allocating.
  wchar_t *value = (wchar_t *)malloc(length);
  if (!value)
    return NULL;

  rc = RegQueryValueExW(key, version, NULL, NULL, (LPBYTE)value,
                        &length); // We know that version is zero-terminated...
  if (rc != 0)
    return NULL;

  // The documentation says that if the string for some reason was not stored
  // with zero-termination, we need to manually terminate it. Sigh!!

  if (value[length]) {
    value[length + 1] = 0;
  }

  return value;
}

void win10_best(wchar_t *short_name, wchar_t *full_name, Version_Data *data) {
  // Find the Windows 10 subdirectory with the highest version number.

  int i0, i1, i2, i3;
  auto success = swscanf_s(short_name, L"%d.%d.%d.%d", &i0, &i1, &i2, &i3);
  if (success < 4)
    return;

  if (i0 < data->best_version[0])
    return;
  else if (i0 == data->best_version[0]) {
    if (i1 < data->best_version[1])
      return;
    else if (i1 == data->best_version[1]) {
      if (i2 < data->best_version[2])
        return;
      else if (i2 == data->best_version[2]) {
        if (i3 < data->best_version[3])
          return;
      }
    }
  }

  // we have to copy_string and free here because visit_files free's the
  // full_name string after we execute this function, so Win*_Data would contain
  // an invalid pointer.
  if (data->best_name)
    free(data->best_name);
  data->best_name = _wcsdup(full_name);

  if (data->best_name) {
    data->best_version[0] = i0;
    data->best_version[1] = i1;
    data->best_version[2] = i2;
    data->best_version[3] = i3;
  }
}

void win8_best(wchar_t *short_name, wchar_t *full_name, Version_Data *data) {
  // Find the Windows 8 subdirectory with the highest version number.

  int i0, i1;
  auto success = swscanf_s(short_name, L"winv%d.%d", &i0, &i1);
  if (success < 2)
    return;

  if (i0 < data->best_version[0])
    return;
  else if (i0 == data->best_version[0]) {
    if (i1 < data->best_version[1])
      return;
  }

  // we have to copy_string and free here because visit_files free's the
  // full_name string after we execute this function, so Win*_Data would contain
  // an invalid pointer.
  if (data->best_name)
    free(data->best_name);
  data->best_name = _wcsdup(full_name);

  if (data->best_name) {
    data->best_version[0] = i0;
    data->best_version[1] = i1;
  }
}

void find_windows_kit_root(Find_Result *result) {
  // Information about the Windows 10 and Windows 8 development kits
  // is stored in the same place in the registry. We open a key
  // to that place, first checking preferntially for a Windows 10 kit,
  // then, if that's not found, a Windows 8 kit.

  HKEY main_key;

  LSTATUS rc = RegOpenKeyExA(
      HKEY_LOCAL_MACHINE, "SOFTWARE\\Microsoft\\Windows Kits\\Installed Roots",
      0, KEY_QUERY_VALUE | KEY_WOW64_32KEY | KEY_ENUMERATE_SUB_KEYS, &main_key);
  if (rc != S_OK)
    return;

  // Look for a Windows 10 entry.
  wchar_t *windows10_root =
      find_windows_kit_root_with_key(main_key, L"KitsRoot10");

  if (windows10_root) {
    wchar_t *windows10_lib = concat2(windows10_root, L"Lib");
    free(windows10_root);

    Version_Data data = {0};
    visit_files_w(windows10_lib, &data, win10_best);
    free(windows10_lib);

    if (data.best_name) {
      result->windows_sdk_version = 10;
      result->windows_sdk_root = data.best_name;
      RegCloseKey(main_key);
      return;
    }
  }

  // Look for a Windows 8 entry.
  wchar_t *windows8_root =
      find_windows_kit_root_with_key(main_key, L"KitsRoot81");

  if (windows8_root) {
    wchar_t *windows8_lib = concat2(windows8_root, L"Lib");
    free(windows8_root);

    Version_Data data = {0};
    visit_files_w(windows8_lib, &data, win8_best);
    free(windows8_lib);

    if (data.best_name) {
      result->windows_sdk_version = 8;
      result->windows_sdk_root = data.best_name;
      RegCloseKey(main_key);
      return;
    }
  }

  // If we get here, we failed to find anything.
  RegCloseKey(main_key);
}

bool find_visual_studio_2017_by_fighting_through_microsoft_craziness(
    Find_Result *result) {
  HRESULT rc = CoInitialize(NULL);
  // "Subsequent valid calls return false." So ignore false.
  // if rc != S_OK  return false;

  GUID my_uid = {0x42843719,
                 0xDB4C,
                 0x46C2,
                 {0x8E, 0x7C, 0x64, 0xF1, 0x81, 0x6E, 0xFD, 0x5B}};
  GUID CLSID_SetupConfiguration = {
      0x177F0C4A,
      0x1CD3,
      0x4DE7,
      {0xA3, 0x2C, 0x71, 0xDB, 0xBB, 0x9F, 0xA3, 0x6D}};

  ISetupConfiguration *config = NULL;

  // NOTE(Kalinovcic): This is so stupid... These functions take references, so
  // the code is different for C and C++......
#ifdef __cplusplus
  HRESULT hr = CoCreateInstance(CLSID_SetupConfiguration, NULL,
                                CLSCTX_INPROC_SERVER, my_uid, (void **)&config);
#else
  HRESULT hr =
      CoCreateInstance(&CLSID_SetupConfiguration, NULL, CLSCTX_INPROC_SERVER,
                       &my_uid, (void **)&config);
#endif

  if (hr != 0)
    return false;

  IEnumSetupInstances *instances = NULL;
  hr = CALL_STDMETHOD(config, EnumInstances, &instances);
  CALL_STDMETHOD_(config, Release);
  if (hr != 0)
    return false;
  if (!instances)
    return false;

  bool found_visual_studio_2017 = false;
  while (1) {
    ULONG found = 0;
    ISetupInstance *instance = NULL;
    HRESULT hr = CALL_STDMETHOD(instances, Next, 1, &instance, &found);
    if (hr != S_OK)
      break;

    BSTR bstr_inst_path;
    hr = CALL_STDMETHOD(instance, GetInstallationPath, &bstr_inst_path);
    CALL_STDMETHOD_(instance, Release);
    if (hr != S_OK)
      continue;

    wchar_t *tools_filename = concat2(
        bstr_inst_path,
        L"\\VC\\Auxiliary\\Build\\Microsoft.VCToolsVersion.default.txt");
    SysFreeString(bstr_inst_path);

    FILE *f;
    errno_t open_result = _wfopen_s(&f, tools_filename, L"rt");
    free(tools_filename);
    if (open_result != 0)
      continue;
    if (!f)
      continue;

    LARGE_INTEGER tools_file_size;
    HANDLE file_handle = (HANDLE)_get_osfhandle(_fileno(f));
    BOOL success = GetFileSizeEx(file_handle, &tools_file_size);
    if (!success) {
      fclose(f);
      continue;
    }

    uint64_t version_bytes =
        (tools_file_size.QuadPart + 1) *
        2; // Warning: This multiplication by 2 presumes there is no
           // variable-length encoding in the wchars (wacky characters in the
           // file could betray this expectation).
    wchar_t *version = (wchar_t *)malloc(version_bytes);

    wchar_t *read_result = fgetws(version, version_bytes, f);
    fclose(f);
    if (!read_result)
      continue;

    wchar_t *version_tail = wcschr(version, '\n');
    if (version_tail)
      *version_tail = 0; // Stomp the data, because nobody cares about it.

    wchar_t *library_path =
        concat4(bstr_inst_path, L"\\VC\\Tools\\MSVC\\", version, L"\\lib\\x64");
    wchar_t *library_file =
        concat2(library_path,
                L"\\vcruntime.lib"); // @Speed: Could have library_path point to
                                     // this string, with a smaller count, to
                                     // save on memory flailing!

    if (os_file_exists(library_file)) {
      wchar_t *link_exe_path = concat4(bstr_inst_path, L"\\VC\\Tools\\MSVC\\",
                                       version, L"\\bin\\Hostx64\\x64");
      free(version);

      result->vs_exe_path = link_exe_path;
      result->vs_library_path = library_path;
      found_visual_studio_2017 = true;
      break;
    }

    free(version);

    /*
       Ryan Saunderson said:
       "Clang uses the 'SetupInstance->GetInstallationVersion' /
       ISetupHelper->ParseVersion to find the newest version and then reads the
       tools file to define the tools path - which is definitely better than
       what i did."

       So... @Incomplete: Should probably pick the newest version...
    */
  }

  CALL_STDMETHOD_(instances, Release);
  return found_visual_studio_2017;
}

void find_visual_studio_by_fighting_through_microsoft_craziness(
    Find_Result *result) {
  // The name of this procedure is kind of cryptic. Its purpose is
  // to fight through Microsoft craziness. The things that the fine
  // Visual Studio team want you to do, JUST TO FIND A SINGLE FOLDER
  // THAT EVERYONE NEEDS TO FIND, are ridiculous garbage.

  // For earlier versions of Visual Studio, you'd find this information in the
  // registry, similarly to the Windows Kits above. But no, now it's the future,
  // so to ask the question "Where is the Visual Studio folder?" you have to do
  // a bunch of COM object instantiation, enumeration, and querying. (For extra
  // bonus points, try doing this in a new, underdeveloped programming language
  // where you don't have COM routines up and running yet. So fun.)
  //
  // If all this COM object instantiation, enumeration, and querying doesn't
  // give us a useful result, we drop back to the registry-checking method.

  bool found_visual_studio_2017 =
      find_visual_studio_2017_by_fighting_through_microsoft_craziness(result);
  if (found_visual_studio_2017)
    return;

  // If we get here, we didn't find Visual Studio 2017. Try earlier versions.

  HKEY vs7_key;
  HRESULT rc = RegOpenKeyExA(HKEY_LOCAL_MACHINE,
                             "SOFTWARE\\Microsoft\\VisualStudio\\SxS\\VS7", 0,
                             KEY_QUERY_VALUE | KEY_WOW64_32KEY, &vs7_key);
  if (rc != S_OK)
    return;

  // Hardcoded search for 4 prior Visual Studio versions. Is there something
  // better to do here?
  wchar_t *versions[] = {L"14.0", L"12.0", L"11.0", L"10.0"};
  const int NUM_VERSIONS = sizeof(versions) / sizeof(versions[0]);

  for (int i = 0; i < NUM_VERSIONS; i++) {
    wchar_t *v = versions[i];

    DWORD dw_type;
    DWORD cb_data;

    LSTATUS rc = RegQueryValueExW(vs7_key, v, NULL, &dw_type, NULL, &cb_data);
    if ((rc == ERROR_FILE_NOT_FOUND) || (dw_type != REG_SZ)) {
      continue;
    }

    wchar_t *buffer = (wchar_t *)malloc(cb_data);
    if (!buffer)
      return;

    rc = RegQueryValueExW(vs7_key, v, NULL, NULL, (LPBYTE)buffer, &cb_data);
    if (rc != 0)
      continue;

    // @Robustness: Do the zero-termination thing suggested in the RegQueryValue
    // docs?

    wchar_t *lib_path = concat2(buffer, L"VC\\Lib\\amd64");

    // Check to see whether a vcruntime.lib actually exists here.
    wchar_t *vcruntime_filename = concat2(lib_path, L"\\vcruntime.lib");
    bool vcruntime_exists = os_file_exists(vcruntime_filename);
    free(vcruntime_filename);

    if (vcruntime_exists) {
      result->vs_exe_path = concat2(buffer, L"VC\\bin\\amd64");
      result->vs_library_path = lib_path;

      free(buffer);
      RegCloseKey(vs7_key);
      return;
    }

    free(lib_path);
    free(buffer);
  }

  RegCloseKey(vs7_key);

  // If we get here, we failed to find anything.
}

Find_Result *find_visual_studio_and_windows_sdk() {
  Find_Result *result = malloc(sizeof(Find_Result));

  find_windows_kit_root(result);

  if (result->windows_sdk_root) {
    result->windows_sdk_um_library_path =
        concat2(result->windows_sdk_root, L"\\um\\x64");
    result->windows_sdk_ucrt_library_path =
        concat2(result->windows_sdk_root, L"\\ucrt\\x64");
  }

  find_visual_studio_by_fighting_through_microsoft_craziness(result);

  return result;
}

#endif

#endif // MICROSOFT_CRAZINESS_IMPLEMENTATION_GUARD
#endif // MICROSOFT_CRAZINESS_IMPLEMENTATION

#ifdef __cplusplus
}
#endif