Add GetCloudProvider API function

This new `GetCloudProvider` function provides the ability to query
whether a directory is under a cloud provider sync root for a system
like OneDrive and whether that provider is active or inhibited.

This could be used to help diagnose user reports where the Lua code can
open but not read from files.

Author: zao

ui_api.cpp

@@ -52,6 +52,8 @@
 ** fileSize = searchHandle:GetFileSize()
 ** modified, date, time = searchHande:GetFileModifiedTime()
 **
+** provider, version, status = GetCloudProvider(path)
+**
 ** SetWindowTitle("<title>")
 ** x, y = GetCursorPos()
 ** SetCursorPos(x, y)
@@ -646,6 +648,96 @@ static int l_searchHandleGetFileModifiedTime(lua_State* L)
 	return 1;
 }
 
+// ===================
+// Cloud provider info
+// ===================
+
+struct CloudProviderInfo {
+	std::string name;
+	std::string version;
+	uint32_t status;
+};
+
+#ifdef _WIN32
+#include <Windows.h>
+#include <cfapi.h>
+
+static std::string NarrowString(std::wstring_view ws) {
+	auto cb = WideCharToMultiByte(CP_UTF8, 0, ws.data(), ws.size(), nullptr, 0, nullptr, nullptr);
+	std::string ret(cb, '\0');
+	WideCharToMultiByte(CP_UTF8, 0, ws.data(), ws.size(), ret.data(), ret.size(), nullptr, nullptr);
+	return ret;
+}
+
+struct CloudProviderLibrary {
+	CloudProviderLibrary() {
+		cldLib = LoadLibraryW(L"cldapi.dll");
+		if (cldLib != nullptr) {
+			CfGetSyncRootInfoByPath = (decltype (CfGetSyncRootInfoByPath))GetProcAddress(cldLib, "CfGetSyncRootInfoByPath");
+		}
+	}
+
+	~CloudProviderLibrary() {
+		FreeLibrary(cldLib);
+	}
+
+	bool Loaded() const { return cldLib != nullptr; }
+
+	CloudProviderLibrary(CloudProviderLibrary const&) = delete;
+	CloudProviderLibrary& operator = (CloudProviderLibrary const&) = delete;
+
+	decltype (&::CfGetSyncRootInfoByPath) CfGetSyncRootInfoByPath;
+
+	HMODULE cldLib{};
+};
+
+static std::optional<CloudProviderInfo> GetCloudProviderInfo(std::filesystem::path const& path) {
+	HRESULT hr{ S_OK };
+	DWORD len{};
+	static std::vector<char> buf(65536);
+	static CloudProviderLibrary lib;
+	if (!lib.Loaded()) {
+		return {};
+	}
+	hr = lib.CfGetSyncRootInfoByPath(path.generic_wstring().c_str(), CF_SYNC_ROOT_INFO_PROVIDER, buf.data(), buf.size(), &len);
+	if (FAILED(hr) && GetLastError() != ERROR_MORE_DATA) {
+		return {};
+	}
+	auto* syncRootInfo = (CF_SYNC_ROOT_PROVIDER_INFO const*)buf.data();
+	buf.resize(len);
+	hr = lib.CfGetSyncRootInfoByPath(path.c_str(), CF_SYNC_ROOT_INFO_PROVIDER, buf.data(), len, &len);
+	if (FAILED(hr)) {
+		return {};
+	}
+	CloudProviderInfo ret{};
+	ret.name = NarrowString(syncRootInfo->ProviderName);
+	ret.version = NarrowString(syncRootInfo->ProviderVersion);
+	ret.status = syncRootInfo->ProviderStatus;
+	return ret;
+}
+#else
+static std::optional<CloudProviderInfo> GetCloudProviderInfo(std::filesystem::path const& path) {
+	return {};
+}
+#endif
+
+static int l_GetCloudProvider(lua_State* L) {
+	ui_main_c* ui = GetUIPtr(L);
+	int n = lua_gettop(L);
+	ui->LAssert(L, n >= 1, "Usage: GetCloudProvider(path)");
+	ui->LAssert(L, lua_isstring(L, 1), "GetCloudProvider() argument 1: expected string, got %s", luaL_typename(L, 1));
+
+	auto info = GetCloudProviderInfo(lua_tostring(L, 1));
+	if (info) {
+		lua_pushstring(L, info->name.c_str());
+		lua_pushstring(L, info->version.c_str());
+		lua_pushinteger(L, info->status);
+		return 3;
+	}
+
+	return 0;
+}
+
 // =================
 // General Functions
 // =================
@@ -1287,6 +1379,7 @@ int ui_main_c::InitAPI(lua_State* L)
 	lua_setfield(L, LUA_REGISTRYINDEX, "uisearchhandlemeta");
 
 	// General function
+	ADDFUNC(GetCloudProvider);
 	ADDFUNC(SetWindowTitle);
 	ADDFUNC(GetCursorPos);
 	ADDFUNC(SetCursorPos);