Utils.h

#pragma once
#include <pch.h>

using namespace Platform;
using namespace Windows::Storage;

namespace RingClientUWP
{
namespace Utils
{

task<bool>
fileExists(StorageFolder^ folder, String^ fileName)
{
    return create_task(folder->GetFileAsync(fileName))
           .then([](task<StorageFile^> taskResult)
    {
        bool exists;
        try {
            taskResult.get();
            exists = true;
        }
        catch (COMException ^e) {
            if (e->HResult == HRESULT_FROM_WIN32(ERROR_FILE_NOT_FOUND)) {
                exists = false;
            }
            else {
                throw;
            }
        }
        return exists;
    });
}

std::string makeString(const std::wstring& wstr)
{
    auto wideData = wstr.c_str();
    int bufferSize = WideCharToMultiByte(CP_UTF8, 0, wideData, -1, nullptr, 0, NULL, NULL);

    std::unique_ptr<char[]> utf8;
    utf8.reset(new char[bufferSize]);

    if (WideCharToMultiByte(CP_UTF8, 0, wideData, -1, utf8.get(), bufferSize, NULL, NULL) == 0) {
        return std::string();
    }

    return std::string(utf8.get());
}

std::wstring makeWString(const std::string& str)
{
    auto utf8Data = str.c_str();
    int bufferSize = MultiByteToWideChar(CP_UTF8, 0, utf8Data, -1, nullptr, 0);

    std::unique_ptr<wchar_t[]> wide;
    wide.reset(new wchar_t[bufferSize]);

    if (MultiByteToWideChar(CP_UTF8, 0, utf8Data, -1, wide.get(), bufferSize) == 0) {
        return std::wstring();
    }

    return std::wstring(wide.get());;
}

std::string toString(Platform::String ^str)
{
    std::wstring wsstr(str->Data());
    return makeString(wsstr);
}

Platform::String^ toPlatformString(const std::string& str)
{
    std::wstring wsstr = makeWString(str);
    return ref new Platform::String(wsstr.c_str(), wsstr.length());
}

}
}