// Copyright (c) 2020 Egor Tensin <egor@tensin.name>
// This file is part of the "winapi-common" project.
// For details, see https://github.com/egor-tensin/winapi-common
// Distributed under the MIT License.

#include <winapi/error.hpp>
#include <winapi/utf8.hpp>

#include <windows.h>

#include <cstdint>
#include <format>
#include <string>
#include <string_view>
#include <system_error>

namespace winapi::error {
namespace {

std::wstring trim_trailing_newline(std::wstring_view s) {
    const auto last_pos = s.find_last_not_of(L"\r\n");
    if (std::wstring_view::npos == last_pos)
        return {};
    const auto sub = s.substr(0, last_pos + 1);
    return {sub.data(), sub.length()};
}

std::string build_what(DWORD code, std::string_view function) {
    return std::format("Function {} failed with error code {}", function, code);
}

std::string format_message(int32_t code) {
    wchar_t* buf;

    const auto len = ::FormatMessageW(
        FORMAT_MESSAGE_ALLOCATE_BUFFER | FORMAT_MESSAGE_FROM_SYSTEM | FORMAT_MESSAGE_IGNORE_INSERTS,
        NULL,
        code,
        MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),
        reinterpret_cast<wchar_t*>(&buf),
        0,
        NULL
    );

    if (0 == len) {
        ::LocalFree(buf);
        return "Couldn't format the error message";
    }

    std::wstring msg{buf, len};
    ::LocalFree(buf);
    return narrow(trim_trailing_newline(msg));
}

} // namespace

std::string CategoryWindows::message(int32_t code) const {
    return format_message(code);
}

std::system_error windows(DWORD code, const char* function) {
    static_assert(sizeof(DWORD) == sizeof(int32_t), "Aren't DWORDs the same size as ints?");
    return std::system_error{
        static_cast<int32_t>(code), category_windows(), build_what(code, function)
    };
}

} // namespace winapi::error