http/utility.hpp

#pragma once

#include <boost/callable_traits.hpp>
#include <boost/url/decode_view.hpp>
#include <boost/url/parse.hpp>
#include <boost/url/url.hpp>
#include <boost/url/url_view.hpp>
#include <nlohmann/json.hpp>

#include <array>
#include <chrono>
#include <cstddef>
#include <cstdint>
#include <ctime>
#include <functional>
#include <iomanip>
#include <limits>
#include <stdexcept>
#include <string>
#include <string_view>
#include <tuple>
#include <type_traits>
#include <utility>
#include <variant>

namespace crow
{
namespace black_magic
{

enum class TypeCode : std::uint8_t
{
    Unspecified = 0,
    Integer = 1,
    UnsignedInteger = 2,
    Float = 3,
    String = 4,
    Path = 5,
    Max = 6,
};

// Remove when we have c++23
template <typename E>
constexpr typename std::underlying_type<E>::type toUnderlying(E e) noexcept
{
    return static_cast<typename std::underlying_type<E>::type>(e);
}

template <typename T>
constexpr TypeCode getParameterTag()
{
    if constexpr (std::is_same_v<int, T>)
    {
        return TypeCode::Integer;
    }
    if constexpr (std::is_same_v<char, T>)
    {
        return TypeCode::Integer;
    }
    if constexpr (std::is_same_v<int16_t, T>)
    {
        return TypeCode::Integer;
    }
    if constexpr (std::is_same_v<int32_t, T>)
    {
        return TypeCode::Integer;
    }
    if constexpr (std::is_same_v<int64_t, T>)
    {
        return TypeCode::Integer;
    }
    if constexpr (std::is_same_v<unsigned int, T>)
    {
        return TypeCode::UnsignedInteger;
    }
    if constexpr (std::is_same_v<unsigned char, T>)
    {
        return TypeCode::UnsignedInteger;
    }
    if constexpr (std::is_same_v<uint16_t, T>)
    {
        return TypeCode::UnsignedInteger;
    }
    if constexpr (std::is_same_v<uint32_t, T>)
    {
        return TypeCode::UnsignedInteger;
    }
    if constexpr (std::is_same_v<uint64_t, T>)
    {
        return TypeCode::UnsignedInteger;
    }
    if constexpr (std::is_same_v<double, T>)
    {
        return TypeCode::Float;
    }
    if constexpr (std::is_same_v<std::string, T>)
    {
        return TypeCode::String;
    }
    return TypeCode::Unspecified;
}

template <typename... Args>
struct computeParameterTagFromArgsList;

template <>
struct computeParameterTagFromArgsList<>
{
    static constexpr int value = 0;
};

constexpr uint64_t getParameterTag(std::string_view url)
{
    uint64_t tagValue = 0;
    size_t urlSegmentIndex = std::string_view::npos;

    size_t paramIndex = 0;

    for (size_t urlIndex = 0; urlIndex < url.size(); urlIndex++)
    {
        char character = url[urlIndex];
        if (character == '<')
        {
            if (urlSegmentIndex != std::string_view::npos)
            {
                return 0;
            }
            urlSegmentIndex = urlIndex;
        }
        if (character == '>')
        {
            if (urlSegmentIndex == std::string_view::npos)
            {
                return 0;
            }
            std::string_view tag =
                url.substr(urlSegmentIndex, urlIndex + 1 - urlSegmentIndex);

            // Note, this is a really lame way to do std::pow(6, paramIndex)
            // std::pow doesn't work in constexpr in clang.
            // Ideally in the future we'd move this to use a power of 2 packing
            // (probably 8 instead of 6) so that these just become bit shifts
            uint64_t insertIndex = 1;
            for (size_t unused = 0; unused < paramIndex; unused++)
            {
                insertIndex *= 6;
            }

            if (tag == "<int>")
            {
                tagValue += insertIndex * toUnderlying(TypeCode::Integer);
            }
            if (tag == "<uint>")
            {
                tagValue +=
                    insertIndex * toUnderlying(TypeCode::UnsignedInteger);
            }
            if (tag == "<float>" || tag == "<double>")
            {
                tagValue += insertIndex * toUnderlying(TypeCode::Float);
            }
            if (tag == "<str>" || tag == "<string>")
            {
                tagValue += insertIndex * toUnderlying(TypeCode::String);
            }
            if (tag == "<path>")
            {
                tagValue += insertIndex * toUnderlying(TypeCode::Path);
            }
            paramIndex++;
            urlSegmentIndex = std::string_view::npos;
        }
    }
    if (urlSegmentIndex != std::string_view::npos)
    {
        return 0;
    }
    return tagValue;
}

template <typename Arg, typename... Args>
struct computeParameterTagFromArgsList<Arg, Args...>
{
    static constexpr int subValue =
        computeParameterTagFromArgsList<Args...>::value;
    static constexpr int value =
        getParameterTag<typename std::decay<Arg>::type>() !=
                TypeCode::Unspecified
            ? static_cast<uint64_t>(subValue *
                                         toUnderlying(TypeCode::Max)) +
                  static_cast<uint64_t>(
                      getParameterTag<typename std::decay<Arg>::type>())
            : subValue;
};

bool isParameterTagCompatible(uint64_t a, uint64_t b);

template <typename... T>
struct S
{
    template <typename U>
    using push = S<U, T...>;
    template <typename U>
    using push_back = S<T..., U>;
    template <template <typename... Args> class U>
    using rebind = U<T...>;
};

template <typename F, typename Set>
struct CallHelper;

template <typename F, typename... Args>
struct CallHelper<F, S<Args...>>
{
    template <typename F1, typename... Args1,
              typename = decltype(std::declval<F1>()(std::declval<Args1>()...))>
    static char test(int);

    template <typename...>
    static int test(...);

    static constexpr bool value = sizeof(test<F, Args...>(0)) == sizeof(char);
};

template <uint64_t N>
struct SingleTagToType
{};

template <>
struct SingleTagToType<1>
{
    using type = int64_t;
};

template <>
struct SingleTagToType<2>
{
    using type = uint64_t;
};

template <>
struct SingleTagToType<3>
{
    using type = double;
};

template <>
struct SingleTagToType<4>
{
    using type = std::string;
};

template <>
struct SingleTagToType<5>
{
    using type = std::string;
};

template <uint64_t Tag>
struct Arguments
{
    using subarguments = typename Arguments<Tag / 6>::type;
    using type = typename subarguments::template push<
        typename SingleTagToType<Tag % 6>::type>;
};

template <>
struct Arguments<0>
{
    using type = S<>;
};

template <typename T>
struct Promote
{
    using type = T;
};

template <typename T>
using PromoteT = typename Promote<T>::type;

template <>
struct Promote<char>
{
    using type = int64_t;
};
template <>
struct Promote<int16_t>
{
    using type = int64_t;
};
template <>
struct Promote<int>
{
    using type = int64_t;
};
template <>
struct Promote<int64_t>
{
    using type = int64_t;
};
template <>
struct Promote<unsigned char>
{
    using type = uint64_t;
};
template <>
struct Promote<uint16_t>
{
    using type = uint64_t;
};
template <>
struct Promote<unsigned int>
{
    using type = uint64_t;
};
template <>
struct Promote<uint64_t>
{
    using type = uint64_t;
};

} // namespace black_magic

namespace utility
{

template <typename T>
struct FunctionTraits
{
    template <size_t i>
    using arg = std::tuple_element_t<i, boost::callable_traits::args_t<T>>;
};

std::string base64encode(std::string_view data);

// TODO this is temporary and should be deleted once base64 is refactored out of
// crow
bool base64Decode(std::string_view input, std::string& output);

bool constantTimeStringCompare(std::string_view a, std::string_view b);

struct ConstantTimeCompare
{
    bool operator()(std::string_view a, std::string_view b) const
    {
        return constantTimeStringCompare(a, b);
    }
};

namespace details
{
inline boost::urls::url
    appendUrlPieces(boost::urls::url& url,
                    const std::initializer_list<std::string_view> args)
{
    for (std::string_view arg : args)
    {
        url.segments().push_back(arg);
    }
    return url;
}

inline boost::urls::url
    urlFromPiecesDetail(const std::initializer_list<std::string_view> args)
{
    boost::urls::url url("/");
    appendUrlPieces(url, args);
    return url;
}
} // namespace details

class OrMorePaths
{};

template <typename... AV>
inline boost::urls::url urlFromPieces(const AV... args)
{
    return details::urlFromPiecesDetail({args...});
}

template <typename... AV>
inline void appendUrlPieces(boost::urls::url& url, const AV... args)
{
    details::appendUrlPieces(url, {args...});
}

namespace details
{

// std::reference_wrapper<std::string> - extracts segment to variable
//                    std::string_view - checks if segment is equal to variable
using UrlSegment = std::variant<std::reference_wrapper<std::string>,
                                std::string_view, OrMorePaths>;

enum class UrlParseResult : uint8_t
{
    Continue,
    Fail,
    Done,
};

class UrlSegmentMatcherVisitor
{
  public:
    UrlParseResult operator()(std::string& output)
    {
        output = segment;
        return UrlParseResult::Continue;
    }

    UrlParseResult operator()(std::string_view expected)
    {
        if (segment == expected)
        {
            return UrlParseResult::Continue;
        }
        return UrlParseResult::Fail;
    }

    UrlParseResult operator()(OrMorePaths /*unused*/)
    {
        return UrlParseResult::Done;
    }

    explicit UrlSegmentMatcherVisitor(std::string_view segmentIn) :
        segment(segmentIn)
    {}

  private:
    std::string_view segment;
};

bool readUrlSegments(boost::urls::url_view url, // NOLINT
                     std::initializer_list<UrlSegment>&& segments);

} // namespace details

template <typename... Args>
inline bool readUrlSegments(boost::urls::url_view url, Args&&... args) // NOLINT
{
    return details::readUrlSegments(url, {std::forward<Args>(args)...});
}

boost::urls::url replaceUrlSegment(boost::urls::url_view urlView, // NOLINT
                                   uint replaceLoc,
                                   std::string_view newSegment);

std::string setProtocolDefaults(boost::urls::url_view urlView); // NOLINT

uint16_t setPortDefaults(boost::urls::url_view url); // NOLINT

bool validateAndSplitUrl(std::string_view destUrl, std::string& urlProto,
                         std::string& host, uint16_t& port, std::string& path);

} // namespace utility
} // namespace crow

namespace nlohmann
{
template <>
struct adl_serializer<boost::urls::url>
{
    // nlohmann requires a specific casing to look these up in adl
    // NOLINTNEXTLINE(readability-identifier-naming)
    static void to_json(json& j, const boost::urls::url& url)
    {
        boost::urls::decode_view url_decoded{url};
        j = std::string(url_decoded.begin(), url_decoded.end());
    }
};

template <>
struct adl_serializer<boost::urls::url_view>
{
    // NOLINTNEXTLINE(readability-identifier-naming, performance-unnecessary-value-param)
    static void to_json(json& j, boost::urls::url_view url)
    {
        boost::urls::decode_view url_decoded{url};
        j = std::string(url_decoded.begin(), url_decoded.end());
    }
};
} // namespace nlohmann