http/routing/dynamicrule.hpp

#pragma once
#include "baserule.hpp"
#include "ruleparametertraits.hpp"
#include "websocket.hpp"

#include <boost/beast/http/verb.hpp>

#include <functional>
#include <limits>
#include <string>
#include <type_traits>

namespace crow
{
namespace detail
{
namespace routing_handler_call_helper
{

template <typename Func, typename... ArgsWrapped>
struct Wrapped
{
    template <typename... Args>
    void set(Func f)
    {
        handler = std::move(f);
    }

    std::function<void(ArgsWrapped...)> handler;

    void operator()(const Request& req,
                    const std::shared_ptr<bmcweb::AsyncResp>& asyncResp,
                    const std::vector<std::string>& params)
    {
        if constexpr (sizeof...(ArgsWrapped) == 2)
        {
            handler(req, asyncResp);
        }
        else if constexpr (sizeof...(ArgsWrapped) == 3)
        {
            handler(req, asyncResp, params[0]);
        }
        else if constexpr (sizeof...(ArgsWrapped) == 4)
        {
            handler(req, asyncResp, params[0], params[1]);
        }
        else if constexpr (sizeof...(ArgsWrapped) == 5)
        {
            handler(req, asyncResp, params[0], params[1], params[2]);
        }
        else if constexpr (sizeof...(ArgsWrapped) == 6)
        {
            handler(req, asyncResp, params[0], params[1], params[2], params[3]);
        }
        else if constexpr (sizeof...(ArgsWrapped) == 7)
        {
            handler(req, asyncResp, params[0], params[1], params[2], params[3],
                    params[4]);
        }
    }
};
} // namespace routing_handler_call_helper
} // namespace detail

class DynamicRule : public BaseRule, public RuleParameterTraits<DynamicRule>
{
  public:
    explicit DynamicRule(const std::string& ruleIn) : BaseRule(ruleIn) {}

    void validate() override
    {
        if (!erasedHandler)
        {
            throw std::runtime_error("no handler for url " + rule);
        }
    }

    void handle(const Request& req,
                const std::shared_ptr<bmcweb::AsyncResp>& asyncResp,
                const std::vector<std::string>& params) override
    {
        erasedHandler(req, asyncResp, params);
    }

    template <typename Func>
    void operator()(Func f)
    {
        using boost::callable_traits::args_t;
        constexpr size_t arity = std::tuple_size<args_t<Func>>::value;
        constexpr auto is = std::make_integer_sequence<unsigned, arity>{};
        erasedHandler = wrap(std::move(f), is);
    }

    // enable_if Arg1 == request && Arg2 == Response
    // enable_if Arg1 == request && Arg2 != response
    // enable_if Arg1 != request

    template <typename Func, unsigned... Indices>
    std::function<void(const Request&,
                       const std::shared_ptr<bmcweb::AsyncResp>&,
                       const std::vector<std::string>&)>
        wrap(Func f, std::integer_sequence<unsigned, Indices...> /*is*/)
    {
        using function_t = crow::utility::FunctionTraits<Func>;

        auto ret = detail::routing_handler_call_helper::Wrapped<
            Func, typename function_t::template arg<Indices>...>();
        ret.template set<typename function_t::template arg<Indices>...>(
            std::move(f));
        return ret;
    }

  private:
    std::function<void(const Request&,
                       const std::shared_ptr<bmcweb::AsyncResp>&,
                       const std::vector<std::string>&)>
        erasedHandler;
};

} // namespace crow