rest_rpc/include/router.h

#ifndef REST_RPC_ROUTER_H_
#define REST_RPC_ROUTER_H_

#include "use_asio.hpp"
#include "codec.h"
#include "meta_util.hpp"

namespace rest_rpc {
	enum class ExecMode { sync, async };
	const constexpr ExecMode Async = ExecMode::async;

	namespace rpc_service {
		class connection;

		class router : asio::noncopyable {
		public:
			static router& get() {
				static router instance;
				return instance;
			}

			template<ExecMode model, typename Function>
			void register_handler(std::string const& name, Function f) {
				return register_nonmember_func<model>(name, std::move(f));
			}

			template<ExecMode model, typename Function, typename Self>
			void register_handler(std::string const& name, const Function& f, Self* self) {
				return register_member_func<model>(name, f, self);
			}

			void remove_handler(std::string const& name) { this->map_invokers_.erase(name); }

			template<typename T>
			void route(const char* data, std::size_t size, std::weak_ptr<T> conn) {
				auto conn_sp = conn.lock();
				if (!conn_sp) {
					return;
				}

				auto req_id = conn_sp->request_id();
				std::string result;
				try {
					msgpack_codec codec;
					auto p = codec.unpack<std::tuple<std::string>>(data, size);
					auto& func_name = std::get<0>(p);
					auto it = map_invokers_.find(func_name);
					if (it == map_invokers_.end()) {
						result = codec.pack_args_str(result_code::FAIL, "unknown function: " + func_name);
						conn_sp->response(req_id, std::move(result));
						return;
					}

					ExecMode model;
					it->second(conn, data, size, result, model);
					if (model == ExecMode::sync) {
						if (result.size() >= MAX_BUF_LEN) {
							result = codec.pack_args_str(result_code::FAIL, "the response result is out of range: more than 10M " + func_name);
						}
						conn_sp->response(req_id, std::move(result));
					}
				}
				catch (const std::exception & ex) {
					msgpack_codec codec;
					result = codec.pack_args_str(result_code::FAIL, ex.what());
					conn_sp->response(req_id, std::move(result));
				}
			}

			router() = default;

		private:
			router(const router&) = delete;
			router(router&&) = delete;

			template<typename F, size_t... I, typename Arg, typename... Args>
			static typename std::result_of<F(std::weak_ptr<connection>, Args...)>::type call_helper(
				const F & f, const std::index_sequence<I...>&, const std::tuple<Arg, Args...> & tup, std::weak_ptr<connection> ptr) {
				return f(ptr, std::get<I + 1>(tup)...);
			}

			template<typename F, typename Arg, typename... Args>
			static
				typename std::enable_if<std::is_void<typename std::result_of<F(std::weak_ptr<connection>, Args...)>::type>::value>::type
				call(const F & f, std::weak_ptr<connection> ptr, std::string & result, std::tuple<Arg, Args...> & tp) {
				call_helper(f, std::make_index_sequence<sizeof...(Args)>{}, tp, ptr);
				result = msgpack_codec::pack_args_str(result_code::OK);
			}

			template<typename F, typename Arg, typename... Args>
			static
				typename std::enable_if<!std::is_void<typename std::result_of<F(std::weak_ptr<connection>, Args...)>::type>::value>::type
				call(const F & f, std::weak_ptr<connection> ptr, std::string & result, const std::tuple<Arg, Args...> & tp) {
				auto r = call_helper(f, std::make_index_sequence<sizeof...(Args)>{}, tp, ptr);
				msgpack_codec codec;
				result = msgpack_codec::pack_args_str(result_code::OK, r);
			}

			template<typename F, typename Self, size_t... Indexes, typename Arg, typename... Args>
			static typename std::result_of<F(Self, std::weak_ptr<connection>, Args...)>::type call_member_helper(
				const F & f, Self * self, const std::index_sequence<Indexes...>&,
				const std::tuple<Arg, Args...> & tup, std::weak_ptr<connection> ptr = 0) {
				return (*self.*f)(ptr, std::get<Indexes + 1>(tup)...);
			}

			template<typename F, typename Self, typename Arg, typename... Args>
			static typename std::enable_if<
				std::is_void<typename std::result_of<F(Self, std::weak_ptr<connection>, Args...)>::type>::value>::type
				call_member(const F & f, Self * self, std::weak_ptr<connection> ptr, std::string & result,
					const std::tuple<Arg, Args...> & tp) {
				call_member_helper(f, self, typename std::make_index_sequence<sizeof...(Args)>{}, tp, ptr);
				result = msgpack_codec::pack_args_str(result_code::OK);
			}

			template<typename F, typename Self, typename Arg, typename... Args>
			static typename std::enable_if<
				!std::is_void<typename std::result_of<F(Self, std::weak_ptr<connection>, Args...)>::type>::value>::type
				call_member(const F & f, Self * self, std::weak_ptr<connection> ptr, std::string & result,
					const std::tuple<Arg, Args...> & tp) {
				auto r =
					call_member_helper(f, self, typename std::make_index_sequence<sizeof...(Args)>{}, tp, ptr);
				result = msgpack_codec::pack_args_str(result_code::OK, r);
			}

			template<typename Function, ExecMode mode = ExecMode::sync>
			struct invoker {
				template<ExecMode model>
				static inline void apply(const Function& func, std::weak_ptr<connection> conn, const char* data, size_t size,
					std::string& result, ExecMode& exe_model) {
					using args_tuple = typename function_traits<Function>::args_tuple_2nd;
					exe_model = ExecMode::sync;
					msgpack_codec codec;
					try {
						auto tp = codec.unpack<args_tuple>(data, size);
						call(func, conn, result, tp);
						exe_model = model;
					}
					catch (std::invalid_argument & e) {
						result = codec.pack_args_str(result_code::FAIL, e.what());
					}
					catch (const std::exception & e) {
						result = codec.pack_args_str(result_code::FAIL, e.what());
					}
				}

				template<ExecMode model, typename Self>
				static inline void apply_member(const Function& func, Self* self, std::weak_ptr<connection> conn,
					const char* data, size_t size, std::string& result,
					ExecMode& exe_model) {
					using args_tuple = typename function_traits<Function>::args_tuple_2nd;
					exe_model = ExecMode::sync;
					msgpack_codec codec;
					try {
						auto tp = codec.unpack<args_tuple>(data, size);
						call_member(func, self, conn, result, tp);
						exe_model = model;
					}
					catch (std::invalid_argument & e) {
						result = codec.pack_args_str(result_code::FAIL, e.what());
					}
					catch (const std::exception & e) {
						result = codec.pack_args_str(result_code::FAIL, e.what());
					}
				}
			};

			template<ExecMode model, typename Function>
			void register_nonmember_func(std::string const& name, Function f) {
				this->map_invokers_[name] = { std::bind(&invoker<Function>::template apply<model>, std::move(f), std::placeholders::_1,
													   std::placeholders::_2, std::placeholders::_3,
													   std::placeholders::_4, std::placeholders::_5) };
			}

			template<ExecMode model, typename Function, typename Self>
			void register_member_func(const std::string& name, const Function& f, Self* self) {
				this->map_invokers_[name] = { std::bind(&invoker<Function>::template apply_member<model, Self>,
													   f, self, std::placeholders::_1, std::placeholders::_2,
													   std::placeholders::_3, std::placeholders::_4,
													   std::placeholders::_5) };
			}

			std::unordered_map<std::string,
				std::function<void(std::weak_ptr<connection>, const char*, size_t, std::string&, ExecMode& model)>>
				map_invokers_;
		};
	}  // namespace rpc_service
}  // namespace rest_rpc

#endif  // REST_RPC_ROUTER_H_