SSX3LobbyServer/lib/http/server.cpp

#include <spdlog/spdlog.h>

#include <boost/beast/core/flat_buffer.hpp>
#include <boost/beast/http/read.hpp>
#include <boost/beast/http/write.hpp>
#include <boost/beast/websocket/rfc6455.hpp>
#include <boost/url.hpp>
#include <boost/url/parse.hpp>
#include <http/proxy_address.hpp>
#include <http/r3_helpers.hpp>
#include <http/server.hpp>
#include <http/utils.hpp>
#include <r3.hpp>

namespace base::http {

	namespace detail {

// method list for the below functions
#define ML()                  \
	C(get, METHOD_GET)        \
	C(post, METHOD_POST)      \
	C(put, METHOD_PUT)        \
	C(delete_, METHOD_DELETE) \
	C(patch, METHOD_PATCH)    \
	C(head, METHOD_HEAD)      \
	C(options, METHOD_OPTIONS)

		constexpr auto BeastToR3(beast::http::verb verb) {
			using enum beast::http::verb;
			switch(verb) {
#define C(v, r) \
	case v: return r;
				ML()
#undef C
				default: return 0;
			}
		}

		constexpr beast::http::verb R3ToBeast(int method) {
			using enum beast::http::verb;
			switch(method) {
#define C(v, r) \
	case r: return v;
				ML()
#undef C
				default: BASE_CHECK(false, "should not reach this :)");
			}
		}

#undef ML

	} // namespace detail

	// make this a global helper?
	constexpr auto stlify(boost::core::string_view sv) {
		return std::string_view { sv.data(), sv.length() };
	}

	inline bool IsTcp(GenericProtocol p) {
		const auto family = p.family();
		const auto protocol = p.protocol();

		if(family != AF_INET && family != AF_INET6)
			return false;

		// IPPROTO_IP is also used for remote TCP connections. Thanks BSD
		return protocol == IPPROTO_TCP || protocol == IPPROTO_IP;
	}

	struct Server::Impl {
		struct Session {
			Session(Impl& impl, Server::StreamType&& stream)
				: impl(impl), stream(std::move(stream)) {}

			void Close() {
				if(stream.socket().is_open()) {
					bsys::error_code ec;
					stream.socket().shutdown(asio::socket_base::shutdown_send, ec);
				}
			}

			Awaitable<void> DoSession() {
				beast::flat_buffer buffer {};
				try {
					while(true) {
						curReq = {};

						// Set the timeout.
						stream.expires_after(std::chrono::seconds(30));

						co_await beast::http::async_read(stream, buffer, curReq, asio::deferred);

						auto addr = GetProxyAddress(GetAddress(), curReq);

						auto res = co_await impl.Route(curReq, addr, *this);

						// This usually means that some higher level stuff (e.g: WebSockets)
						// did the thing
						if(!res.has_value())
							co_return;

						co_await WriteResponse(std::move(*res));

						if(!stream.socket().is_open())
							break;
					}
				} catch(bsys::system_error& ec) {
					// if(ec.code() != beast::http::error::end_of_stream)
					//	spdlog::error("Error in http::BasicServer::DoSession(): {}", ec.what());
				}

				// todo: standalone close() function
				Close();
				co_return;
			}

			asio::ip::address GetAddress() const {
				const auto protocol = stream.socket().remote_endpoint().protocol();

				if(IsTcp(protocol)) {
					// ugghhhhhhhhnhhnhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhh
					auto* sa = stream.socket().remote_endpoint().data();

					switch(sa->sa_family) {
						case AF_INET: {
							auto* sain = std::bit_cast<sockaddr_in*>(sa);
							return asio::ip::address_v4 { htonl(sain->sin_addr.s_addr) };
						} break;

						case AF_INET6: {
							auto* sain6 = std::bit_cast<sockaddr_in6*>(sa);

							// This is really annoying
							// N.B: The array here isn't zerofilled because we copy into its whole capacity
							// anyways so it's not really like it even matters
							asio::ip::address_v6::bytes_type addr;
							memcpy(&addr[0], sain6->sin6_addr.s6_addr, 16);

							return asio::ip::address_v6 { addr, sain6->sin6_scope_id };
						} break;
					}
				}

				// This is one of the reasons we should probably switch to a variant for this
				// so we can expose unix support while not being wonky and broken, but we
				// currently don't use unix support in the codebase or production so it's not really like it matters
				// all that much
				return asio::ip::make_address("1.2.3.4");
			}

			Awaitable<void> WriteResponse(Response res) {
				if(!stream.socket().is_open())
					co_return;

				auto addr = GetProxyAddress(GetAddress(), curReq);

				auto responseBytesWritten = co_await beast::async_write(stream, res.Release(), asio::deferred);

#ifdef BASE_HTTP_REQUEST_LOGGING
				impl.logger.Info("{} - {} {} HTTP/{}.{} ({})", addr.to_string(), stlify(curReq.method_string()), stlify(curReq.target()),
								 curReq.version() / 10, curReq.version() % 10, responseBytesWritten);
#else
				static_cast<void>(addr);
				static_cast<void>(responseBytesWritten);
#endif

				// Handle `Connection: close` semantics
				if(!curReq.keep_alive())
					Close();
				co_return;
			}

			// private:
			Impl& impl;
			Server::StreamType stream;
			Request::BeastRequest curReq {};
		};

		using RouteVariant = std::variant<Server::RouteHandler, Server::WebSocketRouteHandler>;

		template <class ProtocolEndpoint>
		Impl(asio::any_io_executor ioc, ProtocolEndpoint ep)
			: exec(ioc), ep(ep), acceptor(ioc) {}

		void On(beast::http::verb verb, std::string_view path, Server::RouteHandler handler) {
			handlerStorage.emplace_back(handler);
			char* errstr { nullptr };

			// We use the "data" user pointer to instead index into our handler storage.
			// It's messy and awful, but it does work!
			tree.insert_routel(detail::BeastToR3(verb), path.data(), path.length(), std::bit_cast<void*>(handlerStorage.size() - 1), &errstr);

			if(errstr) {
				// error inserting into tree
				spdlog::error("Error inserting route \"{}\" into tree: {}", path, errstr);
				free(errstr);
				return;
			}
		}

		void OnWebSocket(std::string_view path, Server::WebSocketRouteHandler handler) {
			handlerStorage.emplace_back(handler);
			char* errstr { nullptr };
			tree.insert_routel(detail::BeastToR3(beast::http::verb::get), path.data(), path.length(), std::bit_cast<void*>(handlerStorage.size() - 1),
							   &errstr);
			if(errstr) {
				// error inserting into tree
				spdlog::error("Error inserting route \"{}\" into tree: {}", path, errstr);
				free(errstr);
				return;
			}
		}

		// Call this after creating all required routes with On().
		bool CompileTree() {
			char* errstr { nullptr };
			tree.compile(&errstr);
			if(errstr) {
				spdlog::error("Error compiling route tree: {}", errstr);
				free(errstr);
				return false;
			}
			return true;
		}

		Awaitable<std::optional<Response>> Route(Request::BeastRequest& req, asio::ip::address srcAddress, Session& session) {
			auto const noSuchRouteError = [&]() -> beast::http::message_generator {
				beast::http::response<beast::http::string_body> resp { beast::http::status::bad_request, req.version() };
				SetCommonResponseFields(resp);
				resp.set(beast::http::field::content_type, "text/plain");
				resp.keep_alive(false);
				resp.body() = std::format("No such route \"{} {}\"", std::string_view { req.method_string().data(), req.method_string().length() },
										  std::string_view { req.target().data(), req.target().length() });
				resp.prepare_payload();
				return resp;
			};

			auto const internalServerError = [&]() -> beast::http::message_generator {
				beast::http::response<beast::http::string_body> resp { beast::http::status::internal_server_error, req.version() };
				SetCommonResponseFields(resp);
				resp.set(beast::http::field::content_type, "text/plain");
				resp.keep_alive(false);
				resp.body() = "HTTP/1.1 500 Internal Server Error";
				resp.prepare_payload();
				return resp;
			};

			auto const wsRequired = [&]() -> beast::http::message_generator {
				beast::http::response<beast::http::string_body> resp { beast::http::status::bad_request, req.version() };
				SetCommonResponseFields(resp);
				resp.set(beast::http::field::content_type, "text/plain");
				resp.keep_alive(false);
				resp.body() = "Invalid HTTP request to WebSockets endpoint";
				resp.prepare_payload();
				return resp;
			};

			auto url = burl::parse_origin_form(req.target());
			if(url.has_error()) {
				// If we were unable to parse the URL (somehow), then gracefully handle that
				co_return Response { internalServerError() };
			}

			auto path = url->path();

			r3::MatchEntry me { path.data(), static_cast<i32>(path.length()) };
			me.set_request_method(detail::BeastToR3(req.method()));

			auto route = tree.match_route(me);
			if(auto rp = route.get()) {
				// this is a mess but it's a mess which works :)
				auto handlerIndex = std::bit_cast<usize>(rp->data);
				auto& handler = handlerStorage[handlerIndex];

				auto routed_request = Request { req, url.value(), me };
				routed_request.src = srcAddress;

				// Dispatch to the given handler variant
				if(auto* httpHandler = std::get_if<Server::RouteHandler>(&handler); httpHandler) {
					co_return co_await (*httpHandler)(routed_request);
				} else if(auto* wsHandler = std::get_if<Server::WebSocketRouteHandler>(&handler); wsHandler) {
					if(!beast::websocket::is_upgrade(routed_request.Native())) {
						auto res = wsRequired();
						co_return Response { std::move(res) };
					}

					auto ws = std::make_shared<WebSocketClient>(std::move(session.stream), routed_request);

					if(!co_await ws->Handshake()) {
						co_return std::nullopt;
					}

					co_await (*wsHandler)(routed_request, std::move(ws));
					co_return std::nullopt;
				}
			} else {
				// TODO: maybe a catch-all handler at some point. for now this is fine enough

				// Send a bad request detailing that a route is not available for the given
				// URL path.
				co_return Response { noSuchRouteError() };
			}
			co_return std::nullopt;
		}

		Awaitable<void> Listener() {
			try {
				// Setup the acceptor
				acceptor.open(ep.protocol());
				acceptor.set_option(asio::socket_base::reuse_address(true));

				if(IsTcp(ep.protocol())) {
					// set SO_REUSEPORT using a custom type. This is flaky but we pin boost
					// so this will be ok I suppose
					using reuse_port = asio::detail::socket_option::boolean<SOL_SOCKET, SO_REUSEPORT>;
					acceptor.set_option(reuse_port(true));

					spdlog::info("Able to enable SO_NODELAY; doing so");
					acceptor.set_option(asio::ip::tcp::no_delay { true });
				}

				acceptor.bind(ep);
				acceptor.listen(asio::socket_base::max_listen_connections);

				listening = true;

				// Now do the thing..
				while(true) {
					auto socket = co_await acceptor.async_accept(asio::deferred);
					asio::co_spawn(acceptor.get_executor(), RunSession(StreamType { std::move(socket) }), asio::detached);
				}
			} catch(bsys::system_error& ec) {
				// Filter out "operation cancelled", because that's not really an error we need to know about.
				if(ec.code() != asio::error::operation_aborted)
					spdlog::error("Error in http::BasicServer::Listener(): {}", ec.what());
			}

			listening = false;
		}

		// TODO: Maybe we should actually store all sessions or something, and use shared_ptrs to refer to them
		// That way on server shutdown we can cleanly shut them all down

		/// Runs a single HTTP client session.
		Awaitable<void> RunSession(StreamType stream) {
			// std::shared_ptr<Session> session = std::make_shared<Session>(*this, std::move(stream));
			Session session { *this, std::move(stream) };
			co_await session.DoSession();
			co_return;
		}

		void Start() {
			if(!CompileTree()) {
				BASE_CHECK(false, "Route tree compilation failure, cannot start HTTP server");
			}

			asio::co_spawn(exec, Listener(), asio::detached);
		}

		void Stop() {
			bsys::error_code ec;
			acceptor.close(ec);
		}

		// Router tree.
		r3::Tree tree { 16 };

		std::vector<RouteVariant> handlerStorage;

		asio::any_io_executor exec;
		EndpointType ep;
		bool listening { false };

		asio::basic_socket_acceptor<GenericProtocol> acceptor;
	};

	Server::Server(asio::any_io_executor ioc, asio::ip::tcp::endpoint ep) {
		impl = std::make_unique<Impl>(ioc, ep);
	}

	Server::~Server() = default;

	bool Server::Listening() const {
		return impl->listening;
	}

	void Server::On(beast::http::verb verb, std::string_view path, RouteHandler handler) {
		impl->On(verb, path, handler);
	}

	void Server::GetWebSockets(std::string_view path, WebSocketRouteHandler wsRoute) {
		impl->OnWebSocket(path, wsRoute);
	}

	void Server::Start() {
		impl->Start();
	}

	void Server::Stop() {
		if(impl->listening)
			impl->Stop();
	}

} // namespace base::http