beats-server/websockets.h

#include <string>
#include <memory>
#include <functional>
#include <stdexcept>

#include <syslog.h>
#include <getopt.h>
#include <signal.h>
#include <string.h>

#include <lib/libwebsockets.h>

namespace websockets {
	struct Log {
		Log(std::string const & name, int syslog_options, int debug_level){
			setlogmask(LOG_UPTO (LOG_DEBUG));
			openlog(name.c_str(), syslog_options, LOG_DAEMON);
			lws_set_log_level(debug_level, lwsl_emit_syslog);
		}

		#define log_function(nice_name, lwsl_name)\
		template <typename... T>\
		void nice_name(std::string const & format, T... args){\
			lwsl_name(format.c_str(), args...);\
		}

		log_function(notice, lwsl_notice)
		log_function(error, lwsl_err)
		log_function(warning, lwsl_warn)
		log_function(debug, lwsl_debug)

		#undef log_function

		~Log(){
			closelog();
		}
	};

	struct Context {
		std::unique_ptr<libwebsocket_context, decltype(libwebsocket_context_destroy)*> context;

		Context(lws_context_creation_info& info)
		: context(libwebsocket_create_context(&info), &libwebsocket_context_destroy)
		{
			if(context == nullptr){
				lwsl_err("libwebsocket init failed\n");
				throw std::runtime_error("libwebsocket init failed");
			}
		}

		libwebsocket_context const * get_raw() const {
			return context.get();
		}

		libwebsocket_context * get_raw() {
			return context.get();
		}
	};

	template <typename T>
	struct Protocol	{
		typedef T user_type;
		int callback(libwebsocket_context *context, libwebsocket *wsi, libwebsocket_callback_reasons reason, void *user, void *in, size_t len){
			return call(*context, *wsi, reason, *static_cast<T*>(user), in, len);
		}
		virtual int call(libwebsocket_context& context, libwebsocket& wsi, libwebsocket_callback_reasons reason, T& user, void *in, size_t len){
			return 0;
		};
	};

	template <typename T>
	struct TestProtocol : public Protocol<T> {
		std::function<int(T&)> establish_func;
		std::function<int(T&)> close_func;
		std::function<std::string(T&)> write_func;
		std::function<int(T&, std::string)> receive_func;

		TestProtocol(decltype(establish_func) establish_func, decltype(close_func) close_func, decltype(write_func) write_func, decltype(receive_func) receive_func)
		: establish_func(establish_func)
		, close_func(close_func)
		, write_func(write_func)
		, receive_func(receive_func)
		{}

		virtual int call(libwebsocket_context& context, libwebsocket& wsi, libwebsocket_callback_reasons reason, T& user, void *in, size_t len){
			switch (reason) {
				case LWS_CALLBACK_ESTABLISHED:
					establish_func(user);
					break;
				case LWS_CALLBACK_CLOSED:
					close_func(user);
					break;
				case LWS_CALLBACK_SERVER_WRITEABLE:{
					std::string string_to_send = write_func(user);
					// we need the extra bytes padding on both sides :(
					unsigned char * buf = new unsigned char [LWS_SEND_BUFFER_PRE_PADDING + string_to_send.size() + LWS_SEND_BUFFER_POST_PADDING];
					memcpy(&buf[LWS_SEND_BUFFER_PRE_PADDING], string_to_send.c_str(), string_to_send.size());
					int n = libwebsocket_write(&wsi, &buf[LWS_SEND_BUFFER_PRE_PADDING], string_to_send.size(), LWS_WRITE_TEXT);
					if (n < 0) {
						lwsl_err("ERROR %d writing to socket, hanging up\n", n);
						return 1;
					}
					if (n < string_to_send.size()) {
						lwsl_err("Partial write\n");
						return -1;
					}
					break;
				}
				case LWS_CALLBACK_RECEIVE:
					receive_func(user, std::string((char*)in, len));
					libwebsocket_callback_on_writable(&context, &wsi);
					break;
				default:
					break;
			}
			return 0;
		}
	};

#define WSprotocol_callback(protocol)\
[](libwebsocket_context *context, libwebsocket *wsi, libwebsocket_callback_reasons reason, void *user, void *in, size_t len)\
{return protocol.callback(context, wsi, reason, user, in, len);}

#define WSstandard_protocol(name, protocol)\
{ name, WSprotocol_callback(protocol), sizeof(decltype(protocol)::user_type) }

	int default_main(int argc, char **argv, libwebsocket_protocols* protocols);

} // namespace websockets