Infrastructure for incoming MIDI messages ready

Makefile

@@ -6,7 +6,7 @@ DEBUG_FLAGS=-O0 -ggdb -fsanitize=undefined
 CXX=g++
 
 LDFLAGS=-L./lib/midi/
-LDLIBS=-lmidi-alsa -lasound -lreadline
+LDLIBS=-lmidi-alsa -lasound -lpthread
 
 Obj=                 \
 		context.o        \

src/interpreter.cc

@@ -5,6 +5,46 @@
 #include <random>
 #include <thread>
 
+struct Interpreter::Incoming_Midi_Callbacks
+{
+	Value note_on{};
+	Value note_off{};
+
+	Incoming_Midi_Callbacks() = default;
+
+	Incoming_Midi_Callbacks(Incoming_Midi_Callbacks &&) = delete;
+	Incoming_Midi_Callbacks(Incoming_Midi_Callbacks const&) = delete;
+
+	Incoming_Midi_Callbacks& operator=(Incoming_Midi_Callbacks &&) = delete;
+	Incoming_Midi_Callbacks& operator=(Incoming_Midi_Callbacks const&) = delete;
+
+	void add_callbacks(midi::Connection &midi, Interpreter &interpreter)
+	{
+		register_callback(midi.note_on_callback, note_on, interpreter);
+		register_callback(midi.note_off_callback, note_off, interpreter);
+	}
+
+	template<typename ...T>
+	void register_callback(std::function<void(T...)> &target, Value &callback, Interpreter &i)
+	{
+		target = [interpreter = &i, callback = &callback](T ...source_args)
+		{
+			std::cout << "hello from callback!" << std::endl;
+			if (callback->type != Value::Type::Nil) {
+				auto result = (*callback)(*interpreter, { Value::from(Number(source_args))...  });
+				// We discard this since callback is running in another thread.
+				(void) result;
+			}
+		};
+	}
+};
+
+void Interpreter::register_callbacks()
+{
+	assert(callbacks != nullptr, "Interpreter constructor should initialize this field");
+	callbacks->add_callbacks(*midi_connection, *this);
+}
+
 /// Intrinsic implementation primitive providing a short way to check if arguments match required type signature
 static inline bool typecheck(std::vector<Value> const& args, auto const& ...expected_types)
 {
@@ -340,6 +380,9 @@ Interpreter::Interpreter()
 		assert(!bool(Env::global), "Only one instance of interpreter can be at one time");
 		env = Env::global = Env::make();
 	}
+	{ // MIDI input callbacks initialization
+		callbacks = std::make_unique<Interpreter::Incoming_Midi_Callbacks>();
+	}
 	{ // Global default functions initialization
 		auto &global = *Env::global;
 

src/main.cc

@@ -4,6 +4,7 @@
 #include <fstream>
 #include <iostream>
 #include <span>
+#include <thread>
 
 #include <musique.hh>
 #include <midi.hh>
@@ -79,10 +80,12 @@ struct Runner
 
 	midi::ALSA alsa;
 	Interpreter interpreter;
+	std::thread midi_input_event_loop;
 
 	/// Setup interpreter and midi connection with given port
 	Runner(std::string input_port, std::string output_port)
 		: alsa("musique")
+		, interpreter{}
 	{
 		assert(the == nullptr, "Only one instance of runner is supported");
 		the = this;
@@ -92,8 +95,18 @@ struct Runner
 			alsa.init_sequencer();
 			interpreter.midi_connection = &alsa;
 		}
-		if (output_port.size()) alsa.connect_output(output_port);
-		if (input_port.size())  alsa.connect_input(input_port);
+		if (output_port.size()) {
+			std::cout << "Connected MIDI output to port " << output_port << ". Ready to play!" << std::endl;
+			alsa.connect_output(output_port);
+		}
+		if (input_port.size()) {
+			std::cout << "Connected MIDI input to port " << input_port << ". Ready for incoming messages!" << std::endl;
+			alsa.connect_input(input_port);
+		}
+		if (alsa_go) {
+			interpreter.register_callbacks();
+			midi_input_event_loop = std::thread([this] { handle_midi_event_loop(); });
+		}
 
 		Env::global->force_define("say", +[](Interpreter&, std::vector<Value> args) -> Result<Value> {
 			for (auto it = args.begin(); it != args.end(); ++it) {
@@ -111,6 +124,11 @@ struct Runner
 	Runner& operator=(Runner const&) = delete;
 	Runner& operator=(Runner &&) = delete;
 
+	void handle_midi_event_loop()
+	{
+		alsa.input_event_loop();
+	}
+
 	/// Run given source
 	Result<void> run(std::string_view source, std::string_view filename, bool output = false)
 	{

src/musique.hh

@@ -920,6 +920,10 @@ struct Interpreter
 	/// There is always at least one context
 	std::vector<Context> context_stack;
 
+	struct Incoming_Midi_Callbacks;
+	std::unique_ptr<Incoming_Midi_Callbacks> callbacks;
+	void register_callbacks();
+
 	Interpreter();
 	~Interpreter();
 	Interpreter(Interpreter const&) = delete;