Early text-based snapshot system

CHANGELOG.md

@@ -13,6 +13,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - `<note><octave>` notation like `c4` that mimics [scientific notation](https://en.wikipedia.org/wiki/Scientific_pitch_notation)
 - operator pretty printing while printing values
 - macros: builtin functions that takes AST and produces value
+- early text-based snapshot system available via `:snap` command inside interactive session
 
 ### Changed
 

musique/interpreter/interpreter.cc

@@ -277,3 +277,132 @@ std::optional<Error> ensure_midi_connection_available(Interpreter &i, std::strin
 	}
 	return {};
 }
+
+static void snapshot(std::ostream& out, Note const& note) {
+	if (note.length) {
+		out << "(" << note << ")";
+	} else {
+		out << note;
+	}
+}
+
+static void snapshot(std::ostream &out, Ast const& ast) {
+	switch (ast.type) {
+	break; case Ast::Type::Sequence:
+	{
+		for (auto const& a : ast.arguments) {
+			snapshot(out, a);
+			out << ", ";
+		}
+	}
+	break; case Ast::Type::Block:
+		ensure(ast.arguments.size() == 1, "Block can contain only one node which contains its body");
+		out << "(";
+		snapshot(out, ast.arguments.front());
+		out << ")";
+
+	break; case Ast::Type::Lambda:
+		out << "(";
+		for (auto i = 0u; i+1 < ast.arguments.size(); ++i) {
+			ensure(ast.arguments[i].type == Ast::Type::Literal, "Lambda arguments should be an identifiers");
+			out << ast.arguments[i].token.source << " ";
+		}
+		out << "|";
+		snapshot(out, ast.arguments.back());
+		out << ")";
+
+	break; case Ast::Type::Variable_Declaration:
+		ensure(ast.arguments.size() == 2, "Variable declaration snapshots only support single lhs variables");
+		ensure(ast.arguments.front().type == Ast::Type::Literal, "Expected first value to be an identifier");
+		out << ast.arguments[0].token.source << " := ";
+		return snapshot(out, ast.arguments.back());
+
+	break; case Ast::Type::Literal:
+		out << ast.token.source;
+
+	break; case Ast::Type::Binary:
+		out << "(";
+		snapshot(out, ast.arguments[0]);
+		out << ") ";
+		out << ast.token.source;
+		out << " (";
+		snapshot(out, ast.arguments[1]);
+		out << ")";
+
+	break; case Ast::Type::Call:
+		out << "(";
+		for (auto const& a : ast.arguments) {
+			out << "(";
+			snapshot(out, a);
+			out << ") ";
+		}
+		out << ")";
+	}
+}
+
+static void snapshot(std::ostream& out, Value const& value) {
+	std::visit(Overloaded{
+		[&](Nil) { out << "nil"; },
+		[&](Bool const& b) {
+			out << (b ? "true" : "false");
+		},
+		[&](Number const& n) {
+			out << "(" << n.num << "/" << n.den << ")";
+		},
+		[&](Array const& array) {
+			out << "(flat (";
+			for (auto const& nested : array.elements) {
+				snapshot(out, nested);
+				out << ", ";
+			}
+			out << "))";
+		},
+		[&](Chord const& chord) {
+			if (chord.notes.size() == 1) {
+				auto note = chord.notes.front();
+				snapshot(out, note);
+			} else {
+				out << "(chord ";
+				for (auto const &note : chord.notes) {
+					snapshot(out, note);
+					out << " ";
+				}
+				out << ")";
+			}
+		},
+		[&](Symbol const& symbol) {
+			out << "'" << symbol;
+		},
+		[&](Block const& block) {
+			out << "(";
+			for (auto const& param : block.parameters) {
+				out << param << ' ';
+			}
+			out << "| ";
+			snapshot(out, block.body);
+			out << ")";
+		},
+		[](Intrinsic const&) { unreachable(); },
+		[](Macro const&) { unreachable(); }
+	}, value.data);
+}
+
+void Interpreter::snapshot(std::ostream& out)
+{
+	auto const& ctx = context_stack.back();
+	out << ", oct " << int(ctx.octave) << '\n';
+	out << ", len (" << ctx.length.num << "/" << ctx.length.den << ")\n";
+	out << ", bpm " << ctx.bpm << '\n';
+
+	for (auto current = env.get(); current; current = current->parent.get()) {
+		for (auto const& [name, value] : current->variables) {
+			if (std::holds_alternative<Intrinsic>(value.data) || std::holds_alternative<Macro>(value.data)) {
+				continue;
+			}
+			out << ", " << name << " := ";
+			::snapshot(out, value);
+			out << '\n';
+		}
+	}
+	out << std::flush;
+}

musique/interpreter/interpreter.hh

@@ -51,6 +51,9 @@ struct Interpreter
 	///
 	/// Invoked during construction
 	void register_builtin_operators();
+
+	/// Dumps snapshot of interpreter into stream
+	void snapshot(std::ostream& out);
 };
 
 std::optional<Error> ensure_midi_connection_available(Interpreter&, std::string_view operation_name);

musique/main.cc

@@ -314,6 +314,18 @@ static Result<bool> handle_repl_session_commands(std::string_view input, Runner
 				return runner.run(eternal_sources.back(), path);
 			}
 		},
+		Command {
+			"snap",
+			+[](Runner &runner, std::optional<std::string_view> arg) -> std::optional<Error> {
+				std::ostream *out = &std::cout;
+				std::fstream file;
+				if (arg.has_value() && arg->size()) {
+					file.open(std::string(*arg));
+				}
+				runner.interpreter.snapshot(*out);
+				return std::nullopt;
+			}
+		},
 	};
 
 	if (input.starts_with('!')) {