call info encoder

crates/nu-plugin/schema/value.capnp

@@ -1,13 +1,29 @@
 @0xb299d30dc02d72bc;
 
+# Generic structs used as helpers for the encoding
+struct Option(Value) {
+	union {
+		none @0 :Void;
+		some @1 :Value;
+	}
+}
+
+struct Map(Key, Value) {
+  struct Entry {
+    key @0 :Key;
+    value @1 :Value;
+  }
+  entries @0 :List(Entry);
+}
+
+struct Span {
+	start @0 :UInt64;
+	end @1 :UInt64;
+}
+
 struct Value {
 	span @0: Span;
 
-	struct Span {
-		start @0 :UInt64;
-		end @1 :UInt64;
-	}
-
 	union {
 		void @1 :Void;
 		bool @2 :Bool;
@@ -17,3 +33,25 @@ struct Value {
 		list @6 :List(Value);
 	}
 }
+
+struct Expression {
+	union {
+		garbage @0 :Void;
+		bool @1 :Bool;
+		int @2 :Int64;
+		float @3 :Float64;
+		string @4 :Text;
+		list @5 :List(Expression);
+	}
+}
+
+struct Call {
+	head @0: Span;
+	positional @1 :List(Expression);
+	named @2 :Map(Text, Option(Expression));
+}
+
+struct CallInfo {
+	call @0: Call;
+	input @1: Value;
+}