RNT interface

Co-authored-by: Estevan Castilho <tevo@riajuu.net>

1 files changed, 28 insertions, 10 deletions

diff --git a/lib/storable.ml b/lib/storable.ml
index 5d87846..5527044 100644
--- a/lib/storable.ml
+++ b/lib/storable.ml
@@ -63,11 +63,17 @@ module Tuple = struct
 end
 
 module Relation = struct
-  type t = { name : string; schema : (string * string) list }
+  type t = {
+    name : string;
+    schema : (string * string) list;
+    (** Hex Merkle root of the relation's tuple set.  Empty string = empty relation. *)
+    tree_pointer : string;
+  }
 
   let to_bytes relation =
     Wire.encode
-      ([ ("type", "relation"); ("name", relation.name); ("kind", "stored") ]
+      ([ ("type", "relation"); ("name", relation.name); ("kind", "stored");
+         ("tree_pointer", relation.tree_pointer) ]
        @ List.map
            (fun (name, domain) -> ("attribute", name ^ ":" ^ domain))
            relation.schema)
@@ -76,31 +82,43 @@ module Relation = struct
     let fields = Wire.fields bytes in
     Wire.require_type "relation" fields;
     {
-      name = Wire.required "name" fields;
-      schema = List.map Wire.attribute (Wire.values "attribute" fields);
+      name         = Wire.required "name" fields;
+      schema       = List.map Wire.attribute (Wire.values "attribute" fields);
+      tree_pointer = Option.value (List.assoc_opt "tree_pointer" fields) ~default:"";
     }
 end
 
 module Multigroup = struct
   type t = { name : string; relations : Relation.t list }
 
+  (* Wire format: "name|attr1:dom1,attr2:dom2|<merkle_root>"
+     The third segment is the Merkle root hex; empty string = empty relation.
+     A fourth segment for constraints is reserved but not yet implemented.
+     TODO: add constraints serialisation once a canonical sexp representation
+     is agreed upon (two syntactically distinct bodies may be semantically
+     equivalent — the round-trip must account for that). *)
   let relation_value relation =
     let attrs =
       relation.Relation.schema
       |> List.map (fun (name, domain) -> name ^ ":" ^ domain)
       |> String.concat ","
     in
-    relation.name ^ "|" ^ attrs
+    relation.name ^ "|" ^ attrs ^ "|" ^ relation.tree_pointer
 
   let parse_relation value =
     match Wire.split_once '|' value with
-    | None -> { Relation.name = value; schema = [] }
-    | Some (name, attrs) ->
+    | None -> { Relation.name = value; schema = []; tree_pointer = "" }
+    | Some (name, rest) ->
+        let attrs_str, tree_pointer =
+          match Wire.split_once '|' rest with
+          | None         -> (rest, "")
+          | Some (a, tp) -> (a, tp)
+        in
         let schema =
-          if attrs = "" then []
-          else attrs |> String.split_on_char ',' |> List.map Wire.attribute
+          if attrs_str = "" then []
+          else attrs_str |> String.split_on_char ',' |> List.map Wire.attribute
         in
-        { Relation.name; schema }
+        { Relation.name; schema; tree_pointer }
 
   let to_bytes multigroup =
     Wire.encode