schema as a meta relation

3 files changed, 60 insertions, 2 deletions

diff --git a/lib/disk.ml b/lib/disk.ml
index 0629a9e..ea863a5 100644
--- a/lib/disk.ml
+++ b/lib/disk.ml
@@ -200,6 +200,7 @@ module Command = struct
     | OPEN
     | WRITE
     | READ
+    (* | CREATE_RELATION *)
   let command_kind_encoding =
     union [
       case ~title:"open" (Tag 0)
@@ -214,6 +215,10 @@ module Command = struct
         Data_encoding.empty
         (function READ -> Some () | _ -> None)
         (function () -> READ);
+      (* case ~title:"create_relation" (Tag 3) *)
+        (* Data_encoding.empty *)
+        (* (function CREATE_RELATION -> Some () | _ -> None) *)
+        (* (function () -> CREATE_RELATION); *)
       ]
   
   type t =
diff --git a/lib/relation.ml b/lib/relation.ml
index 5c8d1e0..ed644dd 100644
--- a/lib/relation.ml
+++ b/lib/relation.ml
@@ -1,5 +1,3 @@
-
-
 module Protocol = struct
   open Protocol_conv_xml
   open Sexplib0.Sexp_conv
diff --git a/lib/schema.ml b/lib/schema.ml
new file mode 100644
index 0000000..74ce720
--- /dev/null
+++ b/lib/schema.ml
@@ -0,0 +1,55 @@
+module Protocol = struct
+  open Data_encoding
+  type attribute =
+    { name: string;
+      attr_type: string }
+  type relation =
+    { name: string;
+      attributes: attribute list }
+  let attribute_encoding =
+    conv 
+      (fun {name; attr_type} -> (name, attr_type))
+      (fun (name, attr_type) -> {name; attr_type})
+      Data_encoding.(tup2 string string)
+  
+  let parse_attribute ~data =
+    let contract_encoding = Data_encoding.(tup2 string string) in
+    match Binary.of_bytes_opt contract_encoding data with
+    | Some (name, attr_type) -> Ok {name; attr_type}
+    | None -> Error "Failed to parse attribute"
+  
+  let relation_encoding =
+    conv 
+      (fun {name; attributes} -> (name, attributes))
+      (fun (name, attributes) -> {name; attributes})
+      Data_encoding.(tup2 string (list attribute_encoding))
+  
+  let parse_relation ~data =
+    let contract_encoding = Data_encoding.(tup2 string (list attribute_encoding)) in
+    match Binary.of_bytes_opt contract_encoding data with
+    | Some (name, attributes) -> Ok {name; attributes}
+    | None -> Error "Failed to parse relation"
+end
+
+let test_schema_write_and_retrieve() =
+  let open Disk in
+  let open Data_encoding in
+  let stream: Executor.history = [{state = Executor._EMPTY_SHA_HASH_; files = Executor.StringMap.empty}] in
+  let locations: Executor.locations = Executor.StringMap.empty in
+  let open Extensions.Result in
+  let+ user_relation =
+    let relation: Protocol.relation = { name = "user"; attributes = [{name = "first-name"; attr_type = "string"}; {name = "last-name"; attr_type = "string"}] } in
+    Result.map_error (fun _ -> "Failed to serialize relation to binary format.")
+        @@ Binary.to_bytes Protocol.relation_encoding relation
+  in
+  let command_write: Command.t =
+    {kind = Command.WRITE; timestamp = 10.0; hash = ""; content = Bytes.to_string user_relation; filename = "user"; references = []} in
+  let+ ((stream, locations), Command.ComputedHash handle) = Command.commit_and_perform stream locations command_write in
+  let command_read: Command.t =
+    {kind = Command.READ; timestamp = 10.0; hash = handle; content = ""; filename = "user"; references = []} in
+  let+ ((stream, locations), Command.Read content) = Command.commit_and_perform stream locations command_read in
+  let+ user_relation =
+    Result.map_error (fun _ -> "Failed to deserialize relation from binary format.")
+        @@ Binary.of_bytes Protocol.relation_encoding (Bytes.concat Bytes.empty content) in
+  Ok (stream, locations, user_relation)
+    [@@warning "-8"] (* Suppress pattern match incomplete warnings *)