The branch manager should persist changes to the root

3 files changed, 14 insertions, 2 deletions

diff --git a/lib/concepts/Hash.ml b/lib/concepts/Hash.ml
index ae0a178..b2ed4b2 100644
--- a/lib/concepts/Hash.ml
+++ b/lib/concepts/Hash.ml
@@ -11,6 +11,10 @@ let hash_of_bytes bytes = Digestif.SHA256.digest_bytes bytes
 
 let hash_of_blob blob = Blob.bytes_of_blob blob |> Digestif.SHA256.digest_bytes
 
+let bytes_of_hash (h : hash) = Bytes.of_string (Digestif.SHA256.to_raw_string h)
+
+let blob_of_hash h = bytes_of_hash h |> Blob.blob_of_bytes
+
 let to_raw_string hash = Digestif.SHA256.to_raw_string hash
 
 let of_raw_string str = Digestif.SHA256.of_raw_string str
@@ -18,7 +22,6 @@ let of_raw_string str = Digestif.SHA256.of_raw_string str
 let to_hum_string hash = Digestif.SHA256.to_hex hash
 
 let hash_equals = Digestif.SHA256.equal
-let bytes_of_hash (h : hash) = Bytes.of_string (Digestif.SHA256.to_raw_string h)
 
 let power_of_two p =
   let b = Bytes.make 32 '\x00' in
diff --git a/lib/concepts/Hash.mli b/lib/concepts/Hash.mli
index b3ae2dc..0e71fda 100644
--- a/lib/concepts/Hash.mli
+++ b/lib/concepts/Hash.mli
@@ -28,5 +28,8 @@ val hash_equals : hash -> hash -> bool
 (** given a hash, return a `bytes` representation of it *)
 val bytes_of_hash : hash -> bytes
 
+(** given a hash, return a `blob` representation of it *)
+val blob_of_hash : hash -> Blob.t
+
 (** pick one every 1/2^n hashes *)
 val pick : int -> hash -> bool
diff --git a/lib/kernel/BranchManager.ml b/lib/kernel/BranchManager.ml
index a698a87..bdc461e 100644
--- a/lib/kernel/BranchManager.ml
+++ b/lib/kernel/BranchManager.ml
@@ -26,6 +26,10 @@ module Make (S : Abstract.Storage.STORAGE) = struct
     let label = Option.map Concepts.Hash.hash_of_blob label in
     Ok label
 
+  let persist_root tx label addr =
+    let data = Concepts.Hash.blob_of_hash addr in
+    S.put tx (S.Label label) data
+
   class manager storage label head = object (self)
     inherit Lifecycle.null
 
@@ -46,6 +50,7 @@ module Make (S : Abstract.Storage.STORAGE) = struct
                             |> fmap (Option.to_result ~none:(Error.no_such_branch branch_name)) in
               if branch = reference then
                 let* new_head = M.insert tx label new_branch head in
+                let* _ = persist_root tx label (M.hash_of new_head) in
                 Ok new_head
               else
                 Error (Error.branch_head_mismatch branch_name reference branch)))
@@ -63,7 +68,8 @@ module Make (S : Abstract.Storage.STORAGE) = struct
     SI.with_transaction storage (fun tx ->
         let* addr = root_for tx label in
         match addr with
-        | None -> failwith "TODO"
+        | None ->
+           Ok (new manager storage label M.empty |> Protocols.Handle.make)
         | Some addr ->
            let* head = M.find tx addr in
            let* head = Option.to_result ~none:(Error.invalid_root addr) head in