Introduce Multigroups (#65)

3 files changed, 90 insertions, 77 deletions

diff --git a/lib/dcl/ast.ml b/lib/dcl/ast.ml
index 0b6107f..a55ec19 100644
--- a/lib/dcl/ast.ml
+++ b/lib/dcl/ast.ml
@@ -10,4 +10,6 @@ type statement =
   | GetBranchTip of string
   | UpdateBranchTip of { name : string; hash : string }
   | Merge of { left : string; right : string; strategy : merge_strategy }
+  | Use of string
+  | CreateMultigroup of string
 [@@deriving sexp]
diff --git a/lib/dcl/executor.ml b/lib/dcl/executor.ml
index a651067..b83f629 100644
--- a/lib/dcl/executor.ml
+++ b/lib/dcl/executor.ml
@@ -4,24 +4,24 @@ module Make (Storage : Management.Physical.S with type error = string) = struct
   module MergeOps = Management.Merge.Make (Storage) (Ops)
 
   type error =
-    | ParseError       of string
-    | BranchError      of Error.t
-    | BranchNotFound   of string
+    | ParseError of string
+    | BranchError of Error.t
+    | BranchNotFound of string
     | NoDatabaseAtHash of Conventions.Hash.t
-    | StorageError     of string
-    | MergeError       of Error.t
-    | Conflict         of string
+    | StorageError of string
+    | MergeError of Error.t
+    | Conflict of string
 
   let sexp_of_error e =
     let open Sexplib.Sexp in
     match e with
-    | ParseError        s -> List [Atom "parse-error";  Atom s]
-    | BranchError       s -> List [Atom "branch-error"; Error.sexp_of_error s]
-    | BranchNotFound    s -> List [Atom "branch-not-found"; Atom s]
-    | NoDatabaseAtHash  s -> List [Atom "no-database-at-hash"; Atom s]
-    | StorageError      s -> List [Atom "storage-error"; Atom s]
-    | MergeError        s -> List [Atom "merge-error";  Error.sexp_of_error s]
-    | Conflict          s -> List [Atom "conflict"; Atom s]
+    | ParseError s -> List [ Atom "parse-error"; Atom s ]
+    | BranchError s -> List [ Atom "branch-error"; Error.sexp_of_error s ]
+    | BranchNotFound s -> List [ Atom "branch-not-found"; Atom s ]
+    | NoDatabaseAtHash s -> List [ Atom "no-database-at-hash"; Atom s ]
+    | StorageError s -> List [ Atom "storage-error"; Atom s ]
+    | MergeError s -> List [ Atom "merge-error"; Error.sexp_of_error s ]
+    | Conflict s -> List [ Atom "conflict"; Atom s ]
 
   let convert_strategy : Ast.merge_strategy -> Management.Merge.strategy =
     function
@@ -29,71 +29,80 @@ module Make (Storage : Management.Physical.S with type error = string) = struct
     | Ast.PreferRight -> Management.Merge.PreferRight
     | Ast.RevertToAncestor -> Management.Merge.RevertToAncestor
 
+  type exec_result =
+    | DbResult of Management.Database.t * string
+    | Switch of string
+    | NewMultigroup of string
+
   let execute (storage : Storage.t) (db : Management.Database.t)
-      (stmt : Ast.statement) : (Management.Database.t * string, error) result =
+      (stmt : Ast.statement) : (exec_result, error) result =
     match stmt with
-    | Ast.CreateBranch { name; hash } ->
-      let tip = match hash with
-        | Some h -> h
-        | None   -> db.Management.Database.hash
-      in
-      (match Branch.create storage ~name ~tip with
-       | Error e -> Error (StorageError e)
-       | Ok ()   -> Ok (db, "Branch " ^ name ^ " created"))
-
-    | Ast.Checkout branch_name ->
-      (match Branch.get_tip storage branch_name with
-       | Error e       -> Error (StorageError e)
-       | Ok None       -> Error (BranchNotFound branch_name)
-       | Ok (Some tip) ->
-         (match Branch.checkout storage branch_name with
-          | Error e -> Error (StorageError e)
-          | Ok ()   ->
-            (match Ops.load_database storage tip with
-             | Error e -> Error (BranchError e)
-             | Ok None -> Error (NoDatabaseAtHash tip)
-             | Ok (Some loaded_db) ->
-               Ok (loaded_db, "HEAD:" ^ branch_name))))
-
-    | Ast.GetHead ->
-      (match Branch.get_head storage with
-       | Error e        -> Error (StorageError e)
-       | Ok None        -> Ok (db, "HEAD is unset")
-       | Ok (Some name) -> Ok (db, "HEAD:" ^ name))
-
-    | Ast.GetBranchTip name ->
-      (match Branch.get_tip storage name with
-       | Error e        -> Error (StorageError e)
-       | Ok None        -> Error (BranchNotFound name)
-       | Ok (Some hash) -> Ok (db, "branch:" ^ name ^ "=" ^ hash))
-
-    | Ast.UpdateBranchTip { name; hash } ->
-      (match Branch.update_tip storage ~name ~tip:hash with
-       | Error e -> Error (StorageError e)
-       | Ok ()   -> Ok (db, "Branch " ^ name ^ " updated"))
-
-    | Ast.Merge { left; right; strategy } ->
-      (match Branch.get_tip storage left, Branch.get_tip storage right with
-       | Error e, _ | _, Error e -> Error (StorageError e)
-       | Ok None, _  -> Error (BranchNotFound left)
-       | _, Ok None  -> Error (BranchNotFound right)
-       | Ok (Some left_tip), Ok (Some right_tip) ->
-         let strat = convert_strategy strategy in
-         (match MergeOps.merge ~storage ~strategy:strat ~left_tip ~right_tip with
-          | Error e -> Error (MergeError e)
-          | Ok (Management.Merge.Failed conflicts) ->
-            let msgs = List.map (function
-              | Management.Merge.TupleConflict    { relation; hash } ->
-                "tuple conflict in " ^ relation ^ " (" ^ hash ^ ")"
-              | Management.Merge.SchemaConflict   r -> "schema conflict in " ^ r
-              | Management.Merge.ConstraintConflict r -> "constraint conflict in " ^ r
-            ) conflicts in
-            Error (Conflict ("Merge failed: " ^ String.concat "; " msgs))
-          | Ok (Management.Merge.Clean merged_db) ->
-            let _ = Branch.update_tip storage ~name:left
-                      ~tip:merged_db.Management.Database.hash in
-            Ok (merged_db,
-                "Merged:" ^ right ^ "→" ^ left)))
+    | Ast.CreateBranch { name; hash } -> (
+        let tip =
+          match hash with Some h -> h | None -> db.Management.Database.hash
+        in
+        match Branch.create storage ~name ~tip with
+        | Error e -> Error (StorageError e)
+        | Ok () -> Ok (DbResult (db, "Branch " ^ name ^ " created")))
+    | Ast.Checkout branch_name -> (
+        match Branch.get_tip storage branch_name with
+        | Error e -> Error (StorageError e)
+        | Ok None -> Error (BranchNotFound branch_name)
+        | Ok (Some tip) -> (
+            match Branch.checkout storage branch_name with
+            | Error e -> Error (StorageError e)
+            | Ok () -> (
+                match Ops.load_database storage tip with
+                | Error e -> Error (BranchError e)
+                | Ok None -> Error (NoDatabaseAtHash tip)
+                | Ok (Some loaded_db) ->
+                    Ok (DbResult (loaded_db, "HEAD:" ^ branch_name)))))
+    | Ast.GetHead -> (
+        match Branch.get_head storage with
+        | Error e -> Error (StorageError e)
+        | Ok None -> Ok (DbResult (db, "HEAD is unset"))
+        | Ok (Some name) -> Ok (DbResult (db, "HEAD:" ^ name)))
+    | Ast.GetBranchTip name -> (
+        match Branch.get_tip storage name with
+        | Error e -> Error (StorageError e)
+        | Ok None -> Error (BranchNotFound name)
+        | Ok (Some hash) -> Ok (DbResult (db, "branch:" ^ name ^ "=" ^ hash)))
+    | Ast.UpdateBranchTip { name; hash } -> (
+        match Branch.update_tip storage ~name ~tip:hash with
+        | Error e -> Error (StorageError e)
+        | Ok () -> Ok (DbResult (db, "Branch " ^ name ^ " updated")))
+    | Ast.Merge { left; right; strategy } -> (
+        match (Branch.get_tip storage left, Branch.get_tip storage right) with
+        | Error e, _ | _, Error e -> Error (StorageError e)
+        | Ok None, _ -> Error (BranchNotFound left)
+        | _, Ok None -> Error (BranchNotFound right)
+        | Ok (Some left_tip), Ok (Some right_tip) -> (
+            let strat = convert_strategy strategy in
+            match
+              MergeOps.merge ~storage ~strategy:strat ~left_tip ~right_tip
+            with
+            | Error e -> Error (MergeError e)
+            | Ok (Management.Merge.Failed conflicts) ->
+                let msgs =
+                  List.map
+                    (function
+                      | Management.Merge.TupleConflict { relation; hash } ->
+                          "tuple conflict in " ^ relation ^ " (" ^ hash ^ ")"
+                      | Management.Merge.SchemaConflict r ->
+                          "schema conflict in " ^ r
+                      | Management.Merge.ConstraintConflict r ->
+                          "constraint conflict in " ^ r)
+                    conflicts
+                in
+                Error (Conflict ("Merge failed: " ^ String.concat "; " msgs))
+            | Ok (Management.Merge.Clean merged_db) ->
+                let _ =
+                  Branch.update_tip storage ~name:left
+                    ~tip:merged_db.Management.Database.hash
+                in
+                Ok (DbResult (merged_db, "Merged:" ^ right ^ "→" ^ left))))
+    | Ast.Use multigroup -> Ok (Switch multigroup)
+    | Ast.CreateMultigroup name -> Ok (NewMultigroup name)
 end
 
 module Memory = Make (Management.Physical.Memory)
diff --git a/lib/dcl/sublanguage.ml b/lib/dcl/sublanguage.ml
index eab5ecb..7af0703 100644
--- a/lib/dcl/sublanguage.ml
+++ b/lib/dcl/sublanguage.ml
@@ -16,7 +16,9 @@ module Make (Storage : Management.Physical.S with type error = string) = struct
 
   let execute storage db ast =
     match Exec.execute storage db ast with
-    | Ok (db, msg) -> Ok (Sublanguage_types.Transition (db, msg))
+    | Ok (Exec.DbResult (db, msg)) -> Ok (Sublanguage_types.Transition (db, msg))
+    | Ok (Exec.Switch multigroup) -> Ok (Sublanguage_types.SessionSwitch multigroup)
+    | Ok (Exec.NewMultigroup name) -> Ok (Sublanguage_types.CreateMultigroup name)
     | Error e -> Error e
 
   let sexp_of_error = Exec.sexp_of_error