From c5bc3a4992b4968780c286a084ad7c02b2b58f1e Mon Sep 17 00:00:00 2001
From: Marcos Magueta <maguetamarcos@gmail.com>
Date: Fri, 3 Apr 2026 16:04:05 -0300
Subject: Polarity walker, constraint and manipulation refactor with batteries

---
 lib/management/diff.ml | 82 ++++++++++++++++++++++++++++----------------------
 1 file changed, 46 insertions(+), 36 deletions(-)

(limited to 'lib/management/diff.ml')

diff --git a/lib/management/diff.ml b/lib/management/diff.ml
index 865c757..8fca0af 100644
--- a/lib/management/diff.ml
+++ b/lib/management/diff.ml
@@ -1,24 +1,24 @@
-(** Structural delta between two Database.t states.
-    Computes what changed from ancestor → target at the relation level. *)
+(** Structural delta between two Database.t states. Computes what changed from
+    ancestor -> target at the relation level. *)
 
 type relation_diff =
-  | RelationAdded   of Relation.t
+  | RelationAdded of Relation.t
   | RelationRemoved of string
   | RelationModified of {
-      name           : string;
-      added_tuples   : Conventions.Hash.t list;
+      name : string;
+      added_tuples : Conventions.Hash.t list;
       removed_tuples : Conventions.Hash.t list;
       schema_changed : bool;
     }
 
 type t = {
-  ancestor       : Conventions.Hash.t;
-  left           : Conventions.Hash.t;
-  right          : Conventions.Hash.t;
+  ancestor : Conventions.Hash.t;
+  left : Conventions.Hash.t;
+  right : Conventions.Hash.t;
   relation_diffs : relation_diff list;
 }
 
-module StringSet = Set.Make(String)
+module StringSet = Set.Make (String)
 
 let relation_keys rel =
   match rel.Relation.tree with
@@ -30,31 +30,41 @@ let diff ~ancestor ~(target : Database.t) =
   let ancestor_names =
     Database.get_relation_names ancestor |> StringSet.of_list
   in
-  let target_names =
-    Database.get_relation_names target |> StringSet.of_list
-  in
+  let target_names = Database.get_relation_names target |> StringSet.of_list in
   let all_names = StringSet.union ancestor_names target_names in
-  StringSet.fold (fun name acc ->
-    let in_ancestor = StringSet.mem name ancestor_names in
-    let in_target   = StringSet.mem name target_names   in
-    match in_ancestor, in_target with
-    | false, true ->
-      let rel = Option.get (Database.get_relation target name) in
-      RelationAdded rel :: acc
-    | true, false ->
-      RelationRemoved name :: acc
-    | true, true ->
-      let anc_rel = Option.get (Database.get_relation ancestor name) in
-      let tgt_rel = Option.get (Database.get_relation target  name) in
-      (* Compare hashes — if identical, no diff *)
-      if anc_rel.Relation.hash = tgt_rel.Relation.hash then acc
-      else begin
-        let anc_keys = relation_keys anc_rel in
-        let tgt_keys = relation_keys tgt_rel in
-        let added_tuples   = StringSet.diff tgt_keys anc_keys |> StringSet.elements in
-        let removed_tuples = StringSet.diff anc_keys tgt_keys |> StringSet.elements in
-        let schema_changed = anc_rel.Relation.schema <> tgt_rel.Relation.schema in
-        RelationModified { name; added_tuples; removed_tuples; schema_changed } :: acc
-      end
-    | false, false -> acc (* impossible *)
-  ) all_names []
+  StringSet.fold
+    (fun name acc ->
+      let in_ancestor = StringSet.mem name ancestor_names in
+      let in_target = StringSet.mem name target_names in
+      match (in_ancestor, in_target) with
+      | false, true -> (
+          match Database.get_relation target name with
+          | Some rel -> RelationAdded rel :: acc
+          | None -> acc)
+      | true, false -> RelationRemoved name :: acc
+      | true, true -> (
+          match
+            ( Database.get_relation ancestor name,
+              Database.get_relation target name )
+          with
+          | Some anc_rel, Some tgt_rel ->
+              (* Compare hashes — if identical, no diff *)
+              if anc_rel.Relation.hash = tgt_rel.Relation.hash then acc
+              else
+                let anc_keys = relation_keys anc_rel in
+                let tgt_keys = relation_keys tgt_rel in
+                let added_tuples =
+                  StringSet.diff tgt_keys anc_keys |> StringSet.elements
+                in
+                let removed_tuples =
+                  StringSet.diff anc_keys tgt_keys |> StringSet.elements
+                in
+                let schema_changed =
+                  anc_rel.Relation.schema <> tgt_rel.Relation.schema
+                in
+                RelationModified
+                  { name; added_tuples; removed_tuples; schema_changed }
+                :: acc
+          | _ -> acc)
+      | false, false -> acc (* impossible *))
+    all_names []
-- 
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