refactor: email validations

lib/mv/accounts/user/validations/email_not_used_by_other_member.ex

@@ -1,9 +1,7 @@
 defmodule Mv.Accounts.User.Validations.EmailNotUsedByOtherMember do
   @moduledoc """
-  Validates that the user's email is not already used by another member
-  (unless that member is linked to this user).
-
-  This prevents email conflicts when syncing between users and members.
+  Validates that the user's email is not already used by another member.
+  Allows syncing with linked member (excludes member_id from check).
   """
   use Ash.Resource.Validation
 
@@ -11,42 +9,32 @@ defmodule Mv.Accounts.User.Validations.EmailNotUsedByOtherMember do
   def validate(changeset, _opts, _context) do
     case Ash.Changeset.fetch_change(changeset, :email) do
       {:ok, new_email} ->
-        check_email_not_used_by_other_member(changeset, new_email)
+        member_id = Ash.Changeset.get_attribute(changeset, :member_id)
+        check_email_uniqueness(new_email, member_id)
 
       :error ->
-        # Email not being changed
         :ok
     end
   end
 
-  defp check_email_not_used_by_other_member(changeset, new_email) do
-    member_id = Ash.Changeset.get_attribute(changeset, :member_id)
-
-    # Check if any member has this email
-    # Exclude the member linked to this user (if any)
+  defp check_email_uniqueness(new_email, exclude_member_id) do
     query =
       Mv.Membership.Member
       |> Ash.Query.filter(email == ^to_string(new_email))
-      |> then(fn q ->
-        if member_id do
-          Ash.Query.filter(q, id != ^member_id)
-        else
-          q
-        end
-      end)
+      |> maybe_exclude_id(exclude_member_id)
 
     case Ash.read(query) do
       {:ok, []} ->
-        # No conflicting member found
         :ok
 
-      {:ok, members} when is_list(members) and length(members) > 0 ->
-        # Email is already used by another member
+      {:ok, _} ->
         {:error, field: :email, message: "is already used by another member", value: new_email}
 
       {:error, _} ->
-        # Error reading members - be safe and allow
         :ok
     end
   end
+
+  defp maybe_exclude_id(query, nil), do: query
+  defp maybe_exclude_id(query, id), do: Ash.Query.filter(query, id != ^id)
 end