Update Book to sync only a new non-local data.

lib/decentralised_book_index/metadata.ex

@@ -74,6 +74,7 @@ defmodule DecentralisedBookIndex.Metadata do
       define :search_book_by_bid, action: :search_by_bid, args: [:type, :bid]
       define :update_book, action: :update
       define :assign_book_cover_image, args: [:cover_image_url], action: :assign_cover_image
+      define :assign_book_dbi_server, args: [:dbi_server_id], action: :assign_dbi_server_id
       define :destroy_book, action: :destroy
     end
 

lib/decentralised_book_index/metadata/book.ex

@@ -40,7 +40,8 @@ defmodule DecentralisedBookIndex.Metadata.Book do
         :published,
         :publisher_id,
         :cover_image_url,
-        :book_editions_registry_id
+        :book_editions_registry_id,
+        :dbi_server_id
       ]
 
       argument :bids, {:array, :map}
@@ -276,6 +277,10 @@ defmodule DecentralisedBookIndex.Metadata.Book do
     update :assign_cover_image do
       accept [:cover_image_url]
     end
+
+    update :assign_dbi_server_id do
+      accept [:dbi_server_id]
+    end
   end
 
   policies do

lib/decentralised_book_index/sync/sync/book_sync.ex

@@ -8,15 +8,18 @@ defmodule DecentralisedBookIndex.Sync.BookSync do
 
     case Metadata.get_book_by_id(attrs.id) do
       {:ok, book} ->
-        attrs =
-          attrs
-          |> Map.delete(:id)
-          |> update_registry(registry_info)
-          |> Map.put(:dbi_server_id, server_id)
 
-        book
-        |> Ash.Changeset.for_update(:sync, attrs)
-        |> Ash.update!(authorize?: false)
+        if not is_local(book) and is_new(attrs, book) do
+          attrs =
+            attrs
+            |> Map.delete(:id)
+            |> update_registry(registry_info)
+            |> Map.put_new(:dbi_server_id, server_id)
+
+          book
+          |> Ash.Changeset.for_update(:sync, attrs)
+          |> Ash.update!(authorize?: false)
+        end
 
         :ok
 
@@ -24,7 +27,7 @@ defmodule DecentralisedBookIndex.Sync.BookSync do
         attrs =
           attrs
           |> update_registry(registry_info)
-          |> Map.put(:dbi_server_id, server_id)
+          |> Map.put_new(:dbi_server_id, server_id)
 
         Book
         |> Ash.Changeset.for_create(:sync_create, attrs)
@@ -58,4 +61,17 @@ defmodule DecentralisedBookIndex.Sync.BookSync do
         |> Map.delete(:book_editions_registry_id)
     end
   end
+
+  defp is_local(book) do
+    is_nil(book.dbi_server_id)
+  end
+
+  defp is_new(new_book, book) do
+    with {:ok, datetime, _offset} <- DateTime.from_iso8601(new_book[:updated_at]) do
+      DateTime.after?(datetime, book.updated_at)
+    else
+      {:error, reason} ->
+        false
+    end
+  end
 end