Resolve bug and Test

lib/archethic/db/embedded_impl/chain_reader.ex

@@ -64,34 +64,46 @@ defmodule Archethic.DB.EmbeddedImpl.ChainReader do
         {[], false, ""}
 
       {:ok, %{genesis_address: genesis_address}} ->
-        filepath = ChainWriter.chain_path(db_path, genesis_address)
-        fd = File.open!(filepath, [:binary, :read])
+        {transactions, more?, paging_state} =
+          process_get_chain({address, fields, opts, db_path}, genesis_address)
 
-        # Set the file cursor position to the paging state
-        case Keyword.get(opts, :paging_state) do
-          nil ->
-            :file.position(fd, 0)
-            0
+        :telemetry.execute([:archethic, :db], %{duration: System.monotonic_time() - start}, %{
+          query: "get_transaction_chain"
+        })
 
-          paging_address ->
-            {:ok, %{offset: offset, size: size}} =
-              ChainIndex.get_tx_entry(paging_address, db_path)
+        {transactions, more?, paging_state}
+    end
+  end
 
+  defp process_get_chain({address, fields, opts, db_path}, genesis_address) do
+    filepath = ChainWriter.chain_path(db_path, genesis_address)
+    fd = File.open!(filepath, [:binary, :read])
+    # Set the file cursor position to the paging state
+    case Keyword.get(opts, :paging_state) do
+      nil ->
+        :file.position(fd, 0)
+        process_get_chain({address, fields}, {fd})
+
+      paging_address ->
+        case ChainIndex.get_tx_entry(paging_address, db_path) do
+          {:ok, %{offset: offset, size: size}} ->
             :file.position(fd, offset + size)
-        end
+            process_get_chain({address, fields}, {fd})
 
-        column_names = fields_to_column_names(fields)
+          {:error, :not_exists} ->
+            {[], false, ""}
+        end
+    end
+  end
 
-        # Read the transactions until the nb of transactions to fullfil the page (ie. 10 transactions)
-        {transactions, more?, paging_state} = scan_chain(fd, column_names, address)
-        :file.close(fd)
+  defp process_get_chain({address, fields}, {fd}) do
+    column_names = fields_to_column_names(fields)
 
-        :telemetry.execute([:archethic, :db], %{duration: System.monotonic_time() - start}, %{
-          query: "get_transaction_chain"
-        })
+    # Read the transactions until the nb of transactions to fullfil the page (ie. 10 transactions)
+    {transactions, more?, paging_state} = scan_chain(fd, column_names, address)
+    :file.close(fd)
 
-        {transactions, more?, paging_state}
-    end
+    {transactions, more?, paging_state}
   end
 
   defp read_transaction(fd, fields, limit, position, acc \\ %{})

test/archethic/db/embedded_impl_test.exs

@@ -218,6 +218,30 @@ defmodule Archethic.DB.EmbeddedTest do
       assert length(page2) == 10
       assert page2 == Enum.slice(transactions, 10, 10)
     end
+
+    test "should return an empty list when the Paging Address is not found" do
+      transactions =
+        Enum.map(1..15, fn i ->
+          TransactionFactory.create_valid_transaction([],
+            index: i,
+            timestamp: DateTime.utc_now() |> DateTime.add(i * 60)
+          )
+        end)
+
+      EmbeddedImpl.write_transaction_chain(transactions)
+
+      {page, true, paging_state} =
+        EmbeddedImpl.get_transaction_chain(List.last(transactions).address)
+
+      assert length(page) == 10
+      assert page == Enum.take(transactions, 10)
+      assert paging_state == List.last(page).address
+
+      assert {[], false, ""} =
+               EmbeddedImpl.get_transaction_chain(List.last(transactions).address, [],
+                 paging_state: :crypto.strong_rand_bytes(32)
+               )
+    end
   end
 
   describe "chain_size/1" do