Don’t show paging button on last page for transactions list

apps/explorer_web/lib/explorer_web/controllers/transaction_controller.ex

@@ -3,7 +3,8 @@ defmodule ExplorerWeb.TransactionController do
 
   alias Explorer.{Chain, PagingOptions}
 
-  @default_paging_options %PagingOptions{page_size: 50}
+  @page_size 50
+  @default_paging_options %PagingOptions{page_size: @page_size + 1}
 
   def index(conn, %{"block_number" => block_number_string, "index" => index_string}) do
     with {block_number, ""} <- Integer.parse(block_number_string),
@@ -37,21 +38,24 @@ defmodule ExplorerWeb.TransactionController do
         options
       )
 
-    transactions = Chain.recent_collated_transactions(full_options)
+    transactions_plus_one = Chain.recent_collated_transactions(full_options)
+
+    {next_page, transactions} = List.pop_at(transactions_plus_one, @page_size)
+
     transaction_estimated_count = Chain.transaction_estimated_count()
 
     render(
       conn,
       "index.html",
-      earliest: earliest(transactions),
+      next_page_params: next_page_params(next_page, transactions),
       transaction_estimated_count: transaction_estimated_count,
       transactions: transactions
     )
   end
 
-  defp earliest([]), do: nil
+  defp next_page_params(nil, _transactions), do: nil
 
-  defp earliest(transactions) do
+  defp next_page_params(_, transactions) do
     last = List.last(transactions)
     %{block_number: last.block_number, index: last.index}
   end

apps/explorer_web/lib/explorer_web/templates/transaction/index.html.eex

@@ -85,7 +85,7 @@
       </table>
     </div>
   </div>
-  <%= if @earliest do %>
+  <%= if @next_page_params do %>
     <%= link(
       gettext("Older"),
       class: "button button--secondary button--sm u-float-right mt-3",
@@ -93,7 +93,7 @@
         @conn,
         :index,
         @conn.assigns.locale,
-        %{"block_number" => @earliest.block_number, "index" => @earliest.index}
+        @next_page_params
       )
     ) %>
   <% end %>

apps/explorer_web/test/explorer_web/controllers/transaction_controller_test.exs

@@ -65,6 +65,30 @@ defmodule ExplorerWeb.TransactionControllerTest do
       assert second_page_hashes == actual_hashes
     end
 
+    test "next_page_params exist if not on last page", %{conn: conn} do
+      address = insert(:address)
+
+      60
+      |> insert_list(:transaction, from_address_hash: address.hash)
+      |> with_block()
+
+      conn = get(conn, "/en/transactions")
+
+      assert conn.assigns.next_page_params
+    end
+
+    test "next_page_params are empty if on last page", %{conn: conn} do
+      address = insert(:address)
+
+      :transaction
+      |> insert(from_address_hash: address.hash)
+      |> with_block()
+
+      conn = get(conn, "/en/transactions")
+
+      refute conn.assigns.next_page_params
+    end
+
     test "guards against bad block_number input", %{conn: conn} do
       conn = get(conn, "/en/transactions", %{"block_number" => "foo", "index" => "2"})
       assert html_response(conn, 422)