Format the amount of token transfers in the view

apps/explorer_web/lib/explorer_web/templates/address_transaction/_transaction.html.eex

@@ -76,7 +76,7 @@
       </div>
       <div class="col-sm-3 col-lg-2 d-flex flex-row flex-sm-column align-items-end">
         <span class="tile-title">
-          <%= token_transfer.amount %> <%= token_transfer.token.symbol %>
+          <%= formatted_token_amount(token_transfer.amount, token_transfer.token.decimals) %> <%= token_transfer.token.symbol %>
         </span>
       </div>
     <% end %>

apps/explorer_web/lib/explorer_web/views/address_transaction_view.ex

@@ -21,4 +21,27 @@ defmodule ExplorerWeb.AddressTransactionView do
   def transaction_from_or_to_current_address?(transaction, address_hash) do
     transaction.from_address_hash == address_hash || transaction.to_address_hash == address_hash
   end
+
+  @doc """
+  Formats the given amount according to given decimals.
+
+  ## Examples
+
+  iex> ExplorerWeb.AddressTransactionView.formatted_token_amount(Decimal.new(20500000), 5)
+  "205"
+
+  iex> ExplorerWeb.AddressTransactionView.formatted_token_amount(Decimal.new(20500000), 7)
+  "2.05"
+
+  iex> ExplorerWeb.AddressTransactionView.formatted_token_amount(Decimal.new(205000), 12)
+  "0.000000205"
+
+  """
+  @spec formatted_token_amount(Decimal.t(), non_neg_integer()) :: String.t()
+  def formatted_token_amount(%Decimal{sign: sign, coef: coef, exp: exp}, decimals) do
+    sign
+    |> Decimal.new(coef, exp - decimals)
+    |> Decimal.reduce()
+    |> Decimal.to_string(:normal)
+  end
 end

apps/explorer_web/test/explorer_web/views/address_transaction_view_test.exs

@@ -0,0 +1,37 @@
+defmodule ExplorerWeb.AddresstransactionViewTest do
+  use ExplorerWeb.ConnCase, async: true
+
+  alias ExplorerWeb.AddressTransactionView
+
+  doctest ExplorerWeb.AddressTransactionView
+
+  describe "formatted_token_amount/1" do
+    test "formats the amount as value considering the given decimals" do
+      amount = Decimal.new(205_000_000_000_000)
+      decimals = 12
+
+      assert AddressTransactionView.formatted_token_amount(amount, decimals) == "205"
+    end
+
+    test "considers the decimal places according to the given decimals" do
+      amount = Decimal.new(205_000)
+      decimals = 12
+
+      assert AddressTransactionView.formatted_token_amount(amount, decimals) == "0.000000205"
+    end
+
+    test "does not consider right zeros in decimal places" do
+      amount = Decimal.new(90_000_000)
+      decimals = 6
+
+      assert AddressTransactionView.formatted_token_amount(amount, decimals) == "90"
+    end
+
+    test "returns the full number when there is no right zeros in decimal places" do
+      amount = Decimal.new(9_324_876)
+      decimals = 6
+
+      assert AddressTransactionView.formatted_token_amount(amount, decimals) == "9.324876"
+    end
+  end
+end