add incoming transactions count to contract view

apps/block_scout_web/lib/block_scout_web/templates/address/overview.html.eex

@@ -35,10 +35,17 @@
             <% end %>
             <span>
               <span class="address-detail-item">
+                <%= if contract?(@address) do %>
+                  <span data-selector="transaction-count">
+                    <%= Cldr.Number.to_string!(incoming_transaction_count(@address), format: "#,###") %>
+                  </span>
+                  <%= gettext("Incoming Transactions") %>
+                <% else %>
                   <span data-selector="transaction-count">
                     <%= Cldr.Number.to_string!(@transaction_count, format: "#,###") %>
                   </span>
                   <%= gettext("Transactions Sent") %>
+                <% end %>
               </span>
               <span class="address-detail-item">
                 <%= gettext("Last Balance Update: Block #") %><span data-selector="fetched-coin-balance-block-number"><%= @address.fetched_coin_balance_block_number %></span>

apps/block_scout_web/lib/block_scout_web/views/address_view.ex

@@ -213,6 +213,10 @@ defmodule BlockScoutWeb.AddressView do
 
   def token_title(%Token{name: name, symbol: symbol}), do: "#{name} (#{symbol})"
 
+  def incoming_transaction_count(%Address{} = address) do
+    Chain.address_to_incoming_transaction_count(address)
+  end
+
   def trimmed_hash(%Hash{} = hash) do
     string_hash = to_string(hash)
     "#{String.slice(string_hash, 0..5)}–#{String.slice(string_hash, -6..-1)}"

apps/explorer/lib/explorer/chain.ex

@@ -417,6 +417,17 @@ defmodule Explorer.Chain do
     Repo.aggregate(query, :count, :hash)
   end
 
+  @spec address_to_incoming_transaction_count(Address.t()) :: non_neg_integer()
+  def address_to_incoming_transaction_count(%Address{hash: address_hash}) do
+    query =
+      from(
+        transaction in Transaction,
+        where: transaction.to_address_hash == ^address_hash
+      )
+
+    Repo.aggregate(query, :count, :hash)
+  end
+
   @doc """
   How many blocks have confirmed `block` based on the current `max_block_number`
 

apps/explorer/priv/repo/migrations/20190314084907_add_index_to_to_address_hash.exs

@@ -0,0 +1,7 @@
+defmodule Explorer.Repo.Migrations.AddIndexToToAddressHash do
+  use Ecto.Migration
+
+  def change do
+    create(index(:transactions, [:to_address_hash]))
+  end
+end

apps/explorer/test/explorer/chain_test.exs

@@ -597,6 +597,20 @@ defmodule Explorer.ChainTest do
     end
   end
 
+  describe "address_to_incoming_transaction_count/1" do
+    test "without transactions" do
+      address = insert(:address)
+
+      assert Chain.address_to_incoming_transaction_count(address) == 0
+    end
+
+    test "with transactions" do
+      %Transaction{to_address: to_address} = insert(:transaction)
+
+      assert Chain.address_to_incoming_transaction_count(to_address) == 1
+    end
+  end
+
   describe "confirmations/1" do
     test "with block.number == block_height " do
       block = insert(:block)