Display a calculated balance on an address page.

assets/css/components/_address.scss

@@ -0,0 +1,21 @@
+.address {
+  &__header { @extend %section-header; }
+  &__heading { @extend %section-header__heading; }
+  &__subheading { @extend %section-header__subheading; }
+  &__attributes {
+    @extend %paper;
+    @include explorer-typography("body1");
+    padding: explorer-size(-1) explorer-size(1);
+  }
+  &__item { @extend %section-list__item; }
+  &__item-key { @extend %section-list__item-key; }
+  &__item-value { @extend %section-list__item-value; }
+}
+
+@media (min-width: $explorer-breakpoint-lg) {
+  .address {
+    &__container {
+      max-width: explorer-size(6);
+    }
+  }
+}

assets/css/components/_all.scss

@@ -1,5 +1,6 @@
 @import "section";
 
+@import "address";
 @import "block";
 @import "blocks";
 @import "container";

lib/explorer/forms/address_form.ex

@@ -0,0 +1,42 @@
+defmodule Explorer.AddressForm do
+  @moduledoc false
+  alias Explorer.Address
+  alias Explorer.FromAddress
+  alias Explorer.Repo
+  alias Explorer.ToAddress
+  alias Explorer.Transaction
+  import Ecto.Query
+
+  def build(address) do
+    address
+    |> Map.merge(%{
+      balance: address |> calculate_balance,
+    })
+  end
+
+  def calculate_balance(address) do
+    Decimal.sub(credits(address), debits(address))
+  end
+
+  def credits(address) do
+    query = from transaction in Transaction,
+      join: to_address in ToAddress,
+        where: to_address.transaction_id == transaction.id,
+      join: address in Address,
+        where: to_address.address_id == address.id,
+      select: sum(transaction.value),
+      where: address.id == ^address.id
+    Repo.one(query) || Decimal.new(0)
+  end
+
+  def debits(address) do
+    query = from transaction in Transaction,
+      join: from_address in FromAddress,
+        where: from_address.transaction_id == transaction.id,
+      join: address in Address,
+        where: from_address.address_id == address.id,
+      select: sum(transaction.value),
+      where: address.id == ^address.id
+    Repo.one(query) || Decimal.new(0)
+  end
+end

lib/explorer_web/controllers/address_controller.ex

@@ -3,12 +3,14 @@ defmodule ExplorerWeb.AddressController do
   import Ecto.Query
   alias Explorer.Address
   alias Explorer.Repo
+  alias Explorer.AddressForm
 
   def show(conn, params) do
     address = Address
       |> where(hash: ^params["id"])
       |> first
       |> Repo.one
+      |> AddressForm.build
     render(conn, "show.html", address: address)
   end
 end

lib/explorer_web/templates/address/show.html.eex

@@ -3,5 +3,15 @@
     <h1 class="address__heading"><%= gettext "Address" %></h1>
     <h3 class="address__subheading"><%= @address.hash %></h3>
   </div>
+  <div class="address__container">
+    <div class="address__attributes">
+      <dl>
+        <div class="address__item">
+          <dt class="address__item-key"><%= gettext "Balance" %></dt>
+          <dd class="address__item-value" title="<%= @address.hash %>"><%= @address.balance %> <%= gettext "POA" %></dd>
+        </div>
+      </dl>
+    </div>
+  </div>
 </section>
 

lib/explorer_web/templates/page/index.html.eex

@@ -50,7 +50,7 @@
               </td>
               <td class="transactions__column transactions__column--block"><%= transaction.block_number %></td>
               <td class="transactions__column transactions__column--age"><%= transaction.age  %></td>
-              <td class="transactions__column transactions__column--value"><%= Decimal.div(Decimal.new(transaction.value), Decimal.new(1_000_000_000_000_000_000)) |> Decimal.to_string(:normal) %> POA</td>
+              <td class="transactions__column transactions__column--value"><%= Decimal.div(Decimal.new(transaction.value), Decimal.new(1_000_000_000_000_000_000)) |> Decimal.to_string(:normal) %> <%= gettext "POA" %></td>
             </tr>
           <% end %>
         </tbody>

lib/explorer_web/templates/transaction/show.html.eex

@@ -35,7 +35,7 @@
           </div>
           <div class="transaction__item">
             <dt class="transaction__item-key"><%= gettext "Value" %></dt>
-            <dd class="transaction__item-value"><%= Decimal.div(Decimal.new(@transaction.value), Decimal.new(1_000_000_000_000_000_000)) |> Decimal.to_string(:normal) %> POA</dd>
+            <dd class="transaction__item-value"><%= Decimal.div(Decimal.new(@transaction.value), Decimal.new(1_000_000_000_000_000_000)) |> Decimal.to_string(:normal) %> <%= gettext "POA" %></dd>
           </div>
           <div class="transaction__item">
             <dt class="transaction__item-key"><%= gettext "From" %></dt>

priv/gettext/default.pot

@@ -149,3 +149,13 @@ msgstr ""
 #: lib/explorer_web/templates/transaction/show.html.eex:18
 msgid "Transaction Status"
 msgstr ""
+
+#: lib/explorer_web/templates/address/show.html.eex:10
+msgid "Balance"
+msgstr ""
+
+#: lib/explorer_web/templates/address/show.html.eex:11
+#: lib/explorer_web/templates/page/index.html.eex:53
+#: lib/explorer_web/templates/transaction/show.html.eex:38
+msgid "POA"
+msgstr ""

priv/gettext/en/LC_MESSAGES/default.po

@@ -161,3 +161,13 @@ msgstr "Transaction Hash"
 #: lib/explorer_web/templates/transaction/show.html.eex:18
 msgid "Transaction Status"
 msgstr "Transaction Status"
+
+#: lib/explorer_web/templates/address/show.html.eex:10
+msgid "Balance"
+msgstr "Balance"
+
+#: lib/explorer_web/templates/address/show.html.eex:11
+#: lib/explorer_web/templates/page/index.html.eex:53
+#: lib/explorer_web/templates/transaction/show.html.eex:38
+msgid "POA"
+msgstr "POA"

test/explorer/forms/address_form_test.exs

@@ -0,0 +1,72 @@
+defmodule Explorer.AddressFormTest do
+  use Explorer.DataCase
+  alias Explorer.AddressForm
+
+  describe "build/1" do
+    test "that it has a balance" do
+      address = insert(:address, %{hash: "bert"})
+      insert(:transaction, value: 5) |> with_addresses(%{to: "bert", from: "ernie"})
+      insert(:transaction, value: 5) |> with_addresses(%{to: "bert", from: "kermit"})
+
+      assert AddressForm.build(address).balance == Decimal.new(10)
+    end
+  end
+
+  describe "calculate_balance/1" do
+    test "when there are more credits than debits it returns a positive value" do
+      address = insert(:address, %{hash: "bert"})
+      insert(:transaction, value: 5) |> with_addresses(%{to: "bert", from: "ernie"})
+      insert(:transaction, value: 5) |> with_addresses(%{to: "bert", from: "kermit"})
+
+      assert AddressForm.calculate_balance(address) == Decimal.new(10)
+    end
+
+    test "when credits and debits are equal it returns zero" do
+      address = insert(:address, %{hash: "bert"})
+      insert(:transaction, value: 5) |> with_addresses(%{to: "bert", from: "ernie"})
+      insert(:transaction, value: 5) |> with_addresses(%{to: "ernie", from: "bert"})
+
+      assert AddressForm.calculate_balance(address) == Decimal.new(0)
+    end
+
+    test "when there are more debits than credits it returns a negative value" do
+      address = insert(:address, %{hash: "bert"})
+      insert(:transaction, value: 5) |> with_addresses(%{to: "ernie", from: "bert"})
+      insert(:transaction, value: 5) |> with_addresses(%{to: "ernie", from: "bert"})
+
+      assert AddressForm.calculate_balance(address) ==  Decimal.new(-10)
+    end
+  end
+
+  describe "credits/1" do
+    test "when there are no transactions" do
+      address = insert(:address, %{hash: "bert"})
+      assert AddressForm.credits(address) == Decimal.new(0)
+    end
+
+    test "that it calculates credits" do
+      address = insert(:address, %{hash: "bert"})
+      insert(:transaction, value: 5) |> with_addresses(%{from: "ernie", to: "bert"})
+      insert(:transaction, value: 5) |> with_addresses(%{from: "bert", to: "kermit"})
+      insert(:transaction, value: 5) |> with_addresses(%{from: "janice", to: "bert"})
+
+      assert AddressForm.credits(address) == Decimal.new(10)
+    end
+  end
+
+  describe "debits/1" do
+    test "when there are no transactions" do
+      address = insert(:address, %{hash: "bert"})
+      assert AddressForm.debits(address) == Decimal.new(0)
+    end
+
+    test "that it calculates debits" do
+      address = insert(:address, %{hash: "ernie"})
+      insert(:transaction, value: 5) |> with_addresses(%{from: "ernie", to: "bert"})
+      insert(:transaction, value: 5) |> with_addresses(%{from: "ernie", to: "kermit"})
+      insert(:transaction, value: 5) |> with_addresses(%{from: "janice", to: "ernie"})
+
+      assert AddressForm.debits(address) == Decimal.new(10)
+    end
+  end
+end

test/support/factories/transaction_factory.ex

@@ -20,8 +20,8 @@ defmodule Explorer.TransactionFactory do
       end
 
       def with_addresses(transaction, %{to: to, from: from} \\ %{to: nil, from: nil}) do
-        to_address = if to, do: insert(:address, hash: to), else: insert(:address)
-        from_address = if from, do: insert(:address, hash: from), else: insert(:address)
+        to_address = if to, do: Explorer.Repo.get_by(Explorer.Address, %{hash: to}) || insert(:address, hash: to), else: insert(:address)
+        from_address = if from, do: Explorer.Repo.get_by(Explorer.Address, %{hash: from}) ||insert(:address, hash: from), else: insert(:address)
         insert(:to_address, %{transaction_id: transaction.id, address_id: to_address.id})
         insert(:from_address, %{transaction_id: transaction.id, address_id: from_address.id})
         transaction