Build a Scrape task that grabs the latest block.

config/config.exs

@@ -27,3 +27,8 @@ config :logger, :console,
 # Import environment specific config. This must remain at the bottom
 # of this file so it overrides the configuration defined above.
 import_config "#{Mix.env}.exs"
+
+config :ethereumex,
+  scheme: "https",
+  host: "sokol.poa.network",
+  port: 443

lib/mix/tasks/scrape.ex

@@ -0,0 +1,72 @@
+defmodule Mix.Tasks.Scrape do
+  use Mix.Task
+  alias Explorer.Block
+  alias Explorer.Repo
+  import Ethereumex.HttpClient, only: [
+    eth_block_number: 0,
+    eth_get_block_by_number: 2
+  ]
+
+  @shortdoc "Scrape the blockchain."
+  @moduledoc false
+
+  def run(_) do
+    persist()
+  end
+
+  def persist do
+    {:ok, _} = Repo.insert(changeset())
+  end
+
+  def changeset do
+    Block.changeset(attributes(), %{})
+  end
+
+  def attributes do
+    %Block{
+      hash: hash(),
+      number: number(),
+      timestamp: timestamp(),
+      gas_used: gas_used(),
+      parent_hash: "0x0",
+      nonce: "0",
+      miner: "0x0",
+      difficulty: "0",
+      total_difficulty: "0",
+      size: "0",
+      gas_limit: "0",
+    }
+  end
+
+  def hash do
+    latest_block()["hash"]
+  end
+
+  def number do
+    decode_integer_field(latest_block()["number"])
+  end
+
+  def timestamp do
+    epoch_to_datetime(decode_integer_field(latest_block()["timestamp"]))
+  end
+
+  def gas_used do
+    decode_integer_field(latest_block()["gasUsed"])
+  end
+
+  def latest_block do
+    Mix.Task.run "app.start"
+    {:ok, latest_block_number} = eth_block_number()
+    {:ok, latest_block} = eth_get_block_by_number(latest_block_number, true)
+    latest_block
+  end
+
+  def decode_integer_field(field) do
+    {"0x", base_16} = String.split_at(field, 2)
+    String.to_integer(base_16, 16)
+  end
+
+  def epoch_to_datetime(epoch) do
+    Timex.from_unix(epoch)
+  end
+end

mix.exs

@@ -29,8 +29,8 @@ defmodule Explorer.Mixfile do
   defp elixirc_paths(_),     do: ["lib"]
 
   # Specifies extra applications to start per environment
-  defp extra_applications(:prod), do: [:timex, :timex_ecto, :set_locale, :logger, :runtime_tools, :phoenix_pubsub_redis, :new_relixir]
-  defp extra_applications(_), do: [:timex, :timex_ecto, :set_locale, :logger, :runtime_tools]
+  defp extra_applications(:prod), do: [:ethereumex, :timex, :timex_ecto, :set_locale, :logger, :runtime_tools, :phoenix_pubsub_redis, :new_relixir]
+  defp extra_applications(_), do: [:ethereumex, :timex, :timex_ecto, :set_locale, :logger, :runtime_tools]
 
   # Specifies your project dependencies.
   #
@@ -39,6 +39,7 @@ defmodule Explorer.Mixfile do
     [
       {:cowboy, "~> 1.0"},
       {:credo, "~> 0.8", only: [:dev, :test], runtime: false},
+      {:ethereumex, github: "exthereum/ethereumex", commit: "262f1d81ae163ffb46e127283658249dac1c8318"}, # Waiting for this version to be pushed to Hex.
       {:ex_machina, "~> 2.1", only: [:test]},
       {:gettext, "~> 0.11"},
       {:junit_formatter, ">= 0.0.0"},

mix.lock

@@ -8,6 +8,7 @@
   "db_connection": {:hex, :db_connection, "1.1.3", "89b30ca1ef0a3b469b1c779579590688561d586694a3ce8792985d4d7e575a61", [:mix], [{:connection, "~> 1.0.2", [hex: :connection, repo: "hexpm", optional: false]}, {:poolboy, "~> 1.5", [hex: :poolboy, repo: "hexpm", optional: true]}, {:sbroker, "~> 1.0", [hex: :sbroker, repo: "hexpm", optional: true]}], "hexpm"},
   "decimal": {:hex, :decimal, "1.4.1", "ad9e501edf7322f122f7fc151cce7c2a0c9ada96f2b0155b8a09a795c2029770", [:mix], [], "hexpm"},
   "ecto": {:hex, :ecto, "2.2.8", "a4463c0928b970f2cee722cd29aaac154e866a15882c5737e0038bbfcf03ec2c", [:mix], [{:db_connection, "~> 1.1", [hex: :db_connection, repo: "hexpm", optional: true]}, {:decimal, "~> 1.2", [hex: :decimal, repo: "hexpm", optional: false]}, {:mariaex, "~> 0.8.0", [hex: :mariaex, repo: "hexpm", optional: true]}, {:poison, "~> 2.2 or ~> 3.0", [hex: :poison, repo: "hexpm", optional: true]}, {:poolboy, "~> 1.5", [hex: :poolboy, repo: "hexpm", optional: false]}, {:postgrex, "~> 0.13.0", [hex: :postgrex, repo: "hexpm", optional: true]}, {:sbroker, "~> 1.0", [hex: :sbroker, repo: "hexpm", optional: true]}], "hexpm"},
+  "ethereumex": {:git, "https://github.com/exthereum/ethereumex.git", "262f1d81ae163ffb46e127283658249dac1c8318", []},
   "ex_machina": {:hex, :ex_machina, "2.1.0", "4874dc9c78e7cf2d429f24dc3c4005674d4e4da6a08be961ffccc08fb528e28b", [:mix], [{:ecto, "~> 2.1", [hex: :ecto, repo: "hexpm", optional: true]}], "hexpm"},
   "file_system": {:hex, :file_system, "0.2.4", "f0bdda195c0e46e987333e986452ec523aed21d784189144f647c43eaf307064", [:mix], [], "hexpm"},
   "gettext": {:hex, :gettext, "0.14.0", "1a019a2e51d5ad3d126efe166dcdf6563768e5d06c32a99ad2281a1fa94b4c72", [:mix], [], "hexpm"},

test/mix/tasks/scrape_test.exs

@@ -0,0 +1,17 @@
+defmodule Scrape.Test do
+  use Explorer.DataCase
+  alias Explorer.Block
+  alias Explorer.Repo
+
+  test "it downloads a new block" do
+    Mix.Tasks.Scrape.run([])
+
+    last_block = Block
+      |> order_by(desc: :inserted_at)
+      |> limit(1)
+      |> Repo.all
+      |> List.first
+
+    assert(last_block.height)
+  end
+end