parse emission reward ranges

apps/explorer/lib/explorer/chain/block/emission_reward.ex

@@ -24,4 +24,10 @@ defmodule Explorer.Chain.Block.EmissionReward do
     field(:block_range, Range)
     field(:reward, Wei)
   end
+
+  def changeset(%__MODULE__{} = emission_reward, attrs) do
+    emission_reward
+    |> cast(attr, [:block_range, :reward])
+    |> validate_required([:block_range, :reward])
+  end
 end

apps/explorer/lib/explorer/chain_spec/parity/importer.ex

@@ -0,0 +1,52 @@
+defmodule Explorer.ChainSpec.Parity.Importer do
+  @moduledoc """
+  Imports data from parity chain spec.
+  """
+
+  @max_block_number 9_999_999_999_999_999_999
+
+  def emission_rewards(chain_spec) do
+    rewards = chain_spec["engine"]["Ethash"]["params"]["blockReward"]
+
+    rewards
+    |> parse_hex_numbers()
+    |> format_ranges()
+  end
+
+  defp format_ranges(block_number_reward_pairs) do
+    block_number_reward_pairs
+    |> Enum.chunk_every(2, 1)
+    |> Enum.map(fn values ->
+      create_range(values)
+    end)
+  end
+
+  defp create_range([{block_number1, reward}, {block_number2, _}]) do
+    %{
+      block_range: block_number1..block_number2,
+      reward: reward
+    }
+  end
+
+  defp create_range([{block_number, reward}]) do
+    %{
+      block_range: block_number..@max_block_number,
+      reward: reward
+    }
+  end
+
+  defp parse_hex_numbers(rewards) do
+    Enum.map(rewards, fn {hex_block_number, hex_reward} ->
+      block_number = parse_hex_number(hex_block_number)
+      reward = parse_hex_number(hex_reward)
+
+      {block_number, reward}
+    end)
+  end
+
+  defp parse_hex_number("0x" <> hex_number) do
+    {number, ""} = Integer.parse(hex_number, 16)
+
+    number
+  end
+end

apps/explorer/test/explorer/chain_spec/parity/importer_test.exs

@@ -0,0 +1,19 @@
+defmodule Explorer.ChainSpec.Parity.ImporterTest do
+  use ExUnit.Case
+
+  alias Explorer.ChainSpec.Parity.Importer
+
+  @chain_spec "#{File.cwd!()}/test/support/fixture/chain_spec/foundation.json"
+              |> File.read!()
+              |> Jason.decode!()
+
+  describe "emission_rewards/1" do
+    test "fetches and formats reward ranges" do
+      assert Importer.emission_rewards(@chain_spec) == [
+               %{block_range: 0..4_370_000, reward: 5_000_000_000_000_000_000},
+               %{block_range: 4_370_000..7_280_000, reward: 3_000_000_000_000_000_000},
+               %{block_range: 7_280_000..9_999_999_999_999_999_999, reward: 2_000_000_000_000_000_000}
+             ]
+    end
+  end
+end