add POA emission rewards importer

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

@@ -0,0 +1,79 @@
+defmodule Explorer.ChainSpec.POA.Importer do
+  @moduledoc """
+  Imports emission reward range for POA chain.
+  """
+
+  alias Explorer.Chain.Wei
+  alias Explorer.Repo
+  alias Explorer.SmartContract.Reader
+  alias Explorer.Chain.Block.{EmissionReward, Range}
+
+  @reward_by_block_contract_address "0xeca443e8e1ab29971a45a9c57a6a9875701698a5"
+  @block_reward_amount_abi %{
+    "type" => "function",
+    "stateMutability" => "view",
+    "payable" => false,
+    "outputs" => [%{"type" => "uint256", "name" => ""}],
+    "name" => "blockRewardAmount",
+    "inputs" => [],
+    "constant" => true
+  }
+  @block_reward_amount_params %{"blockRewardAmount" => []}
+  @emission_funds_amount_abi %{
+    "type" => "function",
+    "stateMutability" => "view",
+    "payable" => false,
+    "outputs" => [%{"type" => "uint256", "name" => ""}],
+    "name" => "emissionFundsAmount",
+    "inputs" => [],
+    "constant" => true
+  }
+  @emission_funds_amount_params %{"emissionFundsAmount" => []}
+  @emission_funds_block_start 5_098_087
+
+  def import_emission_rewards do
+    block_reward = block_reward_amount()
+    emission_funds = emission_funds_amount()
+
+    rewards = [
+      %{
+        block_range: %Range{from: 0, to: @emission_funds_block_start},
+        reward: %Wei{value: block_reward}
+      },
+      %{
+        block_range: %Range{from: @emission_funds_block_start + 1, to: :infinity},
+        reward: %Wei{value: Decimal.add(block_reward, emission_funds)}
+      }
+    ]
+
+    {_, nil} = Repo.delete_all(EmissionReward)
+    {_, nil} = Repo.insert_all(EmissionReward, rewards)
+  end
+
+  def block_reward_amount do
+    call_contract(@reward_by_block_contract_address, @block_reward_amount_abi, @block_reward_amount_params)
+  end
+
+  def emission_funds_amount do
+    call_contract(@reward_by_block_contract_address, @emission_funds_amount_abi, @emission_funds_amount_params)
+  end
+
+  defp call_contract(address, abi, params) do
+    abi = [abi]
+
+    method_name =
+      params
+      |> Enum.map(fn {key, _value} -> key end)
+      |> List.first()
+
+    Reader.query_contract(address, abi, params)
+
+    value =
+      case Reader.query_contract(address, abi, params) do
+        %{^method_name => {:ok, [result]}} -> result
+        _ -> 0
+      end
+
+    Decimal.new(value)
+  end
+end