Merge pull request #73 from alisinabh/add-get-balance

Implement `Ethers.get_balance/2` with tests

Author: alisinabh

CHANGELOG.md

@@ -2,6 +2,10 @@
 
 ## Unreleased
 
+### New features
+
+- Add `Ethers.get_balance/2` function to query native chain balance of accounts.
+
 ### Bug fixes
 
 - Encode integers to hex even when they are part of params

lib/ethers.ex

@@ -69,7 +69,12 @@ defmodule Ethers do
   alias Ethers.Utils
 
   @option_keys [:rpc_client, :rpc_opts, :signer, :signer_opts, :tx_type]
-  @hex_decode_post_process [:estimate_gas, :current_gas_price, :current_block_number]
+  @hex_decode_post_process [
+    :estimate_gas,
+    :current_gas_price,
+    :current_block_number,
+    :get_balance
+  ]
   @rpc_actions_map %{
     call: :eth_call,
     chain_id: :eth_chain_id,
@@ -108,6 +113,29 @@ defmodule Ethers do
     |> post_process(nil, :current_block_number)
   end
 
+  @doc """
+  Returns the native token (ETH) balance of an account in wei.
+
+  ## Parameters
+  - account: Account which the balance is queried for.
+  - overrides:
+    - block: The block you want to query the balance of account in (defaults to `latest`).
+    - rpc_client: The RPC module to use for this request (overrides default).
+    - rpc_opts: Specific RPC options to specify for this request.
+  """
+  @spec get_balance(Types.t_address(), Keyword.t()) ::
+          {:ok, non_neg_integer()} | {:error, term()}
+  def get_balance(account, overrides \\ []) do
+    {opts, overrides} = Keyword.split(overrides, @option_keys)
+
+    {rpc_client, rpc_opts} = get_rpc_client(opts)
+
+    with {:ok, account, block} <- pre_process(account, overrides, :get_balance, opts) do
+      rpc_client.eth_get_balance(account, block, rpc_opts)
+      |> post_process(nil, :get_balance)
+    end
+  end
+
   @doc """
   Deploys a contract to the blockchain.
 
@@ -485,6 +513,20 @@ defmodule Ethers do
     end
   end
 
+  defp pre_process(account, overrides, :get_balance = _action, _opts) do
+    block =
+      case Keyword.get(overrides, :block, "latest") do
+        number when is_integer(number) -> Utils.integer_to_hex(number)
+        v -> v
+      end
+
+    case account do
+      "0x" <> _ -> {:ok, account, block}
+      <<_::binary-20>> -> {:ok, Utils.hex_encode(account), block}
+      _ -> {:error, :invalid_account}
+    end
+  end
+
   defp pre_process(contract_binary, overrides, :deploy = _action, opts) do
     {encoded_constructor, overrides} = Keyword.pop(overrides, :encoded_constructor)
 

test/ethers_test.exs

@@ -41,6 +41,25 @@ defmodule EthersTest do
     end
   end
 
+  describe "get_balance" do
+    test "returns correct balance for account" do
+      assert {:ok, 0} == Ethers.get_balance("0xd8dA6BF26964aF9D7eEd9e03E53415D37aA96045")
+
+      assert {:ok, 1_000_000_000_000_000_000_000} ==
+               Ethers.get_balance("0x95cED938F7991cd0dFcb48F0a06a40FA1aF46EBC")
+    end
+
+    test "works with binary accounts" do
+      bin = Ethers.Utils.hex_decode!("0x95cED938F7991cd0dFcb48F0a06a40FA1aF46EBC")
+
+      assert {:ok, 1_000_000_000_000_000_000_000} == Ethers.get_balance(bin)
+    end
+
+    test "returns error with invalid account" do
+      assert {:error, :invalid_account} == Ethers.get_balance("invalid account")
+    end
+  end
+
   describe "contract deployment" do
     test "can deploy a contract given a module which has the binary" do
       assert {:ok, tx} = Ethers.deploy(HelloWorldContract, from: @from)