From 0b46d9c103a7e22c85b5f080ad6a00f9c8e94162 Mon Sep 17 00:00:00 2001
From: Chris Wawer <krzysztof.wawer@gmail.com>
Date: Sun, 23 Jun 2024 21:50:55 +0200
Subject: [PATCH] Allow to call JSON RPC with custom block number (#268)

---
 lib/eth/client.rb       |  6 +++++-
 spec/eth/client_spec.rb | 29 +++++++++++++++++++++++++++++
 2 files changed, 34 insertions(+), 1 deletion(-)

diff --git a/lib/eth/client.rb b/lib/eth/client.rb
index ecd9dff6..7b203b5b 100644
--- a/lib/eth/client.rb
+++ b/lib/eth/client.rb
@@ -34,6 +34,9 @@ class Client
     # The default transaction max fee per gas in Wei, defaults to {Tx::DEFAULT_GAS_PRICE}.
     attr_accessor :max_fee_per_gas
 
+    # The block number used for archive calls.
+    attr_accessor :block_number
+
     # A custom error type if a contract interaction fails.
     class ContractExecutionError < StandardError; end
 
@@ -469,7 +472,8 @@ def encode_constructor_params(contract, args)
 
     # Prepares parameters and sends the command to the client.
     def send_command(command, args)
-      args << "latest" if ["eth_getBalance", "eth_call"].include? command
+      @block_number ||= "latest"
+      args << block_number if ["eth_getBalance", "eth_call"].include? command
       payload = {
         jsonrpc: "2.0",
         method: command,
diff --git a/spec/eth/client_spec.rb b/spec/eth/client_spec.rb
index 46439e07..c9a6a2c5 100644
--- a/spec/eth/client_spec.rb
+++ b/spec/eth/client_spec.rb
@@ -220,6 +220,35 @@
       expect(geth_http.call(erc20_contract, "balanceOf", address)).to be_nil
     end
 
+    it "allows to call client with custom block numberreturn nil if raw result is 0x" do
+      block_number = 123
+
+      geth_http.block_number = block_number
+
+      expected_payload = {
+        jsonrpc: "2.0",
+        method: "eth_call",
+        params: [{
+          data: "0x70a08231000000000000000000000000d496b23d61f88a8c7758fca7560dcfac7b3b01f9",
+          to: "0xD496b23D61F88A8C7758fca7560dCFac7b3b01F9"
+        }, "0x#{block_number.to_s(16)}"],
+        id: 1
+      }.to_json
+
+      mock_response = {
+        jsonrpc: "2.0",
+        id: 1,
+        result: "0x0000000000000000000000000000000000000000000000000000000000000000"
+      }
+
+      expect_any_instance_of(Eth::Client::Http)
+        .to receive(:send_request)
+              .with(expected_payload)
+              .and_return(mock_response.to_json)
+
+      geth_http.call(erc20_contract, "balanceOf", address)
+    end
+
     it "called function name not defined" do
       expect {
         geth_http.call(contract, "ge")