Merge pull request #970 from dfinity/tl/eth_get_balance

Add get_balance endpoint to the basic_ethereum example

rust/basic_ethereum/Cargo.toml

@@ -21,5 +21,7 @@ ic-crypto-extended-bip32 = { git = "https://github.com/dfinity/ic", tag = "relea
 ic-crypto-sha3 = { git = "https://github.com/dfinity/ic", tag = "release-2024-06-26_23-01-base", package = "ic-crypto-sha3" }
 ic-ethereum-types = { git = "https://github.com/dfinity/ic", tag = "release-2024-06-26_23-01-base", package = "ic-ethereum-types" }
 serde = "1.0"
+serde_json = "1.0"
 serde_bytes = "0.11.15"
-num-traits = "0.2.19"
+num-traits = "0.2.19"
+num = "0.4.3"

rust/basic_ethereum/basic_ethereum.did

@@ -42,6 +42,9 @@ service : (opt InitArg) -> {
     // If the owner is not set, it defaults to the caller's principal.
     ethereum_address : (owner: opt principal) -> (text);
 
+    // Returns the balance of the given Ethereum address.
+    get_balance : (address: text) -> (Wei);
+
     // Returns the transaction count for the Ethereum address derived for the given principal.
     //
     // If the owner is not set, it defaults to the caller's principal.

rust/basic_ethereum/src/lib.rs

@@ -8,12 +8,13 @@ use alloy_consensus::{SignableTransaction, TxEip1559, TxEnvelope};
 use alloy_primitives::{hex, Signature, TxKind, U256};
 use candid::{CandidType, Deserialize, Nat, Principal};
 use evm_rpc_canister_types::{
-    BlockTag, EvmRpcCanister, GetTransactionCountArgs, GetTransactionCountResult,
-    MultiGetTransactionCountResult,
+    BlockTag, EthMainnetService, EthSepoliaService, EvmRpcCanister, GetTransactionCountArgs,
+    GetTransactionCountResult, MultiGetTransactionCountResult, RequestResult, RpcService,
 };
 use ic_cdk::api::management_canister::ecdsa::{EcdsaCurve, EcdsaKeyId};
 use ic_cdk::{init, update};
 use ic_ethereum_types::Address;
+use num::{BigUint, Num};
 use std::str::FromStr;
 
 pub const EVM_RPC_CANISTER_ID: Principal =
@@ -35,6 +36,47 @@ pub async fn ethereum_address(owner: Option<Principal>) -> String {
     wallet.ethereum_address().to_string()
 }
 
+#[update]
+pub async fn get_balance(address: String) -> Nat {
+    let _caller = validate_caller_not_anonymous();
+    let json = format!(
+        r#"{{ "jsonrpc": "2.0", "method": "eth_getBalance", "params": ["{}", "latest"], "id": 1 }}"#,
+        address
+    );
+
+    let max_response_size_bytes = 500_u64;
+    let num_cycles = 1_000_000_000u128;
+
+    let ethereum_network = read_state(|s| s.ethereum_network());
+
+    let rpc_service = match ethereum_network {
+        EthereumNetwork::Mainnet => RpcService::EthMainnet(EthMainnetService::PublicNode),
+        EthereumNetwork::Sepolia => RpcService::EthSepolia(EthSepoliaService::PublicNode),
+    };
+
+    let (response,) = EVM_RPC
+        .request(rpc_service, json, max_response_size_bytes, num_cycles)
+        .await
+        .expect("RPC call failed");
+
+    let hex_balance = match response {
+        RequestResult::Ok(balance_result) => {
+            // The response to a successful `eth_getBalance` call has the following format:
+            // { "id": "[ID]", "jsonrpc": "2.0", "result": "[BALANCE IN HEX]" }
+            let response: serde_json::Value = serde_json::from_str(&balance_result).unwrap();
+            response
+                .get("result")
+                .and_then(|v| v.as_str())
+                .unwrap()
+                .to_string()
+        }
+        RequestResult::Err(e) => panic!("Received an error response: {:?}", e),
+    };
+
+    // Remove the "0x" prefix before converting to a decimal number.
+    Nat(BigUint::from_str_radix(&hex_balance[2..], 16).unwrap())
+}
+
 #[update]
 pub async fn transaction_count(owner: Option<Principal>, block: Option<BlockTag>) -> Nat {
     let caller = validate_caller_not_anonymous();