refactor: add format_max_gas_fee helper for type-safe MaxGasFee serialisation

bridge-cli/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "bridge-cli"
-version = "0.3.37"
+version = "0.3.38"
 edition = "2021"
 repository = "https://github.com/Near-One/bridge-sdk-rs"
 rust-version = "1.88.0"

bridge-cli/src/omni_connector_command.rs

@@ -7,7 +7,7 @@ use alloy::primitives::{Address as EvmH160, TxHash};
 use alloy::signers::local::PrivateKeySigner;
 use evm_bridge_client::EvmBridgeClientBuilder;
 use light_client::LightClientBuilder;
-use near_bridge_client::{NearBridgeClientBuilder, TransactionOptions, UTXOChainAccounts};
+use near_bridge_client::{btc::format_max_gas_fee, NearBridgeClientBuilder, TransactionOptions, UTXOChainAccounts};
 use near_primitives::{hash::CryptoHash, types::AccountId};
 use omni_connector::{
     BindTokenArgs, BtcDepositArgs, DeployTokenArgs, FinTransferArgs, InitTransferArgs,
@@ -236,7 +236,7 @@ pub enum OmniConnectorSubCommand {
         fee: Option<u128>,
         #[clap(short, long, help = "Native fee to charge for the transfer")]
         native_fee: Option<u128>,
-        #[clap(short, long, help = "Additional message")]
+        #[clap(short, long, help = "Additional message (JSON format, e.g. '{\"MaxGasFee\": \"400\"}' for BTC transfers)")]
         message: Option<String>,
         #[command(flatten)]
         config_cli: CliConfig,
@@ -355,7 +355,7 @@ pub enum OmniConnectorSubCommand {
         fee: Option<u128>,
         #[clap(short, long, help = "Native fee to charge for the transfer")]
         native_fee: Option<u64>,
-        #[clap(short, long, help = "Additional message")]
+        #[clap(short, long, help = "Additional message (JSON format, e.g. '{\"MaxGasFee\": \"400\"}' for BTC transfers)")]
         message: Option<String>,
         #[command(flatten)]
         config_cli: CliConfig,
@@ -770,7 +770,7 @@ pub async fn match_subcommand(cmd: OmniConnectorSubCommand, network: Network) {
                 && matches!(recipient.get_chain(), ChainKind::Btc | ChainKind::Zcash)
             {
                 if let Some(gas_fee) = gas_fee {
-                    message = format!("{{\"MaxGasFee\": \"{gas_fee}\"}}");
+                    message = format_max_gas_fee(u64::try_from(gas_fee).unwrap());
                 }
             }
 

bridge-sdk/bridge-clients/near-bridge-client/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "near-bridge-client"
-version = "0.2.14"
+version = "0.2.15"
 edition = "2021"
 
 [dependencies]

bridge-sdk/bridge-clients/near-bridge-client/src/btc.rs

@@ -224,6 +224,13 @@ impl TxBytes {
     }
 }
 
+/// Format a MaxGasFee message for UTXO chain transfers.
+/// This produces JSON like: `{"MaxGasFee":"400"}`
+pub fn format_max_gas_fee(gas_fee: u64) -> String {
+    serde_json::to_string(&UTXOChainMsg::MaxGasFee(U64::from(gas_fee)))
+        .expect("Failed to serialize UTXOChainMsg")
+}
+
 impl NearBridgeClient {
     /// Signs a NEAR transfer to BTC by calling `sign_btc_transaction` on the BTC connector contract.
     #[tracing::instrument(skip_all, name = "NEAR SIGN BTC TRANSACTION")]