refactor: stricter EVM signer balance check

src/components/LockupEvm.tsx

@@ -10,6 +10,8 @@ import ConnectWallet from "./ConnectWallet";
 import ContractTransaction from "./ContractTransaction";
 import LoadingSpinner from "./LoadingSpinner";
 
+const lockupGasUsage = 46_000n;
+
 const InsufficientBalance = () => {
     const { t } = useGlobalContext();
 
@@ -47,11 +49,16 @@ const LockupEvm = (props: {
             return;
         }
 
-        const balance = await signer().provider.getBalance(
-            await signer().getAddress(),
-        );
-        log.info("EVM signer balance", balance);
-        setSignerBalance(balance);
+        const [balance, gasPrice] = await Promise.all([
+            signer().provider.getBalance(await signer().getAddress()),
+            signer()
+                .provider.getFeeData()
+                .then((data) => data.gasPrice),
+        ]);
+
+        const spendable = balance - gasPrice * lockupGasUsage;
+        log.info("EVM signer spendable balance", spendable);
+        setSignerBalance(spendable);
     });
 
     return (

src/context/Web3.tsx

@@ -1,6 +1,11 @@
 import { abi as EtherSwapAbi } from "boltz-core/out/EtherSwap.sol/EtherSwap.json";
 import { EtherSwap } from "boltz-core/typechain/EtherSwap";
-import { BrowserProvider, Contract, JsonRpcSigner } from "ethers";
+import {
+    BrowserProvider,
+    Contract,
+    JsonRpcProvider,
+    JsonRpcSigner,
+} from "ethers";
 import log from "loglevel";
 import {
     Accessor,
@@ -160,7 +165,8 @@ const Web3SignerProvider = (props: {
         return new Contract(
             contracts().swapContracts.EtherSwap,
             EtherSwapAbi,
-            signer(),
+            signer() ||
+                new JsonRpcProvider(config.assets["RBTC"]?.network?.rpcUrls[0]),
         ) as unknown as EtherSwap;
     };