fix(oft-main): add STRK approval for LayerZero fee payment on Starknet

Author: St0rmBr3w

examples/oft-main/tasks/starknet/sendStarknet.ts

@@ -9,6 +9,23 @@ import { parseDecimalToUnits } from '../solana/utils'
 
 import { assertStarknetEid, getStarknetAccountFromEnv } from './utils'
 
+// STRK token address on Starknet mainnet
+const STRK_TOKEN_ADDRESS = '0x04718f5a0fc34cc1af16a1cdee98ffb20c31f5cd61d6ab07201858f4287c938d'
+
+// Minimal ERC20 ABI for approve
+const ERC20_ABI = [
+    {
+        name: 'approve',
+        type: 'function',
+        inputs: [
+            { name: 'spender', type: 'core::starknet::contract_address::ContractAddress' },
+            { name: 'amount', type: 'core::integer::u256' },
+        ],
+        outputs: [{ type: 'core::bool' }],
+        state_mutability: 'external',
+    },
+]
+
 /**
  * Convert hex string to a string for Cairo ByteArray.
  * In starknet.js v8, ByteArray parameters accept plain strings.
@@ -72,7 +89,17 @@ export async function sendStarknet({
     }
 
     const feeQuote = await oftContract.quote_send(sendParam, false)
-    const call = await oftContract.populateTransaction.send(
+
+    // Create STRK approval for the native fee (with 10% buffer for price fluctuation)
+    const feeWithBuffer = (BigInt(feeQuote.native_fee) * 110n) / 100n
+    const strkContract = new Contract({
+        abi: ERC20_ABI as any,
+        address: STRK_TOKEN_ADDRESS,
+        providerOrAccount: account,
+    })
+    const approveCall = strkContract.populateTransaction.approve(oftAddress, { low: feeWithBuffer, high: 0n })
+
+    const sendCall = oftContract.populateTransaction.send(
         sendParam,
         {
             native_fee: feeQuote.native_fee,
@@ -81,7 +108,8 @@ export async function sendStarknet({
         account.address
     )
 
-    const response = await account.execute([call])
+    // Execute approval and send in a single multicall
+    const response = await account.execute([approveCall, sendCall])
     const txHash = response.transaction_hash
     await provider.waitForTransaction(txHash)