Update index.html

Author: plagtech

index.html

@@ -963,6 +963,7 @@ <h3 class="font-bold text-orange-800 mb-2 text-sm">🎯 Target Price</h3>
     <script>
         const CONTRACT_ADDRESS = '0xb81fea65B45D743AB62a1A2B351f4f92fb1d4D16'; // MangoSwap V4 - NEW CONTRACT
         const BASE_CHAIN_ID = '0x2105';
+        const GAS_BUFFER_ETH = 0.001; // Reserves ETH for gas estimation
 
         // PAYMASTER CONFIGURATION - Update this with your paymaster service URL
         const PAYMASTER_URL = 'https://api.developer.coinbase.com/rpc/v1/base/0XFTXVSOwf0H30PN84h07BmJgiJhNtRw';
@@ -1511,13 +1512,25 @@ <h3 class="font-bold text-orange-800 mb-2 text-sm">🎯 Target Price</h3>
         document.getElementById('tokenOut').addEventListener('change', getQuote);
 
         document.getElementById('maxBtn').addEventListener('click', () => {
-            if (!isConnected) {
-                alert('Please connect your wallet first');
-                return;
-            }
-            document.getElementById('amountIn').value = userBalanceFrom;
-            getQuote();
-        });
+    if (!isConnected) {
+        alert('Please connect your wallet first');
+        return;
+    }
+    
+    // For native ETH, leave a buffer for gas
+    const tokenIn = document.getElementById('tokenIn').value;
+    const isNativeToken = tokenIn === '0x0000000000000000000000000000000000000000';
+    const gasBuffer = isNativeToken ? GAS_BUFFER_ETH : 0;
+    const maxAmount = Math.max(0, userBalanceFrom - gasBuffer);
+    
+    if (maxAmount <= 0 && isNativeToken) {
+        alert(`Please leave ${GAS_BUFFER_ETH} ETH for gas fees.\n\nYour balance: ${userBalanceFrom.toFixed(4)} ETH\nGas buffer needed: ${GAS_BUFFER_ETH} ETH`);
+        return;
+    }
+    
+    document.getElementById('amountIn').value = maxAmount.toFixed(6);
+    getQuote();
+});
 
         document.getElementById('swapArrow').addEventListener('click', function() {
             const tokenInSelect = document.getElementById('tokenIn');
@@ -2012,8 +2025,27 @@ <h3 class="font-bold text-orange-800 mb-2 text-sm">🎯 Target Price</h3>
                 if (isInstant) {
                     console.log('Executing instant swap...');
 
-                    document.getElementById('btnText').innerHTML = '<span class="spinner"></span> Swapping...';
-                    document.getElementById('scheduleSwapBtn').disabled = true;
+                    if (isInstant) {
+    console.log('Executing instant swap...');
+    
+    // Check if user has enough balance including buffer for gas
+    const isNativeToken = tokenIn === '0x0000000000000000000000000000000000000000';
+    if (isNativeToken) {
+        const amountFloat = parseFloat(amount);
+        if (amountFloat > (userBalanceFrom - GAS_BUFFER_ETH)) {
+            const available = Math.max(0, userBalanceFrom - GAS_BUFFER_ETH);
+            alert(`❌ Insufficient Balance\n\n` +
+                  `Your balance: ${userBalanceFrom.toFixed(4)} ETH\n` +
+                  `Trying to swap: ${amountFloat.toFixed(4)} ETH\n` +
+                  `Gas buffer needed: ${GAS_BUFFER_ETH} ETH\n\n` +
+                  `💡 Maximum you can swap: ${available.toFixed(4)} ETH\n\n` +
+                  `Tip: Click the MAX button to fill in the correct amount!`);
+            return;
+        }
+    }
+    
+    document.getElementById('btnText').innerHTML = '<span class="spinner"></span> Swapping...';
+    document.getElementById('scheduleSwapBtn').disabled = true;
 
                     // Try batched swap first (GAS FREE with paymaster)
                     const batchedResult = await executeBatchedSwap(tokenIn, tokenOut, amountWei, minOutWei);