Fixed withdrawal functionality

Author: hara-desu

frontend/lib/forestOnchain.ts

@@ -3,7 +3,7 @@ import type { Abi } from "viem";
 
 // 👉 Replace this with your actual deployed address
 export const FOREST_ONCHAIN_ADDRESS =
-  "0x732b3f7eff51a10A515BC2e2666f9b334B1e78E9" as const;
+  "0xB48e40b165A4cC7A54A955888E5232B6c4f05bdb" as const;
 
 // 👉 Paste the ABI generated by Foundry here (from out/ForestOnchain.sol/ForestOnchain.json)
 export const FOREST_ONCHAIN_ABI = [
@@ -222,6 +222,13 @@ export const FOREST_ONCHAIN_ABI = [
       "outputs": [],
       "stateMutability": "nonpayable"
     },
+    {
+      "type": "function",
+      "name": "totalStaked",
+      "inputs": [],
+      "outputs": [{ "name": "", "type": "uint256", "internalType": "uint256" }],
+      "stateMutability": "view"
+    },
     {
       "type": "function",
       "name": "withdraw",

src/ForestOnchain.sol

@@ -57,6 +57,7 @@ contract ForestOnchain {
     uint constant MAX_SESSION_DURATION = 60 minutes;
     uint constant MIN_SESSION_DURATION = 20 minutes;
     uint constant MIN_NUM_TREES_PER_GOAL = 1;
+    uint256 public totalStaked;
 
     event ActivityAdded(string indexed activityType);
     event SessionStarted(
@@ -160,6 +161,7 @@ contract ForestOnchain {
         }
         uint stakeAmount = goal.stakeAmount;
         delete userGoals[msg.sender][_activityType];
+        totalStaked -= stakeAmount;
         (bool success, ) = payable(msg.sender).call{value: stakeAmount}("");
         if (!success) {
             revert ForestOnchain__TransferFailed();
@@ -180,6 +182,10 @@ contract ForestOnchain {
         if (_amount > address(this).balance) {
             revert ForestOnchain__InsufficientFunds();
         }
+        uint256 available = address(this).balance - totalStaked;
+        if (_amount > available) {
+            revert ForestOnchain__InsufficientFunds();
+        }
         (bool success, ) = _to.call{value: _amount}("");
         if (!success) {
             revert ForestOnchain__TransferFailed();
@@ -340,6 +346,7 @@ contract ForestOnchain {
                     stakeAmount
                 );
             }
+            totalStaked += stakeAmount;
             userGoals[msg.sender][_activityType].activityType = _activityType;
             userGoals[msg.sender][_activityType].startTime = block.timestamp;
             userGoals[msg.sender][_activityType].endTime =