Create Bank.sol

Contracts/Bank.sol

@@ -0,0 +1,26 @@
+// SPDX-License-Identifier: MIT
+pragma solidity 0.8.26;
+
+error etherNotSent();
+error amountTooBig();
+
+// Modified from: https://programtheblockchain.com/posts/2018/01/05/writing-a-banking-contract/
+contract Bank {
+
+    mapping(address => uint256) public balanceOf;   // Balances, indexed by addresses.
+
+    function deposit() public payable {
+        //Effects
+        balanceOf[msg.sender] += msg.value;     // Increase the account's balance.
+    }
+
+    function withdraw(uint256 amount) public {
+        //Checks
+        if(amount > balanceOf[msg.sender]) revert amountTooBig();
+        //Effects
+        balanceOf[msg.sender] -= amount; // Decrease the account's balance BEFORE any external address calls.
+        //Interactions
+        (bool sent, ) = (msg.sender).call{value: amount}(""); // Externally call the user's address to send Ether.
+        if(sent == false) revert etherNotSent(); // Revert if msg.sender is not a payable contract of fails in general.
+    }
+}