Vault.sol

pragma solidity ^0.4.24;

contract ERC20 {
    
    function transferFrom(address from, address to, uint amount) public returns (bool);
}

contract ERC777 {
    
    function send(address to, uint amount, bytes data) public;
}

contract Vault {
    
    mapping (address => mapping (address => uint)) private balances;
    bool private duringDeposit;
    
    // ERC20 (requires approval)
    function deposit(ERC20 erc20, uint amount) external setDuringDeposit {
        require(erc20.transferFrom(msg.sender, this, amount));
        balances[erc20][msg.sender] += amount;
    }
    
    function withdraw(ERC20 erc20, uint amount) external {
        require(balances[erc20][msg.sender] >= amount);
        balances[erc20][msg.sender] -= amount;
        require(erc20.transferFrom(this, msg.sender, amount));
    }
    
    // ERC223 / ERC677 compatibility
    function tokenFallback(address from, uint amount, bytes /*data*/) external notDuringDeposit returns (bytes4) {
        balances[msg.sender][from] += amount;
        return 0xc0ee0b8a;
    }
    
    // ERC777 compatibility (assume this contract has registered itself as defined in ERC820/ERC777)
    function tokensReceived(address operator, address /*from*/, address /*to*/, uint amount, bytes /*userData*/, bytes /*operatorData*/) external notDuringDeposit {
        balances[msg.sender][operator] += amount;
    }
    
    function safeWithdraw777(ERC777 erc777, uint amount, bytes data) external {
        require(balances[erc777][msg.sender] >= amount);
        balances[erc777][msg.sender] -= amount;
        erc777.send(msg.sender, amount, data);
    }
    
    modifier setDuringDeposit {
        duringDeposit = true;
        _;
        duringDeposit = false;
    }
    
    modifier notDuringDeposit {
        if (!duringDeposit) {
            _;
        }
    }
}