#6 airdrop

[Ddorsmt]

No description provided.

[huy525]

Overall everything is good! Nice use of modifiers, code is easy to understand and error-free (from what I see). Just a few small thoughts:

• address(0) convention for balanceToken()/balanceETH() and claimAllToken() is a bit unusual, but OK. Should there be a test for balanceETH(address(0))?
• Maybe shouldn't use the word "approve" because it's in ERC20 (I think so not really sure). And the "true" boolean return value isn't necessary as code would revert otherwise. It's mentioned in yesterday's impromptu session, but I guess you missed the first part lol.
• Small typo in tests, should be "test approveETH: too poor" instead of "test approveETH: not owner".
• I guess your code doesn't support direct ERC20 transfer the native transfer() function, huh. Will the funds be lost forever if someone accidentally used transfer()? Maybe instead of _undistributedToken and _undistributed just call IERC20().balanceOf() and address(this).getBalance()? Just my two cents tho lol.
• Brilliant gamble() function! Add tests to ensure it works perfectly ... as expected ...?

Edit: Oh, and Duong commented on my PR that gas can be explicitly calculated in testing, so that might help.

[hruiyang]

Interesting gamble function! Not sure if there's really a gambling element or it's a 100% sure-lose tho LMAO.

That's aside, the code is mostly fine, it is quite sound!

1. I think you can use Ownable or BoringOwnable for ownership of smart contracts!
2. Also, you can use SafeERC20 or TransferHelper to do transfers, this way you don't need to worry about whether or not there is enough balance for the user (in your require statements)
3. I think you can change some of the public functions to external