feat(ics20): initial version of transfer app

[gjermundgaraba]

Implements one-way transfer (i.e. receive is not implemented here, will be done in a separate PR).

[srdtrk]

Amazing work! And so quick. I gave some initial feedback. Looks good overall. The only major change needed is that the sendTransfer flow should be starting in ICS20Transfer.sol, not ICS26Router.sol. You can refer to my comments and the CosmWasm implementation for this.

So the flow goes ICS20Transfer.sol -> ICS26Router.sol -> ICS20Transfer.sol

I actually think what we did is also ok, and could be supported, but this is the main flow Aditya and I decided.

[srdtrk]

Can we check that the number of decimals make sense. For example, if cosmos is uint64 and eth is uint256. Then we need to normalize the decimals?

Have you thought about how we might handle this?

[gjermundgaraba]

This is a good question. There are two issues here I suppose.

• One is the actual uint256 which might cause problems (can be too big for go, I guess?)
• The other is the decimals variable itself, which is mostly required for frontends to make sense of a token. If the contract implements IERC20Metadata we can get this info, but not sure if we can do much with it. Even if the number of decimals makes sense, the number might still be too big.

One thing we could do is to check the size of the number and if it would not fit into go uint64, we would reject? Not sure what the alternative is, if the Cosmos SDK and ibc-go doesn't support big numbers.

I saw someone mentioning this problem, but not sure where things break: https://x.com/brane_trix/status/1818055801463812494

[srdtrk]

I think we can handle this situation if we know the decimals variable. Can discuss this later I suppose

[srdtrk]

Lgtm!