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osmosis-labs / isotonic

Smart Contracts for the Lendex Protocol
MIT License
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Lendex Market - charge interests #35

Closed ueco-jb closed 2 years ago

ueco-jb commented 2 years ago

closes https://github.com/confio/lendex/issues/9

A lot of TODOs. Most (if not all) are related to precision. Ethan suggested changing default MULTIPLIER in lendex-token from 1% to 1 permille, but it breakes a lot of tests in token so probably better do this in separate PR.

ueco-jb commented 2 years ago

Actually it's not 100% ready for review. In some test I stumbled upon error: if there's no ltokens minted (so no one deposited tokens), charge interests function will fail on this formula:

l_ratio = b_supply() * ratio / l_supply()

because of lack of ltokens supply.

@ethanfrey how should this case be handled? Just return an error and cancel operation? This is bit weird, because: 1) I create Market contracts with some tokens in proper denom. 2) Borrower borrows some tokens 3) Move time forward 4) Only next operation that requires mint/burn will trigger counting interest charges, which will fail.

So I guess we probably should forbid borrow when no ltokens are minted? Actually that might be a first bit of can_borrow implementation? https://github.com/confio/lendex/blob/main/contracts/lendex-market/src/contract.rs#L218

ethanfrey commented 2 years ago

You should never be able to have more broken than ltokens. how could you have funds to borrow ?

but yeah, good to protect against divide by zero stuff. If there are no ltokens, then just don't give out interest payments.

ethanfrey commented 2 years ago

We will need some follow up issues here

ueco-jb commented 2 years ago

We will need some follow up issues here

https://github.com/confio/lendex/issues/40

uint commented 2 years ago

The conflicts are probably because I moved Interest from lendex-market to utils in the last PR.