Derify protocol Ⅱ

There is no competition between investors and liquidity providers. All the funds, profits and losses are contained in the project pool. So the development team assumes the profit and loss are flat in the position part or they have sufficient liquidity or a robust operating strategy to maintain this pool in balance. Financial models of blockchain protocols need to be resilient to attacks. They need to pass simulations and verifications to guarantee the security of the overall protocol. The financial model of this protocol is not in the scope of this audit.

The function `deleteOrderedLimitPositions()` no longer use the index parameter to do the precise deletion (in the old version), but uses the three conditions price, timestamp, and leverage to do the match. It's a little confusing because in any case, an index is more accurate than these conditional matches. Since the prototype of conditional deletion has already been formed, we recommend that the client use conditional matching to do batch deletions.

The contract is serving as the underlying entity to interact with third party `priceFeed` protocols. The scope of the audit treats 3rd party entities as black boxes and assume their functional correctness. However, in the real world, 3rd parties can be compromised and this may lead to lost or stolen assets. In addition, upgrades of 3rd parties can possibly create severe impacts, such as increasing fees of 3rd parties, migrating to new LP pools, etc.