Create Uniswap Exchange Wrapper

[richardliang]

Summary

Integrate Uniswap as a liquidity provider for Set issuance orders by creating an Exchange Wrapper contract similar to what we have done with 0x and Kyber.

Implementation

Our exchanges wrappers expose a single public function exchange which implements the necessary logic behind the exchange protocol. Our current exchange wrapper implementations are here for reference.

In the case of Uniswap, there are 3 functions that will execute the swap: 1) ethToTokenSwapInput to swap ETH with ERC-20 Tokens, 2) tokenToEthSwapInput to swap ERC-20 Tokens with ETH, and 3) tokenToTokenSwapInput to swap ERC-20 Tokens with ERC-20 Tokens. More information on the Solidity interface here. Each function above takes in a number of parameters as specified in the interface. The Uniswap frontend code shows how these 3 functions work.

The exchange function should:

1. check allowance for transfer
2. parse order data from the Set issuance order
3. execute ethToTokenSwapInput, tokenToEthSwapInput, or tokenToTokenSwapInput depending on ETH or ERC-20 swap
4. transfer unused maker token back to the issuance order user

A good source of reference is how we've implemented our exchange wrappers linked above. Feel free to discuss with us further on Telegram!