This repository contains solidity contracts to enable limit orders for Sushiswap.
On Sushiswap, you can swap any ERC20 token for another ERC20 token instantly.
However it does not support limit order feature. It only allows you to submit an order with a pair of amount and price. It will either succeed or fail instantly so that you cannot submit an order of a expectedly lower price than now and wait for it to be settled.
Contracts in this repo help you submit a limit order with a lower price than what it is now. Later, when the price gets lower enough to meet the requirement of your order, it gets settled.
It works in a decentralized manner, without the need of any centralized authority.
OrderBook is deployed at 0xc425f76fa58d92e8732d48ab61ef494c73561d96 on kovan and rinkeby testnets.
OrderBook keeps limit orders that users have submitted. Anyone can call createOrder() to create a limit order with the amount to sell and the minimum price. He/she needs to approve the amount to sell for the Settlement contract.
The maker of the order can cancel it with cancelOrder(). It accepts the hash of the order created.
To reduce users' gas fee, OrderBook isn't deployed on the mainnet. The one on kovan testnet is used for production.
Settlement is deployed at 0x82b9d42b2779af7a40c93ac0df2ba76ffc5fbbc8 on the Ethereum mainnet, kovan and rinkeby testnets.
Settlement is in charge of swapping tokens for orders. Anyone can call fillOrder() to fill the order submitted. We'll call this caller a 'relayer'. Relayers need to call it with proper parameters to meet the minimum price requirement set in the order. If the call is successful, fee will be transferred to the relayer.
It is possible to fill only a certain amount of tokens, not all. In most cases, submitted orders will reside on the OrderBook and their amount will be filled by different callers in different blocks.
Settlement is a wrapper contract around UniswapV2Router02. Every function in this contract has a duplicated version in the Settlement with an extra parameter args. If args is not empty, it is used for filling orders; see Settlement.fillOrders() for details.
So, users for sushiswap can choose to be a relayer or not. If he/she decided to do so, calling any swap functions in Settlement will benefit them. Otherwise, he/she can just call functions in UniswapV2Router02 without receiving any fee.
For every fillOrder() call, 0.2% of fee for the amount sold is transferred to the relayer. The fee is deducted prior to the swap.
Let's assume Alice created an order to sell 1 ETH with the minimum price of 500 DAI. Current price of ETH is 400 DAI so this order cannot be filled right away. Leter, when the market price goes up to 500 DAI, Bob is trying to fill the entire amount of this order as a relayer.
If the call is successful, amounts of tokens transferred are:
- Limit Order Fee: 1 ETH x 0.2% = 0.002 ETH (goes to Bob; relayer)
- Swap Fee: (1 ETH - 0.002 ETH) x 0.3% = 0.002994 ETH (goes to the liquidity provider)
- ETH Amount Sold: 1 ETH - 0.002 ETH - 0.002994 ETH = 0.995006 ETH (goes to the liquidity pool)
- DAI Amount Bought: 0.995006 ETH x 500 DAI = 497.503 DAI (goes to Alice; maker)
MIT