HaloDAO AMM v1

A decentralized foreign exchange protocol optimized for stablecoins.

Overview

HaloDAO AMM is a clone of DFX.

There are two major parts to the protocol: Assimilators and Curves (formerly Shells). Assimilators allow the AMM to handle pairs of different value while also retrieving reported oracle prices for respective currencies. Curves allow the custom parameterization of the bonding curve with dynamic fees, halting bounderies, etc.

Assimilators

Assimilators are a key part of the protocol, it converts all amounts to a "numeraire" which is essentially a base value used for computations across the entire protocol. This is necessary as we are dealing with pairs of different values.

Oracle price feeds are also piped in through the assimilator as they inform what numeraire amounts should be set. Since oracle price feeds report their values in USD, all assimilators attempt to convert token values to a numeraire amount based on USD.

Curve Parameter Terminology

High level overview.

Name	Description
Weights	Weighting of the pair (only 50/50)
Alpha	The maximum and minimum allocation for each reserve
Beta	Liquidity depth of the exchange; The higher the value, the flatter the curve at the reported oracle price
Delta/Max	Slippage when exchange is not at the reported oracle price
Epsilon	Fixed fee
Lambda	Dynamic fee captured when slippage occurs

For a more in-depth discussion, refer to section 3 of the shellprotocol whitepaper

Major changes from the Shell Protocol

The main changes between our implementation and the original code can be found in the following files:

• All the assimilators
• Curve.sol (formerly Shell.sol)
• CurveFactory.sol (formerly ShellFactory.sol)
• Router.sol
• ProportionalLiquidity.sol
• Swaps.sol

Changing the term "Shell" to "Curve"

Throughout the repository, the term Shell has been changed to Curve. For example, Shell.sol has been renamed to Curve.sol, and ShellFactory.sol to CurveFactory.sol, etc.

Different Valued Pairs

In the original implementation, all pools are assumed to be baskets of like-valued tokens. In our implementation, all pools are assumed to be pairs of different-valued FX stablecoins (of which one side is always USDC).

This is achieved by having custom assimilators that normalize the foreign currencies to their USD counterparts. We're sourcing our FX price feed from chainlink oracles. See above for more information about assimilators.

Withdrawing and depositing related operations will respect the existing LP ratio. As long as the pool ratio hasn't changed since the deposit, amount in ~= amount out (minus fees), even if the reported price on the oracle changes. The oracle is only here to assist with efficient swaps.

Third Party Libraries

• Openzeppelin contracts (v3.3.0)
• ABDKMath (v2.4)
• Shell Protocol@48dac1c

Deployment

Deployment Doc

Router API

Views

viewOriginSwap

function viewOriginSwap(
    address _quoteCurrency,
    address _origin,
    address _target,
    uint256 _originAmount
) external view returns (uint256 targetAmount_)

Views how much a target amount is returned given a fixed origin amount.

Name	Type
_quoteCurrency	address	Address of the intermediate currency (USDC)
_origin	address	Address of the origin token
_target	address	Address of the target
_originAmount	uint256	Amount of origin tokens to swap
targetAmount_	uint256	Amount of target tokens to received

viewTargetSwap

function viewTargetSwap(
    address _quoteCurrency,
    address _origin,
    address _target,
    uint256 _targetAmount
) external view returns (uint256 originAmount_)

Views how much a origin amount is required given a wanted target amount.

Name	Type
_quoteCurrency	address	Address of the intermediate currency (USDC)
_origin	address	Address of the origin token
_target	address	Address of the target
_targetAmount	uint256	Amount of target tokens wanted
originAmount_	uint256	Amount of origin tokens required

State Changing

originSwap

function originSwap(
    address _quoteCurrency,
    address _origin,
    address _target,
    uint256 _originAmount,
    uint256 _minTargetAmount,
    uint256 _deadline
)

Swaps a fixed origin amount for a dynamic target amount.

Name	Type
_quoteCurrency	address	Address of the intermediate currency (USDC)
_origin	address	Address of the origin token
_target	address	Address of the target
_originAmount	uint256	Amount of origin tokens to swap
_minTargetAmount	uint256	Minimum amount of target tokens to receive
_deadline	uint256	Epoch time of which the transaction must be completed by

Curve API

Views

viewOriginSwap

function viewOriginSwap(
    address _origin,
    address _target,
    uint256 _originAmount
) external view returns (uint256 targetAmount_)

Views how much a target amount is returned given a fixed origin amount.

Name	Type
_origin	address	Address of the origin token
_target	address	Address of the target
_originAmount	uint256	Amount of origin tokens to swap
targetAmount_	uint256	Amount of target tokens to received

viewTargetSwap

function viewTargetSwap(
    address _origin,
    address _target,
    uint256 _targetAmount
) external view returns (uint256 originAmount_)

Views how much a origin amount is needed given for a fixed target amount.

Name	Type
_origin	address	Address of the origin token
_target	address	Address of the target
_targetAmount	uint256	Amount of target tokens to receive
originAmount_	uint256	Amount of origin tokens to needed to supply

viewDeposit

function viewDeposit(
    uint256 _deposit
) external view returns (uint256 curveTokens_, uint256[] memory amounts_)

Views how many curve lp tokens will be minted for a given deposit, as well as the amount of tokens required from each asset.

Note that _deposit is denominated in 18 decimals.

Name	Type
_deposit	address	Total amount of tokens to deposit (denominated in USD)
curveTokens_	uint256	Amount of LP tokens received
amounts_	uint256[]	Amount of tokens for each address required

For example, if the CAD/USD rate was 0.8, a deposit of 100e18 will require 50 USDC and 50 USDC worth of CAD, which is 50/0.8 = 62.5 CADC.

viewWithdraw

function viewWithdraw(
    uint256 _curvesToBurn
) external view returns (uint256[] memory amounts_)

Views how many tokens you will receive for each address when you burn _curvesToBurn amount of curve LP tokens.

Name	Type
_curvesToBurn	uint256	Amount of LP tokens to burn
amounts_	uint256[]	Amount of tokens for each address received

State Changing

Note you'll need to approve tokens to the curve address before any of the following can be performed.

originSwap

function originSwap(
    address _origin,
    address _target,
    uint256 _originAmount,
    uint256 _targetAmount,
    uint256 _deadline
)

Swaps a fixed origin amount for a dynamic target amount.

Name	Type
_origin	address	Address of the origin token
_target	address	Address of the target
_originAmount	uint256	Amount of origin tokens to swap
_minTargetAmount	uint256	Minimum amount of target tokens to receive
_deadline	uint256	Epoch time of which the transaction must be completed by

targetSwap

function targetSwap(
    address _origin,
    address _target,
    uint256 _maxOriginAmount,
    uint256 _targetAmount,
    uint256 _deadline
)

Swaps a dynamic origin amount for a fixed target amount

Name	Type
_origin	address	Address of the origin token
_target	address	Address of the target
_maxOriginAmount	uint256	Maximum amount of origin tokens to swap
_targetAmount	uint256	Amount of target tokens that wants to be received
_deadline	uint256	Epoch time of which the transaction must be completed by

deposit

function deposit(
    uint256 _deposit,
    uint256 _deadline
)

Deposit into the pool a proportional amount of assets. The ratio used to calculate the proportional amount is determined by the pool's ratio, not the oracles. This is to prevent LPs from getting rekt'ed.

On completion, a corresponding amount of curve LP tokens is given to the user.

Note that _deposit is denominated in 18 decimals.

Name	Type
_deposit	address	Total amount of tokens to deposit (denominated in USD)
_deadline	address	Epoch time of which the transaction must be completed by

For example, if the CAD/USD rate was 0.8, a deposit of 100e18 will require 50 USDC and 50 USDC worth of CAD, which is 50/0.8 = 62.5 CADC.

withdraw

function withdraw(
    uint256 _curvesToBurn,
    uint256 _deadline
)

Withdraw amount of tokens from the pool equally.

Note that the amount is denominated in 18 decimals.

Name	Type
_curvesToBurn	address	The amount of curve LP tokens to burn
_deadline	address	Epoch time of which the transaction must be completed by