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Example Contract Implementation

Once the key functions are understood, the implementation of a contract that inherits SingleSidedLiquidityVault will be easier and safer.

For instance, let's take the StethLiquidityVault implementation as an example (check the source code here). In this case, the vault will be harvesting rewards from Aura. Therefore, it will first deposit its liquidity on Balancer and, afterwards, deposit the received BPT on Aura.

Custom Variables and Getters​

The SingleSidedLiquidityVault defines custom variables that help handle the interactions with Balancer and Aura Finance.

Integration State​

IVault public vault;

vault holds the interface to interact with the Balancer Vault (on Balancer all the liquidity is managed in a single core vault).

struct AuraPool {
    uint256 pid;
    IAuraBooster booster;
    IAuraRewardPool rewardsPool;
}

AuraPool public auraPool;

auraPool stores the necessary information to deposit (BPTs managed by auraPool.booster and deposited on auraPool.pid) and harvest (rewards are claimed from auraPool.rewardsPool) on Aura.

struct OracleFeed {
    AggregatorV3Interface feed;
    uint48 updateThreshold;
}

OracleFeed public ohmEthPriceFeed;
OracleFeed public ethUsdPriceFeed;
OracleFeed public stethUsdPriceFeed;

Finally, to handle the price conversions, different Chainlink price oracles must be used.

Overriding Virtual Functions​

The easiest way to implement a these functions is by directly checking the StethLiquidityVault code). Nevertheless, this section will list some of the this that any developer should have in mind.

deposit​

When implementing the _deposit function:

  1. Cast the liquidity pool address from abstract to Balancer Base pool.
  2. Fetch the underlying liquidity before joinning the pool (it will be used later to know the resulting LP tokens).
  3. Approve the core Balancer Vault as spender of both tokens (OHM and the pair token).
  4. Make a request to the Balancer Vault to join the liquidity pool.
  5. Calculate the amount of resulting LP tokens, approve the Aura Booster as a spender, and deposit them there.
  6. Return the amount of resulting BPT tokens.

withdraw​

When implementing the _withdraw function:

  1. Cast the liquidity pool address from abstract to Balancer Base pool.
  2. Fetch the underlying naked assets (OHM and the pair token) held by the vault.
  3. Unstake the BPT tokens from Aura.
  4. Make a request to the Balancer Vault to leave the liquidity pool.
  5. Return the amount of extra tokens (OHM and the pair token) held in the vault.

accumulateExternalRewards​

When implementing the _accumulateExternalRewards function:

  1. Loop over the externalRewardTokens to cast the balances of the vault.
  2. Harvest the rewards from Aura.
  3. Loop over the externalRewardTokens again to cast the new balances of the vault.
  4. Return a list with the harvested rewards for each token in the externalRewardTokens array.

valueCollateral​

When implementing the _valueCollateral function:

  1. Fetch the necessary price feed oracles to get the ratio of OHM / PairToken. Make sure that the decimals are in place.
  2. Return the conversion of the input _amount of pair token in OHM terms.

getPoolPrice​

When implementing the _getPoolPrice function:

  1. Calculate the OHM / pairToken ratio of the Liquidity pool by fetching the amount of each token in the pool.

getPoolOhmShare​

When implementing the _getPoolOhmShare function:

  1. Calculate the vault's share on the liquidity pool.