There is a Liquidity Providers’ Pool (LPP) instance per denomination (LPN, i.e., native currency of an LPP), serving all lenders that provide liquidity in that same currency. Upon deposits, lenders obtain an amount of CW20 interest-bearing token or nLPN. Interest amounts are computed via index-based interest accrual.
Each nLPN represents a fraction of the deposited amount relative to the total amount of the pool. The interest accrued and paid by the borrowers enters the pool and increases the nLPN price. Once a lender withdraws nLPN, the received amount includes the interest accrued for providing the loan to the borrowers.
If a user wants to become a lender in an LPP, they need to have some LPN in their wallet, for example, USDC. This amount is transferred with an input message and handled by the bank module of the Cosmos SDK.
Since lenders are depositing to a pool, they need a receipt token back. It guarantees a share of the pool and can be used to withdraw the underlying assets. The balance of this receipt token is introduced to the state of the LPP smart contract initialized at 0 alongside an additional parameter describing its initial price. The price of the underlying LPN tokens is also specified as another parameter. If the balance of the nLPN tokens is empty, then the price of a single nLPN token would be equal to the initial derivative price (1 nLPN = 1 LPN). Otherwise, one needs to take into account the newly deposited LPN tokens and the loan interest rate from the borrowers. As time passes, the nLPN to LPN ratio will increase, which means one nLPN token would increase its price relative to a single LPN token. The lender's balance can always be calculated by:
lender's balance in LPN = lender's deposited nLPN * price per nLPN
The amount of deposited nLPN tokens by the lender is extracted from the record with the lender’s wallet address as a key that has been provided with the deposit transaction.
To withdraw LPN tokens, the wallet address needs to have a positive amount of nLPN tokens. The request can be called multiple times, and the amount can be withdrawn in tranches.
Initially, the price of the provided nLPN in LPN is computed to determine how much the lender can withdraw:
withdraw amount in LPN = withrawn nLPN * price per nLPN
Afterward, the balance of the nLPN in the LPP smart contract is decreased accordingly alongside the balance of the LPN tokens. Should the user wish to withdraw everything, then the rewards will be claimed and the user will not be a lender anymore. If the user wishes to withdraw only 50% of their deposited amount, then their nLPN token holdings would decrease by 50%.
Each LPP instance regularly receives rewards from the Rewards Dispatcher smart contract based on LPP instance’s total value locked (TVL) and the cumulative TVLs of all other LPP instances. The LPP keeps track of incoming and outgoing rewards, as well as minting and burning lenders’ CW-20 tokens by maintaining a global amount of rewards in uNLS per nLPN. Each new reward increases the global reward per nLPN**.** When a lender deposits or withdraws/burns nLPN, rewards accrued by that lender for the balance so far is calculated based on the value of the global reward per nLPN. That amount is added to the pending rewards balance of uNLS for that user.
<aside> ℹ️ The rewards per nLPN in uNLS are part of the global deposits’ state managed by the LPP smart contract, whereas the uNLS balance is kept by the bank module.
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<aside> ℹ️ Lender is an instance per lender containing the lender’s address, their deposited nLPN, the rewards per nLPN denominated in uNLS, and any pending rewards in uNLS.
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