# PalPool
**PalPools** are the main component of the Protocol.
Each **PalPool** is independent and holds its own underlying **ERC20** governance token.
Users can deposit the underlying token in the **PalPool**, receiving an amount of **PalToken** representing their share in the **PalPool**, and receive part of the fees of the **PalPool**.
The main use of the **PalPool** is to **Borrow** voting/proposition power. When starting a **Borrow**, the **PalPool** will create a **PalLoan**, by cloning the **Delegator** contract set in the **PalPool**, it will transfer the amount of tokens borrowed and the fees paid by the borrower, delegate the **PalLoan** voting power to the borrower, and issue a **PalLoanToken** to represent the ownership of the **PalLoan**.
The **Borrow** can later be extended, closed (and the unused fees will be returned to the borrower), or killed if all the fees were used. The owner of the **Borrow** can also change the recipient of his **PalLoan** voting power.
{% hint style="info" %}
A Borrow is the data struct listed in the PalPool storage, listing all the data relative to the borrowed voting power. A PalLoan (also referred as Loan) is the contract holding the voting power, and delegating it to the given address.
Each PalLoan is linked to a Borrow, and to a PalLoanToken (ERC 721 token representing ownership of a PalLoan and its Borrow)
{% endhint %}
## Methods :
### Events :
**Deposit**
`event Deposit(address user, uint amount, address palPool);`
When a user deposits in the Pool.\
**Withdraw**
`event Withdraw(address user, uint amount, address palPool);`
When a user withdraws from the Pool.\
**NewLoan**
`event NewLoan(address borrower, address delegatee, address underlying, uint amount, address palPool, address loanAddress, uint256 palLoanTokenId, uint startBlock);`
When a Borrow is started and a PalLoan is created.\
**ExpandLoan**
`event ExpandLoan(address borrower, address delegatee, address underlying, address palPool, uint newFeesAmount, address loanAddress, uint256 palLoanTokenId);`
When the borrower adds more fees to the PalLoan to extend the duration of the loan.\
**ChangeLoanDelegatee**
`event ChangeLoanDelegatee( address borrower, address newDelegatee, address underlying, address palPool, address loanAddress, uint256 palLoanTokenId);`
When the borrower change the delegatee (recipient of the voting power) of the PalLoan\
**CloseLoan**
`event CloseLoan(address borrower, address delegatee, address underlying, uint amount, address palPool, uint usedFees, address loanAddress, uint256 palLoanTokenId, bool wasKilled);`
When the Borrow is either closed or killed (the wasKilled flag is ‘true’ if the Borrow was killed).\
\
### Read-only methods :
**palLoanToken**
`function palLoanToken() public view returns(address);`
Returns the address of the PalLoanToken contract\
**underlying**
`function underlying() public view returns(address);`
Returns the underlying governance token held by the Pool\
**palToken**
`function palToken() public view returns(address);`
Returns the address of the palToken linked to this Pool\
**totalReserve**
`function totalReserve() public view returns(uint);`
Returns the amount in the Pool’s Reserve (in wei)\
**totalBorrowed**
`function totalBorrowed() public view returns(uint);`
Returns the current total amount of funds borrowed from the Pool (in wei)\
**minBorrowLength**
`function minBorrowLength() public view returns(uint);`
Returns the minimum duration of a Borrow (in number of blocks)\
**killFactor**
`function killFactor() public view returns(uint);`
Returns the health factor value at which a Borrow can be killed (scale 1e18)\
**killerRatio**
`function killerRatio() public view returns(uint);`
Returns the ratio of fees to reward the killer of a Borrow (scale 1e18)\
**reserveFactor**
`function reserveFactor() public view returns(uint);`
Returns the factor of fees to set as Reserve (scale 1e18)\
**accrualBlockNumber**
`function accrualBlockNumber() public view returns(uint);`
Returns the block number for the last interest update for this Pool\
**borrowIndex**
`function borrowIndex() public view returns(uint);`
Returns the last computed Borrow Index for this Pool (scale 1e18)\
**controller**
`function controller() public view returns(address);`
Returns the address of the current Controller for this Pool\
**underlyingBalance**
`function underlyingBalance() public view returns(uint);`
Returns the amount of underlying token in the Pool (in wei)\
**balanceOf**
`function balanceOf(address _account) external view returns(uint);`
Returns balance of the user in palToken (in wei)\
**underlyingBalanceOf**
`function underlyingBalanceOf(address _account) external view returns(uint)`
Returns balance of the user in the underlying token (in wei)\
**isLoanOwner**
`function isLoanOwner(address _loanAddress, address _user) external view returns(bool)`
Returns 'true' if the given user is the owner of the PalLoan\
**idOfLoan**
`function idOfLoan(address _loanAddress) external view returns(uint256)`
Returns the PalLoanToken Id for the given PalLoan\
**getLoansPools**
`function getLoansPools() external view returns(address [] memory);`
Returns a list of all the Loans (active or closed)\
**getLoansByBorrower**
`function getLoansByBorrower(address _borrower) external view returns(address [] memory);`
Returns a list of all the user's Loans (active or closed)\
**getBorrowData**
`function getBorrowData(address _loanAddress) external view returns (address _borrower, address _loan, uint _amount, address _underlying, uint _feesAmount, uint _feesUsed, uint _startBlock, bool _closed)`
Returns all the data stored for the given Borrow (for the given PalLoan)
***Parameters :***
| name | type | desc |
| --------------------------- | --------------------- | ------------------------------------ |
| \_loanAddress
| address
| address of the PalLoan
|
***Returns :***
| name | type | desc |
| ---------------- | ------- | ----------------------------------------------------------------------- |
| \_borrower | address | address of the owner of the Borrow (by being owner of the PalLoanToken) |
| \_delegatee | address | address of the recipient of the voting power |
| \_loanPool | address | address of the PalLoan for this Borrow |
| \_palLoanTokenId | uint256 | id of the PalLoanToken for this PalLoan |
| \_amount | uint | amount of token borrowed for delegation |
| \_underlying | address | address of the governance token |
| \_feesAmount | uint | amount of fees paid by the borrower |
| \_feesUsed | uint | amount of fees already used by the Borrow |
| \_startBlock | uint | block where the Borrow was started |
| \_closed | bool | ‘false’ if the Borrow is still active |
| \_killed | bool | 'true' if the Borrow was killed |
**borrowRatePerBlock**
`function borrowRatePerBlock() external view returns (uint);`
Returns the current Borrow Rate (scale 1e18)\
**supplyRatePerBlock**
`function supplyRatePerBlock() external view returns (uint);`
Returns the current Supply Rate (scale 1e18)\
**exchangeRateStored**
`function exchangeRateStored() external view returns (uint);`
Returns the last updated Exchange Rate (scale 1e18)\
**minBorrowFees**
`function minBorrowFees(uint _amount) external view returns (uint);`
Amount minimum of fees to allow the borrow() method. Calculated on the given amount parameter (in wei). Return the minimum amount of fees (in wei)\
**isKillable**
`function isKillable(address _loan) external view returns(bool);`
Returns true if the health factor of a Borrow (given by the PalLoan address) is low enough to be killed\
### **State-changing methods :**
**deposit**
`function deposit(uint _amount) external returns(uint);`
Deposit the underlying token into the Pool, and receive an amount of palToken corresponding to the deposit.
***Parameters :***
| name | type | desc |
| -------- | ---- | -------------------------------------- |
| \_amount | uint | amount of token to deposit in the Pool |
***Returns :***
| name | type | desc |
| ---- | ---- | -------------------------------------- |
| | uint | amount of palTokens minted to the user |
{% hint style="info" %}
The \_amount value must be approved for the PalPool before this transaction
{% endhint %}
**withdraw**
`function withdraw(uint _amount) external returns(uint);`
Burn an amount of palToken to withdraw the underlying token of the Pool.
***Parameters :***
| name | type | desc |
| -------- | ---- | -------------------------- |
| \_amount | uint | amount of palToken to burn |
***Returns :***
| name | type | desc |
| ---- | ---- | ----------------------------------------------- |
| | uint | amount of underlying token returned to the user |
###
**borrow**
`function borrow(address _delegatee, uint _amount, uint _feeAmount) external returns(uint);`
Starts a Borrow, creates a PalLoan (and mint the PalLoanToken linked to this PalLoan), and sends the borrowed amount and the fees to the PalLoan, to delegate the voting/proposition power to the delegatee.
A minimum of fees, to cover the Minimum Borrow Length, is required to start the Borrow
***Parameters :***
| name | type | desc |
| ----------- | ------- | ------------------------------------------------------------------------------------------------ |
| \_delegatee | address | address to receive the voting power |
| \_amount | uint | amount of governance token to borrow (representing how much power to receive through delegation) |
| \_feeAmount | uint | amount of fees paid for the Borrow |
***Returns :***
| name | type | desc |
| ---- | ---- | ----------------------------------------- |
| | uint | amount of token delegated to the borrower |
{% hint style="info" %}
The \_feeAmount value must be approved for the PalPool before this transaction
{% endhint %}
**expandBorrow**
`function expandBorrow(address _loanPool, uint _feeAmount) external returns(uint);`
If the borrower wants to extend his Borrow length, fees can be paid to be added to the Borrow (and transferred to the corresponding PalLoan)
***Parameters :***
| name | type | desc |
| ----------- | ------- | ----------------------------------------------------- |
| \_loanPool | address | address of the PalLoan linked to the Borrow to expand |
| \_feeAmount | uint | amount of fees to add to the Borrow |
***Returns :***
| name | type | desc |
| ---- | ---- | ---------------------------------- |
| | uint | amount of fees added to the Borrow |
{% hint style="info" %}
The \_feeAmount value must be approved for the PalPool before this transaction
{% endhint %}
**closeBorrow**
`function closeBorrow(address _loanPool) external;`
A borrower can close his own Borrows if he wants, recovering the fees not used.
If the borrower tries to close the Borrow before the Minimum Borrow Length, Penalty Fees will be be applied to the fees to return to the users, corresponding to the amount of fees to pay up to the Minimum Borrow Length (applied using the Borrow Rate at the time of closing).
***Parameters :***
| name | type | desc |
| ---------- | ------- | ---------------------------------------------------- |
| \_loanPool | address | address of the PalLoan linked to the Borrow to close |
###
**killBorrow**
`function killBorrow(address _loanPool) external;`
If a Borrow used all its fees, it can be killed to stop the delegation, and return the voting power to the Pool.
The Killer cannot be the user owning the Borrow, and the Killer is rewarded a part of the fees of this Borrow.
***Parameters :***
| name | type | desc |
| ---------- | ------- | --------------------------------------------------- |
| \_loanPool | address | address of the PalLoan linked to the Borrow to kill |
###
**changeBorrowDelegatee**
`function changeBorrowDelegatee(address _loanPool, address _newDelegatee) external;`
Changes the recipient of voting power for the given PalLoan, updating the data in the Borrow, and triggering a delegation process for the PalLoan to give the voting power to the new delegatee address.
***Parameters :***
| name | type | desc |
| -------------- | ------- | ---------------------------------------------------------------- |
| \_loanPool | address | address of the PalLoan |
| \_newDelegatee | address | address of the new delegatee to receive the PalLoan voting power |
###
**exchangeRateCurrent**
`function exchangeRateCurrent() external returns (uint);`
Updates the Pool state & returns the last updated Exchange Rate
***Returns :***
| name | type | desc |
| ---- | ---- | --------------------------------------------------- |
| | uint | current Exchange Rate for the palToken (scale 1e18) |
###
**\_updateInterest**
`function _updateInterest() external returns (uint);`
Update the Pool interests & storage values. This method is called before any deposit/withdraw/borrow/closeBorrow/…, but can also be called to update the Pool state.
***Returns :***
| name | type | desc |
| ---- | ---- | -------------- |
| | bool | Update success |
---
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