# Carbon pool contracts

Toucan's Carbon Pool smart contracts extend the ERC20 standard — carbon reference tokens are ERC20 tokens. Pool contracts are upgradeable. Contract addresses for deployed carbon pools can be found at [app.toucan.earth/contracts](https://app.toucan.earth/contracts).

### calculateDepositFees

```solidity
function calculateDepositFees(address tco2, uint256 amount) external view returns (uint256 feeDistributionTotal)
```

View function to calculate deposit fees pre-execution

*User specifies in front-end the address and amount they want*

#### Parameters

| Name   | Type    | Description           |
| ------ | ------- | --------------------- |
| tco2   | address | TCO2 contract address |
| amount | uint256 | Amount to redeem      |

#### Return Values

| Name                 | Type    | Description                 |
| -------------------- | ------- | --------------------------- |
| feeDistributionTotal | uint256 | Total fee amount to be paid |

### calculateRedemptionOutFees

```solidity
function calculateRedemptionOutFees(address[] tco2s, uint256[] amounts, bool toRetire) external view returns (uint256 feeDistributionTotal)
```

View function to calculate fees pre-execution, according to the amounts of TCO2 to be redeemed.

#### Parameters

| Name     | Type       | Description                                                                                                                                        |
| -------- | ---------- | -------------------------------------------------------------------------------------------------------------------------------------------------- |
| tco2s    | address\[] | Array of TCO2 contract addresses                                                                                                                   |
| amounts  | uint256\[] | Array of TCO2 amounts to redeem The indexes of this array are matching 1:1 with the tco2s array.                                                   |
| toRetire | bool       | Whether the TCO2s will be retired atomically with the redemption. It may be that lower fees will be charged in this case. Currently not supported. |

#### Return Values

| Name                 | Type    | Description                 |
| -------------------- | ------- | --------------------------- |
| feeDistributionTotal | uint256 | Total fee amount to be paid |

### checkEligible

```solidity
function checkEligible(address vintageToken) external view virtual returns (bool isEligible)
```

Checks if token to be deposited is eligible for this pool. Reverts if not. Beware that the revert reason might depend on the underlying implementation of IPoolFilter.checkEligible

#### Parameters

| Name         | Type    | Description           |
| ------------ | ------- | --------------------- |
| vintageToken | address | the contract to check |

#### Return Values

| Name       | Type | Description                                           |
| ---------- | ---- | ----------------------------------------------------- |
| isEligible | bool | true if address is eligible and no other issues occur |

### deposit

```solidity
function deposit(address tco2, uint256 amount, uint256 maxFee) external returns (uint256 mintedPoolTokenAmount)
```

Deposit function for pool that accepts TCO2s and mints pool token 1:1

*Eligibility of the ERC20 token to be deposited is checked via `checkEligible`*

#### Parameters

| Name   | Type    | Description                                                                                                                                                                                                                                                                                     |
| ------ | ------- | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| tco2   | address | TCO2 to be deposited. The pool contract needs to be approved in the TCO2 contract by the caller in order to allow the transfer of TCO2 tokens to the pool                                                                                                                                       |
| amount | uint256 | Amount of TCO2 to be deposited                                                                                                                                                                                                                                                                  |
| maxFee | uint256 | Maximum fee to be paid for the deposit. This value cannot be zero. Use `calculateDepositFees(tco2,amount)` to determine the fee that will be charged given the state of the pool during this call. Add a buffer on top of the returned fee amount up to the maximum fee you are willing to pay. |

#### Return Values

| Name                  | Type    | Description                                |
| --------------------- | ------- | ------------------------------------------ |
| mintedPoolTokenAmount | uint256 | Amount of pool tokens minted to the caller |

### redeemOutMany

```solidity
function redeemOutMany(address[] tco2s, uint256[] amounts, uint256 maxFee) external virtual returns (uint256 poolAmountSpent)
```

Redeem TCO2s for pool tokens 1:1 minus fees The amounts provided are the exact amounts of TCO2s to be redeemed.

#### Parameters

| Name    | Type       | Description                                                                                                                                                                                                                                                                                                      |
| ------- | ---------- | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| tco2s   | address\[] | Array of TCO2 contract addresses                                                                                                                                                                                                                                                                                 |
| amounts | uint256\[] | Array of TCO2 amounts to redeem The indexes of this array are matching 1:1 with the tco2s array.                                                                                                                                                                                                                 |
| maxFee  | uint256    | Maximum fee to be paid for the redemption. This value cannot be zero. Use `calculateRedemptionOutFees(tco2s,amounts,false)` to determine the fee that will be charged given the state of the pool during this call. Add a buffer on top of the returned fee amount up to the maximum fee you are willing to pay. |

#### Return Values

| Name            | Type    | Description                                   |
| --------------- | ------- | --------------------------------------------- |
| poolAmountSpent | uint256 | The amount of pool tokens spent by the caller |