# Methods

#### Deposit principal <a href="#deposit-principal" id="deposit-principal"></a>

```
function depositPrincipal(uint256 _tokenAmount) external returns (uint256);
```

This function will be called whenever a user stakes via the Flashstake Protocol. The Time Vault owner can choose to implement a fee but the resulting “locked” principal the user should expect after the stake has ended must be returned.

{% hint style="warning" %}
This function should be protected such that only the Flashstake Protocol can execute this. This is to ensure users do not accidentally call this function and lose their funds.
{% endhint %}

#### Withdraw principal

```
function withdrawPrincipal(uint256 _tokenAmount) external;
```

This function should withdraw principal from the underlying strategy (eg AAVE).

{% hint style="info" %}
This function should be protected such that only the Flash Protocol can execute this. Keeping this unprotected would of course mean anyone would withdraw principal tokens from your strategy.
{% endhint %}

#### Burn TBT

```
function burnFToken(
    uint256 _tokenAmount,
    uint256 _minimumReturned,
    address _yieldTo
) external returns (uint256);
```

This is the function the user will be calling when performing a [FlashBurn](/time-based-tokens-tbts/burning-tbts-flashburn.md). It is responsible for burning the fToken supplied by the user and returning yield to the user.

#### Get principal balance

```
function getPrincipalBalance() external view returns (uint256);
```

This must return the current total of all principal accepted by the contract.

#### Get yield balance

```
function getYieldBalance() external view returns (uint256);
```

This function must report the total yield balance.

#### Get principal address

```
function getPrincipalAddress() external view returns (address);
```

This must return the principal token address (eg DAI).

#### Quote mint fToken

```
function quoteMintFToken(uint256 _tokenAmount, uint256 duration) external view returns (uint256);
```

This function will be called by the Flash Protocol (and frontends) to determine how many fTokens should be minted for a given \_tokenAmount and \_duration (in seconds).

#### Quote burn fToken

```
function quoteBurnFToken(uint256 _tokenAmount) external view returns (uint256);
```

This function must return the yield a user should expect when burning \_tokenAmount fTokens.

#### Set fToken address

```
function setFTokenAddress(address _fTokenAddress) external;
```

The function to set the fERC20 address within the strategy.

Note

This function should be protected such that only the Flash Protocol can execute this.

#### Get max stake duration

```
function getMaxStakeDuration() external view returns (uint256);
```

This function must report the maximum duration a user can stake for. This can either be hardcoded or be a function of on-chain metrics.


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