# YearnUSDTStrategy

## Overview

The YearnUSDTStrategy contract is a strategy that supplies USDT into a Yearn V2 Vault to earn yield. It handles conversions between the underlying asset and USDT through Curve's 3pool and includes safety margins for liquidations.

## Constants

```solidity
ICurveTriPool public constant triPool = ICurveTriPool(CURVE_3POOL_POOL_MAINNET);  // Curve's 3pool
address constant usdt = USDT_MAINNET;                                              // USDT token address
```

## Functions

### Initialization Functions

#### initialize

```solidity
function initialize(
    IMaxApyVault _vault,
    address[] calldata _keepers,
    bytes32 _strategyName,
    address _strategist,
    IYVault _yVault
) public virtual override initializer
```

Initializes the strategy with required components.

Parameters:

* `_vault`: MaxApy vault address
* `_keepers`: Array of keeper addresses
* `_strategyName`: Name of the strategy
* `_strategist`: Strategist address
* `_yVault`: Yearn V2 vault address

### View Functions

#### previewLiquidate

```solidity
function previewLiquidate(uint256 requestedAmount) public view override returns (uint256 liquidatedAmount)
```

Simulates withdrawal with 1% safety margin.

Parameters:

* `requestedAmount`: Amount to withdraw

Returns:

* `liquidatedAmount`: Expected output amount

#### previewLiquidateExact

```solidity
function previewLiquidateExact(uint256 liquidatedAmount) public view virtual override returns (uint256 requestedAmount)
```

Calculates input needed with 2% buffer.

Parameters:

* `liquidatedAmount`: Desired output amount

Returns:

* `requestedAmount`: Required input amount

### Internal Core Functions

#### \_invest

```solidity
function _invest(uint256 amount, uint256 minOutputAfterInvestment) internal override returns (uint256 depositedAmount)
```

Invests assets by:

1. Swapping underlying to USDT through Curve
2. Depositing USDT into Yearn vault

Parameters:

* `amount`: Amount to invest
* `minOutputAfterInvestment`: Minimum expected shares

Returns:

* `depositedAmount`: Amount of tokens received

#### \_divest

```solidity
function _divest(uint256 shares) internal override returns (uint256 withdrawn)
```

Withdraws assets by:

1. Withdrawing USDT from Yearn vault
2. Swapping USDT to underlying through Curve

Parameters:

* `shares`: Amount of shares to withdraw

Returns:

* `withdrawn`: Amount of assets received

### Internal View Functions

#### \_shareValue

```solidity
function _shareValue(uint256 shares) internal view override returns (uint256)
```

Calculates underlying value including Curve conversion.

Parameters:

* `shares`: Share amount

Returns:

* Underlying value

#### \_sharesForAmount

```solidity
function _sharesForAmount(uint256 amount) internal view override returns (uint256 shares)
```

Calculates shares needed including Curve conversion.

Parameters:

* `amount`: Asset amount

Returns:

* Required shares

Key Features:

* Uses Curve's 3pool for token conversions
* Sets 1M USD maximum trade size
* Sets minimum trade size to 0.01 token units
* Includes safety margins for withdrawals
* Handles conversions between USDT and underlying asset


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