contract wOHM is ERC20 {
    using SafeERC20 for ERC20;
    using Address for address;
    using SafeMath for uint;

    address public immutable staking;
    address public immutable OHM;
    address public immutable sOHM;

    constructor( address _staking, address _OHM, address _sOHM ) ERC20( 'Wrapped sSQUID', 'wsSQUID' ) {
        require( _staking != address(0) );
        staking = _staking;
        require( _OHM != address(0) );
        OHM = _OHM;
        require( _sOHM != address(0) );
        sOHM = _sOHM;
    }

        /**
        @notice stakes OHM and wraps sOHM
        @param _amount uint
        @return uint
     */
    function wrapFromOHM( uint _amount ) external returns ( uint ) {
        IERC20( OHM ).transferFrom( msg.sender, address(this), _amount );

        IERC20( OHM ).approve( staking, _amount ); // stake OHM for sOHM
        IStaking( staking ).stake( _amount, address(this) );

        uint value = wOHMValue( _amount );
        _mint( msg.sender, value );
        return value;
    }

    /**
        @notice unwrap sOHM and unstake OHM
        @param _amount uint
        @return uint
     */
    function unwrapToOHM( uint _amount ) external returns ( uint ) {
        _burn( msg.sender, _amount );
        
        uint value = sOHMValue( _amount );
        IERC20( sOHM ).approve( staking, value ); // unstake sOHM for OHM
        IStaking( staking ).unstake( value, address(this) );

        IERC20( OHM ).transfer( msg.sender, value );
        return value;
    }

    /**
        @notice wrap sOHM
        @param _amount uint
        @return uint
     */
    function wrapFromsOHM( uint _amount ) external returns ( uint ) {
        IERC20( sOHM ).transferFrom( msg.sender, address(this), _amount );
        
        uint value = wOHMValue( _amount );
        _mint( msg.sender, value );
        return value;
    }

    /**
        @notice unwrap sOHM
        @param _amount uint
        @return uint
     */
    function unwrapTosOHM( uint _amount ) external returns ( uint ) {
        _burn( msg.sender, _amount );

        uint value = sOHMValue( _amount );
        IERC20( sOHM ).transfer( msg.sender, value );
        return value;
    }

    /**
        @notice converts wOHM amount to sOHM
        @param _amount uint
        @return uint
     */
    function sOHMValue( uint _amount ) public view returns ( uint ) {
        return _amount.mul( IStaking( staking ).index() ).div( 10 ** decimals() );
    }

    /**
        @notice converts sOHM amount to wOHM
        @param _amount uint
        @return uint
     */
    function wOHMValue( uint _amount ) public view returns ( uint ) {
        return _amount.mul( 10 ** decimals() ).div( IStaking( staking ).index() );
    }

}
function unwrapToOHM( uint _amount ) external returns ( uint ) {
        _burn( msg.sender, _amount );
        
        uint value = sOHMValue( _amount );
        IERC20( sOHM ).approve( staking, value ); // unstake sOHM for OHM
        IStaking( staking ).unstake( value, address(this) );

        IERC20( OHM ).transfer( msg.sender, value );
        return value;
    }
/**
 @notice unwrap sOHM and unstake OHM
 @param _amount uint
 @return uint
 */