Strategy.sol

pragma solidity ^ 0.5.1;


/// @title Strategy contract
/// @author Andrea Bruno 585457
/// @notice This abstract contract describes what a strategy should implement.
/// @dev The following comments are written using the Solidity NatSpec Format.
contract Strategy {

    /// @notice This function compute the price.
    /// @param _actualPrice is the current price of the item
    /// @param _deltaBlocks the blocks elapsed.
    /// @return The updated current price.
    function getPrice(uint _actualPrice, uint _deltaBlocks) public view returns(uint);
}




/// @title NormalStrategy contract
/// @notice This contract implement a linear decrease function.
/// @dev This contract extends `Strategy`
contract NormalStrategy is Strategy {

    function getPrice(uint _actualPrice, uint _deltaBlocks) public view returns(uint) {
        uint tmp = _actualPrice - _deltaBlocks;

        //in case of underflow
        if (tmp > _actualPrice) return 0;
        else return tmp;
    }
}





/// @title FastStrategy contract
/// @notice This contract implement a linear decrease function, twice faster than `NormalStrategy`
/// @dev This contract extends `Strategy`
contract FastStrategy is Strategy {

    function getPrice(uint _actualPrice, uint _deltaBlocks) public view returns(uint) {
        uint tmp = _actualPrice - (2 * _deltaBlocks);

        //in case of underflow
        if (tmp > _actualPrice) return 0;
        else return tmp;
    }
}





/// @title SlowStrategy contract
/// @notice This contract implement a linear decrease function, twice slower than `NormalStrategy`
/// @dev This contract extends `Strategy`
contract SlowStrategy is Strategy {

    function getPrice(uint _actualPrice, uint _deltaBlocks) public view returns(uint) {
        uint tmp = _actualPrice - (_deltaBlocks / 2);

        //in case of underflow
        if (tmp > _actualPrice) return 0;
        else return tmp;
    }
}