MovingValue

MovingValue.sol

pragma solidity ^0.5.0;

import "github.com/openzeppelin/openzeppelin-contracts/contracts/math/SafeMath.sol";


library MovingValue {

    using SafeMath for uint256;

    struct Data {
        uint40 time;
        uint216 speed;
        uint256 origin;
    }

    function update(Data storage self, uint256 newSpeed) internal {
        uint256 newOrigin = value(self);
        self.time = uint40(now);
        self.speed = uint216(newSpeed);
        self.origin = newOrigin;
    }

    function value(Data storage self) internal view returns(uint256) {
        return valueMemory(self);
    }

    function valueMemory(Data memory self) internal view returns(uint256) {
        return uint256(self.origin).add(
            now.sub(self.time).mul(self.speed).div(365 days)
        );
    }
}