library AmplificationUtils {
    using SafeMath for uint256;

    event RampA(
        uint256 oldA,
        uint256 newA,
        uint256 initialTime,
        uint256 futureTime
    );
    event StopRampA(uint256 currentA, uint256 time);

    // Constant values used in ramping A calculations
    uint256 public constant A_PRECISION = 100;
    uint256 public constant MAX_A = 10**6;
    uint256 private constant MAX_A_CHANGE = 2;
    uint256 private constant MIN_RAMP_TIME = 14 days;

    /**
     * @notice Return A, the amplification coefficient * n * (n - 1)
     * @dev See the StableSwap paper for details
     * @param self Swap struct to read from
     * @return A parameter
     */
    function getA(SwapUtils.Swap storage self) external view returns (uint256) {
        return _getAPrecise(self).div(A_PRECISION);
    }

    /**
     * @notice Return A in its raw precision
     * @dev See the StableSwap paper for details
     * @param self Swap struct to read from
     * @return A parameter in its raw precision form
     */
    function getAPrecise(SwapUtils.Swap storage self)
        external
        view
        returns (uint256)
    {
        return _getAPrecise(self);
    }

    /**
     * @notice Return A in its raw precision
     * @dev See the StableSwap paper for details
     * @param self Swap struct to read from
     * @return A parameter in its raw precision form
     */
    function _getAPrecise(SwapUtils.Swap storage self)
        internal
        view
        returns (uint256)
    {
        uint256 t1 = self.futureATime; // time when ramp is finished
        uint256 a1 = self.futureA; // final A value when ramp is finished

        if (block.timestamp < t1) {
            uint256 t0 = self.initialATime; // time when ramp is started
            uint256 a0 = self.initialA; // initial A value when ramp is started
            if (a1 > a0) {
                // a0 + (a1 - a0) * (block.timestamp - t0) / (t1 - t0)
                return
                    a0.add(
                        a1.sub(a0).mul(block.timestamp.sub(t0)).div(t1.sub(t0))
                    );
            } else {
                // a0 - (a0 - a1) * (block.timestamp - t0) / (t1 - t0)
                return
                    a0.sub(
                        a0.sub(a1).mul(block.timestamp.sub(t0)).div(t1.sub(t0))
                    );
            }
        } else {
            return a1;
        }
    }

    /**
     * @notice Start ramping up or down A parameter towards given futureA_ and futureTime_
     * Checks if the change is too rapid, and commits the new A value only when it falls under
     * the limit range.
     * @param self Swap struct to update
     * @param futureA_ the new A to ramp towards
     * @param futureTime_ timestamp when the new A should be reached
     */
    function rampA(
        SwapUtils.Swap storage self,
        uint256 futureA_,
        uint256 futureTime_
    ) external {
        require(
            block.timestamp >= self.initialATime.add(1 days),
            "Wait 1 day before starting ramp"
        );
        require(
            futureTime_ >= block.timestamp.add(MIN_RAMP_TIME),
            "Insufficient ramp time"
        );
        require(
            futureA_ > 0 && futureA_ < MAX_A,
            "futureA_ must be > 0 and < MAX_A"
        );

        uint256 initialAPrecise = _getAPrecise(self);
        uint256 futureAPrecise = futureA_.mul(A_PRECISION);

        if (futureAPrecise < initialAPrecise) {
            require(
                futureAPrecise.mul(MAX_A_CHANGE) >= initialAPrecise,
                "futureA_ is too small"
            );
        } else {
            require(
                futureAPrecise <= initialAPrecise.mul(MAX_A_CHANGE),
                "futureA_ is too large"
            );
        }

        self.initialA = initialAPrecise;
        self.futureA = futureAPrecise;
        self.initialATime = block.timestamp;
        self.futureATime = futureTime_;

        emit RampA(
            initialAPrecise,
            futureAPrecise,
            block.timestamp,
            futureTime_
        );
    }

    /**
     * @notice Stops ramping A immediately. Once this function is called, rampA()
     * cannot be called for another 24 hours
     * @param self Swap struct to update
     */
    function stopRampA(SwapUtils.Swap storage self) external {
        require(self.futureATime > block.timestamp, "Ramp is already stopped");

        uint256 currentA = _getAPrecise(self);
        self.initialA = currentA;
        self.futureA = currentA;
        self.initialATime = block.timestamp;
        self.futureATime = block.timestamp;

        emit StopRampA(currentA, block.timestamp);
    }
}
/**
 * @title AmplificationUtils library
 * @notice A library to calculate and ramp the A parameter of a given `SwapUtils.Swap` struct.
 * This library assumes the struct is fully validated.
 */
function _getAPrecise(SwapUtils.Swap storage self)
    internal
    view
    returns (uint256)
{
    uint256 t1 = self.futureATime; // time when ramp is finished
    uint256 a1 = self.futureA; // final A value when ramp is finished

    if (block.timestamp < t1) {
        uint256 t0 = self.initialATime; // time when ramp is started
        uint256 a0 = self.initialA; // initial A value when ramp is started
        if (a1 > a0) {
            // a0 + (a1 - a0) * (block.timestamp - t0) / (t1 - t0)
            return
                a0.add(
                    a1.sub(a0).mul(block.timestamp.sub(t0)).div(t1.sub(t0))
                );
        } else {
            // a0 - (a0 - a1) * (block.timestamp - t0) / (t1 - t0)
            return
                a0.sub(
                    a0.sub(a1).mul(block.timestamp.sub(t0)).div(t1.sub(t0))
                );
        }
    } else {
        return a1;
    }
}

/**
 * @notice Return A in its raw precision
 * @dev See the StableSwap paper for details
 * @param self Swap struct to read from
 * @return A parameter in its raw precision form
 */