function _updateDropPerSecond() internal returns (uint256){
    // If no more need for monthly updates => decrease duration is over
    if(block.timestamp > startDropTimestamp + dropDecreaseDuration) {
        // Set the current DropPerSecond as the end value
        // Plus allows to be updated if the end value is later updated
        if(currentDropPerSecond != endDropPerSecond) {
            currentDropPerSecond = endDropPerSecond;
            lastDropUpdate = block.timestamp;
        }

        return endDropPerSecond;
    }

    if(block.timestamp < lastDropUpdate + MONTH) return currentDropPerSecond; // Update it once a month

    uint256 dropDecreasePerMonth = (startDropPerSecond - endDropPerSecond) / (dropDecreaseDuration / MONTH);
    uint256 nbMonthEllapsed = (block.timestamp - lastDropUpdate) / MONTH;

    uint256 dropPerSecondDecrease = dropDecreasePerMonth * nbMonthEllapsed;

    // We calculate the new dropPerSecond value
    // We don't want to go under the endDropPerSecond
    uint256 newDropPerSecond = currentDropPerSecond - dropPerSecondDecrease > endDropPerSecond ? currentDropPerSecond - dropPerSecondDecrease : endDropPerSecond;

    currentDropPerSecond = newDropPerSecond;
    lastDropUpdate = block.timestamp;

    return newDropPerSecond;
}
function _updateDropPerSecond() internal returns (uint256){
    // If no more need for monthly updates => decrease duration is over
    if(block.timestamp > startDropTimestamp + dropDecreaseDuration) {
        // Set the current DropPerSecond as the end value
        // Plus allows to be updated if the end value is later updated
        if(currentDropPerSecond != endDropPerSecond) {
            currentDropPerSecond = endDropPerSecond;
            lastDropUpdate = block.timestamp;
        }

        return endDropPerSecond;
    }

    if(block.timestamp < lastDropUpdate + MONTH) return currentDropPerSecond; // Update it once a month

    uint256 dropDecreasePerMonth = (startDropPerSecond - endDropPerSecond) / (dropDecreaseDuration / MONTH);
    uint256 nbMonthEllapsed = UNIT * (block.timestamp - lastDropUpdate) / MONTH;

    uint256 dropPerSecondDecrease = dropDecreasePerMonth * nbMonthEllapsed / UNIT;

    // We calculate the new dropPerSecond value
    // We don't want to go under the endDropPerSecond
    uint256 newDropPerSecond = currentDropPerSecond - dropPerSecondDecrease > endDropPerSecond ? currentDropPerSecond - dropPerSecondDecrease : endDropPerSecond;

    currentDropPerSecond = newDropPerSecond;
    lastDropUpdate = block.timestamp;

    return newDropPerSecond;
}
