SNX's Staking rewards contract

Question

Could someone explain to me like I'm 5 the purpose of the notifyRewardAmount() function on the Synthetix's StakingRewards contract please?

I think it's connected to modifying the rewards campaign's finish time if there are still more rewards to distribute, but I can't seem to wrap my head around the purpose of the function in a clear way.

function notifyRewardAmount(uint256 reward) external onlyRewardsDistribution updateReward(address(0)) {
        if (block.timestamp >= periodFinish) {
            rewardRate = reward.div(rewardsDuration);
        } else {
            uint256 remaining = periodFinish.sub(block.timestamp);
            uint256 leftover = remaining.mul(rewardRate);
            rewardRate = reward.add(leftover).div(rewardsDuration);
        }

        uint balance = rewardsToken.balanceOf(address(this));
        require(rewardRate <= balance.div(rewardsDuration), "Provided reward too high");

        lastUpdateTime = block.timestamp;
        periodFinish = block.timestamp.add(rewardsDuration);
        emit RewardAdded(reward);
    } 

Full contract here.

Answer 1

SOLUTION:

The answer to this question can be found in this video in the minute 7:40 --> https://www.youtube.com/watch?v=OJ-IRzCYSXI