Overview

Background

As one of the digital financial derivatives on SUN.io, mining provides crypto holders with stable, secure, and reliable services for subscription and redemption of investment products. Smart Mining V2, also known as fixed-term mining, is an important part of SUN.io's mining service. It converts a user's staked assets to virtual assets of a certain amount according to the amount of assets staked and the staking duration. The total virtual stake is defined as the total amount of virtual assets converted from all users' staked assets. Users are rewarded based on their virtual assets' proportion in the total virtual stake, and they are only allowed to redeem their assets during a specified period of time.

Explanation

Reward Distribution

Suppose the stake amount of a token is "amount". The token's lock-up duration $Duration_{lock}$ meets the following condition: $Duration_{min}<=Duration_{lock}<=Duration_{max}$。 where $Duration_{ma x}$ is 1080 days, $Duration_{min}$ is 30 days, and the maximum acceleration rate$weight_{max}$ is 1400% (magnifying by $e^{12}$ times). The veToken is calculated in the following way：

$$weight=\frac{Duration_{lock}*weight_{amx}*e^{12}}{Duration_{max}}（1）$$

$$balance_{veToken}=amount+amount*weight*e^{-12}（2）$$

Here,$balance_{veToken}$refers to the amount of a user's virtual assets. According to the reward distribution formula (2) of Smart Mining V1, the user's rewards are calculated in the following way:

$$f(t_i,t_n)= \sum_{i=1}^{m}balance_{veToken} \sum_{j=start_i}^{end_i}\frac{(t_i-t_{i-1})r_t}{T_i}（3）$$

Here, $r_t$ denotes the expansion factor of the reward token, $t_i$ denotes the i-th change, $T_i$ denotes the total virtual stake at the time $t_{i-1}$to $t_i$, and $balance_{veToken}$ denotes the amount of the user's virtual assets at the time $t_{i-1}$to $t_i$.

Contract code

function calculateBoostedBalance(uint256 amount, uint256 lockDuration) public view returns (uint256) {
    if (lockDuration == 0) {
        return amount;
    }
    uint256 boostWeight = lockDuration.mul(BOOST_WEIGHT).div(DURATION_FACTOR);
    return amount.add(amount.mul(boostWeight).div(PRECISION_FACTOR));
}

Redemption Time of Fixed-Term Mining

$Duration_{lock}$ denotes the length of a lock-up period, $Duration_{maintenance}$ denotes the length of a cooling-off period for re-staking, $t_{stake}$ denotes the time when the assets are staked, and $t_{no w}$ denotes the current time. Assets can be redeemed when the following conditions are both met:

$$t_{now}-t_{stake}>=Duration_{lock}（4）$$

$$(t_{now}-t_{stake}) mod Duration_{lock} <= Duration_{maintenance}（5）$$

rewards denotes the total amount of rewards, $rewards_{prev}$ denotes the amount of settled rewards, $t_{lastAction}$ denotes the time of the last settlement, and $Duration_{reward}$ denotes the lock-up duration during which the rewards are not settled yet. $Duration_{overdue}$ denotes the duration of time that is after the last lock-up period and shorter than a lock-up period. The user's rewards are calculated in the following way:

$$Duration_{reward}=t_{now}-t_{lastAction}（6）$$

$$Duration_{overdue}=Duration_{reward} mod Duration_{lock}（7）$$

$$rewards_{overdue}=\frac{Duration_{overdue}}{Duration_{reward}}*(rewards-rewards_{prev})（8）$$

$$rewards=rewards-rewards_{overdue}（9）$$

Contract code

function overdueDuration(address account) public view returns (bool, uint256, uint256){
    uint256 duration = userInfo[account].lockDuration;
    if (duration == 0) {
        return (true, 0, 0);
    }
    uint256 totalTime = block.timestamp.sub(userInfo[account].lockStartTime);
    uint256 round = totalTime.div(duration);
    uint256 overdue = totalTime.mod(duration);
    if (round < 1 || overdue > maintenanceDuration || block.timestamp < userInfo[account].lastActionTime) {
        return (false, 0, 0);
    }

    uint256 rewardsDuration = block.timestamp.sub(userInfo[account].lastActionTime);
    return (true, rewardsDuration, overdue);
}