contract BaseShareField {
    using SafeMath for uint;
    
    uint totalProductivity;
    uint accAmountPerShare;
    
    uint public totalShare;
    uint public mintedShare;
    uint public mintCumulation;
    
    address public shareToken;
    
    struct UserInfo {
        uint amount;     // How many tokens the user has provided.
        uint rewardDebt; // Reward debt. 
        uint rewardEarn; // Reward earn and not minted
    }

    mapping(address => UserInfo) public users;
    
    function _setShareToken(address _shareToken) internal {
        shareToken = _shareToken;
    }

    // Update reward variables of the given pool to be up-to-date.
    function _update() internal virtual {
        if (totalProductivity == 0) {
            totalShare = totalShare.add(_currentReward());
            return;
        }
        
        uint256 reward = _currentReward();
        accAmountPerShare = accAmountPerShare.add(reward.mul(1e12).div(totalProductivity));
        totalShare = totalShare.add(reward);
    }
    
    function _currentReward() internal virtual view returns (uint) {
        return mintedShare.add(IERC20(shareToken).balanceOf(address(this))).sub(totalShare);
    }
    
    // Audit user's reward to be up-to-date
    function _audit(address user) internal virtual {
        UserInfo storage userInfo = users[user];
        if (userInfo.amount > 0) {
            uint pending = userInfo.amount.mul(accAmountPerShare).div(1e12).sub(userInfo.rewardDebt);
            userInfo.rewardEarn = userInfo.rewardEarn.add(pending);
            mintCumulation = mintCumulation.add(pending);
            userInfo.rewardDebt = userInfo.amount.mul(accAmountPerShare).div(1e12);
        }
    }

    // External function call
    // This function increase user's productivity and updates the global productivity.
    // the users' actual share percentage will calculated by:
    // Formula:     user_productivity / global_productivity
    function _increaseProductivity(address user, uint value) internal virtual returns (bool) {
        require(value > 0, 'PRODUCTIVITY_VALUE_MUST_BE_GREATER_THAN_ZERO');

        UserInfo storage userInfo = users[user];
        _update();
        _audit(user);

        totalProductivity = totalProductivity.add(value);

        userInfo.amount = userInfo.amount.add(value);
        userInfo.rewardDebt = userInfo.amount.mul(accAmountPerShare).div(1e12);
        return true;
    }

    // External function call 
    // This function will decreases user's productivity by value, and updates the global productivity
    // it will record which block this is happenning and accumulates the area of (productivity * time)
    function _decreaseProductivity(address user, uint value) internal virtual returns (bool) {
        UserInfo storage userInfo = users[user];
        require(value > 0 && userInfo.amount >= value, 'INSUFFICIENT_PRODUCTIVITY');
        
        _update();
        _audit(user);
        
        userInfo.amount = userInfo.amount.sub(value);
        userInfo.rewardDebt = userInfo.amount.mul(accAmountPerShare).div(1e12);
        totalProductivity = totalProductivity.sub(value);
        
        return true;
    }
    
    function _takeWithAddress(address user) internal view returns (uint) {
        UserInfo storage userInfo = users[user];
        uint _accAmountPerShare = accAmountPerShare;
        // uint256 lpSupply = totalProductivity;
        if (totalProductivity != 0) {
            uint reward = _currentReward();
            _accAmountPerShare = _accAmountPerShare.add(reward.mul(1e12).div(totalProductivity));
        }
        return userInfo.amount.mul(_accAmountPerShare).div(1e12).add(userInfo.rewardEarn).sub(userInfo.rewardDebt);
    }

    // External function call
    // When user calls this function, it will calculate how many token will mint to user from his productivity * time
    // Also it calculates global token supply from last time the user mint to this time.
    function _mint(address user) internal virtual returns (uint) {
        _update();
        _audit(user);
        require(users[user].rewardEarn > 0, "NOTHING TO MINT");
        uint amount = users[user].rewardEarn;
        TransferHelper.safeTransfer(shareToken, msg.sender, amount);
        users[user].rewardEarn = 0;
        mintedShare += amount;
        return amount;
    }

    // Returns how many productivity a user has and global has.
    function getProductivity(address user) public virtual view returns (uint, uint) {
        return (users[user].amount, totalProductivity);
    }

    // Returns the current gorss product rate.
    function interestsPerBlock() public virtual view returns (uint) {
        return accAmountPerShare;
    }
    
}
function _increaseProductivity(address user, uint value) internal virtual returns (bool) {
    require(value > 0, 'PRODUCTIVITY_VALUE_MUST_BE_GREATER_THAN_ZERO');

    UserInfo storage userInfo = users[user];
    _update();
    _audit(user);

    totalProductivity = totalProductivity.add(value);

    userInfo.amount = userInfo.amount.add(value);
    userInfo.rewardDebt = userInfo.amount.mul(accAmountPerShare).div(1e12);
    return true;
}

// External function call
// This function increase user's productivity and updates the global productivity.
// the users' actual share percentage will calculated by:
// Formula:     user_productivity / global_productivity