pragma solidity ^0.4.24;

/**
 * @title SafeMath
 * @dev Math operations with safety checks that throw on error
 */
library SafeMath {

  /**
  * @dev Multiplies two numbers, throws on overflow.
  */
  function mul(uint256 a, uint256 b) internal pure returns (uint256 c) {
    if (a == 0) {
      return 0;
    }
    c = a * b;
    assert(c / a == b);
    return c;
  }

  /**
  * @dev Integer division of two numbers, truncating the quotient.
  */
  function div(uint256 a, uint256 b) internal pure returns (uint256) {
    // assert(b > 0); // Solidity automatically throws when dividing by 0
    // uint256 c = a / b;
    // assert(a == b * c + a % b); // There is no case in which this doesn't hold
    return a / b;
  }

  /**
  * @dev Subtracts two numbers, throws on overflow (i.e. if subtrahend is greater than minuend).
  */
  function sub(uint256 a, uint256 b) internal pure returns (uint256) {
    assert(b <= a);
    return a - b;
  }

  /**
  * @dev Adds two numbers, throws on overflow.
  */
  function add(uint256 a, uint256 b) internal pure returns (uint256 c) {
    c = a + b;
    assert(c >= a);
    return c;
  }
}

contract BasicAccessControl {
    address public owner;
    // address[] public moderators;
    uint16 public totalModerators = 0;
    mapping (address => bool) public moderators;
    bool public isMaintaining = false;

    constructor() public {
        owner = msg.sender;
    }

    modifier onlyOwner {
        require(msg.sender == owner);
        _;
    }

    modifier onlyModerators() {
        require(msg.sender == owner || moderators[msg.sender] == true);
        _;
    }

    modifier isActive {
        require(!isMaintaining);
        _;
    }

    function ChangeOwner(address _newOwner) onlyOwner public {
        if (_newOwner != address(0)) {
            owner = _newOwner;
        }
    }


    function AddModerator(address _newModerator) onlyOwner public {
        if (moderators[_newModerator] == false) {
            moderators[_newModerator] = true;
            totalModerators += 1;
        }
    }
    
    function RemoveModerator(address _oldModerator) onlyOwner public {
        if (moderators[_oldModerator] == true) {
            moderators[_oldModerator] = false;
            totalModerators -= 1;
        }
    }

    function UpdateMaintaining(bool _isMaintaining) onlyOwner public {
        isMaintaining = _isMaintaining;
    }
}

interface IERC20 {
    function totalSupply() external view returns (uint256);
    function balanceOf(address who) external view returns (uint256);
    function allowance(address owner, address spender) external view returns (uint256);
    function transfer(address to, uint256 value) external returns (bool);
    function approve(address spender, uint256 value) external returns (bool);
    function transferFrom(address from, address to, uint256 value) external returns (bool);
    event Transfer(address indexed from, address indexed to, uint256 value);
    event Approval(address indexed owner, address indexed spender, uint256 value);
}

contract CubegoCoreInterface {
    function getMaterialSupply(uint _mId) constant external returns(uint);
    function getMyMaterialById(address _owner, uint _mId) constant external returns(uint);
    function transferMaterial(address _sender, address _receiver, uint _mId, uint _amount) external;
}

contract CubegoPaper is IERC20, BasicAccessControl {
    using SafeMath for uint;
    string public constant name = "CubegoPaper";
    string public constant symbol = "CUBPA";
    uint public constant decimals = 0;
    
    mapping (address => mapping (address => uint256)) private _allowed;
    uint public mId = 2;
    CubegoCoreInterface public cubegoCore;

    function setConfig(address _cubegoCoreAddress, uint _mId) onlyModerators external {
        cubegoCore = CubegoCoreInterface(_cubegoCoreAddress);
        mId = _mId;
    }

    function emitTransferEvent(address from, address to, uint tokens) onlyModerators external {
        emit Transfer(from, to, tokens);
    }

    function totalSupply() public view returns (uint256) {
        return cubegoCore.getMaterialSupply(mId);
    }

    function balanceOf(address owner) public view returns (uint256) {
        return cubegoCore.getMyMaterialById(owner, mId);
    }

    function allowance(address owner, address spender) public view returns (uint256) {
        return _allowed[owner][spender];
    }

    function transfer(address to, uint256 value) public returns (bool) {
        cubegoCore.transferMaterial(msg.sender, to, mId, value);
        return true;
    }

    function approve(address spender, uint256 value) public returns (bool) {
        require(spender != address(0));
        _allowed[msg.sender][spender] = value;
        emit Approval(msg.sender, spender, value);
        return true;
    }

    function transferFrom(address from, address to, uint256 value) public returns (bool) {
        _allowed[from][msg.sender] = _allowed[from][msg.sender].sub(value);
        cubegoCore.transferMaterial(from, to, mId, value);
        return true;
    }

    function increaseAllowance(address spender, uint256 addedValue) public returns (bool) {
        require(spender != address(0));

        _allowed[msg.sender][spender] = (
        _allowed[msg.sender][spender].add(addedValue));
        emit Approval(msg.sender, spender, _allowed[msg.sender][spender]);
        return true;
    }

    function decreaseAllowance(address spender, uint256 subtractedValue) public returns (bool) {
        require(spender != address(0));

        _allowed[msg.sender][spender] = (_allowed[msg.sender][spender].sub(subtractedValue));
        emit Approval(msg.sender, spender, _allowed[msg.sender][spender]);
        return true;
    }

}