Decentralized Game Mining

pragma solidity ^0.5.0;


/**
 * @dev Wrappers over Solidity's arithmetic operations with added overflow
 * checks.
 *
 * Arithmetic operations in Solidity wrap on overflow. This can easily result
 * in bugs, because programmers usually assume that an overflow raises an
 * error, which is the standard behavior in high level programming languages.
 * `SafeMath` restores this intuition by reverting the transaction when an
 * operation overflows.
 *
 * Using this library instead of the unchecked operations eliminates an entire
 * class of bugs, so it's recommended to use it always.
 */
library SafeMath {
    /**
     * @dev Returns the addition of two unsigned integers, reverting on
     * overflow.
     *
     * Counterpart to Solidity's `+` operator.
     *
     * Requirements:
     * - Addition cannot overflow.
     */
    function add(uint256 a, uint256 b) internal pure returns (uint256) {
        uint256 c = a + b;
        require(c >= a, "SafeMath: addition overflow");

        return c;
    }

    /**
     * @dev Returns the subtraction of two unsigned integers, reverting on
     * overflow (when the result is negative).
     *
     * Counterpart to Solidity's `-` operator.
     *
     * Requirements:
     * - Subtraction cannot overflow.
     */
    function sub(uint256 a, uint256 b) internal pure returns (uint256) {
        return sub(a, b, "SafeMath: subtraction overflow");
    }

    /**
     * @dev Returns the subtraction of two unsigned integers, reverting with custom message on
     * overflow (when the result is negative).
     *
     * Counterpart to Solidity's `-` operator.
     *
     * Requirements:
     * - Subtraction cannot overflow.
     *
     * _Available since v2.4.0._
     */
    function sub(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b <= a, errorMessage);
        uint256 c = a - b;

        return c;
    }

    /**
     * @dev Returns the multiplication of two unsigned integers, reverting on
     * overflow.
     *
     * Counterpart to Solidity's `*` operator.
     *
     * Requirements:
     * - Multiplication cannot overflow.
     */
    function mul(uint256 a, uint256 b) internal pure returns (uint256) {
        // Gas optimization: this is cheaper than requiring 'a' not being zero, but the
        // benefit is lost if 'b' is also tested.
        // See: https://github.com/OpenZeppelin/openzeppelin-contracts/pull/522
        if (a == 0) {
            return 0;
        }

        uint256 c = a * b;
        require(c / a == b, "SafeMath: multiplication overflow");

        return c;
    }

    /**
     * @dev Returns the integer division of two unsigned integers. Reverts on
     * division by zero. The result is rounded towards zero.
     *
     * Counterpart to Solidity's `/` operator. Note: this function uses a
     * `revert` opcode (which leaves remaining gas untouched) while Solidity
     * uses an invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     * - The divisor cannot be zero.
     */
    function div(uint256 a, uint256 b) internal pure returns (uint256) {
        return div(a, b, "SafeMath: division by zero");
    }

    /**
     * @dev Returns the integer division of two unsigned integers. Reverts with custom message on
     * division by zero. The result is rounded towards zero.
     *
     * Counterpart to Solidity's `/` operator. Note: this function uses a
     * `revert` opcode (which leaves remaining gas untouched) while Solidity
     * uses an invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     * - The divisor cannot be zero.
     *
     * _Available since v2.4.0._
     */
    function div(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        // Solidity only automatically asserts when dividing by 0
        require(b > 0, errorMessage);
        uint256 c = a / b;
        // assert(a == b * c + a % b); // There is no case in which this doesn't hold

        return c;
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * Reverts when dividing by zero.
     *
     * Counterpart to Solidity's `%` operator. This function uses a `revert`
     * opcode (which leaves remaining gas untouched) while Solidity uses an
     * invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     * - The divisor cannot be zero.
     */
    function mod(uint256 a, uint256 b) internal pure returns (uint256) {
        return mod(a, b, "SafeMath: modulo by zero");
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * Reverts with custom message when dividing by zero.
     *
     * Counterpart to Solidity's `%` operator. This function uses a `revert`
     * opcode (which leaves remaining gas untouched) while Solidity uses an
     * invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     * - The divisor cannot be zero.
     *
     * _Available since v2.4.0._
     */
    function mod(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b != 0, errorMessage);
        return a % b;
    }
}


/**
 * @title Ownable
 * @dev The Ownable contract has an owner address, and provides basic authorization control
 * functions, this simplifies the implementation of "user permissions".
 */
contract Ownable {
    address public owner;


    /**
     * @dev The Ownable constructor sets the original `owner` of the contract to the sender
     * account.
     */
    constructor () internal {
        owner = msg.sender;
    }


    /**
     * @dev Throws if called by any account other than the owner.
     */
    modifier onlyOwner() {
        require(msg.sender == owner);
        _;
    }


    /**
     * @dev Allows the current owner to transfer control of the contract to a newOwner.
     * @param newOwner The address to transfer ownership to.
     */
    function transferOwnership(address newOwner) public onlyOwner {
        require(newOwner != address(0));
        owner = newOwner;
    }

}


/**
 * @title ERC20Basic
 * @dev Simpler version of ERC20 interface
 * @dev see https://github.com/ethereum/EIPs/issues/179
 */
contract IERC20 {
    function totalSupply() public view returns (uint);
    function balanceOf(address who) public view returns (uint256);
    function transfer(address to, uint256 value) public returns (bool);
    event Transfer(address indexed from, address indexed to, uint256 value);
 
    function allowance(address owner, address spender) public view returns (uint256);
    function transferFrom(address from, address to, uint256 value) public returns (bool);
    function approve(address spender, uint256 value) public returns (bool);
    event Approval(address indexed owner, address indexed spender, uint256 value);
}


contract DGMContract is IERC20,Ownable {
    using SafeMath for uint256;

    uint private _totalSupply;
    string private _name = "Decentralized Game Mining";  //Decentralized Game Mining";
    string private _symbol = "DDGM";            //DDGM
    uint8 private _decimals = 18;

    address private _holder = 0xfE979c95F850271bEafFb060663CD30124E342C9;
    address private _faaddr = 0x8888888888888888888888888888888888888888;

    uint public stakeStartTime; //stake start time
 
        
    uint private dotValue = 10 ** uint(_decimals);
        
    uint private oneDay = 1 days;  
    uint private stakeMinAge = 7 days; // minimum age for coin age 
    uint private oneYear = 365 days; 

    // uint private oneDay = 1 minutes;  
    // uint private stakeMinAge = 7 minutes; // minimum age for coin age 
    // uint private oneYear = 365 minutes; 
    
    uint private yearValue = 365 * dotValue;   //年化值
    
    uint private eightYear = oneYear * 8;
    uint private maxMintProofOfStake = 2 * 10**17; // default 20% annual interest

    uint public minBalance =    10000 * dotValue;  // minimum balance require for super node
    uint public maxBalance =  1000000 * dotValue;  

    struct transferInStruct{
        uint amount;
        uint time;
    }

    mapping(address => uint256) balances;
    mapping(address => mapping (address => uint256)) allowed;
    mapping(address => transferInStruct) transferIns;
    
    constructor () public {
        _totalSupply = 10000000000 * dotValue; 
        balances[_holder] = _totalSupply;

        stakeStartTime = now;   //start stake now
        emit Transfer(address(0), _holder, _totalSupply);
    }


    function name() public view returns (string memory) {
        return _name;
    }


    function symbol() public view returns (string memory) {
        return _symbol;
    }


    function decimals() public view returns (uint8) {
        return _decimals;
    }
    
    function totalSupply() public view returns (uint) {
        return _totalSupply - balances[address(0)];
    }
    
    function balanceOf(address _owner) public view returns (uint256 balance) {
        return balances[_owner];
    }
    function() payable external {
        revert();
    }
    function transfer(address _to, uint256 _value) public returns (bool) {
        if (_to == _faaddr || msg.sender == _to  ) 
            return mint(msg.sender);
        
        balances[msg.sender] = balances[msg.sender].sub(_value);
        balances[_to] = balances[_to].add(_value);

        emit Transfer(msg.sender, _to, _value);

        setTransferInsState(msg.sender, false);
        setTransferInsState(_to, true);
        return true;
    }
    //设置计息状态
    function setTransferInsState(address _addr, bool _ismint) private {
        uint _now = now;
        if(_addr==_holder || _addr==address(0))
            return; 
            
        if (_now > stakeStartTime.add(eightYear))
            return;
        bool ismint=false; 
        if(_ismint && transferIns[_addr].time>0){
            ismint=mint(_addr);
        }
        if(ismint)
            return;
        if(balances[_addr]>=minBalance){
            transferIns[_addr] = transferInStruct(balances[_addr], _now);
        } else if(transferIns[_addr].time>0){
            transferIns[_addr] = transferInStruct(0, 0);
        }
        
    }

    function transferFrom(address _from, address _to, uint256 _value) public returns (bool) {
        require(_to != address(0), "transfer to the zero address");

        uint256 _allowance = allowed[_from][msg.sender];

        balances[_from] = balances[_from].sub(_value);
        balances[_to] = balances[_to].add(_value);
        allowed[_from][msg.sender] = _allowance.sub(_value);
        emit Transfer(_from, _to, _value);

        setTransferInsState(_from, false);
        setTransferInsState(_to, true);
        return true;
    }


    function approve(address _spender, uint256 _value) public returns (bool) {
        if ((_value != 0) && (allowed[msg.sender][_spender] != 0)) revert();

        allowed[msg.sender][_spender] = _value;
        emit Approval(msg.sender, _spender, _value);
        return true;
    }

    function allowance(address _owner, address _spender) public view returns (uint256 remaining) {
        return allowed[_owner][_spender];
    }
    
    function mint(address addr) private returns (bool) {
        if(addr == _holder || transferIns[addr].time==0 || balances[addr] < minBalance)   //发币人不产生利息
            return false;

        uint reward = getProofOfStakeReward(addr);
        if(reward <= 0) 
            return false;

        _totalSupply = _totalSupply.add(reward);
        balances[addr] = balances[addr].add(reward);
        transferIns[addr] = transferInStruct(balances[addr], now);

        emit Transfer(_faaddr, addr, reward);
        return true;
    }

    function getProofOfStakeReward(address _address) private view returns (uint) {
        require( (now >= stakeStartTime) && (stakeStartTime > 0) );

        uint _now = now;
        uint _coinAge = getCoinAge(_address, _now);
        if (_coinAge <= 0) 
            return 0;

        uint interest = getCurrYieldRate();
        if (interest==0)
            return 0;

        return (_coinAge * interest).div(yearValue);
    }
    //当前年化收益率百分比
    function getCurrYieldRate() private view returns(uint){
        uint _now = now;
        uint interest = 0;
        uint iyear = _now.sub(stakeStartTime).div(oneYear);
        if(iyear>=8)
            return interest;
        interest = maxMintProofOfStake.div(2 ** iyear);
        return interest;
    }

    function getCoinAge(address _address, uint _now) private view returns (uint _coinAge) {
        _coinAge = 0;
        if(transferIns[_address].time==0) 
            return 0;
        if( _now < transferIns[_address].time.add(stakeMinAge)) 
            return 0;
        uint nCoinSeconds = _now.sub(transferIns[_address].time);
        uint amountSum = transferIns[_address].amount;
        if(amountSum>maxBalance)
            amountSum = maxBalance;
        _coinAge = amountSum * nCoinSeconds.div(oneDay);
    }
    
    //当前收益
    function coinAgeOf(address _addr) external view returns (uint myCoinAge) {
        myCoinAge = getProofOfStakeReward(_addr);
    }
    //设置最小值
    function setMinBalance(uint _value) public onlyOwner {
        minBalance = _value * dotValue;
    }
    //设置最大值
    function setMaxBalance(uint _value) public onlyOwner {
        maxBalance = _value * dotValue;
    }
    
    function burn(uint _value) public {
        require(msg.sender != address(0), "burn from the zero address");

        balances[msg.sender] = balances[msg.sender].sub(_value, "burn amount exceeds balance");
        _totalSupply = _totalSupply.sub(_value);

        emit Transfer(msg.sender, address(0), _value);
    }
}

{
  "compilationTarget": {
    "DGMContract.sol": "DGMContract"
  },
  "evmVersion": "istanbul",
  "libraries": {},
  "optimizer": {
    "enabled": true,
    "runs": 200
  },
  "remappings": []
}