/**
 * Source Code first verified at https://etherscan.io on Wednesday, May 8, 2019
 (UTC) */

pragma solidity ^0.4.23;

library SafeMath {
  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;
  }

  function div(uint256 _a, uint256 _b) internal pure returns (uint256) {
    return _a / _b;
  }

  function sub(uint256 _a, uint256 _b) internal pure returns (uint256) {
    assert(_b <= _a);
    return _a - _b;
  }

  function add(uint256 _a, uint256 _b) internal pure returns (uint256 c) {
    c = _a + _b;
    assert(c >= _a);
    return c;
  }
}

contract ERC20 {
  function totalSupply() public view returns (uint256);

  function balanceOf(address _who) public view returns (uint256);

  function allowance(address _owner, address _spender)
    public view returns (uint256);

  function transfer(address _to, uint256 _value) public returns (bool);

  function approve(address _spender, uint256 _value)
    public returns (bool);

  function transferFrom(address _from, address _to, uint256 _value)
    public returns (bool);

  event Transfer(
    address indexed from,
    address indexed to,
    uint256 value
  );

  event Approval(
    address indexed owner,
    address indexed spender,
    uint256 value
  );
}

contract StandardToken is ERC20 {
  using SafeMath for uint256;

  mapping(address => uint256) balances;

  mapping (address => mapping (address => uint256)) internal allowed;

  uint256 totalSupply_;

  function totalSupply() public view returns (uint256) {
    return totalSupply_;
  }

  function balanceOf(address _owner) public view returns (uint256) {
    return balances[_owner];
  }

  function allowance(
    address _owner,
    address _spender
   )
    public
    view
    returns (uint256)
  {
    return allowed[_owner][_spender];
  }

  function transfer(address _to, uint256 _value) public returns (bool) {
    require(_value <= balances[msg.sender]);
    require(_to != address(0));

    balances[msg.sender] = balances[msg.sender].sub(_value);
    balances[_to] = balances[_to].add(_value);
    emit Transfer(msg.sender, _to, _value);
    return true;
  }

  function approve(address _spender, uint256 _value) public returns (bool) {
    allowed[msg.sender][_spender] = _value;
    emit Approval(msg.sender, _spender, _value);
    return true;
  }

  function transferFrom(
    address _from,
    address _to,
    uint256 _value
  )
    public
    returns (bool)
  {
    require(_value <= balances[_from]);
    require(_value <= allowed[_from][msg.sender]);
    require(_to != address(0));

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

  function increaseApproval(
    address _spender,
    uint256 _addedValue
  )
    public
    returns (bool)
  {
    allowed[msg.sender][_spender] = (
      allowed[msg.sender][_spender].add(_addedValue));
    emit Approval(msg.sender, _spender, allowed[msg.sender][_spender]);
    return true;
  }

  function decreaseApproval(
    address _spender,
    uint256 _subtractedValue
  )
    public
    returns (bool)
  {
    uint256 oldValue = allowed[msg.sender][_spender];
    if (_subtractedValue >= oldValue) {
      allowed[msg.sender][_spender] = 0;
    } else {
      allowed[msg.sender][_spender] = oldValue.sub(_subtractedValue);
    }
    emit Approval(msg.sender, _spender, allowed[msg.sender][_spender]);
    return true;
  }
}

contract Ownable {
  address public owner;

  event OwnershipRenounced(address indexed previousOwner);
  event OwnershipTransferred(
    address indexed previousOwner,
    address indexed newOwner
  );

  constructor() public {
    owner = msg.sender;
  }

  modifier onlyOwner() {
    require(msg.sender == owner);
    _;
  }

  function renounceOwnership() public onlyOwner {
    emit OwnershipRenounced(owner);
    owner = address(0);
  }

  function transferOwnership(address _newOwner) public onlyOwner {
    _transferOwnership(_newOwner);
  }

  function _transferOwnership(address _newOwner) internal {
    require(_newOwner != address(0));
    emit OwnershipTransferred(owner, _newOwner);
    owner = _newOwner;
  }
}

contract Pausable is Ownable {
  event Pause();
  event Unpause();

  bool public paused = false;

  modifier whenNotPaused() {
    require(!paused);
    _;
  }

  modifier whenPaused() {
    require(paused);
    _;
  }

  function pause() public onlyOwner whenNotPaused {
    paused = true;
    emit Pause();
  }

  function unpause() public onlyOwner whenPaused {
    paused = false;
    emit Unpause();
  }
}

contract PausableToken is StandardToken, Pausable {

  function transfer(
    address _to,
    uint256 _value
  )
    public
    whenNotPaused
    returns (bool)
  {
    return super.transfer(_to, _value);
  }

  function transferFrom(
    address _from,
    address _to,
    uint256 _value
  )
    public
    whenNotPaused
    returns (bool)
  {
    return super.transferFrom(_from, _to, _value);
  }

  function approve(
    address _spender,
    uint256 _value
  )
    public
    whenNotPaused
    returns (bool)
  {
    return super.approve(_spender, _value);
  }

  function increaseApproval(
    address _spender,
    uint _addedValue
  )
    public
    whenNotPaused
    returns (bool success)
  {
    return super.increaseApproval(_spender, _addedValue);
  }

  function decreaseApproval(
    address _spender,
    uint _subtractedValue
  )
    public
    whenNotPaused
    returns (bool success)
  {
    return super.decreaseApproval(_spender, _subtractedValue);
  }
}

contract MintableToken is StandardToken, Ownable {
  using SafeMath for uint256;
  event Mint(address indexed to, uint256 amount);

  uint constant YEAR_IN_SECONDS = 31536000;

  uint constant ORIGIN_TIMESTAMP = 1514764800;
  uint16 constant ORIGIN_YEAR = 2018;

  uint256 originSupply_;
  // ufixed8x2 u0.02;

  struct MintRecord {
      uint percent;
      address holder;
      uint16 year;
      uint256 amount;
      uint timestamp;
  }

  // year=> MintRecord
  mapping (uint16 => MintRecord) public mintedHistory;

  function getYear(uint _timestamp) public pure returns (uint16) {
    require(_timestamp > ORIGIN_TIMESTAMP);
    return ORIGIN_YEAR + uint16((_timestamp - ORIGIN_TIMESTAMP) / YEAR_IN_SECONDS);
  }

  modifier hasMintPermission() {
    require(msg.sender == owner);
    _;
  }

  function originSupply() public view returns (uint256) {
    return originSupply_;
  }

  function mint() public hasMintPermission returns (bool) {
    return _mint(block.timestamp);
  }

  function _mint(uint _timestamp) internal hasMintPermission returns (bool) {
    uint16 year = getYear(_timestamp);
    require(mintedHistory[year].percent == 0);
    uint256 amount = totalSupply_.mul(200).div(10000);
    totalSupply_ = totalSupply_.add(amount);
    balances[msg.sender] = balances[msg.sender].add(amount);
    mintedHistory[year] = MintRecord({
        percent: 200,
        amount: amount,
        holder: msg.sender,
        timestamp: _timestamp,
        year: year
    });
    emit Transfer(address(0), msg.sender, amount);
    emit Mint(msg.sender, amount);
    return true;
  }
}

contract HGSToken is PausableToken, MintableToken {

  string public constant name = "Hawthorn Guardian System";
  string public constant symbol = "HGS";
  uint8 public constant decimals = 18;

  uint256 public constant INITIAL_SUPPLY = 2000000000 * (10 ** uint256(decimals));

  constructor() public {
    totalSupply_ = INITIAL_SUPPLY;
    originSupply_ = INITIAL_SUPPLY;
    balances[msg.sender] = INITIAL_SUPPLY;
    emit Transfer(address(0), msg.sender, INITIAL_SUPPLY);
  }
}