pragma solidity ^0.4.18;



contract Ownable {
  address public owner;


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


  
  function Ownable() public {
    owner = msg.sender;
  }


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


  
  function transferOwnership(address newOwner) public onlyOwner {
    require(newOwner != address(0));
    OwnershipTransferred(owner, newOwner);
    owner = newOwner;
  }

}

library SafeMath {
  function mul(uint256 a, uint256 b) internal pure returns (uint256) {
    if (a == 0) {
      return 0;
    }
    uint256 c = a * b;
    assert(c / a == b);
    return c;
  }

  function div(uint256 a, uint256 b) internal pure returns (uint256) {
    
    uint256 c = a / b;
    
    return c;
  }

  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) {
    uint256 c = a + b;
    assert(c >= a);
    return c;
  }
}













contract BionToken is Ownable {
  string public constant name = "BionToken";
  string public constant symbol = "BION";
  uint8 public constant decimals = 18;

  event Transfer(address indexed from, address indexed to, uint256 value);
  event Approval(address indexed owner, address indexed spender, uint256 value);
  event Mint(address indexed to, uint256 amount);
  event MintingFinished();
  event Burn(uint256 amount);

  uint256 public totalSupply;


  
  
  

  using SafeMath for uint256;

  mapping(address => uint256) public balances;

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

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

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


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


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

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

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

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

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

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


  
  
  

  bool public mintingFinished = false;
  address public destroyer;
  address public minter;

  modifier canMint() {
    require(!mintingFinished);
    _;
  }

  modifier whenMintingFinished() {
    require(mintingFinished);
    _;
  }

  modifier onlyMinter() {
    require(msg.sender == minter);
    _;
  }

  function setMinter(address _minter) external onlyOwner {
    minter = _minter;
  }

  function mint(address _to, uint256 _amount) external onlyMinter canMint  returns (bool) {
    require(balances[_to] + _amount > balances[_to]); 
    require(totalSupply + _amount > totalSupply);     
    totalSupply = totalSupply.add(_amount);
    balances[_to] = balances[_to].add(_amount);
    Mint(_to, _amount);
    return true;
  }

  function finishMinting() external onlyMinter returns (bool) {
    mintingFinished = true;
    MintingFinished();
    return true;
  }


  
  
  


  modifier onlyDestroyer() {
     require(msg.sender == destroyer);
     _;
  }

  function setDestroyer(address _destroyer) external onlyOwner {
    destroyer = _destroyer;
  }

  function burn(uint256 _amount) external onlyDestroyer {
    require(balances[destroyer] >= _amount && _amount > 0);
    balances[destroyer] = balances[destroyer].sub(_amount);
    totalSupply = totalSupply.sub(_amount);
    Burn(_amount);
  }
}