pragma solidity 0.4.21;


/**
 * @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) {
    if (a == 0) {
      return 0;
    }
    uint256 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 c;
  }

  /**
  * @dev Substracts 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) {
    uint256 c = a + b;
    assert(c >= a);
    return c;
  }
}


/**
 * @title ERC20Basic
 * @dev Simpler version of ERC20 interface
 * @dev see https://github.com/ethereum/EIPs/issues/179
 */
contract ERC20Basic {
  function totalSupply() public view returns (uint256);
  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);
}


/**
 * @title ERC20 interface
 * @dev see https://github.com/ethereum/EIPs/issues/20
 */
contract ERC20 is ERC20Basic {
  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);
}


/**
 * @title Basic token
 * @dev Basic version of StandardToken, with no allowances.
 */
contract BasicToken is ERC20Basic {
  using SafeMath for uint256;

  mapping(address => uint256) balances;

  uint256 totalSupply_;

  /**
  * @dev total number of tokens in existence
  */
  function totalSupply() public view returns (uint256) {
    return totalSupply_;
  }

  /**
  * @dev transfer token for a specified address
  * @param _to The address to transfer to.
  * @param _value The amount to be transferred.
  */
  function transfer(address _to, uint256 _value) public returns (bool) {
    require(_to != address(0));
    require(_value <= balances[msg.sender]);

    // SafeMath.sub will throw if there is not enough balance.
    balances[msg.sender] = balances[msg.sender].sub(_value);
    balances[_to] = balances[_to].add(_value);
    emit Transfer(msg.sender, _to, _value);
    return true;
  }

  /**
  * @dev Gets the balance of the specified address.
  * @param _owner The address to query the the balance of.
  * @return An uint256 representing the amount owned by the passed address.
  */
  function balanceOf(address _owner) public view returns (uint256 balance) {
    return balances[_owner];
  }

}


/**
 * @title Burnable Token
 * @dev Token that can be irreversibly burned (destroyed).
 */
contract BurnableToken is BasicToken {

  event Burn(address indexed burner, uint256 value);

  /**
   * @dev Burns a specific amount of tokens.
   * @param _value The amount of token to be burned.
   */
  function burn(uint256 _value) public {
    require(_value <= balances[msg.sender]);
    // no need to require value <= totalSupply, since that would imply the
    // sender's balance is greater than the totalSupply, which *should* be an assertion failure

    address burner = msg.sender;
    balances[burner] = balances[burner].sub(_value);
    totalSupply_ = totalSupply_.sub(_value);
    emit Burn(burner, _value);
  }
}


/**
 * @title Standard ERC20 token
 *
 * @dev Implementation of the basic standard token.
 * @dev https://github.com/ethereum/EIPs/issues/20
 * @dev Based on code by FirstBlood: https://github.com/Firstbloodio/token/blob/master/smart_contract/FirstBloodToken.sol
 */
contract StandardToken is ERC20, BasicToken {

  mapping (address => mapping (address => uint256)) internal allowed;


  /**
   * @dev Transfer tokens from one address to another
   * @param _from address The address which you want to send tokens from
   * @param _to address The address which you want to transfer to
   * @param _value uint256 the amount of tokens to be transferred
   */
  function transferFrom(address _from, address _to, uint256 _value) public 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);
    emit Transfer(_from, _to, _value);
    return true;
  }

  /**
   * @dev Approve the passed address to spend the specified amount of tokens on behalf of msg.sender.
   *
   * Beware that changing an allowance with this method brings the risk that someone may use both the old
   * and the new allowance by unfortunate transaction ordering. One possible solution to mitigate this
   * race condition is to first reduce the spender's allowance to 0 and set the desired value afterwards:
   * https://github.com/ethereum/EIPs/issues/20#issuecomment-263524729
   * @param _spender The address which will spend the funds.
   * @param _value The amount of tokens to be spent.
   */
  function approve(address _spender, uint256 _value) public returns (bool) {
    allowed[msg.sender][_spender] = _value;
    emit Approval(msg.sender, _spender, _value);
    return true;
  }

  /**
   * @dev Function to check the amount of tokens that an owner allowed to a spender.
   * @param _owner address The address which owns the funds.
   * @param _spender address The address which will spend the funds.
   * @return A uint256 specifying the amount of tokens still available for the spender.
   */
  function allowance(address _owner, address _spender) public view returns (uint256) {
    return allowed[_owner][_spender];
  }

  /**
   * @dev Increase the amount of tokens that an owner allowed to a spender.
   *
   * approve should be called when allowed[_spender] == 0. To increment
   * allowed value is better to use this function to avoid 2 calls (and wait until
   * the first transaction is mined)
   * From MonolithDAO Token.sol
   * @param _spender The address which will spend the funds.
   * @param _addedValue The amount of tokens to increase the allowance by.
   */
  function increaseApproval(address _spender, uint _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;
  }

  /**
   * @dev Decrease the amount of tokens that an owner allowed to a spender.
   *
   * approve should be called when allowed[_spender] == 0. To decrement
   * allowed value is better to use this function to avoid 2 calls (and wait until
   * the first transaction is mined)
   * From MonolithDAO Token.sol
   * @param _spender The address which will spend the funds.
   * @param _subtractedValue The amount of tokens to decrease the allowance by.
   */
  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);
    }
    emit Approval(msg.sender, _spender, allowed[msg.sender][_spender]);
    return true;
  }

}


/**
 * @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;


  event OwnershipTransferred(address indexed previousOwner, address indexed newOwner);


  /**
   * @dev The Ownable constructor sets the original `owner` of the contract to the sender
   * account.
   */
  function Ownable() public {
    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));
    emit OwnershipTransferred(owner, newOwner);
    owner = newOwner;
  }

}


/**
 * @title Pausable
 * @dev Base contract which allows children to implement an emergency stop mechanism.
 */
contract Pausable is Ownable {
  event Pause();
  event Unpause();

  bool public paused = false;


  /**
   * @dev Modifier to make a function callable only when the contract is not paused.
   */
  modifier whenNotPaused() {
    require(!paused);
    _;
  }

  /**
   * @dev Modifier to make a function callable only when the contract is paused.
   */
  modifier whenPaused() {
    require(paused);
    _;
  }

  /**
   * @dev called by the owner to pause, triggers stopped state
   */
  function pause() onlyOwner whenNotPaused public {
    paused = true;
    emit Pause();
  }

  /**
   * @dev called by the owner to unpause, returns to normal state
   */
  function unpause() onlyOwner whenPaused public {
    paused = false;
    emit Unpause();
  }
}


/**
 * @title Pausable token
 * @dev StandardToken modified with pausable transfers.
 **/
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 DistributableAndPausableToken is PausableToken {
    uint256 public distributedToken;
    address public vraWallet;

    event Distribute(address indexed to, uint256 amount);
    event Mint(address indexed to, uint256 amount);

    function distributeTokens(address _to, uint256 _amount) 
        external
        onlyOwner
        returns (bool)
    {
        require(_to != address(0));
        require(_amount > 0);
        require(balances[vraWallet].sub(_amount) >= 0);
        balances[vraWallet] = balances[vraWallet].sub(_amount);
        balances[_to] = balances[_to].add(_amount);
        distributedToken = distributedToken.add(_amount);
        emit Distribute(_to, _amount);
        emit Transfer(address(0), _to, _amount);
        return true;
    }

    function getDistributedToken() public constant returns (uint256) {
        return distributedToken;
    }

}


/**
 * Token upgrader interface inspired by Lunyr.
 *
 * Token upgrader transfers previous version tokens to a newer version.
 * Token upgrader itself can be the token contract, or just a middle man contract doing the heavy lifting.
 */
contract TokenUpgrader {
    uint public originalSupply;

    /** Interface marker */
    function isTokenUpgrader() external pure returns (bool) {
        return true;
    }

    function upgradeFrom(address _from, uint256 _value) public {}
}


/**
 * A token upgrade mechanism where users can opt-in amount of tokens to the next smart contract revision.
 *
 * First envisioned by Golem and Lunyr projects.
 */

contract UpgradeableToken is DistributableAndPausableToken {
    // Contract or person who can set the upgrade path.
    address public upgradeMaster;
    
    // Bollean value needs to be true to start upgrades
    bool private upgradesAllowed;

    // The next contract where the tokens will be migrated.
    TokenUpgrader public tokenUpgrader;

    // How many tokens we have upgraded by now.
    uint public totalUpgraded;

    /**
    * Upgrade states.
    * - NotAllowed: The child contract has not reached a condition where the upgrade can begin
    * - Waiting: Token allows upgrade, but we don't have a new token version
    * - ReadyToUpgrade: The token version is set, but not a single token has been upgraded yet
    * - Upgrading: Token upgrader is set and the balance holders can upgrade their tokens
    */
    enum UpgradeState { NotAllowed, Waiting, ReadyToUpgrade, Upgrading }

    // Somebody has upgraded some of his tokens.
    event Upgrade(address indexed _from, address indexed _to, uint256 _value);

    // New token version available.
    event TokenUpgraderIsSet(address _newToken);

    modifier onlyUpgradeMaster {
        // Only a master can designate the next token
        require(msg.sender == upgradeMaster);
        _;
    }

    modifier notInUpgradingState {
        // Upgrade has already begun for token
        require(getUpgradeState() != UpgradeState.Upgrading);
        _;
    }

    // Do not allow construction without upgrade master set.
    function UpgradeableToken(address _upgradeMaster) public {
        upgradeMaster = _upgradeMaster;
    }

    // set a token upgrader
    function setTokenUpgrader(address _newToken)
        external
        onlyUpgradeMaster
        notInUpgradingState
    {
        require(canUpgrade());
        require(_newToken != address(0));

        tokenUpgrader = TokenUpgrader(_newToken);

        // Handle bad interface
        require(tokenUpgrader.isTokenUpgrader());

        // Make sure that token supplies match in source and target
        require(tokenUpgrader.originalSupply() == totalSupply_);

        emit TokenUpgraderIsSet(tokenUpgrader);
    }

    // Allow the token holder to upgrade some of their tokens to a new contract.
    function upgrade(uint _value) external {
        UpgradeState state = getUpgradeState();
        
        // Check upgrate state 
        require(state == UpgradeState.ReadyToUpgrade || state == UpgradeState.Upgrading);
        // Validate input value
        require(_value != 0);

        balances[msg.sender] = balances[msg.sender].sub(_value);

        // Take tokens out from circulation
        totalSupply_ = totalSupply_.sub(_value);
        totalUpgraded = totalUpgraded.add(_value);

        // Token Upgrader reissues the tokens
        tokenUpgrader.upgradeFrom(msg.sender, _value);
        emit Upgrade(msg.sender, tokenUpgrader, _value);
    }

    /**
    * Change the upgrade master.
    * This allows us to set a new owner for the upgrade mechanism.
    */
    function setUpgradeMaster(address _newMaster) external onlyUpgradeMaster {
        require(_newMaster != address(0));
        upgradeMaster = _newMaster;
    }

    // To be overriden to add functionality
    function allowUpgrades() external onlyUpgradeMaster () {
        upgradesAllowed = true;
    }

    // To be overriden to add functionality
    function rejectUpgrades() external onlyUpgradeMaster () {
        require(!(totalUpgraded > 0));
        upgradesAllowed = false;
    }

    // Get the state of the token upgrade.
    function getUpgradeState() public view returns(UpgradeState) {
        if (!canUpgrade()) return UpgradeState.NotAllowed;
        else if (address(tokenUpgrader) == address(0)) return UpgradeState.Waiting;
        else if (totalUpgraded == 0) return UpgradeState.ReadyToUpgrade;
        else return UpgradeState.Upgrading;
    }

    // To be overriden to add functionality
    function canUpgrade() public view returns(bool) {
        return upgradesAllowed;
    }
}


contract Token is UpgradeableToken, BurnableToken {
    using SafeMath for uint256;
    
    string public name = "VERA";
    string public symbol = "VRA";
    uint256 public maxTokenSupply;
    string public constant TERMS_AND_CONDITION =  "THE DIGITAL TOKENS REPRESENTED BY THIS BLOCKCHAIN LEDGER RECORD HAVE BEEN ACQUIRED FOR INVESTMENT UNDER CERTAIN SECURITIES EXEMPTIONS AND HAVE NOT BEEN REGISTERED UNDER THE U.S. SECURITIES ACT OF 1933, AS AMENDED (THE 'ACT'). UNTIL THE EXPIRATION OF THIS RESTRICTIVE LEGEND, SUCH TOKENS MAY NOT BE OFFERED, SOLD, ASSIGNED, TRANSFERRED, PLEDGED, ENCUMBERED OR OTHERWISE DISPOSED OF TO ANOTHER U.S. PERSON IN THE ABSENCE OF A REGISTRATION OR AN EXEMPTION THEREFROM UNDER THE ACT AND ANY APPLICABLE U.S. STATE SECURITIES LAWS. THE APPLICABLE RESTRICTED PERIOD (PER RULE 144 PROMULGATED UNDER THE ACT) IS ONE YEAR FROM THE ISSUANCE OF THE TOKENS. ANY PARTIES, INCLUDING EXCHANGES AND THE ORIGINAL ACQUIRERS OF THESE TOKENS, MAY BE HELD LIABLE FOR ANY UNAUTHORIZED TRANSFERS OR SALES OF THESE TOKENS DURING THE RESTRICTIVE PERIOD, AND ANY HOLDER OR ACQUIRER OF THESE TOKENS AGREES, AS A CONDITION OF SUCH HOLDING, THAT THE TOKEN GENERATOR/ISSUER (THE 'COMPANY') SHALL BE FREE OF ANY LIABILITY IN CONNECTION WITH SUCH UNAUTHORIZED TRANSACTIONS. REQUESTS TO TRANSFER THESE TOKENS DURING THE RESTRICTIVE PERIOD WITH LEGAL JUSTIFICATION MAY BE MADE BY WRITTEN REQUEST OF THE HOLDER OF THESE TOKENS TO THE COMPANY, WITH NO GUARANTEE OF APPROVAL.";
    uint8 public constant decimals = 18;

    event UpdatedTokenInformation(string newName, string newSymbol);

    function Token(address _vraWallet, address _upgradeMaster, uint256 _maxTokenSupply)
        public
        UpgradeableToken(_upgradeMaster)
    {
        maxTokenSupply = _maxTokenSupply.mul(10 ** uint256(decimals));
        vraWallet = _vraWallet;
        totalSupply_ = maxTokenSupply;
        balances[vraWallet] = totalSupply_;
        pause();
        emit Mint(vraWallet, totalSupply_);
        emit Transfer(address(0), vraWallet, totalSupply_);
    }

    /**
    * Owner can update token information here
    */
    function setTokenInformation(string _name, string _symbol) external onlyOwner {
        name = _name;
        symbol = _symbol;

        emit UpdatedTokenInformation(name, symbol);
    }

    /**
    * Owner can burn token here
    */
    function burn(uint256 _value) public onlyOwner {
        super.burn(_value);
    }

}