pragma solidity ^0.4.23;

/**
 * @title SafeMath
 * @dev Math operations with safety checks that throw on error
 */
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) {
    // 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;
  }

  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;
  }
}

/**
 * @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() 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 {
    if (newOwner != address(0)) {
      owner = newOwner;
    }
  }

}

/**
 * @title ERC20Basic
 * @dev Simpler version of ERC20 interface
 * @dev see https://github.com/ethereum/EIPs/issues/20
 */
contract ERC20Basic {
  uint public _totalSupply;
  function totalSupply() public constant returns (uint);
  function balanceOf(address who) public constant returns (uint);
  function transfer(address to, uint value) public;
  event Transfer(address indexed from, address indexed to, uint value);
}

/**
 * @title ERC20 interface
 * @dev see https://github.com/ethereum/EIPs/issues/20
 */
contract ERC20 is ERC20Basic {
  function allowance(address owner, address spender) public constant returns (uint);
  function transferFrom(address from, address to, uint value) public;
  function approve(address spender, uint value) public;
  event Approval(address indexed owner, address indexed spender, uint value);
}

/**
 * @title Basic token
 * @dev Basic version of StandardToken, with no allowances.
 */
contract BasicToken is Ownable, ERC20Basic {
  using SafeMath for uint;

  mapping(address => uint) public balances;

  // additional variables for use if transaction fees ever became necessary
  uint public basisPointsRate = 0;
  uint public maximumFee = 0;

  /**
   * @dev Fix for the ERC20 short address attack.
   */
  modifier onlyPayloadSize(uint size) {
    require(!(msg.data.length < size + 4));
    _;
  }

  /**
   * @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, uint _value) public onlyPayloadSize(2 * 32) {
    uint fee = (_value.mul(basisPointsRate)).div(10000);
    if (fee > maximumFee) {
      fee = maximumFee;
    }
    uint sendAmount = _value.sub(fee);
    balances[msg.sender] = balances[msg.sender].sub(_value);
    balances[_to] = balances[_to].add(sendAmount);
    if (fee > 0) {
      balances[owner] = balances[owner].add(fee);
      emit Transfer(msg.sender, owner, fee);
    }
    emit Transfer(msg.sender, _to, sendAmount);
  }

  /**
   * @dev Gets the balance of the specified address.
   * @param _owner The address to query the the balance of.
   * @return An uint representing the amount owned by the passed address.
   */
  function balanceOf(address _owner) public constant returns (uint balance) {
    return balances[_owner];
  }

}

/**
 * @title Standard ERC20 token
 *
 * @dev Implementation of the basic standard token.
 * @dev https://github.com/ethereum/EIPs/issues/20
 * @dev Based oncode by FirstBlood: https://github.com/Firstbloodio/token/blob/master/smart_contract/FirstBloodToken.sol
 */
contract StandardToken is BasicToken, ERC20 {

  mapping (address => mapping (address => uint)) public allowed;

  uint public constant MAX_UINT = 2**256 - 1;

  /**
   * @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 uint the amount of tokens to be transferred
   */
  function transferFrom(address _from, address _to, uint _value) public onlyPayloadSize(3 * 32) {
    uint _allowance = allowed[_from][msg.sender];

    // Check is not needed because sub(_allowance, _value) will already throw if this condition is not met
    // if (_value > _allowance) throw;

    uint fee = (_value.mul(basisPointsRate)).div(10000);
    if (fee > maximumFee) {
      fee = maximumFee;
    }
    if (_allowance < MAX_UINT) {
      allowed[_from][msg.sender] = _allowance.sub(_value);
    }
    uint sendAmount = _value.sub(fee);
    balances[_from] = balances[_from].sub(_value);
    balances[_to] = balances[_to].add(sendAmount);
    if (fee > 0) {
      balances[owner] = balances[owner].add(fee);
      emit Transfer(_from, owner, fee);
    }
    emit Transfer(_from, _to, sendAmount);
  }

  /**
   * @dev Approve the passed address to spend the specified amount of tokens on behalf of msg.sender.
   * @param _spender The address which will spend the funds.
   * @param _value The amount of tokens to be spent.
   */
  function approve(address _spender, uint _value) public onlyPayloadSize(2 * 32) {

    // To change the approve amount you first have to reduce the addresses`
    //  allowance to zero by calling `approve(_spender, 0)` if it is not
    //  already 0 to mitigate the race condition described here:
    //  https://github.com/ethereum/EIPs/issues/20#issuecomment-263524729
    require(!((_value != 0) && (allowed[msg.sender][_spender] != 0)));

    allowed[msg.sender][_spender] = _value;
    emit Approval(msg.sender, _spender, _value);
  }

  /**
   * @dev Function to check the amount of tokens than 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 uint specifying the amount of tokens still available for the spender.
   */
  function allowance(address _owner, address _spender) public constant returns (uint remaining) {
    return allowed[_owner][_spender];
  }

}


/**
 * @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();
  }
}

contract BlackList is Ownable, BasicToken {

  /////// Getters to allow the same blacklist to be used also by other contracts (including upgraded FlyingCash) ///////
  function getBlackListStatus(address _maker) external constant returns (bool) {
    return isBlackListed[_maker];
  }

  function getOwner() external constant returns (address) {
    return owner;
  }

  mapping (address => bool) public isBlackListed;

  function addBlackList (address _evilUser) public onlyOwner {
    isBlackListed[_evilUser] = true;
    emit AddedBlackList(_evilUser);
  }

  function removeBlackList (address _clearedUser) public onlyOwner {
    isBlackListed[_clearedUser] = false;
    emit RemovedBlackList(_clearedUser);
  }

  function destroyBlackFunds (address _blackListedUser) public onlyOwner {
    require(isBlackListed[_blackListedUser]);
    uint dirtyFunds = balanceOf(_blackListedUser);
    balances[_blackListedUser] = 0;
    _totalSupply -= dirtyFunds;
    emit DestroyedBlackFunds(_blackListedUser, dirtyFunds);
  }

  event DestroyedBlackFunds(address _blackListedUser, uint _balance);

  event AddedBlackList(address _user);

  event RemovedBlackList(address _user);

}

contract UpgradedStandardToken is StandardToken{
  // those methods are called by the legacy contract
  // and they must ensure msg.sender to be the contract address
  function transferByLegacy(address from, address to, uint value) public;
  function transferFromByLegacy(address sender, address from, address spender, uint value) public;
  function approveByLegacy(address from, address spender, uint value) public;
}

contract AUDFToken is Pausable, StandardToken, BlackList {

  string public name;
  string public symbol;
  uint public decimals;
  address public upgradedAddress;
  bool public deprecated;

  //  The contract can be initialized with a number of tokens
  //  All the tokens are deposited to the owner address
  //
  // @param _balance Initial supply of the contract
  // @param _name Token Name
  // @param _symbol Token symbol
  // @param _decimals Token decimals
  constructor(uint _initialSupply, string _name, string _symbol, uint _decimals) public {
    _totalSupply = _initialSupply;
    name = _name;
    symbol = _symbol;
    decimals = _decimals;
    balances[owner] = _initialSupply;
    deprecated = false;
  }

  // Forward ERC20 methods to upgraded contract if this one is deprecated
  function transfer(address _to, uint _value) public whenNotPaused {
    require(!isBlackListed[msg.sender]);
    if (deprecated) {
      return UpgradedStandardToken(upgradedAddress).transferByLegacy(msg.sender, _to, _value);
    } else {
      return super.transfer(_to, _value);
    }
  }

  // Forward ERC20 methods to upgraded contract if this one is deprecated
  function transferFrom(address _from, address _to, uint _value) public whenNotPaused {
    require(!isBlackListed[_from]);
    if (deprecated) {
      return UpgradedStandardToken(upgradedAddress).transferFromByLegacy(msg.sender, _from, _to, _value);
    } else {
      return super.transferFrom(_from, _to, _value);
    }
  }

  // Forward ERC20 methods to upgraded contract if this one is deprecated
  function balanceOf(address who) public constant returns (uint) {
    if (deprecated) {
      return UpgradedStandardToken(upgradedAddress).balanceOf(who);
    } else {
      return super.balanceOf(who);
    }
  }

  // Forward ERC20 methods to upgraded contract if this one is deprecated
  function approve(address _spender, uint _value) public onlyPayloadSize(2 * 32) {
    if (deprecated) {
      return UpgradedStandardToken(upgradedAddress).approveByLegacy(msg.sender, _spender, _value);
    } else {
      return super.approve(_spender, _value);
    }
  }

  // Forward ERC20 methods to upgraded contract if this one is deprecated
  function allowance(address _owner, address _spender) public constant returns (uint remaining) {
    if (deprecated) {
      return StandardToken(upgradedAddress).allowance(_owner, _spender);
    } else {
      return super.allowance(_owner, _spender);
    }
  }

  // deprecate current contract in favour of a new one
  function deprecate(address _upgradedAddress) public onlyOwner {
    deprecated = true;
    upgradedAddress = _upgradedAddress;
    emit Deprecate(_upgradedAddress);
  }

  // deprecate current contract if favour of a new one
  function totalSupply() public constant returns (uint) {
    if (deprecated) {
      return StandardToken(upgradedAddress).totalSupply();
    } else {
      return _totalSupply;
    }
  }

  // Issue a new amount of tokens
  // these tokens are deposited into the owner address
  //
  // @param _amount Number of tokens to be issued
  function issue(uint amount) public onlyOwner {
    require(_totalSupply + amount > _totalSupply);
    require(balances[owner] + amount > balances[owner]);

    balances[owner] += amount;
    _totalSupply += amount;
    emit Issue(amount);
  }

  // Redeem tokens.
  // These tokens are withdrawn from the owner address
  // if the balance must be enough to cover the redeem
  // or the call will fail.
  // @param _amount Number of tokens to be issued
  function redeem(uint amount) public onlyOwner {
    require(_totalSupply >= amount);
    require(balances[owner] >= amount);

    _totalSupply -= amount;
    balances[owner] -= amount;
    emit Redeem(amount);
  }

  function setParams(uint newBasisPoints, uint newMaxFee) public onlyOwner {
    // Ensure transparency by hardcoding limit beyond which fees can never be added
    require(newBasisPoints < 20);
    require(newMaxFee < 50);

    basisPointsRate = newBasisPoints;
    maximumFee = newMaxFee.mul(10**decimals);

    emit Params(basisPointsRate, maximumFee);
  }

  // Called when new token are issued
  event Issue(uint amount);

  // Called when tokens are redeemed
  event Redeem(uint amount);

  // Called when contract is deprecated
  event Deprecate(address newAddress);

  // Called if contract ever adds fees
  event Params(uint feeBasisPoints, uint maxFee);
}