pragma solidity 0.4.24;

// File: openzeppelin-solidity/contracts/token/ERC20/ERC20Basic.sol

/**
 * @title ERC20Basic
 * @dev Simpler version of ERC20 interface
 * 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);
}

// File: openzeppelin-solidity/contracts/math/SafeMath.sol

/**
 * @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 c) {
    // Gas optimization: this is cheaper than asserting 'a' not being zero, but the
    // benefit is lost if 'b' is also tested.
    // See: https://github.com/OpenZeppelin/openzeppelin-solidity/pull/522
    if (_a == 0) {
      return 0;
    }

    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 _a / _b;
  }

  /**
  * @dev Subtracts 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 c) {
    c = _a + _b;
    assert(c >= _a);
    return c;
  }
}

// File: openzeppelin-solidity/contracts/token/ERC20/BasicToken.sol

/**
 * @title Basic token
 * @dev Basic version of StandardToken, with no allowances.
 */
contract BasicToken is ERC20Basic {
  using SafeMath for uint256;

  mapping(address => uint256) internal balances;

  uint256 internal 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(_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;
  }

  /**
  * @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) {
    return balances[_owner];
  }

}

// File: openzeppelin-solidity/contracts/token/ERC20/ERC20.sol

/**
 * @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
  );
}

// File: openzeppelin-solidity/contracts/token/ERC20/StandardToken.sol

/**
 * @title Standard ERC20 token
 *
 * @dev Implementation of the basic standard token.
 * https://github.com/ethereum/EIPs/issues/20
 * 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(_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;
  }

  /**
   * @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,
    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;
  }

  /**
   * @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,
    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;
  }

}

// File: openzeppelin-solidity/contracts/ownership/Ownable.sol

/**
 * @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 OwnershipRenounced(address indexed previousOwner);
  event OwnershipTransferred(
    address indexed previousOwner,
    address indexed newOwner
  );


  /**
   * @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 relinquish control of the contract.
   * @notice Renouncing to ownership will leave the contract without an owner.
   * It will not be possible to call the functions with the `onlyOwner`
   * modifier anymore.
   */
  function renounceOwnership() public onlyOwner {
    emit OwnershipRenounced(owner);
    owner = address(0);
  }

  /**
   * @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 {
    _transferOwnership(_newOwner);
  }

  /**
   * @dev Transfers control of the contract to a newOwner.
   * @param _newOwner The address to transfer ownership to.
   */
  function _transferOwnership(address _newOwner) internal {
    require(_newOwner != address(0));
    emit OwnershipTransferred(owner, _newOwner);
    owner = _newOwner;
  }
}

// File: openzeppelin-solidity/contracts/token/ERC20/MintableToken.sol

/**
 * @title Mintable token
 * @dev Simple ERC20 Token example, with mintable token creation
 * Based on code by TokenMarketNet: https://github.com/TokenMarketNet/ico/blob/master/contracts/MintableToken.sol
 */
contract MintableToken is StandardToken, Ownable {
  event Mint(address indexed to, uint256 amount);
  event MintFinished();

  bool public mintingFinished = false;


  modifier canMint() {
    require(!mintingFinished);
    _;
  }

  modifier hasMintPermission() {
    require(msg.sender == owner);
    _;
  }

  /**
   * @dev Function to mint tokens
   * @param _to The address that will receive the minted tokens.
   * @param _amount The amount of tokens to mint.
   * @return A boolean that indicates if the operation was successful.
   */
  function mint(
    address _to,
    uint256 _amount
  )
    public
    hasMintPermission
    canMint
    returns (bool)
  {
    totalSupply_ = totalSupply_.add(_amount);
    balances[_to] = balances[_to].add(_amount);
    emit Mint(_to, _amount);
    emit Transfer(address(0), _to, _amount);
    return true;
  }

  /**
   * @dev Function to stop minting new tokens.
   * @return True if the operation was successful.
   */
  function finishMinting() public onlyOwner canMint returns (bool) {
    mintingFinished = true;
    emit MintFinished();
    return true;
  }
}

// File: openzeppelin-solidity/contracts/token/ERC20/BurnableToken.sol

/**
 * @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 {
    _burn(msg.sender, _value);
  }

  function _burn(address _who, uint256 _value) internal {
    require(_value <= balances[_who]);
    // 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

    balances[_who] = balances[_who].sub(_value);
    totalSupply_ = totalSupply_.sub(_value);
    emit Burn(_who, _value);
    emit Transfer(_who, address(0), _value);
  }
}

// File: contracts/robonomics/XRT.sol

contract XRT is MintableToken, BurnableToken {
    string public constant name     = "Robonomics Beta";
    string public constant symbol   = "XRT";
    uint   public constant decimals = 9;

    uint256 public constant INITIAL_SUPPLY = 1000 * (10 ** uint256(decimals));

    constructor() public {
        totalSupply_ = INITIAL_SUPPLY;
        balances[msg.sender] = INITIAL_SUPPLY;
        emit Transfer(0x0, msg.sender, INITIAL_SUPPLY);
    }
}

// File: contracts/robonomics/DutchAuction.sol

/// @title Dutch auction contract - distribution of XRT tokens using an auction.
/// @author Stefan George - <stefan.george@consensys.net>
/// @author Airalab - <research@aira.life> 
contract DutchAuction {

    /*
     *  Events
     */
    event BidSubmission(address indexed sender, uint256 amount);

    /*
     *  Constants
     */
    uint constant public MAX_TOKENS_SOLD = 800 * 10**9; // 8M XRT = 10M - 1M (Foundation) - 1M (Early investors base)
    uint constant public WAITING_PERIOD = 30 minutes;

    /*
     *  Storage
     */
    XRT     public xrt;
    address public ambix;
    address public wallet;
    address public owner;
    uint public ceiling;
    uint public priceFactor;
    uint public startBlock;
    uint public endTime;
    uint public totalReceived;
    uint public finalPrice;
    mapping (address => uint) public bids;
    Stages public stage;

    /*
     *  Enums
     */
    enum Stages {
        AuctionDeployed,
        AuctionSetUp,
        AuctionStarted,
        AuctionEnded,
        TradingStarted
    }

    /*
     *  Modifiers
     */
    modifier atStage(Stages _stage) {
        // Contract on stage
        require(stage == _stage);
        _;
    }

    modifier isOwner() {
        // Only owner is allowed to proceed
        require(msg.sender == owner);
        _;
    }

    modifier isWallet() {
        // Only wallet is allowed to proceed
        require(msg.sender == wallet);
        _;
    }

    modifier isValidPayload() {
        require(msg.data.length == 4 || msg.data.length == 36);
        _;
    }

    modifier timedTransitions() {
        if (stage == Stages.AuctionStarted && calcTokenPrice() <= calcStopPrice())
            finalizeAuction();
        if (stage == Stages.AuctionEnded && now > endTime + WAITING_PERIOD)
            stage = Stages.TradingStarted;
        _;
    }

    /*
     *  Public functions
     */
    /// @dev Contract constructor function sets owner.
    /// @param _wallet Multisig wallet.
    /// @param _ceiling Auction ceiling.
    /// @param _priceFactor Auction price factor.
    constructor(address _wallet, uint _ceiling, uint _priceFactor)
        public
    {
        require(_wallet != 0 && _ceiling != 0 && _priceFactor != 0);
        owner = msg.sender;
        wallet = _wallet;
        ceiling = _ceiling;
        priceFactor = _priceFactor;
        stage = Stages.AuctionDeployed;
    }

    /// @dev Setup function sets external contracts' addresses.
    /// @param _xrt Robonomics token address.
    /// @param _ambix Distillation cube address.
    function setup(address _xrt, address _ambix)
        public
        isOwner
        atStage(Stages.AuctionDeployed)
    {
        // Validate argument
        require(_xrt != 0 && _ambix != 0);
        xrt = XRT(_xrt);
        ambix = _ambix;

        // Validate token balance
        require(xrt.balanceOf(this) == MAX_TOKENS_SOLD);

        stage = Stages.AuctionSetUp;
    }

    /// @dev Starts auction and sets startBlock.
    function startAuction()
        public
        isWallet
        atStage(Stages.AuctionSetUp)
    {
        stage = Stages.AuctionStarted;
        startBlock = block.number;
    }

    /// @dev Changes auction ceiling and start price factor before auction is started.
    /// @param _ceiling Updated auction ceiling.
    /// @param _priceFactor Updated start price factor.
    function changeSettings(uint _ceiling, uint _priceFactor)
        public
        isWallet
        atStage(Stages.AuctionSetUp)
    {
        ceiling = _ceiling;
        priceFactor = _priceFactor;
    }

    /// @dev Calculates current token price.
    /// @return Returns token price.
    function calcCurrentTokenPrice()
        public
        timedTransitions
        returns (uint)
    {
        if (stage == Stages.AuctionEnded || stage == Stages.TradingStarted)
            return finalPrice;
        return calcTokenPrice();
    }

    /// @dev Returns correct stage, even if a function with timedTransitions modifier has not yet been called yet.
    /// @return Returns current auction stage.
    function updateStage()
        public
        timedTransitions
        returns (Stages)
    {
        return stage;
    }

    /// @dev Allows to send a bid to the auction.
    /// @param receiver Bid will be assigned to this address if set.
    function bid(address receiver)
        public
        payable
        isValidPayload
        timedTransitions
        atStage(Stages.AuctionStarted)
        returns (uint amount)
    {
        require(msg.value > 0);
        amount = msg.value;

        // If a bid is done on behalf of a user via ShapeShift, the receiver address is set.
        if (receiver == 0)
            receiver = msg.sender;

        // Prevent that more than 90% of tokens are sold. Only relevant if cap not reached.
        uint maxWei = MAX_TOKENS_SOLD * calcTokenPrice() / 10**9 - totalReceived;
        uint maxWeiBasedOnTotalReceived = ceiling - totalReceived;
        if (maxWeiBasedOnTotalReceived < maxWei)
            maxWei = maxWeiBasedOnTotalReceived;

        // Only invest maximum possible amount.
        if (amount > maxWei) {
            amount = maxWei;
            // Send change back to receiver address. In case of a ShapeShift bid the user receives the change back directly.
            receiver.transfer(msg.value - amount);
        }

        // Forward funding to ether wallet
        wallet.transfer(amount);

        bids[receiver] += amount;
        totalReceived += amount;
        BidSubmission(receiver, amount);

        // Finalize auction when maxWei reached
        if (amount == maxWei)
            finalizeAuction();
    }

    /// @dev Claims tokens for bidder after auction.
    /// @param receiver Tokens will be assigned to this address if set.
    function claimTokens(address receiver)
        public
        isValidPayload
        timedTransitions
        atStage(Stages.TradingStarted)
    {
        if (receiver == 0)
            receiver = msg.sender;
        uint tokenCount = bids[receiver] * 10**9 / finalPrice;
        bids[receiver] = 0;
        require(xrt.transfer(receiver, tokenCount));
    }

    /// @dev Calculates stop price.
    /// @return Returns stop price.
    function calcStopPrice()
        view
        public
        returns (uint)
    {
        return totalReceived * 10**9 / MAX_TOKENS_SOLD + 1;
    }

    /// @dev Calculates token price.
    /// @return Returns token price.
    function calcTokenPrice()
        view
        public
        returns (uint)
    {
        return priceFactor * 10**18 / (block.number - startBlock + 7500) + 1;
    }

    /*
     *  Private functions
     */
    function finalizeAuction()
        private
    {
        stage = Stages.AuctionEnded;
        finalPrice = totalReceived == ceiling ? calcTokenPrice() : calcStopPrice();
        uint soldTokens = totalReceived * 10**9 / finalPrice;

        if (totalReceived == ceiling) {
            // Auction contract transfers all unsold tokens to Ambix contract
            require(xrt.transfer(ambix, MAX_TOKENS_SOLD - soldTokens));
        } else {
            // Auction contract burn all unsold tokens
            xrt.burn(MAX_TOKENS_SOLD - soldTokens);
        }

        endTime = now;
    }
}