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 c) {
    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;
  }
}



/**
 * @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 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]);

    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];
  }

}



/**
 * @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 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;
  }

}



/* solium-disable security/no-low-level-calls */

/**
 * @title ERC827 interface, an extension of ERC20 token standard
 *
 * @dev Interface of a ERC827 token, following the ERC20 standard with extra
 * @dev methods to transfer value and data and execute calls in transfers and
 * @dev approvals.
 */
contract ERC827 is ERC20 {
  function approveAndCall( address _spender, uint256 _value, bytes _data) public payable returns (bool);
  function transferAndCall( address _to, uint256 _value, bytes _data) public payable returns (bool);
  function transferFromAndCall(
    address _from,
    address _to,
    uint256 _value,
    bytes _data
  )
    public
    payable
    returns (bool);
}



/**
 * @title ERC827, an extension of ERC20 token standard
 *
 * @dev Implementation the ERC827, following the ERC20 standard with extra
 * @dev methods to transfer value and data and execute calls in transfers and
 * @dev approvals.
 *
 * @dev Uses OpenZeppelin StandardToken.
 */
contract ERC827Token is ERC827, StandardToken {

  /**
   * @dev Addition to ERC20 token methods. It allows to
   * @dev approve the transfer of value and execute a call with the sent data.
   *
   * @dev Beware that changing an allowance with this method brings the risk that
   * @dev someone may use both the old and the new allowance by unfortunate
   * @dev transaction ordering. One possible solution to mitigate this race condition
   * @dev is to first reduce the spender's allowance to 0 and set the desired value
   * @dev afterwards:
   * @dev https://github.com/ethereum/EIPs/issues/20#issuecomment-263524729
   *
   * @param _spender The address that will spend the funds.
   * @param _value The amount of tokens to be spent.
   * @param _data ABI-encoded contract call to call `_to` address.
   *
   * @return true if the call function was executed successfully
   */
  function approveAndCall(address _spender, uint256 _value, bytes _data) public payable returns (bool) {
    require(_spender != address(this));

    super.approve(_spender, _value);

    // solium-disable-next-line security/no-call-value
    require(_spender.call.value(msg.value)(_data));

    return true;
  }

  /**
   * @dev Addition to ERC20 token methods. Transfer tokens to a specified
   * @dev address and execute a call with the sent data on the same transaction
   *
   * @param _to address The address which you want to transfer to
   * @param _value uint256 the amout of tokens to be transfered
   * @param _data ABI-encoded contract call to call `_to` address.
   *
   * @return true if the call function was executed successfully
   */
  function transferAndCall(address _to, uint256 _value, bytes _data) public payable returns (bool) {
    require(_to != address(this));

    super.transfer(_to, _value);

    // solium-disable-next-line security/no-call-value
    require(_to.call.value(msg.value)(_data));
    return true;
  }

  /**
   * @dev Addition to ERC20 token methods. Transfer tokens from one address to
   * @dev another and make a contract call on the same transaction
   *
   * @param _from The address which you want to send tokens from
   * @param _to The address which you want to transfer to
   * @param _value The amout of tokens to be transferred
   * @param _data ABI-encoded contract call to call `_to` address.
   *
   * @return true if the call function was executed successfully
   */
  function transferFromAndCall(
    address _from,
    address _to,
    uint256 _value,
    bytes _data
  )
    public payable returns (bool)
  {
    require(_to != address(this));

    super.transferFrom(_from, _to, _value);

    // solium-disable-next-line security/no-call-value
    require(_to.call.value(msg.value)(_data));
    return true;
  }

  /**
   * @dev Addition to StandardToken methods. Increase the amount of tokens that
   * @dev an owner allowed to a spender and execute a call with the sent data.
   *
   * @dev approve should be called when allowed[_spender] == 0. To increment
   * @dev allowed value is better to use this function to avoid 2 calls (and wait until
   * @dev the first transaction is mined)
   * @dev From MonolithDAO Token.sol
   *
   * @param _spender The address which will spend the funds.
   * @param _addedValue The amount of tokens to increase the allowance by.
   * @param _data ABI-encoded contract call to call `_spender` address.
   */
  function increaseApprovalAndCall(address _spender, uint _addedValue, bytes _data) public payable returns (bool) {
    require(_spender != address(this));

    super.increaseApproval(_spender, _addedValue);

    // solium-disable-next-line security/no-call-value
    require(_spender.call.value(msg.value)(_data));

    return true;
  }

  /**
   * @dev Addition to StandardToken methods. Decrease the amount of tokens that
   * @dev an owner allowed to a spender and execute a call with the sent data.
   *
   * @dev approve should be called when allowed[_spender] == 0. To decrement
   * @dev allowed value is better to use this function to avoid 2 calls (and wait until
   * @dev the first transaction is mined)
   * @dev From MonolithDAO Token.sol
   *
   * @param _spender The address which will spend the funds.
   * @param _subtractedValue The amount of tokens to decrease the allowance by.
   * @param _data ABI-encoded contract call to call `_spender` address.
   */
  function decreaseApprovalAndCall(address _spender, uint _subtractedValue, bytes _data) public payable returns (bool) {
    require(_spender != address(this));

    super.decreaseApproval(_spender, _subtractedValue);

    // solium-disable-next-line security/no-call-value
    require(_spender.call.value(msg.value)(_data));

    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 Claimable
 * @dev Extension for the Ownable contract, where the ownership needs to be claimed.
 * This allows the new owner to accept the transfer.
 */
contract Claimable is Ownable {
  address public pendingOwner;

  /**
   * @dev Modifier throws if called by any account other than the pendingOwner.
   */
  modifier onlyPendingOwner() {
    require(msg.sender == pendingOwner);
    _;
  }

  /**
   * @dev Allows the current owner to set the pendingOwner address.
   * @param newOwner The address to transfer ownership to.
   */
  function transferOwnership(address newOwner) onlyOwner public {
    pendingOwner = newOwner;
  }

  /**
   * @dev Allows the pendingOwner address to finalize the transfer.
   */
  function claimOwnership() onlyPendingOwner public {
    emit OwnershipTransferred(owner, pendingOwner);
    owner = pendingOwner;
    pendingOwner = address(0);
  }
}



/**
 * @title MainframeToken
 */

contract MainframeToken is ERC827Token, Pausable, Claimable {
  string public constant name = "Mainframe Token";
  string public constant symbol = "MFT";
  uint8  public constant decimals = 18;
  address public distributor;

  modifier validDestination(address to) {
    require(to != address(this));
    _;
  }

  modifier isTradeable() {
    require(
      !paused ||
      msg.sender == owner ||
      msg.sender == distributor
    );
    _;
  }

  constructor() public {
    totalSupply_ = 10000000000 ether; // 10 billion, 18 decimals (ether = 10^18)
    balances[msg.sender] = totalSupply_;
    emit Transfer(address(0x0), msg.sender, totalSupply_);
  }

  // ERC20 Methods

  function transfer(address to, uint256 value) public validDestination(to) isTradeable returns (bool) {
    return super.transfer(to, value);
  }

  function transferFrom(address from, address to, uint256 value) public validDestination(to) isTradeable returns (bool) {
    return super.transferFrom(from, to, value);
  }

  function approve(address spender, uint256 value) public isTradeable returns (bool) {
    return super.approve(spender, value);
  }

  function increaseApproval(address spender, uint addedValue) public isTradeable returns (bool) {
    return super.increaseApproval(spender, addedValue);
  }

  function decreaseApproval(address spender, uint subtractedValue) public isTradeable returns (bool) {
    return super.decreaseApproval(spender, subtractedValue);
  }

  // ERC827 Methods

  function transferAndCall(address to, uint256 value, bytes data) public payable isTradeable returns (bool) {
    return super.transferAndCall(to, value, data);
  }

  function transferFromAndCall(address from, address to, uint256 value, bytes data) public payable isTradeable returns (bool) {
    return super.transferFromAndCall(from, to, value, data);
  }

  function approveAndCall(address spender, uint256 value, bytes data) public payable isTradeable returns (bool) {
    return super.approveAndCall(spender, value, data);
  }

  function increaseApprovalAndCall(address spender, uint addedValue, bytes data) public payable isTradeable returns (bool) {
    return super.increaseApprovalAndCall(spender, addedValue, data);
  }

  function decreaseApprovalAndCall(address spender, uint subtractedValue, bytes data) public payable isTradeable returns (bool) {
    return super.decreaseApprovalAndCall(spender, subtractedValue, data);
  }

  // Setters

  function setDistributor(address newDistributor) external onlyOwner {
    distributor = newDistributor;
  }

  // Token Drain

  function emergencyERC20Drain(ERC20 token, uint256 amount) external onlyOwner {
    // owner can drain tokens that are sent here by mistake
    token.transfer(owner, amount);
  }
}



contract StakeInterface {
  function hasStake(address _address) external view returns (bool);
}



contract MainframeStake is Ownable, StakeInterface {
  using SafeMath for uint256;

  ERC20 token;
  uint256 public arrayLimit = 200;
  uint256 public totalDepositBalance;
  uint256 public requiredStake;
  mapping (address => uint256) public balances;

  struct Staker {
    uint256 stakedAmount;
    address stakerAddress;
  }

  mapping (address => Staker) public whitelist; // map of whitelisted addresses for efficient hasStaked check

  constructor(address tokenAddress) public {
    token = ERC20(tokenAddress);
    requiredStake = 1 ether; // ether = 10^18
  }

  /**
  * @dev Staking MFT for a node address
  * @param staker representing the address of the person staking (not msg.sender in case of calling from other contract)
  * @param whitelistAddress representing the address of the node you want to stake for
  */

  function stake(address staker, address whitelistAddress) external returns (bool success) {
    require(whitelist[whitelistAddress].stakerAddress == 0x0);
    require(staker == msg.sender || (msg.sender == address(token) && staker == tx.origin));

    whitelist[whitelistAddress].stakerAddress = staker;
    whitelist[whitelistAddress].stakedAmount = requiredStake;

    deposit(staker, requiredStake);
    emit Staked(staker);
    return true;
  }

  /**
  * @dev Unstake a staked node address, will remove from whitelist and refund stake
  * @param whitelistAddress representing the staked node address
  */

  function unstake(address whitelistAddress) external {
    require(whitelist[whitelistAddress].stakerAddress == msg.sender);

    uint256 stakedAmount = whitelist[whitelistAddress].stakedAmount;
    delete whitelist[whitelistAddress];

    withdraw(msg.sender, stakedAmount);
    emit Unstaked(msg.sender);
  }

  /**
  * @dev Deposit stake amount
  * @param fromAddress representing the address to deposit from
  * @param depositAmount representing amount being deposited
  */

  function deposit(address fromAddress, uint256 depositAmount) private returns (bool success) {
    token.transferFrom(fromAddress, this, depositAmount);
    balances[fromAddress] = balances[fromAddress].add(depositAmount);
    totalDepositBalance = totalDepositBalance.add(depositAmount);
    emit Deposit(fromAddress, depositAmount, balances[fromAddress]);
    return true;
  }

  /**
  * @dev Withdraw funds after unstaking
  * @param toAddress representing the stakers address to withdraw to
  * @param withdrawAmount representing stake amount being withdrawn
  */

  function withdraw(address toAddress, uint256 withdrawAmount) private returns (bool success) {
    require(balances[toAddress] >= withdrawAmount);
    token.transfer(toAddress, withdrawAmount);
    balances[toAddress] = balances[toAddress].sub(withdrawAmount);
    totalDepositBalance = totalDepositBalance.sub(withdrawAmount);
    emit Withdrawal(toAddress, withdrawAmount, balances[toAddress]);
    return true;
  }

  function balanceOf(address _address) external view returns (uint256 balance) {
    return balances[_address];
  }

  function totalStaked() external view returns (uint256) {
    return totalDepositBalance;
  }

  function hasStake(address _address) external view returns (bool) {
    return whitelist[_address].stakedAmount > 0;
  }

  function requiredStake() external view returns (uint256) {
    return requiredStake;
  }

  function setRequiredStake(uint256 value) external onlyOwner {
    requiredStake = value;
  }

  function setArrayLimit(uint256 newLimit) external onlyOwner {
    arrayLimit = newLimit;
  }

  function refundBalances(address[] addresses) external onlyOwner {
    require(addresses.length <= arrayLimit);
    for (uint256 i = 0; i < addresses.length; i++) {
      address _address = addresses[i];
      require(balances[_address] > 0);
      token.transfer(_address, balances[_address]);
      totalDepositBalance = totalDepositBalance.sub(balances[_address]);
      emit RefundedBalance(_address, balances[_address]);
      balances[_address] = 0;
    }
  }

  function emergencyERC20Drain(ERC20 _token) external onlyOwner {
    // owner can drain tokens that are sent here by mistake
    uint256 drainAmount;
    if (address(_token) == address(token)) {
      drainAmount = _token.balanceOf(this).sub(totalDepositBalance);
    } else {
      drainAmount = _token.balanceOf(this);
    }
    _token.transfer(owner, drainAmount);
  }

  function destroy() external onlyOwner {
    require(token.balanceOf(this) == 0);
    selfdestruct(owner);
  }

  event Staked(address indexed owner);
  event Unstaked(address indexed owner);
  event Deposit(address indexed _address, uint256 depositAmount, uint256 balance);
  event Withdrawal(address indexed _address, uint256 withdrawAmount, uint256 balance);
  event RefundedBalance(address indexed _address, uint256 refundAmount);
}