pragma solidity ^0.4.24;

// File: openzeppelin-solidity/contracts/access/rbac/Roles.sol

/**
 * @title Roles
 * @author Francisco Giordano (@frangio)
 * @dev Library for managing addresses assigned to a Role.
 * See RBAC.sol for example usage.
 */
library Roles {
  struct Role {
    mapping (address => bool) bearer;
  }

  /**
   * @dev give an address access to this role
   */
  function add(Role storage _role, address _addr)
    internal
  {
    _role.bearer[_addr] = true;
  }

  /**
   * @dev remove an address' access to this role
   */
  function remove(Role storage _role, address _addr)
    internal
  {
    _role.bearer[_addr] = false;
  }

  /**
   * @dev check if an address has this role
   * // reverts
   */
  function check(Role storage _role, address _addr)
    internal
    view
  {
    require(has(_role, _addr));
  }

  /**
   * @dev check if an address has this role
   * @return bool
   */
  function has(Role storage _role, address _addr)
    internal
    view
    returns (bool)
  {
    return _role.bearer[_addr];
  }
}

// File: openzeppelin-solidity/contracts/access/rbac/RBAC.sol

/**
 * @title RBAC (Role-Based Access Control)
 * @author Matt Condon (@Shrugs)
 * @dev Stores and provides setters and getters for roles and addresses.
 * Supports unlimited numbers of roles and addresses.
 * See //contracts/mocks/RBACMock.sol for an example of usage.
 * This RBAC method uses strings to key roles. It may be beneficial
 * for you to write your own implementation of this interface using Enums or similar.
 */
contract RBAC {
  using Roles for Roles.Role;

  mapping (string => Roles.Role) private roles;

  event RoleAdded(address indexed operator, string role);
  event RoleRemoved(address indexed operator, string role);

  /**
   * @dev reverts if addr does not have role
   * @param _operator address
   * @param _role the name of the role
   * // reverts
   */
  function checkRole(address _operator, string _role)
    public
    view
  {
    roles[_role].check(_operator);
  }

  /**
   * @dev determine if addr has role
   * @param _operator address
   * @param _role the name of the role
   * @return bool
   */
  function hasRole(address _operator, string _role)
    public
    view
    returns (bool)
  {
    return roles[_role].has(_operator);
  }

  /**
   * @dev add a role to an address
   * @param _operator address
   * @param _role the name of the role
   */
  function addRole(address _operator, string _role)
    internal
  {
    roles[_role].add(_operator);
    emit RoleAdded(_operator, _role);
  }

  /**
   * @dev remove a role from an address
   * @param _operator address
   * @param _role the name of the role
   */
  function removeRole(address _operator, string _role)
    internal
  {
    roles[_role].remove(_operator);
    emit RoleRemoved(_operator, _role);
  }

  /**
   * @dev modifier to scope access to a single role (uses msg.sender as addr)
   * @param _role the name of the role
   * // reverts
   */
  modifier onlyRole(string _role)
  {
    checkRole(msg.sender, _role);
    _;
  }

  /**
   * @dev modifier to scope access to a set of roles (uses msg.sender as addr)
   * @param _roles the names of the roles to scope access to
   * // reverts
   *
   * @TODO - when solidity supports dynamic arrays as arguments to modifiers, provide this
   *  see: https://github.com/ethereum/solidity/issues/2467
   */
  // modifier onlyRoles(string[] _roles) {
  //     bool hasAnyRole = false;
  //     for (uint8 i = 0; i < _roles.length; i++) {
  //         if (hasRole(msg.sender, _roles[i])) {
  //             hasAnyRole = true;
  //             break;
  //         }
  //     }

  //     require(hasAnyRole);

  //     _;
  // }
}

// 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/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/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/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: 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/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/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: contracts/FUTM.sol

contract FUTM is MintableToken, BurnableToken, RBAC {
  using SafeMath for uint256;

  string public constant name = "Futereum Markets";
  string public constant symbol = "FUTM";
  uint8 public constant decimals = 18;

  string public constant ROLE_ADMIN = "admin";
  string public constant ROLE_SUPER = "super";

  uint public swapLimit;
  uint public constant CYCLE_CAP = 100000 * (10 ** uint256(decimals));
  uint public constant BILLION = 10 ** 9;

  event SwapStarted(uint256 startTime);
  event MiningRestart(uint256 endTime);
  event CMCUpdate(string updateType, uint value);

  uint offset = 10**18;
  // these rates are offset. divide by 1e18 to get actual rate.
  uint public exchangeRateFUTB;
  uint public exchangeRateFUTX;

  //initial state
  uint public cycleMintSupply = 0;
  bool public isMiningOpen = false;
  uint public CMC = 129238998229;
  uint public cycleEndTime;

  address public constant FUTC = 0xdaa6CD28E6aA9d656930cE4BB4FA93eEC96ee791;
  address public constant FUTB = 0x42D8F8E19F73707397B6e9eB7dD022d3c0aE736c;
  address public constant FUTX = 0x8b7d07b6ffB9364e97B89cEA8b84F94249bE459F;

  constructor() public {
    //only the contract itself can mint as the owner
    owner = this;
    totalSupply_ = 0;
    addRole(msg.sender, ROLE_ADMIN);
    addRole(msg.sender, ROLE_SUPER);

    // initial market data to set rates.
    exchangeRateFUTB = offset.mul(offset).div(CMC.mul(offset).div(BILLION)).mul(65).div(100);
    exchangeRateFUTX = offset.mul(offset).div(uint(14757117940).mul(offset).div(uint(67447696614)).mul(CMC).div(BILLION)).mul(65).div(100);
  }

  modifier canMine() {
    require(isMiningOpen);
    _;
  }

  // first call (futb address).approve(futm address, amount) for FUTM to transfer on your behalf.
  function mine(uint amount) canMine external {
    require(amount > 0);
    require(cycleMintSupply < CYCLE_CAP);
    require(ERC20(FUTB).transferFrom(msg.sender, address(this), amount));

    uint refund = _mine(exchangeRateFUTB, amount);
    if(refund > 0) {
      ERC20(FUTB).transfer(msg.sender, refund);
    }
    if (cycleMintSupply == CYCLE_CAP) {
      //start swap
      _startSwap();
    }
  }

  function _mine(uint _rate, uint _inAmount) private returns (uint) {
    assert(_rate > 0);

    // took too long; return tokens and start swap.
    if (now > cycleEndTime && cycleMintSupply > 0) {
      _startSwap();
      return _inAmount;
    }
    uint tokens = _rate.mul(_inAmount).div(offset);
    uint refund = 0;

    // for every 65 tokens mined, we mine 35 for the futc contract.
    uint futcFeed = tokens.mul(35).div(65);

    if (tokens + futcFeed + cycleMintSupply > CYCLE_CAP) {
      uint overage = tokens + futcFeed + cycleMintSupply - CYCLE_CAP;
      uint tokenOverage = overage.mul(65).div(100);
      futcFeed -= (overage - tokenOverage);
      tokens -= tokenOverage;

      // refund token overage
      refund = tokenOverage.mul(offset).div(_rate);
    }
    cycleMintSupply += (tokens + futcFeed);
    require(futcFeed > 0, "Mining payment too small.");
    MintableToken(this).mint(msg.sender, tokens);
    MintableToken(this).mint(FUTC, futcFeed);

    return refund;
  }

  // swap data
  bool public swapOpen = false;
  mapping(address => uint) public swapRates;

  function _startSwap() private {
    swapOpen = true;
    isMiningOpen = false;

    // set swap rates
    // 35% of holdings split among a number equal to 35% of newly minted futm
    swapLimit = cycleMintSupply.mul(35).div(100);
    swapRates[FUTX] = ERC20(FUTX).balanceOf(address(this)).mul(offset).mul(35).div(100).div(swapLimit);
    swapRates[FUTB] = ERC20(FUTB).balanceOf(address(this)).mul(offset).mul(35).div(100).div(swapLimit);

    emit SwapStarted(now);
  }

  function swap(uint amt) public {
    require(swapOpen && swapLimit > 0);
    if (amt > swapLimit) {
      amt = swapLimit;
    }
    swapLimit -= amt;
    // burn verifies msg.sender has balance
    burn(amt);

    if (amt.mul(swapRates[FUTX]) > 0) {
      ERC20(FUTX).transfer(msg.sender, amt.mul(swapRates[FUTX]).div(offset));
    }

    if (amt.mul(swapRates[FUTB]) > 0) {
      ERC20(FUTB).transfer(msg.sender, amt.mul(swapRates[FUTB]).div(offset));
    }

    if (swapLimit == 0) {
      _restart();
    }
  }

  function _restart() private {
    require(swapOpen);
    require(swapLimit == 0);

    cycleMintSupply = 0;
    swapOpen = false;
    isMiningOpen = true;
    cycleEndTime = now + 100 days;

    emit MiningRestart(cycleEndTime);
  }

  function updateCMC(uint _cmc) private {
    require(_cmc > 0);
    CMC = _cmc;
    emit CMCUpdate("TOTAL_CMC", _cmc);
    exchangeRateFUTB = offset.mul(offset).div(CMC.mul(offset).div(BILLION)).mul(65).div(100);
  }

  function updateCMC(uint _cmc, uint _btc, uint _eth) public onlyAdmin{
    require(_btc > 0 && _eth > 0);
    updateCMC(_cmc);
    emit CMCUpdate("BTC_CMC", _btc);
    emit CMCUpdate("ETH_CMC", _eth);
    exchangeRateFUTX = offset.mul(offset).div(_eth.mul(offset).div(_btc).mul(CMC).div(BILLION)).mul(65).div(100);
  }

  modifier onlySuper() {
    checkRole(msg.sender, ROLE_SUPER);
    _;
  }

  modifier onlyAdmin() {
    checkRole(msg.sender, ROLE_ADMIN);
    _;
  }

  function addAdmin(address _addr) public onlySuper {
    addRole(_addr, ROLE_ADMIN);
  }

  function removeAdmin(address _addr) public onlySuper {
    removeRole(_addr, ROLE_ADMIN);
  }

  function changeSuper(address _addr) public onlySuper {
    addRole(_addr, ROLE_SUPER);
    removeRole(msg.sender, ROLE_SUPER);
  }
}