pragma solidity ^0.4.18;

/**
 * @title ERC20Basic
 * @dev Simpler version of ERC20 interface
 * @dev see https://github.com/ethereum/EIPs/issues/179
 */
contract ERC20Basic {
  uint256 public totalSupply;
  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 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));
    OwnershipTransferred(owner, newOwner);
    owner = newOwner;
  }

}

/**
 * @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;
  }
}

contract MinerOnePromoToken is ERC20, Ownable {
	using SafeMath for uint256;

	string public constant name = "MinerOne.io Discount";
  	string public constant symbol = "MIO DISCOUNT";
  	uint8 public constant decimals = 18;

	mapping (address => uint256) balances;
	mapping (address => mapping (address => uint256)) internal allowed;

	event Mint(address indexed to, uint256 amount);

	/**
	* @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);
		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];
	}

	/**
	* @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);
		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;
		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);
		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);
		}
		Approval(msg.sender, _spender, allowed[msg.sender][_spender]);
		return true;
	}

	/**
	* @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) onlyOwner public returns (bool) {
		totalSupply = totalSupply.add(_amount);
		balances[_to] = balances[_to].add(_amount);
		Mint(_to, _amount);
		Transfer(address(0), _to, _amount);
		return true;
	}

  	function mintTokens(address[] _receivers, uint256[] _amounts) onlyOwner external  {
		require(_receivers.length > 0 && _receivers.length <= 100);
		require(_receivers.length == _amounts.length);
		for (uint256 i = 0; i < _receivers.length; i++) {
			address receiver = _receivers[i];
			uint256 amount = _amounts[i];

	  		require(receiver != address(0));
	  		require(amount > 0);

			mint(receiver, amount);
		}
  	}
}