pragma solidity ^0.4.23;

/**
 * @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 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 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 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;
  }

}
 
/**
 * @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 internal 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 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;
  }

  /**
   * @dev Allows the current owner to relinquish control of the contract.
   */
  function renounceOwnership() public onlyOwner {
    emit OwnershipRenounced(owner);
    owner = address(0);
  }
  
}
 
/**
 * @title Mintable token
 * @dev Simple ERC20 Token example, with mintable token creation
 * @dev Issue: * https://github.com/OpenZeppelin/zeppelin-solidity/issues/120
 * 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();
  event MintStarted();
 
  bool public mintingFinished = false;
 
  modifier canMint() {
    require(!mintingFinished);
    _;
  }
 
  /**
   * @dev Function to mint tokens
   * @param _to The address that will recieve 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 onlyOwner 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 returns (bool) {
    mintingFinished = true;
    emit MintFinished();
    return true;
  }
  
  /**
   * @dev Function to start minting new tokens.
   * @return True if the operation was successful.
   */
  function startMinting() public onlyOwner returns (bool) {
    mintingFinished = false;
    emit MintStarted();
    return true;
  }
  
}

contract KassotBasicToken is MintableToken {
    
  string public constant name = "Kassot Token";  
  string public constant symbol = "KATOK";  
  uint8 public constant decimals = 18;
  
  uint public constant decimalMultiply = 1000000000000000000;  
  
}
 
/*
 * @title KassotToken
 * @dev Kassot token crowdsale contract
 * @dev Author: Alexander Kazorin <akazorin@gmail.com>
 */ 
contract KassotToken is ERC20, Ownable {
  
  using SafeMath for uint;
  
  bool public saleFinished = false;
  address internal multisig;
  address internal restricted;
  uint public restrictedPercent;
  uint public hardcap;
  uint public softcap;
  uint public firstBonusPercent;
  uint public secondBonusPercent;
  uint public thirdBonusPercent;
  uint public rate;                       // Price (%rate% KST = 1 ETH)
  uint public currentRound;
  bool public allowRefund = false;        // Set to true if under softcap
  KassotBasicToken internal token = new KassotBasicToken();
  mapping (uint => mapping (address => uint)) public balances;
  mapping(uint => uint) internal bonuses;
  mapping(uint => uint) internal amounts;

  constructor(address _multisig, address _restricted) public {
    multisig = _multisig;
    restricted = _restricted;
    
    // Settings for first round
    restrictedPercent = 10;
    hardcap = 900 * 1 ether;
    softcap = 30 * 1 ether;
    rate = 112600 * token.decimalMultiply();
    currentRound = 1;
    firstBonusPercent = 50;
    secondBonusPercent = 25;
    thirdBonusPercent = 10;
  }

  modifier saleIsOn() {
    require(!saleFinished);
    _;
  }

  modifier isUnderHardCap() {
    require(address(this).balance <= hardcap);
    _;
  }
  
  // ERC20 Inteface methods
  function name() public view returns (string) {
    return token.name();
  }
  
  function symbol() public view returns (string) {
    return token.symbol();
  }
  
  function decimals() public view returns (uint8) {
    return token.decimals();
  }
  
  function totalSupply() public view returns (uint256) {
    return token.totalSupply();
  }

  function transfer(address _to, uint256 _value) public returns (bool) {
    return token.transfer(_to, _value);
  }

  function balanceOf(address _owner) public view returns (uint256) {
    return token.balanceOf(_owner);
  }

  function transferFrom(address _from, address _to, uint256 _value) public returns (bool) {
    return token.transferFrom(_from, _to, _value);
  }

  function approve(address _spender, uint256 _value) public returns (bool) {
    return token.approve(_spender, _value);
  }

  function allowance(address _owner, address _spender) public view returns (uint256) {
    return token.allowance(_owner, _spender);
  }
  // End of ERC20 Inteface methods

  function setMultisig(address _multisig) public onlyOwner returns (bool) {
    multisig = _multisig;
    return true;
  }
  
  function setRestricted(address _restricted) public onlyOwner returns (bool) {
    restricted = _restricted;
    return true;
  }
  
  function setRestrictedPercent(uint _restrictedPercent) public onlyOwner returns (bool) {
    restrictedPercent = _restrictedPercent;
    return true;
  }
  
  function setHardcap(uint _hardcap) public onlyOwner returns (bool) {
    hardcap = _hardcap;
    return true;
  }
  
  function setSoftcap(uint _softcap) public onlyOwner returns (bool) {
    softcap = _softcap;
    return true;
  }
  
  function setRate(uint _rate) public onlyOwner returns (bool) {
    rate = _rate;
    return true;
  }
  
  function setCurrentRound(uint _currentRound) public onlyOwner returns (bool) {
    currentRound = _currentRound;
    return true;
  }
  
  function setFirstBonusPercent(uint _firstBonusPercent) public onlyOwner returns (bool) {
    firstBonusPercent = _firstBonusPercent;
    return true;
  }
  
  function setSecondBonusPercent(uint _secondBonusPercent) public onlyOwner returns (bool) {
    secondBonusPercent = _secondBonusPercent;
    return true;
  }
  
  function setThirdBonusPercent(uint _thirdBonusPercent) public onlyOwner returns (bool) {
    thirdBonusPercent = _thirdBonusPercent;
    return true;
  }
  
  function getMultisig() public view onlyOwner returns (address) {
    // only owner can show address for safety reasons
    return multisig;
  }
  
  function getRestricted() public view onlyOwner returns (address) {
    // only owner can show address for safety reasons
    return restricted;
  }

  function refund() public {
    require(allowRefund);
    uint value = balances[currentRound][msg.sender]; 
    balances[currentRound][msg.sender] = 0; 
    msg.sender.transfer(value); 
  }

  function finishSale() public onlyOwner {
    if (address(this).balance > softcap) {
      multisig.transfer(address(this).balance);
      uint issuedTokenSupply = token.totalSupply();
      uint restrictedTokens = issuedTokenSupply.mul(restrictedPercent).div(100);
      token.mint(restricted, restrictedTokens);
    } else {
      allowRefund = true;
    }
    token.finishMinting();
    saleFinished = true;
  }
  
  function startSale() public onlyOwner {
    token.startMinting();
    allowRefund = false;
    saleFinished = false;
  }

  function calculateTokens(uint _amount, uint _stage, uint _stageAmount) public returns (uint) {
    bonuses[1] = firstBonusPercent;
    bonuses[2] = secondBonusPercent;
    bonuses[3] = thirdBonusPercent;
    bonuses[4] = 0;
    
    amounts[1] = 0;
    amounts[2] = 0;
    amounts[3] = 0;
    amounts[4] = 0;
    
    int amount = int(_amount);
    
    uint i = _stage;
    while (amount > 0) {
      if (i > 3) {
        amounts[i] = uint(amount);
        break;
      }
      if (amount - int(_stageAmount) > 0) {
        amounts[i] = _stageAmount;
        amount -= int(_stageAmount);
        i++;
      } else {
        amounts[i] = uint(amount);
        break;
      }
    }
    
    uint tokens = 0;
    uint bonusTokens = 0;
    uint _tokens = 0;
    for (i = _stage; i <= 4; i++) {
      if (amounts[i] == 0) {
        break;
      }
      _tokens = rate.mul(amounts[i]).div(1 ether);
      bonusTokens = _tokens * bonuses[i] / 100;
      tokens += _tokens + bonusTokens;
    }
    
    return tokens;
  }
  
  function createTokens() public isUnderHardCap saleIsOn payable {
    uint amount = msg.value;
    uint tokens = 0;    
    uint stageAmount = hardcap.div(4);
    
    if (address(this).balance <= stageAmount) {
      tokens = calculateTokens(amount, 1, stageAmount);
    } else if (address(this).balance <= stageAmount * 2) {
      tokens = calculateTokens(amount, 2, stageAmount);
    } else if (address(this).balance <= stageAmount * 3) {
      tokens = calculateTokens(amount, 3, stageAmount);
    } else {
      tokens = calculateTokens(amount, 4, stageAmount);
    }
    
    token.mint(msg.sender, tokens);
    balances[currentRound][msg.sender] = balances[currentRound][msg.sender].add(amount);
  }

  function() external payable {
    createTokens();
  }
  
}