pragma solidity ^0.4.18;

/**
 * @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) onlyOwner public {
        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) {
        uint256 c = a * b;
        assert(a == 0 || 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 TempusToken {

    function mint(address receiver, uint256 amount) public returns (bool success);

}

contract TempusIco is Ownable {
    using SafeMath for uint256;

    uint public startTime = 1519894800; //1 March 2018 09:00:00 GMT

    //initial token price
    uint public price0 = 0.005 ether / 1000;
    uint public price1 = price0 * 2;
    uint public price2 = price1 * 2;
    uint public price3 = price2 * 2;
    uint public price4 = price3 * 2;

    //max tokens could be sold during ico
    uint public hardCap = 1000000000 * 1000;
    uint public tokensSold = 0;
    uint[5] public tokensSoldInPeriod;

    uint public periodDuration = 30 days;

    uint public period0End = startTime + periodDuration;
    uint public period1End = period0End + periodDuration;
    uint public period2End = period1End + periodDuration;
    uint public period3End = period2End + periodDuration;

    bool public paused = false;

    address withdrawAddress1;
    address withdrawAddress2;

    TempusToken token;

    mapping(address => bool) public sellers;

    modifier onlySellers() {
        require(sellers[msg.sender]);
        _;
    }

    function TempusIco (address tokenAddress, address _withdrawAddress1,
    address _withdrawAddress2) public {
        token = TempusToken(tokenAddress);
        withdrawAddress1 = _withdrawAddress1;
        withdrawAddress2 = _withdrawAddress2;
    }

    function periodByDate() public view returns (uint periodNum) {
        if(now < period0End) {
            return 0;
        }
        if(now < period1End) {
            return 1;
        }
        if(now < period2End) {
            return 2;
        }
        if(now < period3End) {
            return 3;
        }
        return 4;
    }

    function priceByPeriod() public view returns (uint price) {
        uint periodNum = periodByDate();
        if(periodNum == 0) {
            return price0;
        }
        if(periodNum == 1) {
            return price1;
        }
        if(periodNum == 2) {
            return price2;
        }
        if(periodNum == 3) {
            return price3;
        }
        return price4;
    }

    /**
    * @dev Function that indicates whether pre ico is active or not
    */
    function isActive() public view returns (bool active) {
        bool withinPeriod = now >= startTime;
        bool capIsNotMet = tokensSold < hardCap;
        return capIsNotMet && withinPeriod && !paused;
    }

    function() external payable {
        buyFor(msg.sender);
    }

    /**
    * @dev Low-level purchase function. Purchases tokens for specified address
    * @param beneficiary Address that will get tokens
    */
    function buyFor(address beneficiary) public payable {
        require(msg.value != 0);
        uint amount = msg.value;
        require(amount >= 0.1 ether);
        uint price = priceByPeriod();
        uint tokenAmount = amount.div(price);
        makePurchase(beneficiary, tokenAmount);
    }

    /**
    * @dev Function that is called by our robot to allow users
    * to buy tonkens for various cryptos.
    * @param beneficiary An address that will get tokens
    * @param amount Amount of tokens that address will get
    */
    function externalPurchase(address beneficiary, uint amount) external onlySellers {
        makePurchase(beneficiary, amount);
    }

    function makePurchase(address beneficiary, uint amount) private {
        require(beneficiary != 0x0);
        require(isActive());
        uint minimumTokens = 1000;
        if(tokensSold < hardCap.sub(minimumTokens)) {
            require(amount >= minimumTokens);
        }
        require(amount.add(tokensSold) <= hardCap);
        tokensSold = tokensSold.add(amount);
        token.mint(beneficiary, amount);
        updatePeriodStat(amount);
    }

    function updatePeriodStat(uint amount) private {
        uint periodNum = periodByDate();
        tokensSoldInPeriod[periodNum] = tokensSoldInPeriod[periodNum] + amount;
        if(periodNum == 5) {
            return;
        }
        uint amountOnStart = hardCap - tokensSold + tokensSoldInPeriod[periodNum];
        uint percentSold = (tokensSoldInPeriod[periodNum] * 100) / amountOnStart;
        if(percentSold >= 20) {
            resetPeriodDates(periodNum);
        }
    }

    function resetPeriodDates(uint periodNum) private {
        if(periodNum == 0) {
            period0End = now;
            period1End = period0End + periodDuration;
            period2End = period1End + periodDuration;
            period3End = period2End + periodDuration;
            return;
        }
        if(periodNum == 1) {
            period1End = now;
            period2End = period1End + periodDuration;
            period3End = period2End + periodDuration;
            return;
        }
        if(periodNum == 2) {
            period2End = now;
            period3End = period2End + periodDuration;
            return;
        }
        if(periodNum == 3) {
            period3End = now;
            return;
        }
    }

    function setPaused(bool isPaused) external onlyOwner {
        paused = isPaused;
    }

    /**
    * @dev Sets address of seller robot
    * @param seller Address of seller robot to set
    * @param isSeller Parameter whether set as seller or not
    */
    function setAsSeller(address seller, bool isSeller) external onlyOwner {
        sellers[seller] = isSeller;
    }

    /**
    * @dev Set start time of ICO
    * @param _startTime Start of ICO (unix time)
    */
    function setStartTime(uint _startTime) external onlyOwner {
        startTime = _startTime;
    }

    /**
    * @dev Function to get ether from contract
    * @param amount Amount in wei to withdraw
    */
    function withdrawEther(uint amount) external onlyOwner {
        withdrawAddress1.transfer(amount / 2);
        withdrawAddress2.transfer(amount / 2);
    }
}