pragma solidity ^0.4.18;

/**
 * @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) {
        if (a == 0) {
            return 0;
        }
        uint256 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 c;
    }

    /**
    * @dev Substracts 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) {
        uint256 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 Crowdsale
 * @dev Crowdsale is a base contract for managing a token crowdsale,
 * allowing investors to purchase tokens with ether. This contract implements
 * such functionality in its most fundamental form and can be extended to provide additional
 * functionality and/or custom behavior.
 * The external interface represents the basic interface for purchasing tokens, and conform
 * the base architecture for crowdsales. They are *not* intended to be modified / overriden.
 * The internal interface conforms the extensible and modifiable surface of crowdsales. Override
 * the methods to add functionality. Consider using 'super' where appropiate to concatenate
 * behavior.
 */

contract BitMilleCrowdsale {
    using SafeMath for uint256;

    // The token being sold
    ERC20 public token;

    // Address where funds are collected
    address public wallet;

    // Amount of wei raised
    uint256 public weiRaised;

    uint256 public openingTime;
    uint256 public closingTime;

    /**
     * @dev Reverts if not in crowdsale time range.
     */
    modifier onlyWhileOpen {
        require(now >= openingTime && now <= closingTime);
        _;
    }

    /**
     * @dev Reverts if not in crowdsale time range.
     */
    modifier onlyAfterClosing {
        require(now > closingTime);
        _;
    }

    /**
     * Event for token purchase logging
     * @param purchaser who paid for the tokens
     * @param beneficiary who got the tokens
     * @param value weis paid for purchase
     * @param amount amount of tokens purchased
     */
    event TokenPurchase(address indexed purchaser, address indexed beneficiary, uint256 value, uint256 amount);

    function BitMilleCrowdsale() public {
        wallet = 0x468E9A02c233C3DBb0A1b7F8bd8F8E9f36cbA952;
        token = ERC20(0xabb3148a39fb97af1295c5ee03e713d6ed54fd92);
        openingTime = 1520946000;
        closingTime = 1523970000;
    }

    // -----------------------------------------
    // Crowdsale external interface
    // -----------------------------------------

    /**
     * @dev fallback function ***DO NOT OVERRIDE***
     */
    function () external payable {
        buyTokens(msg.sender);
    }

    /**
     * @dev low level token purchase ***DO NOT OVERRIDE***
     * @param _beneficiary Address performing the token purchase
     */
    function buyTokens(address _beneficiary) public payable {

        uint256 weiAmount = msg.value;
        _preValidatePurchase(_beneficiary, weiAmount);

        // calculate token amount to be created
        uint256 tokens = _getTokenAmount(weiAmount);

        // update state
        weiRaised = weiRaised.add(weiAmount);

        _processPurchase(_beneficiary, tokens);
        TokenPurchase(msg.sender, _beneficiary, weiAmount, tokens);

        _updatePurchasingState(_beneficiary, weiAmount);

        _forwardFunds();
        _postValidatePurchase(_beneficiary, weiAmount);
    }

    // -----------------------------------------
    // Internal interface (extensible)
    // -----------------------------------------

    /**
     * @dev Validation of an incoming purchase. Use require statements to revert state when conditions are not met. Use super to concatenate validations.
     * @param _beneficiary Address performing the token purchase
     * @param _weiAmount Value in wei involved in the purchase
     */
    function _preValidatePurchase(address _beneficiary, uint256 _weiAmount) internal onlyWhileOpen {
        require(_beneficiary != address(0));
        require(_weiAmount != 0);
    }

    /**
     * @dev Validation of an executed purchase. Observe state and use revert statements to undo rollback when valid conditions are not met.
     * @param _beneficiary Address performing the token purchase
     * @param _weiAmount Value in wei involved in the purchase
     */
    function _postValidatePurchase(address _beneficiary, uint256 _weiAmount) internal {
        // optional override
    }

    /**
     * @dev Source of tokens. Override this method to modify the way in which the crowdsale ultimately gets and sends its tokens.
     * @param _beneficiary Address performing the token purchase
     * @param _tokenAmount Number of tokens to be emitted
     */
    function _deliverTokens(address _beneficiary, uint256 _tokenAmount) internal {
        token.transfer(_beneficiary, _tokenAmount);
    }

    /**
     * @dev Executed when a purchase has been validated and is ready to be executed. Not necessarily emits/sends tokens.
     * @param _beneficiary Address receiving the tokens
     * @param _tokenAmount Number of tokens to be purchased
     */
    function _processPurchase(address _beneficiary, uint256 _tokenAmount) internal {
        _deliverTokens(_beneficiary, _tokenAmount);
    }

    /**
     * @dev Override for extensions that require an internal state to check for validity (current user contributions, etc.)
     * @param _beneficiary Address receiving the tokens
     * @param _weiAmount Value in wei involved in the purchase
     */
    function _updatePurchasingState(address _beneficiary, uint256 _weiAmount) internal {
        // optional override
    }

    /**
     * @dev Override to extend the way in which ether is converted to tokens.
     * @param _weiAmount Value in wei to be converted into tokens
     * @return Number of tokens that can be purchased with the specified _weiAmount
     */
    function _getTokenAmount(uint256 _weiAmount) internal view returns (uint256) {

        uint256 period = 7 days;
        uint256 perc;

        if ((now >= openingTime) && (now < openingTime + period)) {
            perc = 10;
        } else if ((now >= openingTime + period) && (now < openingTime + period * 2)) {
            perc = 9;
        } else if ((now >= openingTime + period * 2) && (now < openingTime + period * 3)) {
            perc = 8;
        } else {
            perc = 7;
        }

        return _weiAmount.mul(perc).div(100000);

    }

    /**
       * @dev Determines how ETH is stored/forwarded on purchases.
       */
    function _forwardFunds() internal {
        wallet.transfer(msg.value);
    }

    /**
     * @dev Checks whether the period in which the crowdsale is open has already elapsed.
     * @return Whether crowdsale period has elapsed
     */
    function hasClosed() public view returns (bool) {
        return now > closingTime;
    }

    function withdrawTokens() public onlyAfterClosing returns (bool) {
        token.transfer(wallet, token.balanceOf(this));
        return true;
    }

}