contract Crowdsale {
    using SafeMath for uint256;

    // The token being sold
    ERC20 public token;

    // Address where funds are collected
    address public wallet;

    // How many token units a buyer gets per wei
    uint256 public rate;

    // Amount of wei raised
    uint256 public weiRaised;

    /**
     * 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
    );

    /**
     * @param _rate Number of token units a buyer gets per wei
     * @param _wallet Address where collected funds will be forwarded to
     * @param _token Address of the token being sold
     */
    constructor(uint256 _rate, address _wallet, ERC20 _token) public {
        require(_rate > 0);
        require(_wallet != address(0));
        require(_token != address(0));

        rate = _rate;
        wallet = _wallet;
        token = _token;
    }

    // -----------------------------------------
    // 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);
        emit TokenPurchase(
            msg.sender,
            _beneficiary,
            weiAmount,
            tokens
        );

        _forwardFunds();
    }

    // -----------------------------------------
    // 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 view
    {
        require(_beneficiary != address(0));
        require(_weiAmount != 0);
        require(weiRaised.add(_weiAmount) != 0);
    }

    /**
     * @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 _allocateTokens(
        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
    {
        _allocateTokens(_beneficiary, _tokenAmount);
    }

    /**
     * @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)
    {
        return _weiAmount.mul(rate);
    }

    /**
     * @dev Determines how ETH is stored/forwarded on purchases.
     */
    function _forwardFunds() internal {
        wallet.transfer(msg.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.
 */
function _processPurchase(
    address _beneficiary,
    uint256 _tokenAmount
)
internal
{
    _allocateTokens(_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
 */