contract Crowdsale {
    using SafeMath for uint256;
    using SafeERC20 for ERC20;

    // The token being sold
    ERC20 public token;

    // Address where funds are collected
    address public wallet;

    // How many token units a buyer gets per wei.
    // The rate is the conversion between wei and the smallest and indivisible token unit.
    // So, if you are using a rate of 1 with a DetailedERC20 token with 3 decimals called TOK
    // 1 wei will give you 1 unit, or 0.001 TOK.
    uint256 public rate;

    // Amount of wei raised
    uint256 public weiRaised;

    // Amount tokens Sold
    uint256 public tokensSold;
    
    /**
    * 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;

        // calculate token amount to be created
        uint256 tokens = _getTokenAmount(weiAmount);

        _preValidatePurchase(_beneficiary, weiAmount, tokens);

        // update state
        weiRaised = weiRaised.add(weiAmount);
        tokensSold = tokensSold.add(tokens);

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

        _updatePurchasingState(_beneficiary, weiAmount, tokens);

        _forwardFunds();
        _postValidatePurchase(_beneficiary, weiAmount, tokens);
    }

    // -----------------------------------------
    // Internal interface (extensible)
    // -----------------------------------------

    /**
    * @dev Validation of an incoming purchase. Use require statements to revert state when conditions are not met. Use `super` in contracts that inherit from Crowdsale to extend their validations.
    * Example from CappedCrowdsale.sol's _preValidatePurchase method: 
    *   super._preValidatePurchase(_beneficiary, _weiAmount);
    *   require(weiRaised.add(_weiAmount) <= cap);
    * @param _beneficiary Address performing the token purchase
    * @param _weiAmount Value in wei involved in the purchase
    * @param _tokenAmount Value in token involved in the purchase
    */
    function _preValidatePurchase(
        address _beneficiary,
        uint256 _weiAmount,
        uint256 _tokenAmount
    )
        internal
    {
        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
    * @param _tokenAmount Value in token involved in the purchase
    */
    function _postValidatePurchase(
        address _beneficiary,
        uint256 _weiAmount,
        uint256 _tokenAmount
    )
        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.safeTransfer(_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
    * @param _tokenAmount Value in token involved in the purchase
    */
    function _updatePurchasingState(
        address _beneficiary,
        uint256 _weiAmount,
        uint256 _tokenAmount
    )
        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)
    {
        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 / overridden.
 * The internal interface conforms the extensible and modifiable surface of crowdsales. Override
 * the methods to add functionality. Consider using 'super' where appropriate to concatenate
 * behavior.
 */
function _postValidatePurchase(
    address _beneficiary,
    uint256 _weiAmount,
    uint256 _tokenAmount
)
    internal
{
    // optional override
}

/**
 * @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
 * @param _tokenAmount Value in token involved in the purchase
 */