/**
 * @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;
    }
}

contract FiatContract {
  function ETH(uint _id) constant returns (uint256);
  function USD(uint _id) constant returns (uint256);
  function EUR(uint _id) constant returns (uint256);
  function GBP(uint _id) constant returns (uint256);
  function updatedAt(uint _id) constant returns (uint);
}

/**
 * @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 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 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 Safe Guard Contract
 */
contract SafeGuard is Ownable {

    event Transaction(address indexed destination, uint value, bytes data);

    /**
     * @dev Allows owner to execute a transaction.
     */
    function executeTransaction(address destination, uint value, bytes data)
    public
    onlyOwner
    {
        require(externalCall(destination, value, data.length, data));
        emit Transaction(destination, value, data);
    }

    /**
     * @dev call has been separated into its own function in order to take advantage
     *  of the Solidity's code generator to produce a loop that copies tx.data into memory.
     */
    function externalCall(address destination, uint value, uint dataLength, bytes data)
    private
    returns (bool) {
        bool result;
        assembly { // solhint-disable-line no-inline-assembly
            let x := mload(0x40)   // "Allocate" memory for output
        // (0x40 is where "free memory" pointer is stored by convention)
            let d := add(data, 32) // First 32 bytes are the padded length of data, so exclude that
            result := call(
            sub(gas, 34710), // 34710 is the value that solidity is currently emitting
            // It includes callGas (700) + callVeryLow (3, to pay for SUB) + callValueTransferGas (9000) +
            // callNewAccountGas (25000, in case the destination address does not exist and needs creating)
            destination,
            value,
            d,
            dataLength, // Size of the input (in bytes) - this is what fixes the padding problem
            x,
            0                  // Output is ignored, therefore the output size is zero
            )
        }
        return result;
    }
}

/**
 * @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 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
        );

        _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
    {
        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)
    {
        return _weiAmount.mul(rate);
    }

    /**
     * @dev Determines how ETH is stored/forwarded on purchases.
     */
    function _forwardFunds() internal {
        wallet.transfer(msg.value);
    }
}

/**
 * @title TimedCrowdsale
 * @dev Crowdsale accepting contributions only within a time frame.
 */
contract TimedCrowdsale is Crowdsale {
    using SafeMath for uint256;

    uint256 public openingTime;
    uint256 public closingTime;

    /**
     * @dev Reverts if not in crowdsale time range.
     */
    modifier onlyWhileOpen {
        // solium-disable-next-line security/no-block-members
        require(block.timestamp >= openingTime && block.timestamp <= closingTime);
        _;
    }

    /**
     * @dev Constructor, takes crowdsale opening and closing times.
     * @param _openingTime Crowdsale opening time
     * @param _closingTime Crowdsale closing time
     */
    constructor(uint256 _openingTime, uint256 _closingTime) public {
        // solium-disable-next-line security/no-block-members
        require(_openingTime >= block.timestamp);
        require(_closingTime >= _openingTime);

        openingTime = _openingTime;
        closingTime = _closingTime;
    }

    /**
     * @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) {
        // solium-disable-next-line security/no-block-members
        return block.timestamp > closingTime;
    }

    /**
     * @dev Extend parent behavior requiring to be within contributing period
     * @param _beneficiary Token purchaser
     * @param _weiAmount Amount of wei contributed
     */
    function _preValidatePurchase(
        address _beneficiary,
        uint256 _weiAmount
    )
    internal
    onlyWhileOpen
    {
        super._preValidatePurchase(_beneficiary, _weiAmount);
    }

}

/**
 * @title AllowanceCrowdsale
 * @dev Extension of Crowdsale where tokens are held by a wallet, which approves an allowance to the crowdsale.
 */
contract AllowanceCrowdsale is Crowdsale {
    using SafeMath for uint256;

    address public tokenWallet;

    /**
     * @dev Constructor, takes token wallet address.
     * @param _tokenWallet Address holding the tokens, which has approved allowance to the crowdsale
     */
    constructor(address _tokenWallet) public {
        require(_tokenWallet != address(0));
        tokenWallet = _tokenWallet;
    }

    /**
     * @dev Checks the amount of tokens left in the allowance.
     * @return Amount of tokens left in the allowance
     */
    function remainingTokens() public view returns (uint256) {
        return token.allowance(tokenWallet, this);
    }

    /**
     * @dev Overrides parent behavior by transferring tokens from wallet.
     * @param _beneficiary Token purchaser
     * @param _tokenAmount Amount of tokens purchased
     */
    function _deliverTokens(
        address _beneficiary,
        uint256 _tokenAmount
    )
    internal
    {
        token.transferFrom(tokenWallet, _beneficiary, _tokenAmount);
    }
}

/**
 * @title Antiderivative Pre Token crowdsale
 */
contract PADVTCrowdsale is AllowanceCrowdsale, TimedCrowdsale, SafeGuard {
    
    FiatContract fContract;

    /**
     * @param _rate Multiplied by 0.01$ to calculate final price
     * @param _wallet Address where collected funds will be forwarded to
     * @param _token Address of the token being sold
     * @param _tokenWallet Address holding the tokens, which has approved allowance to the crowdsale
     * @param _openingTime Crowdsale opening time
     * @param _closingTime Crowdsale closing time
     */
    constructor(uint256 _rate, address _wallet, ERC20 _token, address _tokenWallet, uint256 _openingTime, uint256 _closingTime)
    Crowdsale(_rate, _wallet, _token)
    AllowanceCrowdsale(_tokenWallet)
    TimedCrowdsale(_openingTime, _closingTime)
    public
    {
        fContract = FiatContract(0x8055d0504666e2B6942BeB8D6014c964658Ca591);
    }

    /**
     * @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)
    {
        // returns $0.01 ETH wei * rate
        uint256 ethCent = fContract.USD(0) * rate;
        return _weiAmount.div(ethCent);
    }
}