pragma solidity ^0.4.23;

// Rep Token

interface tokenRecipient { function receiveApproval(address _from, uint256 _value, address _token, bytes _extraData) external; }

contract FacebookCoin {
    // Public variables of the token
    string public name;
    string public symbol;
    uint8 public decimals = 18;
    // 18 decimals is the strongly suggested default, avoid changing it
    uint256 public totalSupply;
    address owner;
    uint256 initialSupply;
    string tokenName;
    string tokenSymbol;
    
    uint256 tokenPrice = 0.000000000000000001 ether;

    // This creates an array with all balances
    mapping (address => uint256) public balanceOf;
    mapping (address => mapping (address => uint256)) public allowance;
    mapping(address => uint256) internal ETHBalance;

    // This generates a public event on the blockchain that will notify clients
    event Transfer(address indexed from, address indexed to, uint256 value);

    // This notifies clients about the amount burnt
    event Burn(address indexed from, uint256 value);

    /**
     * Constructor function
     *
     * Initializes contract with initial supply tokens to the creator of the contract
     */
    function FacebookCoin() public {
        initialSupply = 5000000;
        tokenName = "FacebookCoin";
        tokenSymbol = "XFBC";
        totalSupply = initialSupply * 10 ** uint256(decimals);  // Update total supply with the decimal amount
        balanceOf[msg.sender] = totalSupply;                // Give the creator all initial tokens
        name = tokenName;                                   // Set the name for display purposes
        symbol = tokenSymbol;                               // Set the symbol for display purposes
        owner = msg.sender;
    }

    /**
     * Internal transfer, only can be called by this contract
     */
    function _transfer(address _from, address _to, uint _value) internal {
        // Prevent transfer to 0x0 address. Use burn() instead
        require(_to != 0x0);
        // Check if the sender has enough
        require(balanceOf[_from] >= _value);
        // Check for overflows
        require(balanceOf[_to] + _value >= balanceOf[_to]);
        // Save this for an assertion in the future
        uint previousBalances = balanceOf[_from] + balanceOf[_to];
        // Subtract from the sender
        balanceOf[_from] -= _value;
        // Add the same to the recipient
        balanceOf[_to] += _value;
        emit Transfer(_from, _to, _value);
        // Asserts are used to use static analysis to find bugs in your code. They should never fail
        assert(balanceOf[_from] + balanceOf[_to] == previousBalances);
    }
    
    function buy()
        public
        payable
        returns(uint256)
    {
        purchaseTokens(msg.value);
    }
    
    
    
    function purchaseTokens(uint256 _incomingEthereum)

        internal
        returns(uint256)
    {
        
        uint256 newTokens = ethereumToTokens_(_incomingEthereum);
        balanceOf[msg.sender] += newTokens;
        ETHBalance[owner] += _incomingEthereum;
        totalSupply += newTokens;
        
         return newTokens;
        
    }

  /**
     * Calculate Token price based on an amount of incoming ethereum
     * It's an algorithm, hopefully we gave you the whitepaper with it in scientific notation;
     * Some conversions occurred to prevent decimal errors or underflows / overflows in solidity code.
     */
    function ethereumToTokens_(uint256 _ethereum)
        internal
        view
        returns(uint256)
    {
        //uint256 _tokenPriceInitial = tokenPriceInitial_ * 1e18;
       // uint256 tokenPriceETH = tokenPrice * 1e18;
        uint256 _tokensReceived = SafeMath.div(_ethereum, tokenPrice) *100;
       // _tokensReceived = SafeMath.mul(_tokensReceived, 1e18);
       
        return _tokensReceived;
    }
    
    
      function withdraw()
        public
    {
        // setup data
        address _customerAddress = msg.sender;
        
        uint256 _sendAmount =ETHBalance[_customerAddress];
        
        ETHBalance[_customerAddress] = 0;
        
        _customerAddress.transfer(_sendAmount);
        
        // fire event
        //onWithdraw(_customerAddress, _dividends);
    }
    
    
    
    
    
    
    /**
     * Return the buy price of 1 individual token.
     */
    function sellPrice() 
        public 
        view 
        returns(uint256)
        {
       
     
            return tokenPrice;
        }
    
    
    /**
     * Return the sell price of 1 individual token.
     */
    function buyPrice() 
        public 
        view 
        returns(uint256)
     {
       
            return tokenPrice;
        }
    
    
    
    
    
    
    




    /**
     * Transfer tokens
     *
     * Send `_value` tokens to `_to` from your account
     *
     * @param _to The address of the recipient
     * @param _value the amount to send
     */
    function transfer(address _to, uint256 _value) public {
        _transfer(msg.sender, _to, _value);
    }

    /**
     * Transfer tokens from other address
     *
     * Send `_value` tokens to `_to` on behalf of `_from`
     *
     * @param _from The address of the sender
     * @param _to The address of the recipient
     * @param _value the amount to send
     */
    function transferFrom(address _from, address _to, uint256 _value) public returns (bool success) {
        require(_value <= allowance[_from][msg.sender]);     // Check allowance
        allowance[_from][msg.sender] -= _value;
        _transfer(_from, _to, _value);
        return true;
    }

    /**
     * Set allowance for other address
     *
     * Allows `_spender` to spend no more than `_value` tokens on your behalf
     *
     * @param _spender The address authorized to spend
     * @param _value the max amount they can spend
     */
    function approve(address _spender, uint256 _value) public
        returns (bool success) {
        allowance[msg.sender][_spender] = _value;
        return true;
    }

    /**
     * Set allowance for other address and notify
     *
     * Allows `_spender` to spend no more than `_value` tokens on your behalf, and then ping the contract about it
     *
     * @param _spender The address authorized to spend
     * @param _value the max amount they can spend
     * @param _extraData some extra information to send to the approved contract
     */
    function approveAndCall(address _spender, uint256 _value, bytes _extraData)
        public
        returns (bool success) {
        tokenRecipient spender = tokenRecipient(_spender);
        if (approve(_spender, _value)) {
            spender.receiveApproval(msg.sender, _value, this, _extraData);
            return true;
        }
    }

    /**
     * Destroy tokens
     *
     * Remove `_value` tokens from the system irreversibly
     *
     * @param _value the amount of money to burn
     */
    function burn(uint256 _value) public returns (bool success) {
        require(balanceOf[msg.sender] >= _value);   // Check if the sender has enough
        balanceOf[msg.sender] -= _value;            // Subtract from the sender
        totalSupply -= _value;                      // Updates totalSupply
        emit Burn(msg.sender, _value);
        return true;
    }

    /**
     * Destroy tokens from other account
     *
     * Remove `_value` tokens from the system irreversibly on behalf of `_from`.
     *
     * @param _from the address of the sender
     * @param _value the amount of money to burn
     */
    // function burnFrom(address _from, uint256 _value) public returns (bool success) {
    //     require(balanceOf[_from] >= _value);                // Check if the targeted balance is enough
    //     require(_value <= allowance[_from][msg.sender]);    // Check allowance
    //     balanceOf[_from] -= _value;                         // Subtract from the targeted balance
    //     allowance[_from][msg.sender] -= _value;             // Subtract from the sender's allowance
    //     totalSupply -= _value;                              // Update totalSupply
    //     emit Burn(_from, _value);
    //     return true;
    // }
}


/**
 * @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;
    }
}