pragma solidity ^0.4.18;

// ----------------------------------------------------------------------------
//    /######            /#######  /##          
//   /##__  ##          | ##__  ##|__/          
//  | ##  \ ## /##   /##| ##  \ ## /##  /###### 
//  | ##  | ##|  ## /##/| ####### | ## /##__  ##
//  | ##  | ## \  ####/ | ##__  ##| ##| ##  \ ##
//  | ##  | ##  >##  ## | ##  \ ##| ##| ##  | ##
//  |  ######/ /##/\  ##| #######/| ##|  ######/
//   \______/ |__/  \__/|_______/ |__/ \______/ 
//                                              
// 
// Deployed to contract : 0x0c259e7c073c81188917c700a179818f18c5d6f8
// Symbol               : OXB
// Name                 : OxBio
// Total supply         : 500000000 of which 200M available.
// Decimals             : 18
//
// ----------------------------------------------------------------------------


// ----------------------------------------------------------------------------
// Safe maths
// ----------------------------------------------------------------------------
library SafeMath {
    function add(uint a, uint b) internal pure returns (uint c) {
        c = a + b;
        require(c >= a);
    }
    function sub(uint a, uint b) internal pure returns (uint c) {
        require(b <= a);
        c = a - b;
    }
    function mul(uint a, uint b) internal pure returns (uint c) {
        c = a * b;
        require(a == 0 || c / a == b);
    }
    function div(uint a, uint b) internal pure returns (uint c) {
        require(b > 0);
        c = a / b;
    }
}

// ----------------------------------------------------------------------------
// ERC Token Standard #20 Interface
// https://github.com/ethereum/EIPs/blob/master/EIPS/eip-20-token-standard.md
// ----------------------------------------------------------------------------
contract ERC20Interface {
    function totalSupply() public constant returns (uint);
    function balanceOf(address tokenOwner) public constant returns (uint balance);
    function allowance(address tokenOwner, address spender) public constant returns (uint remaining);
    function transfer(address to, uint tokens) public returns (bool success);
    function approve(address spender, uint tokens) public returns (bool success);
    function transferFrom(address from, address to, uint tokens) public returns (bool success);

    event Transfer(address indexed from, address indexed to, uint tokens);
    event Approval(address indexed tokenOwner, address indexed spender, uint tokens);
}

// ----------------------------------------------------------------------------
// Contract function to receive approval and execute function in one call
// ----------------------------------------------------------------------------
contract ApproveAndCallFallBack {
    function receiveApproval(address from, uint256 tokens, address token, bytes data) public;
}

// ----------------------------------------------------------------------------
// Owned contract
// ----------------------------------------------------------------------------
contract Owned {
    address public owner;
    address public newOwner;

    event OwnershipTransferred(address indexed _from, address indexed _to);

    function Owned() public {
        owner = msg.sender;
    }

    modifier onlyOwner {
        require(msg.sender == owner);
        _;
    }

    function transferOwnership(address _newOwner) public onlyOwner {
        newOwner = _newOwner;
    }
    
    function acceptOwnership() public {
        require(msg.sender == newOwner);
        OwnershipTransferred(owner, newOwner);
        owner = newOwner;
        newOwner = address(0);
    }
}

// ----------------------------------------------------------------------------
// ERC20 compliant token, with the addition of symbol, name and decimals and an
// initial fixed supply
// ----------------------------------------------------------------------------
contract OxBioToken is ERC20Interface, Owned {
    using SafeMath for uint;

    string  public symbol;
    string  public  name;
    uint8   public decimals;
    uint256 public _totalSupply;
    uint256 public USDETH;                                 // price of 1 ether in USD
    
    mapping(address => uint) balances;
    mapping(address => mapping(address => uint)) allowed;

    // ------------------------------------------------------------------------
    // Constructor
    // ------------------------------------------------------------------------
    function OxBioToken() public {
      
        symbol = "OXB";
        name = "OxBio";
        decimals = 18;
        USDETH = 530;                                      // 1 ETH = USD 530 

        _totalSupply = 500000000 * 10**uint(decimals);     // 200M out of 500M 
        balances[owner] = _totalSupply;
        Transfer(address(0), owner, _totalSupply);
    }

    // ------------------------------------------------------------------------
    // Total supply
    // ------------------------------------------------------------------------
    function totalSupply() public constant returns (uint) {
        return _totalSupply  - balances[address(0)];
    }

    // ------------------------------------------------------------------------
    // Get the token balance for account `tokenOwner`
    // ------------------------------------------------------------------------
    function balanceOf(address tokenOwner) public constant returns (uint balance) {
        return balances[tokenOwner];
    }

    // ------------------------------------------------------------------------
    // Transfer the balance from token owner's account to `to` account
    // - Owner's account must have sufficient balance to transfer
    // - 0 value transfers are allowed
    // - prevent sending tokens to contracts
    // - max transaction size: 1M 
    // ------------------------------------------------------------------------
    function transfer(address to, uint tokens) public returns (bool success) {
        require( to != address(0) );
        require( tokens <= balances[msg.sender] );
        require( tokens <= 1000000 * 10**18 );
        require( !isContract(to) );                                   
        
        balances[msg.sender] = balances[msg.sender].sub(tokens);
        balances[to] = balances[to].add(tokens);
        Transfer(msg.sender, to, tokens);
        return true;
    }

    // ------------------------------------------------------------------------
    // Token owner can approve for `spender` to transferFrom(...) `tokens`
    // from the token owner's account
    //
    // https://github.com/ethereum/EIPs/blob/master/EIPS/eip-20-token-standard.md
    // recommends that there are no checks for the approval double-spend attack
    // as this should be implemented in user interfaces 
    // ------------------------------------------------------------------------
    function approve(address spender, uint tokens) public returns (bool success) {
        allowed[msg.sender][spender] = tokens;
        Approval(msg.sender, spender, tokens);
        return true;
    }

    // ------------------------------------------------------------------------
    // Transfer `tokens` from the `from` account to the `to` account
    // 
    // The calling account must already have sufficient tokens approve(...)-d
    // for spending from the `from` account and
    // - From account must have sufficient balance to transfer
    // - Spender must have sufficient allowance to transfer
    // - 0 value transfers are allowed
    // ------------------------------------------------------------------------
    function transferFrom(address from, address to, uint tokens) public returns (bool success) {
        balances[from] = balances[from].sub(tokens);
        allowed[from][msg.sender] = allowed[from][msg.sender].sub(tokens);
        balances[to] = balances[to].add(tokens);
        Transfer(from, to, tokens);
        return true;
    }

    // ------------------------------------------------------------------------
    // Returns the amount of tokens approved by the owner that can be
    // transferred to the spender's account
    // ------------------------------------------------------------------------
    function allowance(address tokenOwner, address spender) public constant returns (uint remaining) {
        return allowed[tokenOwner][spender];
    }

    // ------------------------------------------------------------------------
    // Token owner can approve for `spender` to transferFrom(...) `tokens`
    // from the token owner's account. The `spender` contract function
    // `receiveApproval(...)` is then executed
    // ------------------------------------------------------------------------
    function approveAndCall(address spender, uint tokens, bytes data) public returns (bool success) {
        allowed[msg.sender][spender] = tokens;
        Approval(msg.sender, spender, tokens);
        ApproveAndCallFallBack(spender).receiveApproval(msg.sender, tokens, this, data);
        return true;
    }

    // ------------------------------------------------------------------------
    // Accept ETH and convert this into OxBio tokens at a ETH:OxBio respectively 1:XXXX ratio (not in this version of the contract)
    // ------------------------------------------------------------------------
    function () public payable {
        revert();
    }

    // ------------------------------------------------------------------------
    // Owner can transfer out any accidentally sent ERC20 tokens
    // ------------------------------------------------------------------------
    function transferAnyERC20Token(address tokenAddress, uint tokens) public onlyOwner returns (bool success) {
        return ERC20Interface(tokenAddress).transfer(owner, tokens);
    }
    
    // ------------------------------------------------------------------------
    // Owner can change the USDETH rate
    // ------------------------------------------------------------------------
    function updateUSDETH(uint256 _USDETH) public onlyOwner {
      require(_USDETH > 0);
      USDETH = _USDETH;
    }
    
    // ------------------------------------------------------------------------
    // assemble the given address bytecode. If bytecode exists then the _addr is a contract.
    // ------------------------------------------------------------------------
    function isContract(address _addr) private view returns (bool is_contract) {
      uint length;
      assembly {
            //retrieve the size of the code on target address, this needs assembly
            length := extcodesize(_addr)
      }
      return (length>0);
    }    
}