pragma solidity ^0.4.23;

// ----------------------------------------------------------------------------
// Owned contract
// ----------------------------------------------------------------------------
contract Owned {
    address public owner;
    address public newOwner;

    event OwnershipTransferred(address indexed _from, address indexed _to);

    modifier onlyOwner {
        require(msg.sender == owner);
        _;
    }

    function transferOwnership(address _newOwner) public onlyOwner {
        newOwner = _newOwner;
    }
    function acceptOwnership() public {
        require(msg.sender == newOwner);
        emit OwnershipTransferred(owner, newOwner);
        owner = newOwner;
        newOwner = address(0);
    }
}

// ----------------------------------------------------------------------------
// 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
// ----------------------------------------------------------------------------
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 MannaCoin is ERC20Interface, Owned{
    using SafeMath for uint;
    string public symbol;
    string public name;
    uint8 public decimals;
    uint _totalSupply;
    mapping(address => uint) balances;
    mapping(address => mapping(address => uint)) allowed;
    uint256 public rate; // How many token units a buyer gets per wei
    uint256 public weiRaised;  // Amount of wei raised
    address wallet;
    uint _tokenToSale;
    uint _ownersTokens;
    event TokenPurchase(address indexed purchaser, address indexed beneficiary, uint256 value, uint256 amount);
    
    // ------------------------------------------------------------------------
    // Constructor
    // ------------------------------------------------------------------------
    function MannaCoin(address _owner,address _wallet) public{
        symbol = "MAN";
        name = "MANNA TOKEN";
        decimals = 18;
        rate = 600;
        wallet = _wallet;
        owner = _owner;
        _totalSupply = totalSupply();
        _tokenToSale = 20000000 * 10**uint(decimals);
        _ownersTokens = _totalSupply - _tokenToSale;
        balances[this] = _tokenToSale;
        balances[owner] = _ownersTokens;
        emit Transfer(address(0),this,_tokenToSale);
        emit Transfer(address(0),owner,_ownersTokens);
    }

    function totalSupply() public constant returns (uint){
       return 45000000 * 10**uint(decimals);
    }

    // ------------------------------------------------------------------------
    // 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
    // ------------------------------------------------------------------------
    function transfer(address to, uint tokens) public returns (bool success) {
        // prevent transfer to 0x0, use burn instead
        require(to != 0x0);
        require(balances[msg.sender] >= tokens );
        require(balances[to] + tokens >= balances[to]);
        balances[msg.sender] = balances[msg.sender].sub(tokens);
        balances[to] = balances[to].add(tokens);
        emit Transfer(msg.sender,to,tokens);
        return true;
    }
    
    function _transfer(address _to, uint _tokens) internal returns (bool success){
        // prevent transfer to 0x0, use burn instead
        require(_to != 0x0);
        require(balances[this] >= _tokens);
        require(balances[_to] + _tokens >= balances[_to]);
        balances[this] = balances[this].sub(_tokens);
        balances[_to] = balances[_to].add(_tokens);
        emit Transfer(this,_to,_tokens);
        return true;
    }
    
    // ------------------------------------------------------------------------
    // Token owner can approve for `spender` to transferFrom(...) `tokens`
    // from the token owner's account
    // ------------------------------------------------------------------------
    function approve(address spender, uint tokens) public returns (bool success){
        allowed[msg.sender][spender] = tokens;
        emit 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){
        require(tokens <= allowed[from][msg.sender]); //check allowance
        require(balances[from] >= tokens);
        balances[from] = balances[from].sub(tokens);
        balances[to] = balances[to].add(tokens);
        allowed[from][msg.sender] = allowed[from][msg.sender].sub(tokens);
        emit 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];
    }
    
    function () external payable {
        buyTokens(msg.sender);
    }
    
    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);
        TokenPurchase(this, _beneficiary, weiAmount, tokens);

        _forwardFunds();
    }
  
    function _preValidatePurchase(address _beneficiary, uint256 _weiAmount) internal {
        require(_beneficiary != address(0x0));
        require(_weiAmount != 0);
    }
  
    function _getTokenAmount(uint256 _weiAmount) internal returns (uint256) {
        return _weiAmount.mul(rate);
    }
  
    function _deliverTokens(address _beneficiary, uint256 _tokenAmount) internal {
        _transfer(_beneficiary,_tokenAmount);
    }

    function _processPurchase(address _beneficiary, uint256 _tokenAmount) internal {
        _deliverTokens(_beneficiary, _tokenAmount);
    }
  
    function _forwardFunds() internal {
        wallet.transfer(msg.value);
    }
}