pragma solidity ^0.4.25;

library SafeMath {
  function mul(uint256 a, uint256 b) internal constant returns (uint256) {
    uint256 c = a * b;
    assert(a == 0 || c / a == b);
    return c;
  }

  function div(uint256 a, uint256 b) internal constant 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;
  }

  function sub(uint256 a, uint256 b) internal constant returns (uint256) {
    assert(b <= a);
    return a - b;
  }

  function add(uint256 a, uint256 b) internal constant returns (uint256) {
    uint256 c = a + b;
    assert(c >= a);
    return c;
  }
}

// ERC20 Token Smart Contract
contract Kentkoin {
    
    string public constant name = "Kentkoin";
    string public constant symbol = "Kk";
    uint8 public constant decimals = 18;
    uint public _totalSupply = 10000000000;
    uint256 public RATE = 500;
    bool public isMinting = true;
    
    using SafeMath for uint256;
    address public owner;
    
     // Functions with this modifier can only be executed by the owner
     modifier onlyOwner() {
        if (msg.sender != owner) {
            throw;
        }
         _;
     }
     
    // Balances for each account
    mapping(address => uint256) balances;
    // Owner of account approves the transfer of an amount to another account
    mapping(address => mapping(address=>uint256)) allowed;

    // Its a payable function works as a token factory.
    function () payable{
        createTokens();
    }

    // Contructor
function Kentkoin(){
        owner = 0xee1e4c65f234e98c8d398fabfc80579e23a8a04e; 
    }



    // This function creates Tokens  
     function createTokens() payable {
        if(isMinting == true){
            require(msg.value > 0);
            uint256  tokens = msg.value.mul(RATE);
            balances[msg.sender] = balances[msg.sender].add(tokens);
            owner.transfer(msg.value);
        }
        else{
            throw;
        }
    }


    function endCrowdsale() onlyOwner {
        isMinting = false;
    }

    function changeCrowdsaleRate(uint256 _value) onlyOwner {
        RATE = _value;
    }


    
    function totalSupply() constant returns(uint256){
        return _totalSupply;
    }
    // What is the balance of a particular account?
    function balanceOf(address _owner) constant returns(uint256){
        return balances[_owner];
    }

     // Transfer the balance from owner's account to another account   
    function transfer(address _to, uint256 _value)  returns(bool) {
        require(balances[msg.sender] >= _value && _value > 0 );
        balances[msg.sender] = balances[msg.sender].sub(_value);
        balances[_to] = balances[_to].add(_value);
        Transfer(msg.sender, _to, _value);
        return true;
    }
    
    // Send _value amount of tokens from address _from to address _to
    // The transferFrom method is used for a withdraw workflow, allowing contracts to send
    // tokens on your behalf, for example to "deposit" to a contract address and/or to charge
    // fees in sub-currencies; the command should fail unless the _from account has
    // deliberately authorized the sender of the message via some mechanism; we propose
    // these standardized APIs for approval:
    function transferFrom(address _from, address _to, uint256 _value)  returns(bool) {
        require(allowed[_from][msg.sender] >= _value && balances[_from] >= _value && _value > 0);
        balances[_from] = balances[_from].sub(_value);
        balances[_to] = balances[_to].add(_value);
        allowed[_from][msg.sender] = allowed[_from][msg.sender].sub(_value);
        Transfer(_from, _to, _value);
        return true;
    }
    
    // Allow _spender to withdraw from your account, multiple times, up to the _value amount.
    // If this function is called again it overwrites the current allowance with _value.
    function approve(address _spender, uint256 _value) returns(bool){
        allowed[msg.sender][_spender] = _value; 
        Approval(msg.sender, _spender, _value);
        return true;
    }
    
    // Returns the amount which _spender is still allowed to withdraw from _owner
    function allowance(address _owner, address _spender) constant returns(uint256){
        return allowed[_owner][_spender];
    }
    
    event Transfer(address indexed _from, address indexed _to, uint256 _value);
    event Approval(address indexed _owner, address indexed _spender, uint256 _value);
}