pragma solidity ^0.4.15;

//interface tokenRecipient { function receiveApproval(address _from, uint256 _value, address _token, bytes _extraData); }

contract DealerRights {
    // Public variables of the token
    string public name;
    string public symbol;
    uint8 public decimals;
    uint256 public totalSupply;

    // This creates an array with all balances
    mapping (address => uint256) public balanceOf;
    mapping (address => mapping (address => uint256)) public allowance;

    // This generates a public event on the blockchain that will notify clients
    event Transfer(address indexed from, address indexed to, uint256 value);
    event Approval(address indexed owner, address indexed spender, uint256 value);

 
    /**
     * Constrctor function
     *
     * Initializes contract with initial supply tokens to the creator of the contract
     */
    function DealerRights() public {
        totalSupply = 21000000 ether;                        // Update total supply
        balanceOf[msg.sender] = totalSupply;              // Give the creator all initial tokens
        name = "Dealer Rights";                                   // Set the name for display purposes
        symbol = "DRS";                               // Set the symbol for display purposes
        decimals = 18;                            // Amount of decimals for display purposes
    }

    /**
     * Internal transfer, only can be called by this contract
     */
    function _transfer(address _from, address _to, uint _value) internal {
        require(_to != 0x0);                               // Prevent transfer to 0x0 address. Use burn() instead
        require(balanceOf[_from] >= _value);                // Check if the sender has enough
        require(balanceOf[_to] + _value > balanceOf[_to]); // Check for overflows
        uint previousBalances = balanceOf[_from] + balanceOf[_to];  //Save this for an assertion in the future
        balanceOf[_from] -= _value;                         // Subtract from the sender
        balanceOf[_to] += _value;                           // Add the same to the recipient
        Transfer(_from, _to, _value);
        assert(balanceOf[_from] + balanceOf[_to] == previousBalances);  //Asserts are used to use static analysis to find bugs in your code. They should never fail.
    }

    /**
     * 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` in 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 in 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;
        Approval(msg.sender, _spender, _value);
        return true;
    }

    /**
     * Set allowance for other address and notify
     *
     * Allows `_spender` to spend no more than `_value` tokens in 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) {
       if (approve(_spender, _value)) {
           //call the receiveApproval function on the contract you want to be notified. This crafts the function signature manually so one doesn't have to include a contract in here just for this.
           //receiveApproval(address _from, uint256 _value, address _tokenContract, bytes _extraData)
           //it is assumed that when does this that the call *should* succeed, otherwise one would use vanilla approve instead.
           require(_spender.call(bytes4(bytes32(keccak256("receiveApproval(address,uint256,address,bytes)"))), msg.sender, _value, this, _extraData));
           return true;
       }
    }
}