pragma solidity ^ 0.4.17;

library SafeMath {
    function mul(uint a, uint b) pure internal returns(uint) {
        uint c = a * b;
        assert(a == 0 || c / a == b);
        return c;
    }


    function sub(uint a, uint b) pure internal returns(uint) {
        assert(b <= a);
        return a - b;
    }

    function add(uint a, uint b) pure internal returns(uint) {
        uint c = a + b;
        assert(c >= a && c >= b);
        return c;
    }
}

contract ERC20 {
    uint public totalSupply;

    function balanceOf(address who) public view returns(uint);

    function allowance(address owner, address spender) public view returns(uint);

    function transfer(address to, uint value) public returns(bool ok);

    function transferFrom(address from, address to, uint value) public returns(bool ok);

    function approve(address spender, uint value) public returns(bool ok);

    event Transfer(address indexed from, address indexed to, uint value);
    event Approval(address indexed owner, address indexed spender, uint value);
}


contract Ownable {
    address public owner;

    function Ownable() public {
        owner = msg.sender;
    }

    function transferOwnership(address newOwner) public onlyOwner {
        if (newOwner != address(0)) 
            owner = newOwner;
    }

    function kill() public {
        if (msg.sender == owner) 
            selfdestruct(owner);
    }

    modifier onlyOwner() {
        if (msg.sender == owner)
            _;
    }
}






// The token
contract Token is ERC20,  Ownable {

    using SafeMath for uint;
    // Public variables of the token
    string public name;
    string public symbol;
    uint8 public decimals; // How many decimals to show.
    string public version = "v0.1";       
    uint public totalSupply;
    bool public locked;
    address public crowdSaleAddress;
    


    mapping(address => uint) balances;
    mapping(address => mapping(address => uint)) allowed;

    // tokens are locked during the ICO. Allow transfer of tokens after ICO. 
    modifier onlyUnlocked() {
        if (msg.sender != crowdSaleAddress && locked) 
            revert();
        _;
    }


    // allow burning of tokens only by authorized users 
    modifier onlyAuthorized() {
        if (msg.sender != owner && msg.sender != crowdSaleAddress ) 
            revert();
        _;
    }


    // The Token 
    function Token(address _crowdSaleAddress) public {
        
        locked = true;  // Lock the Crowdsale function during the crowdsale
        totalSupply = 60000000e18; 
        name = "Requitix"; // Set the name for display purposes
        symbol = "RQX"; // Set the symbol for display purposes
        decimals = 18; // Amount of decimals for display purposes
        crowdSaleAddress = _crowdSaleAddress;                                  
        balances[crowdSaleAddress] = totalSupply;
    }

    function unlock() public onlyAuthorized {
        locked = false;
    }

    function lock() public onlyAuthorized {
        locked = true;
    }
    

    function burn( address _member, uint256 _value) public onlyAuthorized returns(bool) {
        balances[_member] = balances[_member].sub(_value);
        totalSupply = totalSupply.sub(_value);
        Transfer(_member, 0x0, _value);
        return true;
    }

    function transfer(address _to, uint _value) public onlyUnlocked returns(bool) {
        balances[msg.sender] = balances[msg.sender].sub(_value);
        balances[_to] = balances[_to].add(_value);
        Transfer(msg.sender, _to, _value);
        return true;
    }

    
    function transferFrom(address _from, address _to, uint256 _value) public onlyUnlocked returns(bool success) {
        require (balances[_from] >= _value); // Check if the sender has enough                            
        require (_value <= allowed[_from][msg.sender]); // Check if allowed is greater or equal        
        balances[_from] = balances[_from].sub(_value); // Subtract from the sender
        balances[_to] = balances[_to].add(_value); // Add the same to the recipient
        allowed[_from][msg.sender] = allowed[_from][msg.sender].sub(_value);
        Transfer(_from, _to, _value);
        return true;
    }

    function balanceOf(address _owner) public view returns(uint balance) {
        return balances[_owner];
    }


    /**
    * @dev Approve the passed address to spend the specified amount of tokens on behalf of msg.sender.
    *
    * Beware that changing an allowance with this method brings the risk that someone may use both the old
    * and the new allowance by unfortunate transaction ordering. One possible solution to mitigate this
    * race condition is to first reduce the spender's allowance to 0 and set the desired value afterwards:
    * https://github.com/ethereum/EIPs/issues/20#issuecomment-263524729
    * @param _spender The address which will spend the funds.
    * @param _value The amount of tokens to be spent.
    */
    function approve(address _spender, uint _value) public returns(bool) {
        allowed[msg.sender][_spender] = _value;
        Approval(msg.sender, _spender, _value);
        return true;
    }


    function allowance(address _owner, address _spender) public view returns(uint remaining) {
        return allowed[_owner][_spender];
    }

    /**
    * approve should be called when allowed[_spender] == 0. To increment
    * allowed value is better to use this function to avoid 2 calls (and wait until
    * the first transaction is mined)
    * From MonolithDAO Token.sol
    */
    function increaseApproval (address _spender, uint _addedValue) public returns (bool success) {
        allowed[msg.sender][_spender] = allowed[msg.sender][_spender].add(_addedValue);
        Approval(msg.sender, _spender, allowed[msg.sender][_spender]);
        return true;
    }

    function decreaseApproval (address _spender, uint _subtractedValue) public returns (bool success) {
        uint oldValue = allowed[msg.sender][_spender];
        if (_subtractedValue > oldValue) {
        allowed[msg.sender][_spender] = 0;
        } else {
        allowed[msg.sender][_spender] = oldValue.sub(_subtractedValue);
        }
        Approval(msg.sender, _spender, allowed[msg.sender][_spender]);
        return true;
    }

}