pragma solidity ^0.4.25;


/**
 * @title SafeMath
 * @dev Math operations with safety checks that throw on error
 */
library SafeMath {
    function mul(uint256 a, uint256 b) internal pure returns (uint256) {
        uint256 c = a * b;
        require(a == 0 || c / a == b);
        return c;
    }

    function div(uint256 a, uint256 b) internal pure returns (uint256) {
        // require(b > 0); // Solidity automatically throws when dividing by 0
        uint256 c = a / b;
        // require(a == b * c + a % b); // There is no case in which this doesn't hold
        return c;
    }

    function sub(uint256 a, uint256 b) internal pure returns (uint256) {
        require(b <= a);
        return a - b;
    }

    function add(uint256 a, uint256 b) internal pure returns (uint256) {
        uint256 c = a + b;
        require(c >= a);
        return c;
    }
}


/**
 * @title Ownable
 * @dev The Ownable contract has an owner address, and provides basic authorization control
 * functions, this simplifies the implementation of "user permissions".
 */
contract Ownable {
    address public owner;

    /**
     * @dev The Ownable constructor sets the original `owner` of the contract to the sender
     * account.
     */
    constructor() public {
        owner = msg.sender;
    }

    /**
     * @dev Throws if called by any account other than the owner.
     */
    modifier onlyOwner() {
        require(msg.sender == owner);
        _;
    }

    /**
     * @dev Allows the current owner to transfer control of the contract to a newOwner.
     * @param newOwner The address to transfer ownership to.
     */
    function transferOwnership(address newOwner) public onlyOwner {
        if (newOwner != address(0)) {
            owner = newOwner;
        }
    }
}


/**
 * @title Haltable
 *
 * @dev Abstract contract that allows children to implement an
 * emergency stop mechanism. Differs from Pausable by requiring a state.
 *
 *
 * Originally envisioned in FirstBlood ICO contract.
 */
contract Haltable is Ownable {
    bool public halted;

    modifier inNormalState {
        require(!halted);
        _;
    }

    modifier inEmergencyState {
        require(halted);
        _;
    }

    // called by the owner on emergency, triggers stopped state
    function halt() external onlyOwner inNormalState {
        halted = true;
    }

    // called by the owner on end of emergency, returns to normal state
    function resume() external onlyOwner inEmergencyState {
        halted = false;
    }

}


/**
 * @title ERC20Basic
 * @dev Simpler version of ERC20 interface
 * @dev see https://github.com/ethereum/EIPs/issues/179
 */
contract ERC20Basic {
    uint256 public totalSupply;

    function balanceOf(address who) public view returns (uint256);

    function transfer(address to, uint256 value) public returns (bool);

    event Transfer(address indexed from, address indexed to, uint256 value);
}


/**
 * @title ERC20 interface
 * @dev see https://github.com/ethereum/EIPs/issues/20
 */
contract ERC20 is ERC20Basic {
    function allowance(address owner, address spender) public view returns (uint256);

    function transferFrom(address from, address to, uint256 value) public returns (bool);

    function approve(address spender, uint256 value) public returns (bool);

    event Approval(address indexed owner, address indexed spender, uint256 value);
}


/**
 * @title Basic token
 * @dev Basic version of StandardToken, with no allowances.
 */
contract BasicToken is ERC20Basic {
    using SafeMath for uint256;

    mapping(address => uint256) public balances;

    /* Transfer token for a specified address */
    function transfer(address _to, uint256 _value) public returns (bool) {
        balances[msg.sender] = balances[msg.sender].sub(_value);
        balances[_to] = balances[_to].add(_value);
        emit Transfer(msg.sender, _to, _value);
        return true;
    }

    /**
    * @dev Gets the balance of the specified address.
    * @param _owner The address to query the the balance of.
    * @return A uint256 representing the amount owned by the passed address.
    */
    function balanceOf(address _owner) public view returns (uint256 balance) {
        return balances[_owner];
    }

}


/**
 * @title Standard ERC20 token
 *
 * @dev Implementation of the basic standard token.
 * @dev https://github.com/ethereum/EIPs/issues/20
 * @dev Based on FirstBlood: https://github.com/Firstbloodio/token/blob/master/smart_contract/FirstBloodToken.sol
 */
contract StandardToken is ERC20, BasicToken {

    mapping(address => mapping(address => uint256)) public allowed;

    /**
     * @dev Transfer tokens from one address to another
     * @param _from address The address which you want to send tokens from
     * @param _to address The address which you want to transfer to
     * @param _value uint256 the amount of tokens to be transferred
     */
    function transferFrom(address _from, address _to, uint256 _value) public returns (bool) {
        uint256 _allowance;
        _allowance = allowed[_from][msg.sender];

        // Check is not needed because sub(_allowance, _value) will already throw if this condition is not met
        // require (_value <= _allowance);

        balances[_to] = balances[_to].add(_value);
        balances[_from] = balances[_from].sub(_value);
        allowed[_from][msg.sender] = _allowance.sub(_value);
        emit Transfer(_from, _to, _value);
        return true;
    }

    /**
     * @dev Approve the passed address to spend the specified amount of tokens on behalf of msg.sender.
     * @param _spender The address which will spend the funds.
     * @param _value The amount of tokens to be spent.
     */
    function approve(address _spender, uint256 _value) public returns (bool) {

        // To change the approve amount you first have to reduce the addresses`
        //  allowance to zero by calling `approve(_spender, 0)` if it is not
        //  already 0 to mitigate the race condition described here:
        //  https://github.com/ethereum/EIPs/issues/20#issuecomment-263524729
        require((_value == 0) || (allowed[msg.sender][_spender] == 0));

        allowed[msg.sender][_spender] = _value;
        emit Approval(msg.sender, _spender, _value);
        return true;
    }

    /**
     * @dev Function to check the amount of tokens that an owner allowed to a spender.
     * @param _owner address The address which owns the funds.
     * @param _spender address The address which will spend the funds.
     * @return A uint256 specifing the amount of tokens still available for the spender.
     */
    function allowance(address _owner, address _spender) public view returns (uint256 remaining) {
        return allowed[_owner][_spender];
    }

}


/**
 * @title Burnable
 *
 * @dev Standard ERC20 token
 */
contract Burnable is StandardToken {
    using SafeMath for uint;

    /* This notifies clients about the amount burnt */
    event Burn(address indexed from, uint256 value);

    function burn(uint256 _value) public returns (bool success) {
        require(balances[msg.sender] >= _value);
        // Check if the sender has enough
        balances[msg.sender] = balances[msg.sender].sub(_value);
        // Subtract from the sender
        totalSupply = totalSupply.sub(_value);
        // Updates totalSupply
        emit Burn(msg.sender, _value);
        emit Transfer(msg.sender, address(0), _value);
        return true;
    }

    function burnFrom(address _from, uint256 _value) public returns (bool success) {
        require(balances[_from] >= _value);
        // Check if the sender has enough
        require(_value <= allowed[_from][msg.sender]);
        // Check allowance
        balances[_from] = balances[_from].sub(_value);
        // Subtract from the sender
        totalSupply = totalSupply.sub(_value);
        // Updates totalSupply
        allowed[_from][msg.sender] = allowed[_from][msg.sender].sub(_value);
        emit Burn(_from, _value);
        emit Transfer(_from, address(0), _value);
        return true;
    }

    function transfer(address _to, uint _value) public returns (bool success) {
        require(_to != 0x0);
        //use burn

        return super.transfer(_to, _value);
    }

    function transferFrom(address _from, address _to, uint _value) public returns (bool success) {
        require(_to != 0x0);
        //use burn

        return super.transferFrom(_from, _to, _value);
    }
}


/**
 * @title Centive Token
 *
 * @dev Burnable Ownable ERC20 token
 */
contract Centive is Burnable, Ownable {

    string public name;
    string public symbol;
    uint8 public decimals = 18;

    /* The finalizer contract that removes the transfer restrictions imposed by the lockout period */
    address public releaseAgent;

    /** A crowdsale contract can release us to the wild if ICO success.
    * If false we are are in transfer lock up period.
    *
    */
    bool public released = false;

    /** Map of agents that are allowed to transfer tokens regardless of the lock down period.
    * These are crowdsale contracts and possible the team multisig itself.
    *
    */
    mapping(address => bool) public transferAgents;

    /**
     * Limit token transfer until the crowdsale is over.
     *
     */
    modifier canTransfer(address _sender) {
        require(transferAgents[_sender] || released);
        _;
    }

    /** The function can be called only before or after the tokens have been releasesd */
    modifier inReleaseState(bool releaseState) {
        require(releaseState == released);
        _;
    }

    /** The function can be called only by a whitelisted release agent. */
    modifier onlyReleaseAgent() {
        require(msg.sender == releaseAgent);
        _;
    }

    /** @dev Constructor that gives msg.sender all of existing tokens. */
    constructor(uint256 initialSupply, string tokenName, string tokenSymbol) public {
        totalSupply = initialSupply * 10 ** uint256(decimals);
        // Update total supply with the decimal amount
        balances[msg.sender] = totalSupply;
        // Give the creator all initial tokens
        name = tokenName;
        // Set the name for display purposes
        symbol = tokenSymbol;
        // Set the symbol for display purposes
    }

    /**
     * Set the contract that can call release and make the token transferable.
     *
     * Design choice. Allow reset the release agent to fix fat finger mistakes.
     */
    function setReleaseAgent(address addr) external onlyOwner inReleaseState(false) {

        // We don't do interface check here as we might want to a normal wallet address to act as a release agent
        releaseAgent = addr;
    }

    function release() external onlyReleaseAgent inReleaseState(false) {
        released = true;
    }

    /**
     * Owner can allow a particular address (a crowdsale contract) to transfer tokens despite the lock up period.
     */
    function setTransferAgent(address addr, bool state) external onlyOwner inReleaseState(false) {
        transferAgents[addr] = state;
    }

    function transfer(address _to, uint _value) public canTransfer(msg.sender) returns (bool success) {
        // Call Burnable.transfer()
        return super.transfer(_to, _value);
    }

    function transferFrom(address _from, address _to, uint _value) public canTransfer(_from) returns (bool success) {
        // Call Burnable.transferForm()
        return super.transferFrom(_from, _to, _value);
    }

    function burn(uint256 _value) public onlyOwner returns (bool success) {
        return super.burn(_value);
    }

    function burnFrom(address _from, uint256 _value) public onlyOwner returns (bool success) {
        return super.burnFrom(_from, _value);
    }
}