pragma solidity ^0.4.24;

/**
 * @title Utility contract to allow pausing and unpausing of certain functions
 */
contract Pausable {

    event Pause(uint256 _timestammp);
    event Unpause(uint256 _timestamp);

    bool public paused = false;

    /**
    * @notice Modifier to make a function callable only when the contract is not paused.
    */
    modifier whenNotPaused() {
        require(!paused, "Contract is paused");
        _;
    }

    /**
    * @notice Modifier to make a function callable only when the contract is paused.
    */
    modifier whenPaused() {
        require(paused, "Contract is not paused");
        _;
    }

   /**
    * @notice called by the owner to pause, triggers stopped state
    */
    function _pause() whenNotPaused internal {
        paused = true;
        emit Pause(now);
    }

    /**
    * @notice called by the owner to unpause, returns to normal state
    */
    function _unpause() whenPaused internal {
        paused = false;
        emit Unpause(now);
    }

}