pragma solidity ^0.4.24;

/**
 * @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;


  event OwnershipRenounced(address indexed previousOwner);
  event OwnershipTransferred(
    address indexed previousOwner,
    address indexed newOwner
  );


  /**
   * @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 relinquish control of the contract.
   * @notice Renouncing to ownership will leave the contract without an owner.
   * It will not be possible to call the functions with the `onlyOwner`
   * modifier anymore.
   */
  function renounceOwnership() public onlyOwner {
    emit OwnershipRenounced(owner);
    owner = address(0);
  }

  /**
   * @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 {
    _transferOwnership(_newOwner);
  }

  /**
   * @dev Transfers control of the contract to a newOwner.
   * @param _newOwner The address to transfer ownership to.
   */
  function _transferOwnership(address _newOwner) internal {
    require(_newOwner != address(0));
    emit OwnershipTransferred(owner, _newOwner);
    owner = _newOwner;
  }
}

/**
   Copyright (c) 2017 Harbor Platform, Inc.

   Licensed under the Apache License, Version 2.0 (the “License”);
   you may not use this file except in compliance with the License.
   You may obtain a copy of the License at

   http://www.apache.org/licenses/LICENSE-2.0

   Unless required by applicable law or agreed to in writing, software
   distributed under the License is distributed on an “AS IS” BASIS,
   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   See the License for the specific language governing permissions and
   limitations under the License.
*/

pragma solidity ^0.4.24;



/// @notice A service that points to a `RegulatorService`
contract ServiceRegistry is Ownable {
  address public service;

  /**
   * @notice Triggered when service address is replaced
   */
  event ReplaceService(address oldService, address newService);

  /**
   * @dev Validate contract address
   * Credit: https://github.com/Dexaran/ERC223-token-standard/blob/Recommended/ERC223_Token.sol#L107-L114
   *
   * @param _addr The address of a smart contract
   */
  modifier withContract(address _addr) {
    uint length;
    assembly { length := extcodesize(_addr) }
    require(length > 0);
    _;
  }

  /**
   * @notice Constructor
   *
   * @param _service The address of the `RegulatorService`
   *
   */
  constructor(address _service) public {
    service = _service;
  }

  /**
   * @notice Replaces the address pointer to the `RegulatorService`
   *
   * @dev This method is only callable by the contract's owner
   *
   * @param _service The address of the new `RegulatorService`
   */
  function replaceService(address _service) onlyOwner withContract(_service) public {
    address oldService = service;
    service = _service;
    emit ReplaceService(oldService, service);
  }
}