// File: contracts/PowerSwitch/PowerSwitch.sol



// SPDX-License-Identifier: GPL-3.0-only
pragma solidity 0.7.6;

import {Ownable} from "@openzeppelin/contracts/access/Ownable.sol";

interface IPowerSwitch {
    /* admin events */

    event PowerOn();
    event PowerOff();
    event EmergencyShutdown();

    /* data types */

    enum State {Online, Offline, Shutdown}

    /* admin functions */

    function powerOn() external;

    function powerOff() external;

    function emergencyShutdown() external;

    /* view functions */

    function isOnline() external view returns (bool status);

    function isOffline() external view returns (bool status);

    function isShutdown() external view returns (bool status);

    function getStatus() external view returns (State status);

    function getPowerController() external view returns (address controller);
}

/// @title PowerSwitch
/// @notice Standalone pausing and emergency stop functionality
/// @dev Security contact: dev-support@ampleforth.org
contract PowerSwitch is IPowerSwitch, Ownable {
    /* storage */

    IPowerSwitch.State private _status;

    /* initializer */

    constructor(address owner) {
        // sanity check owner
        require(owner != address(0), "PowerSwitch: invalid owner");
        // transfer ownership
        Ownable.transferOwnership(owner);
    }

    /* admin functions */

    /// @notice Turn Power On
    /// access control: only admin
    /// state machine: only when offline
    /// state scope: only modify _status
    /// token transfer: none
    function powerOn() external override onlyOwner {
        require(_status == IPowerSwitch.State.Offline, "PowerSwitch: cannot power on");
        _status = IPowerSwitch.State.Online;
        emit PowerOn();
    }

    /// @notice Turn Power Off
    /// access control: only admin
    /// state machine: only when online
    /// state scope: only modify _status
    /// token transfer: none
    function powerOff() external override onlyOwner {
        require(_status == IPowerSwitch.State.Online, "PowerSwitch: cannot power off");
        _status = IPowerSwitch.State.Offline;
        emit PowerOff();
    }

    /// @notice Shutdown Permanently
    /// access control: only admin
    /// state machine:
    /// - when online or offline
    /// - can only be called once
    /// state scope: only modify _status
    /// token transfer: none
    function emergencyShutdown() external override onlyOwner {
        require(_status != IPowerSwitch.State.Shutdown, "PowerSwitch: cannot shutdown");
        _status = IPowerSwitch.State.Shutdown;
        emit EmergencyShutdown();
    }

    /* getter functions */

    function isOnline() external view override returns (bool status) {
        return _status == State.Online;
    }

    function isOffline() external view override returns (bool status) {
        return _status == State.Offline;
    }

    function isShutdown() external view override returns (bool status) {
        return _status == State.Shutdown;
    }

    function getStatus() external view override returns (IPowerSwitch.State status) {
        return _status;
    }

    function getPowerController() external view override returns (address controller) {
        return Ownable.owner();
    }
}

// File: @openzeppelin/contracts/access/Ownable.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.7.0;

import "../utils/Context.sol";
/**
 * @dev Contract module which provides a basic access control mechanism, where
 * there is an account (an owner) that can be granted exclusive access to
 * specific functions.
 *
 * By default, the owner account will be the one that deploys the contract. This
 * can later be changed with {transferOwnership}.
 *
 * This module is used through inheritance. It will make available the modifier
 * `onlyOwner`, which can be applied to your functions to restrict their use to
 * the owner.
 */
abstract contract Ownable is Context {
    address private _owner;

    event OwnershipTransferred(address indexed previousOwner, address indexed newOwner);

    /**
     * @dev Initializes the contract setting the deployer as the initial owner.
     */
    constructor () {
        address msgSender = _msgSender();
        _owner = msgSender;
        emit OwnershipTransferred(address(0), msgSender);
    }

    /**
     * @dev Returns the address of the current owner.
     */
    function owner() public view virtual returns (address) {
        return _owner;
    }

    /**
     * @dev Throws if called by any account other than the owner.
     */
    modifier onlyOwner() {
        require(owner() == _msgSender(), "Ownable: caller is not the owner");
        _;
    }

    /**
     * @dev Leaves the contract without owner. It will not be possible to call
     * `onlyOwner` functions anymore. Can only be called by the current owner.
     *
     * NOTE: Renouncing ownership will leave the contract without an owner,
     * thereby removing any functionality that is only available to the owner.
     */
    function renounceOwnership() public virtual onlyOwner {
        emit OwnershipTransferred(_owner, address(0));
        _owner = address(0);
    }

    /**
     * @dev Transfers ownership of the contract to a new account (`newOwner`).
     * Can only be called by the current owner.
     */
    function transferOwnership(address newOwner) public virtual onlyOwner {
        require(newOwner != address(0), "Ownable: new owner is the zero address");
        emit OwnershipTransferred(_owner, newOwner);
        _owner = newOwner;
    }
}

// File: @openzeppelin/contracts/utils/Context.sol



// SPDX-License-Identifier: MIT

pragma solidity >=0.6.0 <0.8.0;

/*
 * @dev Provides information about the current execution context, including the
 * sender of the transaction and its data. While these are generally available
 * via msg.sender and msg.data, they should not be accessed in such a direct
 * manner, since when dealing with GSN meta-transactions the account sending and
 * paying for execution may not be the actual sender (as far as an application
 * is concerned).
 *
 * This contract is only required for intermediate, library-like contracts.
 */
abstract contract Context {
    function _msgSender() internal view virtual returns (address payable) {
        return msg.sender;
    }

    function _msgData() internal view virtual returns (bytes memory) {
        this; // silence state mutability warning without generating bytecode - see https://github.com/ethereum/solidity/issues/2691
        return msg.data;
    }
}