// From https://github.com/securing/SimpleXPCApp/
// MIT License
// 
// Copyright (c) 2020 securing
// 
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
// 
// The above copyright notice and this permission notice shall be included in all
// copies or substantial portions of the Software.
// 
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
// SOFTWARE.
// Installer implemented basing on https://github.com/erikberglund/SwiftPrivilegedHelper

import Foundation
import ServiceManagement

enum HelperAuthorizationError: Error {
    case message(String)
}

class HelperInstaller {
    private static func executeAuthorizationFunction(_ authorizationFunction: () -> (OSStatus) ) throws {
        let osStatus = authorizationFunction()
        guard osStatus == errAuthorizationSuccess else {
            throw HelperAuthorizationError.message(String(describing: SecCopyErrorMessageString(osStatus, nil)))
        }
    }
    
    static func authorizationRef(_ rights: UnsafePointer<AuthorizationRights>?,
                                 _ environment: UnsafePointer<AuthorizationEnvironment>?,
                                 _ flags: AuthorizationFlags) throws -> AuthorizationRef? {
        var authRef: AuthorizationRef?
        try executeAuthorizationFunction { AuthorizationCreate(rights, environment, flags, &authRef) }
        return authRef
    }
    
    static func install() {
        var authItem = kSMRightBlessPrivilegedHelper.withCString { name in
            AuthorizationItem(name: name, valueLength: 0, value:UnsafeMutableRawPointer(bitPattern: 0), flags: 0)
        }
        var authRights = withUnsafeMutablePointer(to: &authItem) { authItem in
            AuthorizationRights(count: 1, items: authItem)
        }

        do {
            let authRef = try authorizationRef(&authRights, nil, [.interactionAllowed, .extendRights, .preAuthorize])
            var cfError: Unmanaged<CFError>?
            SMJobBless(kSMDomainSystemLaunchd, machServiceName as CFString, authRef, &cfError)
        } catch let err {
            print("Error in installing the helper -> \(err.localizedDescription)")
        }
    }
}