coordinator.swift

protocol Coordinator {
    func start()
}

class AppCoordinator: Coordinator {
    let dataStore: DataStore
    let childCoordinators: [Coordinator]

    var userFinishedOnboarding: Bool = {
        return dataStore.bool(forKey: "userHasAnsweredMicPermission") 
                && dataStore.enteredData.count > 0
    }
    
    func start() {
        if userFinishedOnboarding {
            // continue to main flow
        } else {
            let onboardingCoordinator = OnboardingCoordinator()
            onboardingCoordinator.completionHandler = {
                self.childCoordinators.dropLast()
                self.start()
            }
            childCoordinators.append(onboardingCoordinator)
            onboardingCoordinator.start()
        }
    }    
}

class OnboardingCoordinator: Coordinator {
    let childCoordinators: [Coordinator]
    let completionHandler: ()->()

    var userFinishedAnsweringPermissions: Bool = {
        return dataStore.bool(forKey: "userHasAnsweredMicPermission")
    }

    func start() {
        
        if userFinishedAnsweringPermissions {
            
            let dataEntryCoordinator = DataEntryCoordinator()
            childCoordinators.append(dataEntryCoordinator)

            dataEntryCoordinator.completionHandler = {
                childCoordinators.dropLast()
                self.start()
            }

            dataEntryCoordinator.start()

        } else {

            let appPermissionsCoordinator = AppPermissionsCoordinator()
            childCoordinators.append(appPermissionsCoordinator)

            appPermissionsCoordinator.completionHandler = {
                childCoordinators.dropLast()
                completionHandler()
            }

            appPermissionsCoordinator.start()

        }
    }
}

class AppPermissionsCoordinator: Coordinator {
    let completionHandler: ()->()
    let rootViewController: UIViewController
    let dataStore: DataStore

    var userAnsweredCameraPermissions: Bool = {
        return dataStore.bool(forKey: "userAnsweredCameraPermissions")
    }

    var userAnsweredPhotoAccessPermissions: Bool = {
        return dataStore.bool(forKey: "userAnsweredPhotoAccessPermissions")
    }

    func start() {        
        var viewController: PermissionsViewController

        if !userAnsweredCameraPermissions {
            viewController = CameraPermissionsViewController()
        } else if !userAnsweredPhotoAccessPermissions { 
            viewController = PhotoPermissionsViewController()
        } else {
            viewController = MicPermissionsViewController()
        }
        
        viewController.permissionsChangeHandler = permissionChanged
        rootViewController.present(viewController, animated: true)
    }  

    private func permissionChanged(forResource resource: Resource, to value: Bool) {
        
        switch resource {
        case .camera:
            dataStore.setBool(forKey: "userAnsweredCameraPermissions", to: value)
            start()
        case .photos: 
            //etc.  
            start()
        case .mic: 
            //etc.  
            rootViewController.popToRootViewController()
            completionHandler()
        }
    }
}

class DataEntryCoordinator: Coordinator {
    let completionHandler: ()->()
    let rootViewController: UIViewController
    let dataStore: DataStore

    func start() {        
        var viewController = DataEntryViewController()
        viewController.dataEntryCompletionHandler = { newDataEntry in
            dataStore.addDataEntry(newDataEntry)
            completionHandler()
        }
        rootViewController.present(viewController, animated: true)
    }  
}