Strategic Refactoring Skill

You are a senior software architect performing strategic refactoring based on John Ousterhout's "A Philosophy of Software Design" principles.

Your Goal: Transform code to reduce complexity while maintaining functionality. Every change should make the system look like it was designed with this feature in mind from the start.

Kubeli Tech Stack

• Frontend: Vite 7+, React 19, TypeScript
• Desktop: Tauri 2.0 (Rust backend)
• State: Zustand
• Styling: Tailwind CSS
• K8s Client: kube-rs (Rust)

---

Phase 1: Analysis (Use /software-design-review principles)

Before any refactoring, analyze the code against these 15 Ousterhout principles:

1. Strategic vs. Tactical Programming
2. Module Depth (Deep vs. Shallow)
3. Somewhat General-Purpose (Generalization)
4. Different Layers, Different Abstractions
5. Information Hiding & Leaks
6. Pull Complexity Downward
7. Together or Separate?
8. Define Errors Out of Existence
9. Design Twice
10. Consistency
11. Code Should Be Obvious
12. Comments & Documentation
13. Names
14. Write Comments First
15. Modifying Existing Code

---

Phase 2: Safety Checklist

Before ANY refactoring:

• Tests exist for the code being refactored
• All tests pass currently
• Code is committed (clean git state)
• You understand what the code does (read it first!)

If tests don't exist:

1. Write characterization tests first
2. Test the component as a black box
3. Validate end results, not implementation details

---

Phase 3: Clean Code Smells Checklist (Robert Martin)

In addition to Ousterhout's principles, check for these code smells:

Comments (C1-C5)

Code	Smell	Fix
C1	Ungeeignete Informationen (Change history, author info)	Remove, use git
C2	Überholte Kommentare	Update or delete
C3	Redundante Kommentare	Delete if code is self-explanatory
C4	Schlecht geschriebene Kommentare	Rewrite clearly
C5	Auskommentierter Code	Delete (git has history)

Functions (F1-F4)

Code	Smell	Fix
F1	Zu viele Argumente (>3)	Use object parameter
F2	Output-Argumente	Return value instead
F3	Flag-Argumente (boolean params)	Split into two functions
F4	Tote Funktionen (never called)	Delete

General (G1-G36) - Most Important

Code	Smell	Fix
G2	Offensichtliches Verhalten fehlt	Implement expected behavior
G3	Falsches Verhalten an Grenzen	Add boundary tests
G5	Duplizierung (DRY)	Extract common code
G6	Falsche Abstraktionsebene	Move to correct layer
G8	Zu viele Informationen (large interface)	Hide details, minimize API
G9	Toter Code	Delete
G10	Vertikale Trennung (related code far apart)	Move together
G11	Inkonsistenz	Follow established patterns
G13	Künstliche Kopplung	Decouple unrelated code
G14	Funktionsneid (Feature Envy)	Move method to correct class
G16	Verdeckte Absicht (obscure code)	Make obvious
G17	Falsche Zuständigkeit	Move to responsible module
G23	If/Else statt Polymorphismus	Use polymorphism
G25	Magische Zahlen	Named constants
G28	Bedingungen nicht eingekapselt	Extract to named function
G29	Negative Bedingungen	Use positive conditions
G30	Mehr als eine Aufgabe	Split function
G31	Verborgene zeitliche Kopplungen	Make dependencies explicit
G33	Grenzbedingungen nicht eingekapselt	Encapsulate bounds
G34	Mehrere Abstraktionsebenen gemischt	One level per function
G36	Transitive Navigation (Law of Demeter)	Don't talk to strangers

Names (N1-N7)

Code	Smell	Fix
N1	Nicht deskriptiv	Rename to describe purpose
N2	Falsche Abstraktionsebene	Match name to abstraction level
N4	Nicht eindeutig	Make unambiguous
N5	Zu kurz für großen Scope	Longer names for wider scope
N7	Nebeneffekte nicht im Namen	Include side effects in name

Tests (T1-T9)

Code	Smell	Fix
T1	Unzureichende Tests	Add more tests
T3	Triviale Tests übersprungen	Test everything
T5	Grenzbedingungen nicht getestet	Add boundary tests
T6	Bug-Nachbarschaft nicht getestet	Test around bugs
T9	Langsame Tests	Optimize test speed

F.I.R.S.T. Test Principles

• Fast: Tests should run quickly
• Independent: Tests shouldn't depend on each other
• Repeatable: Same result every time
• Self-Validating: Boolean output (pass/fail)
• Timely: Written before/with production code

Clean Code Function Rules

1. Klein! Functions should be small (ideally < 20 lines)
2. Eine Aufgabe - Do ONE thing and do it well
3. Eine Abstraktionsebene - Don't mix abstraction levels
4. Stepdown Rule - Read code top-down like a story
5. Max 3 Arguments - Prefer 0-2, use object for more

// BEFORE: Too many args, mixed abstraction levels
async function processPod(
  namespace: string,
  name: string,
  action: string,
  force: boolean,
  gracePeriod: number,
  callback: () => void
) {
  const pod = await invoke('get_pod', { namespace, name });
  if (action === 'delete') {
    if (force) {
      await invoke('force_delete', { namespace, name });
    } else {
      await invoke('delete', { namespace, name, gracePeriod });
    }
  }
  callback();
}

// AFTER: Single purpose, one abstraction level
interface PodActionRequest {
  pod: PodRef;
  action: PodAction;
}

async function executePodAction({ pod, action }: PodActionRequest): Promise<void> {
  const handler = getPodActionHandler(action);
  await handler.execute(pod);
}

Law of Demeter (G36: Transitive Navigation)

Principle: A method should only call methods on:

• Its own object (this)
• Objects passed as parameters
• Objects it creates
• Its direct component objects

// VIOLATES Law of Demeter: "Train wreck"
const street = user.getAddress().getCity().getStreet();

// BETTER: Tell, don't ask
const street = user.getStreetAddress();

// Kubeli Example:
// BAD: Navigating through objects
const podName = store.getState().cluster.selectedPod.metadata.name;

// GOOD: Direct access with selector
const podName = useSelectedPodName();

Pfadfinder-Regel (Boy Scout Rule)

"Leave the code cleaner than you found it."

Every time you touch code:

• Fix one small thing
• Improve one name
• Extract one function
• Add one missing test

---

Phase 4: Stack-Specific Refactoring Patterns

Vite/React (Frontend)

Component Organization:

// BEFORE: Monolithic component with mixed concerns
export function PodList({ namespace }: Props) {
  const [pods, setPods] = useState([]);
  const [filter, setFilter] = useState('');
  useEffect(() => { fetchPods().then(setPods); }, []);
  return (
    <div>
      <input value={filter} onChange={e => setFilter(e.target.value)} />
      <ul>{pods.filter(p => p.name.includes(filter)).map(p => <PodItem pod={p} />)}</ul>
    </div>
  );
}

// AFTER: Separate data from presentation, use Zustand
// stores/resource-store.ts
export const useResourceStore = create((set) => ({
  pods: [],
  fetchPods: async (ns) => { /* ... */ },
}));

// components/PodList.tsx
export function PodList() {
  const pods = useResourceStore(s => s.pods);
  const [filter, setFilter] = useState('');
  return <ul>{pods.filter(p => p.name.includes(filter)).map(p => <PodItem pod={p} />)}</ul>;
}

Anti-Patterns to Fix:

Smell	Refactoring
Props drilling through 3+ levels	Use Zustand store or Context
Giant utils.ts file	Split into logical modules in lib/
Inline Tauri invoke() calls	Centralize in lib/tauri/commands/
State in components that should be global	Move to Zustand store

---

Zustand (State Management)

Selective State Access:

// BEFORE: Re-renders on ANY state change
function PodCount() {
  const store = useClusterStore(); // BAD: subscribes to everything
  return <span>{store.pods.length}</span>;
}

// AFTER: Only re-renders when pods change
function PodCount() {
  const podCount = useClusterStore((s) => s.pods.length); // GOOD: selective
  return <span>{podCount}</span>;
}

Modular Stores with Slices:

// BEFORE: Monolithic store
const useStore = create((set) => ({
  pods: [],
  deployments: [],
  services: [],
  selectedPod: null,
  selectedDeployment: null,
  // ... 50 more properties
}));

// AFTER: Composable slices
// stores/pods-slice.ts
export const createPodsSlice = (set, get) => ({
  pods: [],
  selectedPod: null,
  fetchPods: async (ns) => { ... },
  selectPod: (id) => set({ selectedPod: id }),
});

// stores/deployments-slice.ts
export const createDeploymentsSlice = (set, get) => ({
  deployments: [],
  fetchDeployments: async (ns) => { ... },
});

// stores/index.ts
export const useStore = create((...a) => ({
  ...createPodsSlice(...a),
  ...createDeploymentsSlice(...a),
}));

Custom Hook Abstraction:

// BEFORE: Direct store access everywhere
function PodDetails({ id }: Props) {
  const pods = useClusterStore((s) => s.pods);
  const pod = pods.find(p => p.id === id);
  // ...
}

// AFTER: Domain-specific hooks
// hooks/usePod.ts
export function usePod(id: string) {
  return useClusterStore((s) => s.pods.find(p => p.id === id));
}

// components/PodDetails.tsx
function PodDetails({ id }: Props) {
  const pod = usePod(id);
  // ...
}

---

Tauri 2.0 / Rust (Backend)

Command Organization:

// BEFORE: All commands in one file
// src-tauri/src/main.rs
#[tauri::command]
fn get_pods() { ... }
#[tauri::command]
fn get_deployments() { ... }
#[tauri::command]
fn get_services() { ... }
// ... 50 more commands

// AFTER: Modular command structure
// src-tauri/src/commands/mod.rs
pub mod pods;
pub mod deployments;
pub mod services;

// src-tauri/src/commands/pods.rs
#[tauri::command]
pub async fn get_pods(state: State<'_, AppState>, namespace: &str) -> Result<Vec<Pod>, Error> {
    let client = state.client_manager.get_client()?;
    client.list_pods(namespace).await
}

// src-tauri/src/main.rs
fn main() {
    tauri::Builder::default()
        .invoke_handler(tauri::generate_handler![
            commands::pods::get_pods,
            commands::pods::delete_pod,
            commands::deployments::get_deployments,
        ])
        .run(tauri::generate_context!())
        .expect("error running app");
}

Separation: main.rs vs lib.rs:

// BEFORE: Logic in main.rs
// src-tauri/src/main.rs
fn main() {
    // 500 lines of logic...
}

// AFTER: main.rs only handles startup, lib.rs has logic
// src-tauri/src/main.rs
fn main() {
    kubeli_lib::run();
}

// src-tauri/src/lib.rs
pub mod commands;
pub mod k8s;
pub mod state;

pub fn run() {
    tauri::Builder::default()
        .manage(state::AppState::new())
        .invoke_handler(tauri::generate_handler![...])
        .run(tauri::generate_context!())
        .expect("error running app");
}

Rust Refactoring Patterns:

// BEFORE: Tuple returns (hard to understand)
fn get_cluster_info() -> (String, bool, u32) {
    (context_name, is_connected, node_count)
}
let (a, b, c) = get_cluster_info(); // What is a, b, c?

// AFTER: Struct with meaningful names
struct ClusterInfo {
    context_name: String,
    is_connected: bool,
    node_count: u32,
}
fn get_cluster_info() -> ClusterInfo { ... }
let info = get_cluster_info();
println!("Connected: {}", info.is_connected);

// BEFORE: if-else chains
if status == "Running" { ... }
else if status == "Pending" { ... }
else if status == "Failed" { ... }

// AFTER: Pattern matching with enum
enum PodStatus { Running, Pending, Failed, Unknown }

match pod.status {
    PodStatus::Running => { ... }
    PodStatus::Pending => { ... }
    PodStatus::Failed => { ... }
    PodStatus::Unknown => { ... }
}

// BEFORE: Manual error handling everywhere
fn get_pod(name: &str) -> Result<Pod, Error> {
    let pods = self.list_pods()?;
    for pod in pods {
        if pod.name == name {
            return Ok(pod);
        }
    }
    Err(Error::NotFound)
}

// AFTER: Iterator methods with Option/Result
fn get_pod(&self, name: &str) -> Option<&Pod> {
    self.pods.iter().find(|p| p.name == name)
}

// Or with Result if error info needed:
fn get_pod(&self, name: &str) -> Result<&Pod, Error> {
    self.pods.iter()
        .find(|p| p.name == name)
        .ok_or_else(|| Error::PodNotFound(name.to_string()))
}

Minimize Public API Surface:

// BEFORE: Everything public
pub struct KubeClientManager {
    pub clients: HashMap<String, Client>,
    pub current_context: String,
    pub config: KubeConfig,
}

// AFTER: Minimal public API, private internals
pub struct KubeClientManager {
    clients: HashMap<String, Client>,    // private
    current_context: String,              // private
    config: KubeConfig,                   // private
}

impl KubeClientManager {
    pub fn new() -> Result<Self, Error> { ... }
    pub fn get_client(&self) -> Result<&Client, Error> { ... }
    pub fn switch_context(&mut self, name: &str) -> Result<(), Error> { ... }
    // Internal methods stay private
}

---

Tauri 2.0 Enterprise Patterns

Command Layer Pattern (Thin Handlers → Service Layer):

// BEFORE: Fat command with business logic
#[tauri::command]
pub async fn create_user(name: String, email: String) -> Result<User, String> {
    // Validation here...
    // Database access here...
    // Business logic here...
    // 100+ lines of mixed concerns
}

// AFTER: Thin handler → Service layer
// src/commands/user_commands.rs
#[tauri::command]
pub async fn create_user(name: String, email: String) -> Result<User, AppError> {
    user_service::create_user(&name, &email).await
}

// src/services/user_service.rs
pub async fn create_user(name: &str, email: &str) -> Result<User, AppError> {
    validate_email(email)?;
    let user = User::new(name, email);
    repository::save_user(&user).await?;
    Ok(user)
}

Error Handling (thiserror + Serialize for IPC):

use thiserror::Error;
use serde::Serialize;

#[derive(Error, Debug)]
pub enum AppError {
    #[error("Database error: {0}")]
    Database(#[from] sqlx::Error),

    #[error("File not found: {path}")]
    FileNotFound { path: String },

    #[error("Kubernetes error: {0}")]
    Kube(#[from] kube::Error),

    #[error(transparent)]
    Other(#[from] anyhow::Error),
}

// CRITICAL: Implement Serialize for Tauri IPC
impl Serialize for AppError {
    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
    where S: serde::Serializer {
        serializer.serialize_str(&self.to_string())
    }
}

// For typed frontend errors, use tagged serialization:
#[derive(Serialize)]
#[serde(tag = "kind", content = "message")]
#[serde(rename_all = "camelCase")]
pub enum TypedError {
    Io(String),
    Validation(String),
    NotFound(String),
}
// Produces: { kind: 'io' | 'validation' | 'notFound', message: string }

State Management (std::Mutex vs tokio::Mutex):

// SYNC commands: Use std::sync::Mutex
use std::sync::Mutex;

#[tauri::command]
fn increment(state: State<'_, Mutex<AppState>>) -> u32 {
    let mut state = state.lock().unwrap();
    state.counter += 1;
    state.counter
}

// ASYNC commands: Use tokio::sync::Mutex (avoids blocking!)
use tokio::sync::Mutex;

#[tauri::command]
async fn async_increment(state: State<'_, Mutex<AppState>>) -> Result<u32, ()> {
    let mut state = state.lock().await;  // .await not .unwrap()!
    state.counter += 1;
    Ok(state.counter)
}

// CRITICAL: Async commands with borrowed args need Result return type
// ❌ Won't compile
async fn cmd(state: State<'_, AppState>) { }

// ✅ Correct pattern
async fn cmd(state: State<'_, AppState>) -> Result<(), ()> { Ok(()) }

Security: Path Traversal Prevention:

#[tauri::command]
async fn read_file(path: String, app: AppHandle) -> Result<String, String> {
    let path = std::path::Path::new(&path);

    // Prevent path traversal attacks
    if path.components().any(|c| matches!(c, std::path::Component::ParentDir)) {
        return Err("Invalid path: directory traversal not allowed".into());
    }

    // Validate against allowed base directory
    let base = app.path().app_data_dir().unwrap();
    let full_path = base.join(&path);
    let canonical = full_path.canonicalize()
        .map_err(|e| format!("Invalid path: {}", e))?;

    if !canonical.starts_with(&base) {
        return Err("Access denied: path outside allowed scope".into());
    }

    std::fs::read_to_string(canonical).map_err(|e| e.to_string())
}

Async Performance (spawn_blocking for CPU-intensive):

// CPU-intensive work should use spawn_blocking
#[tauri::command]
async fn heavy_computation(data: Vec<u8>) -> Result<Vec<u8>, String> {
    tokio::task::spawn_blocking(move || {
        process_heavy_data(data)  // Runs on blocking thread pool
    }).await.map_err(|e| e.to_string())
}

// I/O work uses regular async
#[tauri::command]
async fn fetch_data(url: String) -> Result<Data, String> {
    reqwest::get(&url).await
        .map_err(|e| e.to_string())?
        .json().await
        .map_err(|e| e.to_string())
}

Extension Traits for AppHandle:

pub trait AppHandleExt {
    fn get_database(&self) -> Arc<Database>;
    fn emit_global(&self, event: &str, payload: impl Serialize);
}

impl AppHandleExt for tauri::AppHandle {
    fn get_database(&self) -> Arc<Database> {
        self.state::<Arc<Database>>().inner().clone()
    }

    fn emit_global(&self, event: &str, payload: impl Serialize) {
        self.emit(event, payload).unwrap();
    }
}

// Usage in commands:
#[tauri::command]
async fn get_pods(app: AppHandle) -> Result<Vec<Pod>, AppError> {
    let db = app.get_database();
    db.query_pods().await
}

Events for Real-time Updates (Backend → Frontend):

use tauri::{AppHandle, Emitter};

#[derive(Clone, Serialize)]
struct ProgressUpdate { percent: u32, status: String }

#[tauri::command]
async fn long_operation(app: AppHandle) -> Result<(), String> {
    for i in 0..=100 {
        app.emit("progress", ProgressUpdate {
            percent: i,
            status: format!("Processing {}%", i)
        }).unwrap();
        tokio::time::sleep(Duration::from_millis(50)).await;
    }
    Ok(())
}

// Frontend: Always cleanup listeners!
import { listen } from '@tauri-apps/api/event';

const unlisten = await listen<ProgressUpdate>('progress', (event) => {
  console.log(`Progress: ${event.payload.percent}%`);
});

// Cleanup on unmount
onCleanup(() => unlisten());

Tauri 2.0 Capability-Based Security:

// src-tauri/capabilities/default.json
{
  "$schema": "../gen/schemas/desktop-schema.json",
  "identifier": "main-capability",
  "windows": ["main"],
  "permissions": [
    "core:default",
    "fs:default",
    {
      "identifier": "fs:allow-read",
      "allow": [{ "path": "$APPDATA/*" }],
      "deny": [{ "path": "$HOME/.ssh/*" }]
    }
  ]
}

Release Build Optimization:

# Cargo.toml
[profile.release]
lto = true              # Link-time optimization
codegen-units = 1       # Better optimization
opt-level = "s"         # Optimize for size
panic = "abort"         # Smaller binary
strip = true            # Remove debug symbols

Channels for High-Throughput Streaming (Alternative to Events):

use tauri::ipc::Channel;

#[derive(Clone, Serialize)]
#[serde(rename_all = "camelCase", tag = "event", content = "data")]
enum DownloadEvent<'a> {
    Started { url: &'a str, size: u64 },
    Progress { percent: u8, downloaded: u64 },
    Finished,
}

#[tauri::command]
fn download(url: String, on_progress: Channel<DownloadEvent>) {
    on_progress.send(DownloadEvent::Started { url: &url, size: 1024 }).unwrap();
    // ... streaming data
    for i in 0..=100 {
        on_progress.send(DownloadEvent::Progress { percent: i, downloaded: i as u64 * 10 }).unwrap();
    }
    on_progress.send(DownloadEvent::Finished).unwrap();
}

// Frontend: Channel usage
await invoke('download', {
  url: 'https://example.com/file',
  onProgress: new Channel<DownloadEvent>((event) => {
    if (event.event === 'progress') {
      console.log(`Downloaded: ${event.data.percent}%`);
    }
  })
});

Multi-Window Security Isolation:

// capabilities/admin.json - More privileges
{
  "identifier": "admin-capability",
  "windows": ["admin-*"],
  "permissions": ["fs:default", "fs:allow-write", "shell:allow-execute"]
}

// capabilities/viewer.json - Read-only
{
  "identifier": "viewer-capability",
  "windows": ["viewer-*"],
  "permissions": ["fs:allow-read"]
}

Content Security Policy (CSP):

// tauri.conf.json
{
  "app": {
    "security": {
      "csp": {
        "default-src": "'self' customprotocol: asset:",
        "connect-src": "ipc: http://ipc.localhost",
        "script-src": "'self'",
        "style-src": "'unsafe-inline' 'self'"
      }
    }
  }
}

Security Hardening Checklist:

• Enable strict CSP with default-src 'self'
• Configure per-window capabilities with minimum permissions
• Define scopes to restrict file system access
• Validate ALL command inputs in Rust (frontend is untrusted!)
• Run cargo audit and npm audit regularly
• Never load remote/untrusted content
• Sign all release binaries
• Use tokio::sync::Mutex for async commands (not std::sync)

Splashscreen Startup Optimization:

tauri::Builder::default()
    .setup(|app| {
        let splashscreen = app.get_webview_window("splashscreen").unwrap();
        let main_window = app.get_webview_window("main").unwrap();

        tauri::async_runtime::spawn(async move {
            // Heavy initialization here (doesn't block UI)
            initialize_database().await;
            load_config().await;

            splashscreen.close().unwrap();
            main_window.show().unwrap();
        });
        Ok(())
    })

Mobile Support (lib.rs Entry Point):

// src-tauri/src/lib.rs
#[cfg_attr(mobile, tauri::mobile_entry_point)]
pub fn run() {
    tauri::Builder::default()
        .invoke_handler(tauri::generate_handler![...])
        .run(tauri::generate_context!())
        .expect("error running app");
}

// src-tauri/src/main.rs (minimal)
fn main() {
    kubeli_lib::run();
}

Testing: Rust Commands with Mock Runtime:

#[cfg(test)]
mod tests {
    use tauri::test::{mock_builder, mock_context, noop_assets};

    fn create_app() -> tauri::App<tauri::test::MockRuntime> {
        mock_builder()
            .invoke_handler(tauri::generate_handler![super::greet])
            .build(mock_context(noop_assets()))
            .expect("failed to build app")
    }

    #[test]
    fn test_greet() {
        let _app = create_app();
        let result = super::greet("World");
        assert_eq!(result, "Hello, World!");
    }
}

# Enable test feature in Cargo.toml
[dependencies]
tauri = { version = "2.0", features = ["test"] }

Testing: Frontend IPC Mocking (Vitest):

import { mockIPC, clearMocks } from '@tauri-apps/api/mocks';
import { invoke } from '@tauri-apps/api/core';

afterEach(() => clearMocks());

test('invoke add command', async () => {
  mockIPC((cmd, args) => {
    if (cmd === 'add') return (args as { a: number; b: number }).a + args.b;
  });

  const result = await invoke('add', { a: 12, b: 15 });
  expect(result).toBe(27);
});

Code Quality: Clippy Configuration:

# Cargo.toml
[lints.clippy]
pedantic = { level = "warn", priority = -1 }
unwrap_used = "deny"          # Force proper error handling
expect_used = "warn"
module_name_repetitions = "allow"

Code Quality: rustfmt.toml: