GitHub Copilot

// Wpisz komentarz opisujący co chcesz zrobić:
// Funkcja walidująca email używając regex

// Copilot sugeruje:
function validateEmail(email: string): boolean {
  const emailRegex = /^[^\s@]+@[^\s@]+\.[^\s@]+$/
  return emailRegex.test(email)
}

// Lub zacznij pisać nazwę funkcji:
function calculateShippingCost(
  // Copilot sugeruje parametry i implementację:
  weight: number,
  distance: number,
  expedited: boolean = false
): number {
  const baseRate = 5.00
  const weightRate = weight * 0.50
  const distanceRate = distance * 0.10
  const expeditedMultiplier = expedited ? 1.5 : 1

  return (baseRate + weightRate + distanceRate) * expeditedMultiplier
}

Ty: Wyjaśnij co robi ta funkcja

Copilot: Ta funkcja `calculateShippingCost` oblicza koszt wysyłki
na podstawie trzech parametrów:

1. `weight` - waga paczki w kg
2. `distance` - odległość w km
3. `expedited` - czy wysyłka ma być przyspieszona

Składniki kosztu:
- Bazowa opłata: 5.00
- Opłata za wagę: 0.50 za kg
- Opłata za dystans: 0.10 za km
- Mnożnik dla ekspresowej: 1.5x

Formuła: (baza + waga*0.5 + dystans*0.1) * mnożnik

Przykład:
/tests for the calculateShippingCost function

Copilot generuje:
describe('calculateShippingCost', () => {
  it('calculates base cost correctly', () => {
    expect(calculateShippingCost(0, 0)).toBe(5.00)
  })

  it('adds weight cost', () => {
    expect(calculateShippingCost(10, 0)).toBe(10.00)
  })

  it('adds distance cost', () => {
    expect(calculateShippingCost(0, 100)).toBe(15.00)
  })

  it('applies expedited multiplier', () => {
    expect(calculateShippingCost(0, 0, true)).toBe(7.50)
  })

  it('combines all costs correctly', () => {
    // 5 + (10*0.5) + (100*0.1) = 5 + 5 + 10 = 20
    expect(calculateShippingCost(10, 100)).toBe(20.00)
  })

  it('applies expedited to combined costs', () => {
    // 20 * 1.5 = 30
    expect(calculateShippingCost(10, 100, true)).toBe(30.00)
  })
})

@workspace Jak zaimplementować autentykację w tym projekcie?

@github Stwórz issue dla tego błędu

Workflow:
1. Otwórz GitHub Issue
2. Kliknij "Open in Workspace"
3. Copilot analizuje issue i proponuje plan:

   Plan zmian dla Issue #123: "Add user authentication"

   Pliki do stworzenia:
   ├── src/lib/auth.ts (funkcje auth)
   ├── src/middleware.ts (middleware sprawdzający sesję)
   ├── src/app/api/auth/[...nextauth]/route.ts (NextAuth handler)
   └── src/types/auth.ts (typy TypeScript)

   Pliki do modyfikacji:
   ├── src/app/layout.tsx (dodać SessionProvider)
   ├── package.json (dodać next-auth)
   └── .env.example (dodać zmienne auth)

4. Przejrzyj i zaakceptuj/modyfikuj plan
5. Copilot implementuje zmiany
6. Review i stwórz Pull Request

Ty: Implement a complete user registration flow with email verification

Copilot Agent:
┌─────────────────────────────────────────────────────────────┐
│ Task: User Registration with Email Verification            │
├─────────────────────────────────────────────────────────────┤
│ Step 1/7: Analyzing project structure...              ✓    │
│ Step 2/7: Creating database schema...                 ✓    │
│ Step 3/7: Implementing API endpoints...               ✓    │
│ Step 4/7: Creating UI components...                   ✓    │
│ Step 5/7: Setting up email service...                 ✓    │
│ Step 6/7: Writing tests...                            ✓    │
│ Step 7/7: Creating Pull Request...                    ✓    │
├─────────────────────────────────────────────────────────────┤
│ PR #45: "Add user registration with email verification"    │
│ ✓ 12 files changed                                         │
│ ✓ All tests passing                                        │
│ ✓ Ready for review                                         │
└─────────────────────────────────────────────────────────────┘

## Automatyczne funkcje w PR

### Copilot PR Summary
Automatyczne podsumowanie zmian w PR:

> This PR adds user authentication using NextAuth.js:
> - New login/register pages
> - JWT token handling
> - Protected route middleware
> - Database schema for users

### Copilot Code Review
Automatyczne sugestie podczas review:

⚠️ Line 45: Consider adding rate limiting to prevent brute force attacks
💡 Line 89: This query could be optimized with an index on `email` field
✓ Line 102: Good use of transaction for atomic operations

# Instalacja
gh extension install github/gh-copilot

# Użycie
gh copilot suggest "find all large files in git history"
# Copilot: git rev-list --objects --all | git cat-file --batch-check='%(objecttype) %(objectname) %(objectsize) %(rest)' | awk '/^blob/ {print substr($0,6)}' | sort -rnk3 | head -10

gh copilot explain "git rebase -i HEAD~5"
# Copilot: This command starts an interactive rebase of the last 5 commits...

# Skróty
ghcs "compress images in folder"  # suggest
ghce "explain this error"          # explain

@docker How do I create a multi-stage build for a Node.js app?

@sentry What's causing this error spike?

@stripe Help me implement subscription billing

Settings → Plugins → Marketplace → "GitHub Copilot"

-- lazy.nvim
{
  "github/copilot.vim",
  event = "InsertEnter",
  config = function()
    vim.g.copilot_no_tab_map = true
    vim.keymap.set("i", "<C-J>", 'copilot#Accept("\\<CR>")', {
      expr = true,
      replace_keycodes = false,
    })
  end,
}

-- Lub copilot.lua dla Lua native
{
  "zbirenbaum/copilot.lua",
  cmd = "Copilot",
  event = "InsertEnter",
  config = function()
    require("copilot").setup({
      suggestion = { enabled = true },
      panel = { enabled = true },
    })
  end,
}

Extensions → Manage Extensions → Online → "GitHub Copilot"

# Via Homebrew
brew install --cask copilot-for-xcode

// settings.json
{
  // Włączanie/wyłączanie dla języków
  "github.copilot.enable": {
    "*": true,
    "markdown": true,
    "plaintext": false,
    "yaml": true,
    "json": true
  },

  // Automatyczne sugestie
  "github.copilot.editor.enableAutoCompletions": true,

  // Język czatu
  "github.copilot.chat.localeOverride": "pl",

  // Zaawansowane ustawienia
  "github.copilot.advanced": {
    "inlineSuggestCount": 3,
    "length": 500,
    "temperature": ""
  }
}

# Ignoruj pliki z wrażliwymi danymi
.env
.env.*
*.pem
*.key
credentials.*

# Ignoruj wygenerowane pliki
dist/
build/
*.min.js

# Ignoruj pliki konfiguracyjne
*.lock

// Funkcja sortująca tablicę obiektów po dacie, od najnowszej
// Tab → Copilot generuje:

function sortByDateDesc<T extends { date: Date }>(items: T[]): T[] {
  return [...items].sort((a, b) => b.date.getTime() - a.date.getTime())
}

// Funkcja do formatowania ceny z walutą
// Tab →

function formatPrice(
  amount: number,
  currency: string = 'PLN',
  locale: string = 'pl-PL'
): string {
  return new Intl.NumberFormat(locale, {
    style: 'currency',
    currency: currency,
  }).format(amount)
}

// Typy dla odpowiedzi API użytkowników z paginacją
// Tab →

interface User {
  id: string
  name: string
  email: string
  avatar?: string
  role: 'admin' | 'user' | 'guest'
  createdAt: Date
  updatedAt: Date
}

interface PaginationMeta {
  page: number
  limit: number
  total: number
  totalPages: number
  hasNext: boolean
  hasPrev: boolean
}

interface PaginatedResponse<T> {
  data: T[]
  meta: PaginationMeta
}

type UsersResponse = PaginatedResponse<User>

// Testy jednostkowe dla funkcji validateEmail z edge cases
// Tab →

describe('validateEmail', () => {
  describe('valid emails', () => {
    it('accepts standard email format', () => {
      expect(validateEmail('user@example.com')).toBe(true)
    })

    it('accepts email with subdomain', () => {
      expect(validateEmail('user@mail.example.com')).toBe(true)
    })

    it('accepts email with plus sign', () => {
      expect(validateEmail('user+tag@example.com')).toBe(true)
    })

    it('accepts email with dots in local part', () => {
      expect(validateEmail('first.last@example.com')).toBe(true)
    })
  })

  describe('invalid emails', () => {
    it('rejects email without @', () => {
      expect(validateEmail('userexample.com')).toBe(false)
    })

    it('rejects email without domain', () => {
      expect(validateEmail('user@')).toBe(false)
    })

    it('rejects email without local part', () => {
      expect(validateEmail('@example.com')).toBe(false)
    })

    it('rejects email with spaces', () => {
      expect(validateEmail('user name@example.com')).toBe(false)
    })

    it('rejects empty string', () => {
      expect(validateEmail('')).toBe(false)
    })
  })
})

// Zaznacz kod i użyj /simplify w Chat:

// Przed:
function getFullName(user) {
  let fullName = ''
  if (user.firstName) {
    fullName = user.firstName
  }
  if (user.lastName) {
    if (fullName.length > 0) {
      fullName = fullName + ' '
    }
    fullName = fullName + user.lastName
  }
  return fullName
}

// Po /simplify:
function getFullName(user: { firstName?: string; lastName?: string }): string {
  return [user.firstName, user.lastName].filter(Boolean).join(' ')
}

// Zaznacz funkcję i użyj /doc:

/**
 * Calculates the shipping cost based on weight, distance, and delivery speed.
 *
 * @param weight - The weight of the package in kilograms
 * @param distance - The shipping distance in kilometers
 * @param expedited - Whether to use expedited (express) shipping. Defaults to false.
 * @returns The total shipping cost in PLN
 *
 * @example
 * ```typescript
 * // Standard shipping for 5kg package, 100km
 * calculateShippingCost(5, 100) // Returns: 17.50
 *
 * // Expedited shipping (1.5x cost)
 * calculateShippingCost(5, 100, true) // Returns: 26.25
 * ```
 *
 * @throws {Error} If weight or distance is negative
 */
function calculateShippingCost(
  weight: number,
  distance: number,
  expedited: boolean = false
): number {
  if (weight < 0 || distance < 0) {
    throw new Error('Weight and distance must be non-negative')
  }

  const baseRate = 5.00
  const weightRate = weight * 0.50
  const distanceRate = distance * 0.10
  const expeditedMultiplier = expedited ? 1.5 : 1

  return (baseRate + weightRate + distanceRate) * expeditedMultiplier
}

// Zaznacz JSON i wpisz: "Convert to TypeScript interface"

// JSON:
{
  "id": "123",
  "name": "Product",
  "price": 99.99,
  "categories": ["electronics", "gadgets"],
  "metadata": {
    "sku": "ABC123",
    "weight": 0.5
  }
}

// Copilot generuje:
interface Product {
  id: string
  name: string
  price: number
  categories: string[]
  metadata: {
    sku: string
    weight: number
  }
}

// ❌ Zbyt ogólne:
// Funkcja do walidacji

// ✅ Szczegółowe:
// Funkcja walidująca numer telefonu w formacie polskim (+48 XXX XXX XXX)
// - Akceptuje format z lub bez +48
// - Akceptuje spacje i myślniki jako separatory
// - Zwraca znormalizowany numer bez separatorów lub null jeśli niepoprawny

// ❌ Brak kontekstu:
// API endpoint

// ✅ Z kontekstem:
// Next.js 14 App Router API endpoint (POST)
// - Przyjmuje JSON z polem 'email'
// - Waliduje z Zod
// - Zapisuje do Prisma
// - Zwraca 201 z ID lub 400 z błędami walidacji

// Tech stack: Next.js 15, Prisma, PostgreSQL
// Auth: NextAuth.js z GitHub provider
// Styling: Tailwind CSS
// Validation: Zod

// API route do pobierania profilu zalogowanego użytkownika
// z obsługą błędów i walidacją sesji

export async function GET(request: Request) {
  // Copilot teraz wie o tech stacku i generuje odpowiedni kod
}

# .github/copilot-instructions.md

## Code Style
- Use TypeScript strict mode
- Prefer functional programming patterns
- Use async/await over callbacks
- Maximum function length: 50 lines

## Security
- Always validate user input
- Use parameterized queries
- Never log sensitive data

## Testing
- Write unit tests for all business logic
- Use Jest and Testing Library
- Aim for 80% code coverage

✅ Pisz opisowe komentarze przed kodem
   - Copilot uczy się z kontekstu

✅ Używaj /explain do nauki nowych codebase
   - Szybsze onboarding do projektów

✅ Generuj testy z /tests po napisaniu funkcji
   - Natychmiastowe pokrycie testami

✅ Używaj /fix do szybkiego debugowania
   - Oszczędność czasu na prostych błędach

✅ Przejrzyj KAŻDY wygenerowany kod przed akceptacją
   - Copilot może generować błędy lub nieoptymalne rozwiązania

✅ Używaj Copilot do boilerplate
   - Powtarzalny kod jest idealny dla AI

✅ Korzystaj z Extensions dla specjalistycznych zadań
   - @docker, @azure, itp. znają swoje domeny

✅ Ustaw .copilotignore dla wrażliwych plików
   - Ochrona przed wyciekiem danych

❌ Nie akceptuj kodu bez przeglądu
   - AI może generować błędy logiczne

❌ Nie polegaj na Copilot dla logiki bezpieczeństwa
   - Zawsze weryfikuj security-critical code

❌ Nie używaj do generowania sekretów/kluczy
   - Copilot może sugerować klucze z treningu

❌ Nie ignoruj ostrzeżeń o bezpieczeństwie
   - Linting errors mogą wskazywać na problemy

❌ Nie kopiuj wrażliwych danych do promptów
   - Dane są wysyłane do API

❌ Nie ufaj w 100% wygenerowanym SQL
   - Zawsze sprawdź pod kątem SQL injection

❌ Nie używaj Copilot do tworzenia algorytmów kryptograficznych
   - Użyj sprawdzonych bibliotek

// ❌ Nigdy nie rób tego:
const API_KEY = 'sk-live-...'  // Copilot może zasugerować prawdziwy klucz

// ✅ Zamiast tego:
const API_KEY = process.env.API_KEY
if (!API_KEY) throw new Error('API_KEY not configured')

// ❌ Ryzykowne:
const query = `SELECT * FROM users WHERE id = ${userId}`  // SQL injection

// ✅ Bezpieczne:
const query = `SELECT * FROM users WHERE id = $1`
await client.query(query, [userId])

// ❌ Niebezpieczne:
res.send(`Hello ${req.query.name}`)  // XSS

// ✅ Bezpieczne:
import { escape } from 'lodash'
res.send(`Hello ${escape(req.query.name)}`)

# 1. Sprawdź status
# VS Code: View → Command Palette → "GitHub Copilot: Status"

# 2. Sprawdź czy język jest włączony
# Settings → github.copilot.enable → sprawdź dla danego języka

# 3. Sprawdź połączenie
# View → Output → wybierz "GitHub Copilot" z listy

# 4. Sprawdź subskrypcję
# github.com/settings/copilot

# 5. Wyloguj i zaloguj ponownie
# Command Palette → "GitHub: Sign Out" → "GitHub: Sign In"

// 1. Dodaj więcej kontekstu
// - Importy na górze pliku
// - Typy/interfejsy używane w projekcie
// - Komentarze opisujące oczekiwane zachowanie

// 2. Używaj precyzyjnych komentarzy
// ❌ "funkcja do walidacji"
// ✅ "funkcja walidująca polski PESEL, zwraca true/false"

// 3. Otwórz powiązane pliki
// Copilot czyta otwarte tabs jako kontekst

// 4. Używaj /workspace dla kontekstu projektu

// settings.json - ogranicz sugestie
{
  "github.copilot.advanced": {
    "inlineSuggestCount": 1,  // Mniej sugestii na raz
    "length": 300  // Krótsze sugestie
  },
  "github.copilot.editor.enableAutoCompletions": false  // Ręczne triggerowanie
}

# Dodaj do environment
export HTTPS_PROXY=http://proxy.company.com:8080
export HTTP_PROXY=http://proxy.company.com:8080

# Lub w VS Code settings.json
{
  "http.proxy": "http://proxy.company.com:8080"
}

// Type a comment describing what you want to do:
// Function to validate email using regex

// Copilot suggests:
function validateEmail(email: string): boolean {
  const emailRegex = /^[^\s@]+@[^\s@]+\.[^\s@]+$/
  return emailRegex.test(email)
}

// Or start typing a function name:
function calculateShippingCost(
  // Copilot suggests parameters and implementation:
  weight: number,
  distance: number,
  expedited: boolean = false
): number {
  const baseRate = 5.00
  const weightRate = weight * 0.50
  const distanceRate = distance * 0.10
  const expeditedMultiplier = expedited ? 1.5 : 1

  return (baseRate + weightRate + distanceRate) * expeditedMultiplier
}

You: Explain what this function does

Copilot: This function `calculateShippingCost` calculates shipping cost
based on three parameters:

1. `weight` - package weight in kg
2. `distance` - distance in km
3. `expedited` - whether shipping should be expedited

Cost components:
- Base fee: 5.00
- Weight fee: 0.50 per kg
- Distance fee: 0.10 per km
- Expedited multiplier: 1.5x

Formula: (base + weight*0.5 + distance*0.1) * multiplier

Example:
/tests for the calculateShippingCost function

Copilot generates:
describe('calculateShippingCost', () => {
  it('calculates base cost correctly', () => {
    expect(calculateShippingCost(0, 0)).toBe(5.00)
  })

  it('adds weight cost', () => {
    expect(calculateShippingCost(10, 0)).toBe(10.00)
  })

  it('adds distance cost', () => {
    expect(calculateShippingCost(0, 100)).toBe(15.00)
  })

  it('applies expedited multiplier', () => {
    expect(calculateShippingCost(0, 0, true)).toBe(7.50)
  })

  it('combines all costs correctly', () => {
    // 5 + (10*0.5) + (100*0.1) = 5 + 5 + 10 = 20
    expect(calculateShippingCost(10, 100)).toBe(20.00)
  })

  it('applies expedited to combined costs', () => {
    // 20 * 1.5 = 30
    expect(calculateShippingCost(10, 100, true)).toBe(30.00)
  })
})

@workspace How do I implement authentication in this project?

@github Create an issue for this bug

Workflow:
1. Open GitHub Issue
2. Click "Open in Workspace"
3. Copilot analyzes issue and proposes a plan:

   Change plan for Issue #123: "Add user authentication"

   Files to create:
   ├── src/lib/auth.ts (auth functions)
   ├── src/middleware.ts (session checking middleware)
   ├── src/app/api/auth/[...nextauth]/route.ts (NextAuth handler)
   └── src/types/auth.ts (TypeScript types)

   Files to modify:
   ├── src/app/layout.tsx (add SessionProvider)
   ├── package.json (add next-auth)
   └── .env.example (add auth variables)

4. Review and accept/modify plan
5. Copilot implements changes
6. Review and create Pull Request

You: Implement a complete user registration flow with email verification

Copilot Agent:
┌─────────────────────────────────────────────────────────────┐
│ Task: User Registration with Email Verification            │
├─────────────────────────────────────────────────────────────┤
│ Step 1/7: Analyzing project structure...              ✓    │
│ Step 2/7: Creating database schema...                 ✓    │
│ Step 3/7: Implementing API endpoints...               ✓    │
│ Step 4/7: Creating UI components...                   ✓    │
│ Step 5/7: Setting up email service...                 ✓    │
│ Step 6/7: Writing tests...                            ✓    │
│ Step 7/7: Creating Pull Request...                    ✓    │
├─────────────────────────────────────────────────────────────┤
│ PR #45: "Add user registration with email verification"    │
│ ✓ 12 files changed                                         │
│ ✓ All tests passing                                        │
│ ✓ Ready for review                                         │
└─────────────────────────────────────────────────────────────┘

## Automatic PR Features

### Copilot PR Summary
Automatic summary of PR changes:

> This PR adds user authentication using NextAuth.js:
> - New login/register pages
> - JWT token handling
> - Protected route middleware
> - Database schema for users

### Copilot Code Review
Automatic suggestions during review:

⚠️ Line 45: Consider adding rate limiting to prevent brute force attacks
💡 Line 89: This query could be optimized with an index on `email` field
✓ Line 102: Good use of transaction for atomic operations

# Installation
gh extension install github/gh-copilot

# Usage
gh copilot suggest "find all large files in git history"
# Copilot: git rev-list --objects --all | git cat-file --batch-check='%(objecttype) %(objectname) %(objectsize) %(rest)' | awk '/^blob/ {print substr($0,6)}' | sort -rnk3 | head -10

gh copilot explain "git rebase -i HEAD~5"
# Copilot: This command starts an interactive rebase of the last 5 commits...

# Shortcuts
ghcs "compress images in folder"  # suggest
ghce "explain this error"          # explain

@docker How do I create a multi-stage build for a Node.js app?

@sentry What's causing this error spike?

@stripe Help me implement subscription billing

Settings → Plugins → Marketplace → "GitHub Copilot"

-- lazy.nvim
{
  "github/copilot.vim",
  event = "InsertEnter",
  config = function()
    vim.g.copilot_no_tab_map = true
    vim.keymap.set("i", "<C-J>", 'copilot#Accept("\\<CR>")', {
      expr = true,
      replace_keycodes = false,
    })
  end,
}

-- Or copilot.lua for Lua native
{
  "zbirenbaum/copilot.lua",
  cmd = "Copilot",
  event = "InsertEnter",
  config = function()
    require("copilot").setup({
      suggestion = { enabled = true },
      panel = { enabled = true },
    })
  end,
}

// settings.json
{
  // Enable/disable for languages
  "github.copilot.enable": {
    "*": true,
    "markdown": true,
    "plaintext": false,
    "yaml": true,
    "json": true
  },

  // Automatic suggestions
  "github.copilot.editor.enableAutoCompletions": true,

  // Chat language
  "github.copilot.chat.localeOverride": "en",

  // Advanced settings
  "github.copilot.advanced": {
    "inlineSuggestCount": 3,
    "length": 500,
    "temperature": ""
  }
}

# Ignore files with sensitive data
.env
.env.*
*.pem
*.key
credentials.*

# Ignore generated files
dist/
build/
*.min.js

# Ignore configuration files
*.lock

// Function that sorts an array of objects by date, from newest
// Tab → Copilot generates:

function sortByDateDesc<T extends { date: Date }>(items: T[]): T[] {
  return [...items].sort((a, b) => b.date.getTime() - a.date.getTime())
}

// Function to format price with currency
// Tab →

function formatPrice(
  amount: number,
  currency: string = 'USD',
  locale: string = 'en-US'
): string {
  return new Intl.NumberFormat(locale, {
    style: 'currency',
    currency: currency,
  }).format(amount)
}

// Types for paginated user API response
// Tab →

interface User {
  id: string
  name: string
  email: string
  avatar?: string
  role: 'admin' | 'user' | 'guest'
  createdAt: Date
  updatedAt: Date
}

interface PaginationMeta {
  page: number
  limit: number
  total: number
  totalPages: number
  hasNext: boolean
  hasPrev: boolean
}

interface PaginatedResponse<T> {
  data: T[]
  meta: PaginationMeta
}

type UsersResponse = PaginatedResponse<User>

// Unit tests for validateEmail function with edge cases
// Tab →

describe('validateEmail', () => {
  describe('valid emails', () => {
    it('accepts standard email format', () => {
      expect(validateEmail('user@example.com')).toBe(true)
    })

    it('accepts email with subdomain', () => {
      expect(validateEmail('user@mail.example.com')).toBe(true)
    })

    it('accepts email with plus sign', () => {
      expect(validateEmail('user+tag@example.com')).toBe(true)
    })

    it('accepts email with dots in local part', () => {
      expect(validateEmail('first.last@example.com')).toBe(true)
    })
  })

  describe('invalid emails', () => {
    it('rejects email without @', () => {
      expect(validateEmail('userexample.com')).toBe(false)
    })

    it('rejects email without domain', () => {
      expect(validateEmail('user@')).toBe(false)
    })

    it('rejects email without local part', () => {
      expect(validateEmail('@example.com')).toBe(false)
    })

    it('rejects email with spaces', () => {
      expect(validateEmail('user name@example.com')).toBe(false)
    })

    it('rejects empty string', () => {
      expect(validateEmail('')).toBe(false)
    })
  })
})

// Select code and use /simplify in Chat:

// Before:
function getFullName(user) {
  let fullName = ''
  if (user.firstName) {
    fullName = user.firstName
  }
  if (user.lastName) {
    if (fullName.length > 0) {
      fullName = fullName + ' '
    }
    fullName = fullName + user.lastName
  }
  return fullName
}

// After /simplify:
function getFullName(user: { firstName?: string; lastName?: string }): string {
  return [user.firstName, user.lastName].filter(Boolean).join(' ')
}

// Select function and use /doc:

/**
 * Calculates the shipping cost based on weight, distance, and delivery speed.
 *
 * @param weight - The weight of the package in kilograms
 * @param distance - The shipping distance in kilometers
 * @param expedited - Whether to use expedited (express) shipping. Defaults to false.
 * @returns The total shipping cost
 *
 * @example
 * ```typescript
 * // Standard shipping for 5kg package, 100km
 * calculateShippingCost(5, 100) // Returns: 17.50
 *
 * // Expedited shipping (1.5x cost)
 * calculateShippingCost(5, 100, true) // Returns: 26.25
 * ```
 *
 * @throws {Error} If weight or distance is negative
 */
function calculateShippingCost(
  weight: number,
  distance: number,
  expedited: boolean = false
): number {
  if (weight < 0 || distance < 0) {
    throw new Error('Weight and distance must be non-negative')
  }

  const baseRate = 5.00
  const weightRate = weight * 0.50
  const distanceRate = distance * 0.10
  const expeditedMultiplier = expedited ? 1.5 : 1

  return (baseRate + weightRate + distanceRate) * expeditedMultiplier
}

✅ Write descriptive comments before code
   - Copilot learns from context

✅ Use /explain to learn new codebases
   - Faster onboarding to projects

✅ Generate tests with /tests after writing functions
   - Immediate test coverage

✅ Use /fix for quick debugging
   - Time savings on simple errors

✅ Review EVERY generated code before accepting
   - Copilot can generate errors or suboptimal solutions

✅ Use Copilot for boilerplate
   - Repetitive code is ideal for AI

✅ Use Extensions for specialized tasks
   - @docker, @azure, etc. know their domains

✅ Set up .copilotignore for sensitive files
   - Protection against data leaks

❌ Don't accept code without review
   - AI can generate logical errors

❌ Don't rely on Copilot for security logic
   - Always verify security-critical code

❌ Don't use for generating secrets/keys
   - Copilot might suggest keys from training

❌ Don't ignore security warnings
   - Linting errors may indicate problems

❌ Don't copy sensitive data to prompts
   - Data is sent to API

❌ Don't trust 100% generated SQL
   - Always check for SQL injection

❌ Don't use Copilot to create cryptographic algorithms
   - Use proven libraries

// ❌ Never do this:
const API_KEY = 'sk-live-...'  // Copilot might suggest real keys

// ✅ Instead:
const API_KEY = process.env.API_KEY
if (!API_KEY) throw new Error('API_KEY not configured')

// ❌ Risky:
const query = `SELECT * FROM users WHERE id = ${userId}`  // SQL injection

// ✅ Safe:
const query = `SELECT * FROM users WHERE id = $1`
await client.query(query, [userId])

// ❌ Dangerous:
res.send(`Hello ${req.query.name}`)  // XSS

// ✅ Safe:
import { escape } from 'lodash'
res.send(`Hello ${escape(req.query.name)}`)

# 1. Check status
# VS Code: View → Command Palette → "GitHub Copilot: Status"

# 2. Check if language is enabled
# Settings → github.copilot.enable → check for given language

# 3. Check connection
# View → Output → select "GitHub Copilot" from list

# 4. Check subscription
# github.com/settings/copilot

# 5. Sign out and sign in again
# Command Palette → "GitHub: Sign Out" → "GitHub: Sign In"

// 1. Add more context
// - Imports at file top
// - Types/interfaces used in project
// - Comments describing expected behavior

// 2. Use precise comments
// ❌ "validation function"
// ✅ "function validating phone number in format +1-XXX-XXX-XXXX"

// 3. Open related files
// Copilot reads open tabs as context

// 4. Use /workspace for project context

// settings.json - limit suggestions
{
  "github.copilot.advanced": {
    "inlineSuggestCount": 1,  // Fewer suggestions at once
    "length": 300  // Shorter suggestions
  },
  "github.copilot.editor.enableAutoCompletions": false  // Manual triggering
}