CSS Development: Refactor

Overview

Transforms existing CSS into semantic component patterns:

• Extract inline styles to semantic classes
• Consolidate utility classes from markup into @apply compositions
• Add dark mode variants
• Add test coverage
• Preserve existing functionality (behavior-neutral refactoring)

This is a sub-skill of css-development - typically invoked automatically via the main skill.

When This Skill Applies

Use when:

• Converting inline styles to semantic classes
• Extracting repeated utility combinations from markup
• Migrating from pure utility-first to semantic components
• Adding dark mode to existing CSS
• Cleaning up scattered or duplicated CSS

Pattern Reference

This skill refactors toward patterns documented in the main css-development skill:

Semantic naming: .button-primary not .btn-blue Tailwind composition: Use @apply to compose utilities Dark mode: Include dark: variants Composition first: Reuse existing classes before creating new Test coverage: Static CSS + component rendering tests

Workflow

When this skill is invoked, create a TodoWrite checklist and refactor systematically.

Announce Usage

"I'm using the css-development:refactor skill to transform this CSS into semantic component patterns."

Create TodoWrite Checklist

Use the TodoWrite tool:

Refactoring CSS:
- [ ] Analyze existing CSS (identify what needs refactoring)
- [ ] Find repeated patterns (look for duplicated utility combinations)
- [ ] Check existing components (see if patterns already exist)
- [ ] Extract to semantic classes (create new classes using @apply)
- [ ] Include dark mode (add dark: variants to new classes)
- [ ] Update markup (replace inline/utility classes with semantic names)
- [ ] Add tests (write static CSS and rendering tests)
- [ ] Document components (add usage comments)
- [ ] Verify behavior unchanged (ensure visual output matches original)

Refactoring Checklist Details

Step 1: Analyze Existing CSS

Action: Read and understand the CSS that needs refactoring

Look for:

• Inline styles in component files
• Repeated utility class combinations in markup
• CSS scattered across multiple files
• Missing dark mode support
• Lack of semantic class names

Example patterns to refactor:

// Inline styles
<button style={{ background: 'indigo', padding: '1.5rem 2rem' }}>Click</button>

// Repeated utilities in markup
<button class="bg-indigo-500 hover:bg-indigo-700 px-6 py-3 rounded-lg text-white">
  Click me
</button>
<button class="bg-indigo-500 hover:bg-indigo-700 px-6 py-3 rounded-lg text-white">
  Submit
</button>

// Non-semantic CSS
.btn-blue {
  background: blue;
  padding: 12px 24px;
}

Capture:

• File locations
• Pattern frequency (how many times repeated)
• Current approach (inline, utilities, old CSS)

Mark as completed when analysis is done.

---

Step 2: Find Repeated Patterns

Action: Identify duplicated utility combinations that should become semantic classes

Use Grep tool to search for repeated patterns:

# Search for common utility combinations
grep -r "bg-indigo-500 hover:bg-indigo-700 px-6 py-3" .
grep -r "rounded-lg shadow-md p-6" .

Categorize patterns:

• High frequency (5+ occurrences): Definitely extract
• Medium frequency (2-4 occurrences): Probably extract
• Low frequency (1 occurrence): Keep as-is or compose existing classes

For each pattern:

• Count occurrences
• List file locations
• Identify semantic purpose (is this a button? card? badge?)

Mark as completed when patterns are cataloged.

---

Step 3: Check Existing Components

Action: Read styles/components.css to see if patterns already exist

Before creating new classes, check:

• Does a similar class already exist?
• Can existing classes be composed?
• Would a variant of an existing class work?

Example:

Pattern found: bg-indigo-500 hover:bg-indigo-700 px-6 py-3 rounded-lg text-white
Check: Does .button-primary already exist? YES
Solution: Use .button-primary instead of creating new class

Decision for each pattern:

• ✅ Use existing class as-is
• ✅ Compose existing classes
• ✅ Create variant of existing class
• ⚠️ Create new class (only if no existing solution)

Mark as completed when reuse opportunities are identified.

---

Step 4: Extract to Semantic Classes

Action: Create new semantic classes in styles/components.css for patterns that need extraction

For each pattern being extracted:

1. Choose semantic name following existing patterns
2. Write CSS class using @apply
3. Include dark mode variants
4. Add documentation comment

Example extraction:

Before (in markup):

<button class="bg-indigo-500 hover:bg-indigo-700 px-6 py-3 rounded-lg text-white transition-all duration-200">
  Click me
</button>

After (in components.css):

/* Primary button - Main call-to-action button with hover states
   Usage: <button className="button-primary">Click me</button> */
.button-primary {
  @apply bg-indigo-500 hover:bg-indigo-700 dark:bg-indigo-600 dark:hover:bg-indigo-800;
  @apply px-6 py-3 rounded-lg text-white;
  @apply transition-all duration-200;
}

Use Edit tool to add each new class to components.css

Mark as completed when all semantic classes are created.

---

Step 5: Include Dark Mode

Action: Ensure all new/refactored classes have dark: variants

For each class created in Step 4:

• Add dark: variants for backgrounds
• Add dark: variants for text colors
• Add dark: variants for borders
• Test in dark mode (if possible)

Pattern:

.component {
  @apply bg-white dark:bg-gray-800;
  @apply text-gray-900 dark:text-white;
  @apply border-gray-200 dark:border-gray-700;
}

Mark as completed when dark mode coverage is added.

---

Step 6: Update Markup

Action: Replace inline styles and utility classes with semantic class names

For each file using the old pattern:

1. Read the file with Read tool
2. Use Edit tool to replace old pattern with semantic class
3. Verify the replacement is correct

Example:

Before:

<button class="bg-indigo-500 hover:bg-indigo-700 px-6 py-3 rounded-lg text-white">
  Click me
</button>

After:

<button class="button-primary">
  Click me
</button>

Handle custom classes:

<!-- If there were additional custom classes, preserve them -->
<button class="button-primary w-full mt-4">
  Click me
</button>

Track changes:

• Count files updated
• Count instances replaced
• Note any edge cases

Mark as completed when all markup is updated.

---

Step 7: Add Tests

Action: Add test coverage for refactored components

Static CSS test in styles/__tests__/components.test.ts:

it('should have button-primary class', () => {
  const content = readFileSync('styles/components.css', 'utf-8');
  expect(content).toContain('.button-primary');
});

it('should have dark mode variants in button-primary', () => {
  const content = readFileSync('styles/components.css', 'utf-8');
  expect(content).toContain('dark:bg-indigo');
});

Component rendering test (if applicable):

it('applies button-primary class after refactor', () => {
  render(<Button variant="primary">Click</Button>);
  expect(screen.getByRole('button')).toHaveClass('button-primary');
});

Run tests to ensure they pass:

npm test

Mark as completed when tests are added and passing.

---

Step 8: Document Components

Action: Ensure all refactored classes have documentation

Documentation includes:

• Comment in CSS explaining purpose
• Usage example
• Migration notes (if helpful)

Example:

/* Primary button - Main CTA button (refactored from inline utilities)
   Usage: <button className="button-primary">Click me</button>
   Replaces: bg-indigo-500 hover:bg-indigo-700 px-6 py-3 rounded-lg text-white */
.button-primary {
  @apply bg-indigo-500 hover:bg-indigo-700 dark:bg-indigo-600 dark:hover:bg-indigo-800;
  @apply px-6 py-3 rounded-lg text-white;
  @apply transition-all duration-200;
}

Mark as completed when documentation is added.

---

Step 9: Verify Behavior Unchanged

Action: Ensure visual output and behavior match the original

Verification steps:

1. Run tests (if project has them):

   npm test
   

2. Visual inspection (if possible):

   • Start dev server
   • Check refactored components look the same
   • Test in light and dark mode
   • Test interactive states (hover, focus, active)

3. Check for regressions:

   • Compare before/after screenshots (if available)
   • Verify no console errors
   • Check responsive behavior

If behavior changed:

• Identify the difference
• Fix the semantic class to match original behavior
• Re-test

Behavior must be preserved - refactoring should be visually neutral

Mark as completed when behavior is verified unchanged.

---

Completion

When all checklist items are completed:

1. Generate summary of refactoring work:

## CSS Refactoring Summary

### Changes Made

**Semantic classes created:**
- `.button-primary` (extracted from 8 instances across 5 files)
- `.card` (extracted from 12 instances across 7 files)
- `.badge-success` (extracted from 4 instances across 3 files)

**Files modified:**
- `styles/components.css` (+45 lines, 3 new classes)
- `components/Button.tsx` (replaced utilities with .button-primary)
- `components/Card.tsx` (replaced utilities with .card)
- `components/Badge.tsx` (replaced utilities with .badge-success)
- `styles/__tests__/components.test.ts` (+12 lines, 3 new tests)

**Dark mode support:**
- ✅ All refactored classes include dark: variants
- ✅ Tested in both light and dark mode

**Test coverage:**
- ✅ Static CSS tests added for all new classes
- ✅ Component rendering tests updated
- ✅ All tests passing

**Behavior verification:**
- ✅ Visual output matches original
- ✅ No console errors
- ✅ Interactive states work correctly

### Impact

**Code reduction:**
- Removed 247 lines of repeated utility classes from markup
- Added 45 lines of semantic CSS
- Net reduction: 202 lines

**Maintainability:**
- Styling centralized in components.css
- Changes now made in one place instead of many
- Consistent component appearance

**Dark mode:**
- Added dark mode support that didn't exist before
- All components now work in light and dark themes

2. Suggest next steps:

   • Commit the refactoring
   • Document the new patterns for the team
   • Continue refactoring other components

3. Offer validation: "Would you like me to validate the refactored CSS using the css-development:validate skill?"

Mark as completed when summary is presented.