# ESLint Setup for Unused Code Detection

## ✅ Successfully Configured

ESLint has been added to your project with specialized rules for detecting and auto-fixing unused imports and variables.

## 📦 Installed Packages

```json
"devDependencies": {
  "eslint": "latest",
  "@typescript-eslint/parser": "latest",
  "@typescript-eslint/eslint-plugin": "latest",
  "eslint-plugin-unused-imports": "latest",
  "eslint-plugin-react": "latest",
  "eslint-plugin-react-hooks": "latest",
  "eslint-config-expo": "latest"
}
```

## 🎯 Key Features

### 1. **Automatic Unused Import Removal**
- Detects and removes unused imports automatically with `--fix` flag
- Already cleaned up imports in 50+ files on first run

### 2. **Unused Variable Detection**
- Warns about unused variables and function parameters
- Ignores variables/parameters prefixed with underscore (e.g., `_unused`)
- Respects destructuring patterns and rest operators

### 3. **React-Specific Rules**
- Ensures React hooks are called correctly
- Validates JSX variable usage
- Checks for exhaustive dependencies in hooks

## 📝 Available NPM Scripts

```bash
# Check for linting issues
npm run lint

# Auto-fix all fixable issues (including unused imports)
npm run lint:fix

# Specifically check for unused code
npm run lint:unused

# Format and fix everything
npm run format
```

## 🔧 Configuration

The ESLint configuration (`eslint.config.js`) includes:

- **TypeScript support** with proper type checking
- **React/React Native** optimizations
- **Unused imports** auto-removal
- **Unused variables** detection with smart patterns
- **Proper ignores** for build directories and generated files

## 📊 Initial Cleanup Results

On the first run, ESLint automatically:
- ✅ Removed unused imports from **50+ files**
- ✅ Fixed import duplications in several files
- ✅ Cleaned up commented-out imports
- ✅ Identified variables that can be removed

### Files with Most Cleanup:
1. `app/(protected)/(memo)/[id].tsx` - 32 lines simplified
2. `app/(protected)/(tabs)/index.tsx` - 15 lines cleaned
3. `app/(protected)/(tabs)/memos.tsx` - 15 lines cleaned

## 🚀 Usage Examples

### Check specific file for unused code:
```bash
npx eslint app/_layout.tsx
```

### Auto-fix a specific directory:
```bash
npx eslint features/ --fix
```

### Check entire project (quiet mode, only errors):
```bash
npx eslint . --quiet
```

## ⚠️ Common Warnings to Expect

1. **`_unused` parameters**: Intentionally unused (follows convention)
2. **Hook dependencies**: May need manual review
3. **Console statements**: Warnings for non-error/warn/debug console use
4. **Type imports**: Some type-only imports are necessary for TypeScript

## 🎯 Best Practices

1. **Run before commits**: `npm run lint:fix` before committing
2. **Regular cleanup**: Run monthly to prevent accumulation
3. **CI Integration**: Consider adding to CI/CD pipeline
4. **Pre-commit hook**: Can be added with husky for automatic checking

## 📈 Impact

- **Reduced bundle size**: Removing unused imports helps tree-shaking
- **Cleaner codebase**: Less cognitive overhead from unused code
- **Better maintainability**: Easier to understand actual dependencies
- **Faster builds**: Less code to process and compile

---

**Note**: The configuration is conservative by default. Adjust rules in `eslint.config.js` as needed for your team's preferences.