React MFE Shell

A production-ready micro frontend shell with comprehensive design system, form molecules, and accessibility-first components.

Integration Options

Choose the integration method that best fits your project:

Option 1: Zero-Config (Recommended for quick start)

npm install @jonmatum/react-mfe-shell

import { 
  SettingsProvider, 
  Button, 
  FormField, 
  Input 
} from '@jonmatum/react-mfe-shell';
import '@jonmatum/react-mfe-shell/standalone';

function App() {
  return (
    <SettingsProvider>
      <FormField label="Email" required>
        <Input type="email" placeholder="Enter email" />
      </FormField>
      <Button variant="primary">Submit</Button>
    </SettingsProvider>
  );
}

Option 2: Tailwind Integration (Recommended for Tailwind users)

npm install @jonmatum/react-mfe-shell
npm install -D tailwindcss

// tailwind.config.js
const { mfeShellPreset } = require('@jonmatum/react-mfe-shell/preset');

module.exports = {
  presets: [mfeShellPreset],
  content: [
    './src/**/*.{js,ts,jsx,tsx}',
    './node_modules/@jonmatum/react-mfe-shell/dist/**/*.js'
  ]
}

import { 
  SettingsProvider, 
  Button, 
  FormField, 
  Input 
} from '@jonmatum/react-mfe-shell';
import '@jonmatum/react-mfe-shell/styles';

function App() {
  return (
    <SettingsProvider>
      <div className="p-4 space-y-4">
        <FormField label="Email" required>
          <Input type="email" placeholder="Enter email" className="border-2" />
        </FormField>
        <Button variant="primary" className="w-full">Submit</Button>
      </div>
    </SettingsProvider>
  );
}

What's Included

Atomic Components (14)

• Avatar: User avatars with fallbacks
• Badge: Status indicators with removable option
• Button: All variants, sizes, states, and icons
• Code: Inline and block code formatting
• Divider: Section separators (horizontal/vertical)
• FeatureChip: Feature indicators and tags
• Heading: Semantic headings with typography scale
• Icon: Heroicons integration with size variants
• Input: Text inputs with validation and icons
• Label: Form labels with accessibility features
• LoadingSpinner: Loading states in multiple sizes
• Paragraph: Text blocks with spacing control
• Switch: Toggle controls with theme integration
• Text: Typography with semantic variants

Molecular Components (10)

• Card: Content containers with consistent styling
• Checkbox: Accessible checkboxes with indeterminate state
• FileUpload: Drag-and-drop with preview and validation
• FormField: Universal wrapper with label/error handling
• Modal: Accessible overlays with focus management
• Radio: RadioGroup with full accessibility
• SearchBox: Debounced search with clear functionality
• Select: Dropdown with search and multi-select
• SwitchField: Enhanced switch with form integration
• Textarea: Auto-resizing text areas

Design System

• 666 Tests: 100% passing with 75%+ coverage
• WCAG AA Compliant: Full accessibility support
• Theme System: Light/dark/system modes with persistence
• Design Tokens: Consistent colors, spacing, typography
• TypeScript: Complete type safety and IntelliSense

Key Features

• Zero Configuration: Works out of the box
• Tree Shakeable: Import only what you need
• Responsive: Mobile-first design approach
• Accessible: WCAG AA compliance built-in
• Themeable: Light/dark mode with custom brand colors and design tokens
• Form Ready: Complete form ecosystem with validation
• Production Ready: Used in real applications
• Flexible Integration: Multiple integration paths (zero-config, Tailwind preset, CSS-in-JS)

Usage Examples

Basic Form

import { FormField, Input, Button, Checkbox } from '@jonmatum/react-mfe-shell';

function ContactForm() {
  const [email, setEmail] = useState('');
  const [subscribe, setSubscribe] = useState(false);

  return (
    <form>
      <FormField 
        label="Email Address" 
        description="We'll never share your email"
        required
      >
        <Input
          type="email"
          value={email}
          onChange={(e) => setEmail(e.target.value)}
          placeholder="[email protected]"
        />
      </FormField>
      
      <Checkbox
        checked={subscribe}
        onChange={setSubscribe}
        label="Subscribe to newsletter"
      />
      
      <Button type="submit" variant="primary">
        Submit
      </Button>
    </form>
  );
}

Advanced Select with Search

import { FormField, Select } from '@jonmatum/react-mfe-shell';

const countries = [
  { value: 'us', label: 'United States' },
  { value: 'ca', label: 'Canada' },
  { value: 'uk', label: 'United Kingdom' }
];

function CountrySelector() {
  const [country, setCountry] = useState('');

  return (
    <FormField label="Country" required>
      <Select
        value={country}
        onChange={setCountry}
        options={countries}
        searchable
        placeholder="Choose a country..."
      />
    </FormField>
  );
}

Theme Management

import { SettingsProvider, useSettings, Button } from '@jonmatum/react-mfe-shell';

function ThemeToggle() {
  const { settings, updateSettings } = useSettings();
  
  return (
    <Button
      variant="ghost"
      onClick={() => updateSettings({ 
        theme: settings.theme === 'dark' ? 'light' : 'dark' 
      })}
    >
      Toggle Theme
    </Button>
  );
}

// Wrap your app
function App() {
  return (
    <SettingsProvider>
      <ThemeToggle />
    </SettingsProvider>
  );
}

Custom Brand Colors

// tailwind.config.js - Use your own brand colors
const { mfeShellPreset } = require('@jonmatum/react-mfe-shell/preset');

module.exports = {
  presets: [mfeShellPreset],
  content: [
    './src/**/*.{js,ts,jsx,tsx}',
    './node_modules/@jonmatum/react-mfe-shell/dist/**/*.js'
  ],
  theme: {
    extend: {
      colors: {
        // Your brand colors
        brand: {
          500: '#3b82f6', // Your primary brand color
          600: '#2563eb',
        },
        // Override our primary colors
        primary: {
          500: '#3b82f6', // Components use your brand color
          600: '#2563eb',
        }
      }
    }
  }
}

// Components automatically use your custom colors
<Button variant="primary">Uses your brand color</Button>
<Badge variant="primary">Matches your theme</Badge>

API Reference

Component Props Patterns

All components follow consistent prop patterns:

// Size variants
size?: 'xs' | 'sm' | 'md' | 'lg' | 'xl'

// Color variants  
variant?: 'primary' | 'secondary' | 'success' | 'warning' | 'danger' | 'ghost'

// States
disabled?: boolean
loading?: boolean
required?: boolean

// Form components
label?: string
description?: string
error?: string

Form Validation

import { validateField, validationPatterns } from '@jonmatum/react-mfe-shell';

// Built-in validation
const error = validateField(email, {
  required: true,
  pattern: validationPatterns.email
});

// Custom validation
const error = validateField(password, {
  required: 'Password is required',
  minLength: { value: 8, message: 'Must be at least 8 characters' },
  custom: (value) => value.includes('@') ? 'Cannot contain @' : undefined
});

Styling & Customization

The library uses Tailwind CSS with CSS custom properties for theming:

:root {
  --color-primary-600: 37 99 235;
  --color-success-600: 22 163 74;
  --color-warning-600: 217 119 6;
  --color-danger-600: 220 38 38;
}

.dark {
  --color-primary-600: 59 130 246;
  /* Dark theme overrides */
}

Automated Metrics System

The demo app uses an automated metrics generation system to ensure all displayed statistics are accurate and up-to-date.

Metrics Generation

# Generate fresh metrics from current build
npm run generate:metrics

# Build library and generate metrics in one command
npm run build:with-metrics

What Gets Measured

Bundle Sizes:

• ESM and CJS bundle sizes (raw and gzipped)
• CSS bundle sizes (main and standalone)
• TypeScript definition file sizes

Test Metrics:

• Total test count and test files
• Test coverage percentage
• Pass rate statistics

Code Quality:

• DRY score from design system analysis
• Component analysis results
• Code complexity metrics

Architecture:

• Total files and lines of code
• Component count and structure
• Utility function usage

Automatic Updates

Metrics are automatically updated:

• After every npm run build:lib (via post-build hook)
• In CI/CD pipeline (validates metrics are current)
• When running npm run generate:metrics manually

Files Generated

• demo/utils/metrics.ts - TypeScript metrics for demo app
• metrics.json - JSON metrics for external tools
• Auto-updates demo components with live data

This ensures the demo always shows real, verifiable metrics without manual maintenance.

Bundle Size

• Core Library: ~152KB (29.5KB gzipped)
• Standalone CSS: ~12.2KB (2.8KB gzipped)
• Tailwind CSS: ~48.8KB (8.4KB gzipped)
• Tailwind Preset: ~4.1KB
• TypeScript Definitions: ~81.4KB
• Tree Shakeable: Import only what you use
• Zero Dependencies: No external runtime dependencies
• Modern Build: ESM and CJS formats included

Documentation

Getting Started

• Integration Guide: Complete setup instructions for all integration methods
• Hybrid Approach: Technical details about our multi-path integration system

Component Documentation

• Component Library: Complete component API reference
• Theming Guide: Customization and theme management
• Form Components: Form-specific components and patterns

Migration and Troubleshooting

• Migration Guide: Upgrading from previous versions
• Troubleshooting: Common issues and solutions

Links

• Live Demo: Interactive component showcase
• NPM Package: Install and version info
• GitHub: Source code and issues

License

MIT License - see LICENSE for details.

---

Built with care for scalable React applications

### Using in Your MFE

**[View on npm](https://www.npmjs.com/package/@jonmatum/react-mfe-shell)**

```bash
npm install @jonmatum/react-mfe-shell

import React from 'react';
import { 
  SettingsProvider, 
  Button, 
  Input, 
  Badge,
  useSettings 
} from '@jonmatum/react-mfe-shell';

function App() {
  return (
    <SettingsProvider>
      <MyMicroFrontend />
    </SettingsProvider>
  );
}

function MyMicroFrontend() {
  const { settings, updateSettings } = useSettings();
  
  return (
    <div className="p-4 space-y-4">
      <Button 
        variant="primary"
        onClick={() => updateSettings({ 
          theme: settings.theme === 'light' ? 'dark' : 'light' 
        })}
      >
        Toggle Theme
      </Button>
      
      <Input 
        label="Email"
        type="email"
        placeholder="Enter your email"
      />
      
      <Badge variant="success">
        Active
      </Badge>
    </div>
  );
}

Component Library

Atoms (Basic Building Blocks)

• Button: Multiple variants, sizes, loading states, and icon support
• Input: Form inputs with validation, icons, and accessibility features
• Badge: Status indicators with variants and removable functionality
• LoadingSpinner: Animated loading indicators with customizable appearance
• Switch: Toggle switches with proper form integration

Molecules (Component Combinations)

• Modal: Accessible dialogs with backdrop, keyboard navigation, and focus management
• Card: Layout containers with compound patterns (Header, Body, Footer)

Contexts & Providers

• SettingsProvider: Global state management for theme and layout preferences

Design System

Design Tokens

Complete design token system with:

• Colors: Base colors, semantic colors, and theme-aware color system
• Typography: Font families, sizes, weights, and letter spacing
• Spacing: Consistent spacing scale from 0px to 24rem
• Shadows: Box and drop shadows for elevation
• Border Radius: Consistent corner rounding
• Breakpoints: Mobile-first responsive design
• Animation: Duration and timing functions
• Z-Index: Layering hierarchy

import { tokens } from '@jonmatum/react-mfe-shell';

// Access design tokens
const primaryColor = tokens.colors.semantic.primary[500];
const baseSpacing = tokens.spacing[4];
const mediumShadow = tokens.shadows.box.md;

Theme System

Comprehensive theme management with:

import { setupThemeManagement } from '@jonmatum/react-mfe-shell';

// Set up theme management
const { setTheme, cleanup } = setupThemeManagement((mode, resolvedTheme) => {
  console.log(`Theme changed to ${mode} (resolved: ${resolvedTheme})`);
});

// Change themes
setTheme('dark');    // Dark mode
setTheme('light');   // Light mode
setTheme('system');  // Follow system preference

Available themes:

• light: Light theme with high contrast
• dark: Dark theme optimized for low light
• system: Automatically follows system preference with real-time updates

Features:

• Persistent theme preferences (localStorage)
• Real-time system theme detection
• CSS custom properties for theme-aware styling
• Automatic DOM class management
• TypeScript support with theme validation

Development

Available Scripts

# Development
npm run dev              # Start development server
npm run dev:demo         # Start demo only
npm run build           # Build library for production
npm run build:lib       # Build library only
npm run build:demo      # Build demo only

# Quality Assurance
npm run test            # Run tests in watch mode
npm run test:run        # Run tests once
npm run test:coverage   # Run tests with coverage report
npm run lint            # Run ESLint
npm run lint:fix        # Fix ESLint issues
npm run type-check      # TypeScript type checking

# Formatting
npm run format          # Format with Prettier
npm run format:check    # Check formatting

Code Quality Standards

• Test Coverage: 90%+ across statements, branches, functions, and lines
• Type Safety: Strict TypeScript with comprehensive type definitions
• Accessibility: WCAG AA compliance with proper ARIA attributes
• Performance: Optimized bundle sizes and runtime performance
• Code Analysis: Automated complexity and quality metrics

Adding New Components

Follow atomic design principles:

1. Create the component in the appropriate directory:

   src/components/
   ├── atoms/           # Basic building blocks
   ├── molecules/       # Simple combinations
   └── organisms/       # Complex combinations
   

2. Add comprehensive tests with 90%+ coverage

3. Export the component in src/index.ts

4. Update documentation and add to demo

Example component structure:

// src/components/atoms/NewComponent.tsx
import React from 'react';
import { BaseComponentProps } from '../../types';
import { classNames } from '../../utils';

interface NewComponentProps extends BaseComponentProps {
  variant?: 'default' | 'primary' | 'secondary';
  size?: 'sm' | 'md' | 'lg';
}

const NewComponent = React.memo<NewComponentProps>(({ 
  variant = 'default',
  size = 'md',
  className,
  children,
  ...props 
}) => {
  return (
    <div
      className={classNames(
        'base-styles',
        {
          'size-sm': size === 'sm',
          'size-md': size === 'md',
          'size-lg': size === 'lg',
        },
        {
          'variant-default': variant === 'default',
          'variant-primary': variant === 'primary',
          'variant-secondary': variant === 'secondary',
        },
        className
      )}
      {...props}
    >
      {children}
    </div>
  );
});

NewComponent.displayName = 'NewComponent';

export default NewComponent;

Testing

Using Vitest with comprehensive testing requirements:

// Example test structure
describe('Component', () => {
  it('renders correctly', () => {
    render(<Component>Test</Component>);
    expect(screen.getByText('Test')).toBeInTheDocument();
  });

  it('applies variants correctly', () => {
    render(<Component variant="primary">Primary</Component>);
    expect(screen.getByText('Primary')).toHaveClass('variant-primary');
  });

  it('handles interactions', () => {
    const handleClick = vi.fn();
    render(<Component onClick={handleClick}>Click</Component>);
    
    fireEvent.click(screen.getByText('Click'));
    expect(handleClick).toHaveBeenCalled();
  });

  it('supports accessibility', () => {
    render(<Component aria-label="Test component">Content</Component>);
    expect(screen.getByLabelText('Test component')).toBeInTheDocument();
  });
});

Building and Distribution

Library Build

npm run build:lib

Creates optimized builds:

• ESM: dist/index.js (modern bundlers)
• CJS: dist/index.cjs (Node.js compatibility)
• Types: dist/index.d.ts (TypeScript definitions)
• Styles: dist/style.css (CSS bundle)

Bundle Analysis

Current bundle sizes:

• ESM: ~152KB (gzipped: ~29.5KB)
• CJS: ~161.5KB (gzipped: ~30.2KB)
• Tailwind CSS: ~48.8KB (gzipped: ~8.4KB)
• Standalone CSS: ~12.2KB (gzipped: ~2.8KB)
• TypeScript Definitions: ~81.4KB

Micro Frontend Integration

Installation in MFE Apps

npm install @jonmatum/react-mfe-shell

Integration Patterns

// Complete integration example
import React from 'react';
import { 
  SettingsProvider, 
  Button, 
  Modal, 
  Card,
  tokens,
  useSettings 
} from '@jonmatum/react-mfe-shell';

function MicroFrontendApp() {
  return (
    <SettingsProvider>
      <div className="min-h-screen bg-background-primary">
        <Header />
        <MainContent />
        <Footer />
      </div>
    </SettingsProvider>
  );
}

function Header() {
  const { settings, updateSettings } = useSettings();
  
  return (
    <header className="bg-surface-primary border-b border-border-primary p-4">
      <div className="flex items-center justify-between">
        <h1 className="text-text-primary font-semibold">My MFE App</h1>
        <Button
          variant="ghost"
          onClick={() => updateSettings({ 
            theme: settings.theme === 'light' ? 'dark' : 'light' 
          })}
        >
          Toggle Theme
        </Button>
      </div>
    </header>
  );
}

Configuration

Tailwind CSS Integration

The design tokens are automatically integrated with Tailwind CSS:

// Use theme-aware classes
<div className="bg-surface-primary text-text-primary border border-border-primary">
  Content adapts to theme automatically
</div>

// Use design token utilities
<div className="p-4 rounded-md shadow-md">
  Consistent spacing and styling
</div>

Custom Configuration

// tailwind.config.js
const { mfeShellPreset } = require('@jonmatum/react-mfe-shell/preset');

export default {
  presets: [mfeShellPreset],
  content: [
    './src/**/*.{js,ts,jsx,tsx}',
    './node_modules/@jonmatum/react-mfe-shell/dist/**/*.js'
  ],
  theme: {
    extend: {
      // Your custom overrides here
    },
  },
};

Documentation

• Design Tokens: Comprehensive design token documentation
• Implementation Guide: Detailed implementation instructions
• API Reference: Complete API documentation

Contributing

We welcome contributions! Please see CONTRIBUTING.md for guidelines.

Development Workflow

1. Fork the repository
2. Create a feature branch: git checkout -b feature/amazing-feature
3. Make your changes with tests
4. Run quality checks: npm run test:run && npm run lint && npm run type-check
5. Commit using conventional commits: git commit -m "feat: add amazing feature"
6. Push and create a pull request

License

MIT License - see LICENSE for details.

---

Built with care for the micro frontend community

Pura Vida & Happy Coding!