Next.js Development Rules for Cross-Platform Compatibility

These rules capture the key development patterns from the Web to Mobile Development Primer, focusing specifically on building the initial Next.js application in a way that facilitates future conversion to React Native.

Tech Stack

Next.js with App Router: Core framework for routing, server components, and API routes.
TypeScript: For type-safe code.
Prisma with SQLite: The ORM and database for data persistence.
TailwindCSS: For utility-first styling.
React Hooks (useState, useEffect, useContext): Used for all client-side state management, including component state, context-based global state, data fetching, and form handling.

Project Structure

Follow the
```
/src
```
directory structure with dedicated folders for components, hooks, services, utils, constants, context, types, and styles
Separate UI components (
```
/components/ui
```
) from feature components (
```
/components/features
```
)
Keep component files, styles, types, and documentation together in the same folder
Include README.md files for components documenting props, usage, and implementation details
Maintain a consistent naming convention across all files and components

Component Architecture

Create "dumb" UI components that are highly configurable through props
Implement container/presentational pattern to separate data fetching from UI rendering
Keep components small and focused (under 200 lines of code)
Use composition over inheritance when building complex components
Include props for error and loading states in all data-dependent components
Design with accessibility in mind from the start (proper ARIA attributes)
Document component APIs thoroughly in component README files

TypeScript Implementation

Enable strict TypeScript mode in
```
tsconfig.json
```
Create shared types in the
```
/types
```
directory for domain entities
Use discriminated unions for different event types (e.g., feeding vs. diaper events)
Implement type guards for safe type narrowing
Define constants with type safety using
```
as const
```
assertions
Create specific error types that extend the base Error class
Use TypeScript generics for reusable components and functions
Define readonly properties for immutable data

State Management

Implement custom hooks for complex state logic
Create context providers for global state that needs to be accessed by multiple components
Use React Query for data fetching with proper type definitions
Follow immutable update patterns in all state modifications
Implement memoization for expensive computations with useMemo
Include proper error and loading states in all async operations
Design state management with offline-first principles in mind

Styling Approach

Define a shared design system with consistent variables for colors, spacing, typography, etc.
Use CSS Modules or Styled Components for component styling
Keep styles modular and component-specific
Implement responsive design using media queries
Export theme as TypeScript constants
Support both light and dark modes through a theme context
Create helper functions for complex style logic

Use Next.js's file-system based routing
Define strongly typed route parameters with TypeScript interfaces
Create navigation utilities that consolidate route definitions
Implement type-safe navigation helpers
Create guards for protected routes in middleware
Design consistent route structure that will mirror future mobile routes
Make routes accessible and SEO-friendly

API and Data Fetching

Create a type-safe fetch wrapper with proper error handling
Implement domain-specific API services that use the core API layer
Use React Query for data fetching with consistent query key patterns
Implement error handling that provides clear user feedback
Define optimistic updates for better UX
Structure API responses with consistent types
Design with offline capabilities in mind for future mobile support

Form Handling

Use React Hook Form for form state management and validation
Create reusable validation rules
Implement consistent error message styling
Create type-safe form components
Consider implementing a form builder pattern for complex forms
Handle form submission with loading and error states
Make forms accessible with proper labels and ARIA attributes

Testing

Write tests for all components, custom hooks, and services
Test error and loading states
Verify accessibility features
Test responsive layouts
Implement integration tests for complex features

Mobile Considerations

Avoid web-specific APIs that won't exist in React Native
Design UI with touch interaction in mind (larger touch targets)
Consider offline capabilities from the start
Plan for cross-platform navigation patterns
Document any web-specific behavior that will need adaptation for mobile

Code Modification Guidelines

Challenge yourself to write as few lines of code as possible
When changing existing code, preserve all formatting and styling unless explicitly asked to modify it
Make only the changes that have been discussed and approved
Maintain all existing functionality when making modifications
Ask questions about any ambiguous requirements before implementing changes
Perform due diligence to ensure accuracy and minimize rewrites

Next.js Development Rules for Cross-Platform Compatibility

Tech Stack

Next.js with App Router: Core framework for routing, server components, and API routes.
TypeScript: For type-safe code.
Prisma with SQLite: The ORM and database for data persistence.
TailwindCSS: For utility-first styling.
React Hooks (useState, useEffect, useContext): Used for all client-side state management, including component state, context-based global state, data fetching, and form handling.

Project Structure

Follow the
```
/src
```
directory structure with dedicated folders for components, hooks, services, utils, constants, context, types, and styles
Separate UI components (
```
/components/ui
```
) from feature components (
```
/components/features
```
)
Keep component files, styles, types, and documentation together in the same folder
Include README.md files for components documenting props, usage, and implementation details
Maintain a consistent naming convention across all files and components

Component Architecture

Create "dumb" UI components that are highly configurable through props
Implement container/presentational pattern to separate data fetching from UI rendering
Keep components small and focused (under 200 lines of code)
Use composition over inheritance when building complex components
Include props for error and loading states in all data-dependent components
Design with accessibility in mind from the start (proper ARIA attributes)
Document component APIs thoroughly in component README files

TypeScript Implementation

Enable strict TypeScript mode in
```
tsconfig.json
```
Create shared types in the
```
/types
```
directory for domain entities
Use discriminated unions for different event types (e.g., feeding vs. diaper events)
Implement type guards for safe type narrowing
Define constants with type safety using
```
as const
```
assertions
Create specific error types that extend the base Error class
Use TypeScript generics for reusable components and functions
Define readonly properties for immutable data

State Management

Implement custom hooks for complex state logic
Create context providers for global state that needs to be accessed by multiple components
Use React Query for data fetching with proper type definitions
Follow immutable update patterns in all state modifications
Implement memoization for expensive computations with useMemo
Include proper error and loading states in all async operations
Design state management with offline-first principles in mind

Styling Approach

Define a shared design system with consistent variables for colors, spacing, typography, etc.
Use CSS Modules or Styled Components for component styling
Keep styles modular and component-specific
Implement responsive design using media queries
Export theme as TypeScript constants
Support both light and dark modes through a theme context
Create helper functions for complex style logic

Use Next.js's file-system based routing
Define strongly typed route parameters with TypeScript interfaces
Create navigation utilities that consolidate route definitions
Implement type-safe navigation helpers
Create guards for protected routes in middleware
Design consistent route structure that will mirror future mobile routes
Make routes accessible and SEO-friendly

API and Data Fetching

Create a type-safe fetch wrapper with proper error handling
Implement domain-specific API services that use the core API layer
Use React Query for data fetching with consistent query key patterns
Implement error handling that provides clear user feedback
Define optimistic updates for better UX
Structure API responses with consistent types
Design with offline capabilities in mind for future mobile support

Form Handling

Use React Hook Form for form state management and validation
Create reusable validation rules
Implement consistent error message styling
Create type-safe form components
Consider implementing a form builder pattern for complex forms
Handle form submission with loading and error states
Make forms accessible with proper labels and ARIA attributes

Testing

Write tests for all components, custom hooks, and services
Test error and loading states
Verify accessibility features
Test responsive layouts
Implement integration tests for complex features

Mobile Considerations

Avoid web-specific APIs that won't exist in React Native
Design UI with touch interaction in mind (larger touch targets)
Consider offline capabilities from the start
Plan for cross-platform navigation patterns
Document any web-specific behavior that will need adaptation for mobile

Code Modification Guidelines

Challenge yourself to write as few lines of code as possible
When changing existing code, preserve all formatting and styling unless explicitly asked to modify it
Make only the changes that have been discussed and approved
Maintain all existing functionality when making modifications
Ask questions about any ambiguous requirements before implementing changes
Perform due diligence to ensure accuracy and minimize rewrites

Next.js Development Rules for Cross-Platform Compatibility

Next.js Development Rules for Cross-Platform Compatibility

Tech Stack

Project Structure

Component Architecture

TypeScript Implementation

State Management

Styling Approach

Navigation

API and Data Fetching

Form Handling

Testing

Mobile Considerations

Code Modification Guidelines

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Next.js Development Rules for Cross-Platform Compatibility

Tech Stack

Project Structure

Component Architecture

TypeScript Implementation

State Management

Styling Approach

Navigation

API and Data Fetching

Form Handling

Testing

Mobile Considerations

Code Modification Guidelines