Implementation Patterns

This section provides a catalog of implementation patterns used throughout the ReX content system. These patterns offer practical, reusable solutions to common implementation challenges and promote consistency across the codebase.

Pattern Categories

The patterns are organized into the following categories:

Adapter Patterns

Adapter patterns focus on the implementation of storage adapters, which provide the bridge between the content system and various storage backends:

• Environment-specific adapter patterns - Implementing adapters for Node.js, browser, and service worker environments
• Capability detection patterns - Determining available features and gracefully handling their absence
• Error normalization patterns - Translating storage-specific errors into standard content errors
• URI mapping patterns - Converting between content URIs and storage-specific paths

Middleware Patterns

Middleware patterns address the implementation of enhancement layers that add cross-cutting functionality:

• Middleware composition patterns - Creating chains of middleware functions
• Context propagation patterns - Passing metadata and state through middleware chains
• Conditional middleware patterns - Applying middleware based on runtime conditions
• Performance optimization patterns - Improving middleware performance through caching and batching

Error Handling Patterns

Error handling patterns provide consistent approaches to handling and propagating errors:

• Error class hierarchy patterns - Designing error type relationships
• Error enrichment patterns - Adding context and recovery information to errors
• Error translation patterns - Converting between error domains
• Recovery strategy patterns - Implementing graceful recovery from errors

Capability Detection Patterns

Capability detection patterns focus on runtime feature detection and adaptation:

• Feature detection patterns - Identifying available platform features
• Progressive enhancement patterns - Adding functionality when optional features are available
• Graceful degradation patterns - Maintaining core functionality when features are unavailable
• Capability advertising patterns - Communicating available features to consumers

Testing Patterns

Testing patterns provide approaches for effectively testing different system components:

• Unit testing patterns - Testing individual components in isolation
• Integration testing patterns - Testing component interactions
• Mock implementation patterns - Creating effective test doubles
• Environment simulation patterns - Testing environment-specific behavior

Benefits of Following Patterns

Adopting these implementation patterns provides several benefits:

1. Consistency - Similar problems are solved in similar ways throughout the codebase
2. Maintainability - Pattern-based code is more predictable and easier to understand
3. Reliability - Well-established patterns have known behavior and edge cases
4. Efficiency - Developers can apply proven solutions instead of reinventing approaches

Using This Documentation

Each pattern document follows a consistent structure:

1. Pattern Overview - A high-level description of the pattern and its purpose
2. Implementation Examples - Concrete code examples showing the pattern in use
3. Variations - Common variations of the pattern for different scenarios
4. Considerations - Important factors to consider when applying the pattern
5. Related Patterns - Other patterns that complement or provide alternatives

When to Create New Patterns

While the existing patterns cover many common scenarios, new patterns may be needed when:

1. Encountering a recurring implementation challenge not addressed by existing patterns
2. Identifying opportunities to improve consistency across similar implementations
3. Developing solutions for new platform capabilities or architectural requirements

New patterns should be documented and reviewed before widespread adoption to ensure they align with the system’s architectural principles.