qapinterface/lib/summary.md

Comprehensive API utilities for Node.js applications including authentication, security, request processing, and response handling with zero external dependencies

# Library Folder

This folder contains the core API utility modules organized by responsibility area.

## Purpose
- Houses enterprise-grade API utility functions
- Provides lightweight, production-ready modules
- Implements security-first design patterns
- Offers comprehensive testing coverage

## Module Organization

### Core Utilities (`/core`, `/utility`, `/data`)
- `validation/`: Email validation, API path validation, request structure validation
- `data/sanitizer.js`: Removes sensitive information from API responses
- `id/generator.js`: Generates unique identifiers for tracking
- `versioning/formatter.js`: Formats API version strings consistently

### HTTP Modules (`/http`)
- `success-response-creator.js`: Creates standardized success responses
- `error-response-creator.js`: Creates standardized error responses
- `json-response-sender.js`: Safely sends JSON responses with error handling
- `response-validator.js`: Validates Fetch API responses with comprehensive error handling
- `api-request.js`: Standardized HTTP methods (GET, POST, PUT, DELETE, PATCH)

### Security Modules (`/security`)
- `csp-*.js`: Content Security Policy headers and nonce generation
- `https-enforcer.js`: HTTPS enforcement middleware
- `*-detector.js`: Threat detection (SQL injection, XSS, path traversal)
- `pattern-analyzer.js`: Advanced security pattern analysis
- `event-logger.js`: Security event logging

### Authentication (`/authentication`)
- `api-key-extractor.js`: Multi-source API key extraction
- `api-key-validator.js`: Format validation and timing-safe comparison
- `api-key-middleware.js`: Express middleware for API key validation

### Request Processing (`/request`)
- `id-generator.js`: Request ID generation with correlation
- `context-extractor.js`: Extracts request metadata and timing
- `structure-validator.js`: Validates request structure and payload limits

### Services (`/services`)
- `async-validator.js`: Async service validation with timeout handling
- `health-checker.js`: Multi-service health monitoring
- `retry-handler.js`: Exponential backoff retry logic

### Logging (`/logging`)
- `console-logger.js`: Lightweight console logging with timestamps
- Source-bound loggers for consistent messaging

### Utilities (`/url`, `/timing`, `/rate-limiting`)
- `url/`: Security-first URL parsing, validation, and construction
- `timing/`: High-precision performance timing utilities  
- `rate-limiting/`: Memory-efficient sliding window rate limiting

## Testing Structure
- Unit tests: `lib/**/__tests__` (co-located with modules)
- Integration tests: `tests/` (top-level directory)
- Test runner: `qtests` framework via `test-runner.js`