680 lines
19 KiB
Markdown
680 lines
19 KiB
Markdown
# Phase 9: Middleware and Serialization
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## Overview
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Phase 9 focuses on implementing the middleware system and serialization strategies. The middleware system provides a way to intercept and modify messages as they flow through the network, enabling features like logging, validation, and transformation. The serialization strategies handle converting messages between in-memory objects and transmissible formats, supporting different encodings for various use cases.
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## Key Components
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### 1. MiddlewareManager Implementation (`src/middleware/middleware-manager.ts`)
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The `MiddlewareManager` class orchestrates the middleware chain. It should:
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- Register and manage middleware components
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- Execute middleware in the correct order
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- Handle middleware failures gracefully
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- Support middleware priority and ordering
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- Enable dynamic middleware configuration
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#### Core Features
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- **Middleware Registration**: Add middleware to the processing chain
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- **Priority-Based Ordering**: Execute middleware in priority order
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- **Direction Handling**: Process both incoming and outgoing messages
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- **Error Management**: Handle middleware exceptions
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- **Chain Execution**: Pass messages through the complete middleware chain
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#### Implementation Requirements
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- Support middleware addition and removal at runtime
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- Implement middleware prioritization
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- Handle conditional middleware execution
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- Provide hooks for middleware monitoring
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- Support middleware chain bypassing for special messages
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#### Edge Cases
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- Handle middleware throwing exceptions
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- Manage circular dependencies between middleware
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- Deal with middleware changing message properties
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- Support middleware timeouts
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- Handle middleware chain interruption
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### 2. Core Middleware Implementations (`src/middleware/core-middleware.ts`)
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Implement a set of core middleware components. These should include:
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- **Logging Middleware**: Record message details
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- **Validation Middleware**: Ensure message correctness
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- **Transformation Middleware**: Modify message structure
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- **Metrics Middleware**: Collect performance data
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- **Throttling Middleware**: Control message flow rates
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#### Core Features
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- **Configurable Behavior**: Each middleware should be customizable
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- **Minimal Overhead**: Efficient processing with low performance impact
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- **Selective Processing**: Apply only to relevant messages
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- **Stateful/Stateless Options**: Support both approaches as needed
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- **Composability**: Ability to combine middleware in useful ways
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#### Implementation Requirements
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- Implement the IMiddleware interface for all components
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- Provide default configurations for common use cases
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- Include clear documentation on middleware effects
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- Support asynchronous processing where appropriate
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- Enable middleware disabling without removal
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#### Edge Cases
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- Handle middleware state restoration after failures
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- Support partial application to message subsets
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- Deal with middleware version compatibility
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- Manage middleware resource consumption
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- Handle middleware deadlocks
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### 3. Middleware Interface (`src/middleware/types.ts`)
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Define a clear interface for middleware components:
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```typescript
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interface IMiddleware {
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// Unique identifier for the middleware
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readonly id: string;
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// Priority determines execution order (lower runs first)
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readonly priority: number;
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// Process an outgoing message before it's sent
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processOutgoing(message: NetworkMessage): Promise<NetworkMessage | null>;
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// Process an incoming message after it's received
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processIncoming(message: NetworkMessage): Promise<NetworkMessage | null>;
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// Determine if this middleware should process the given message
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shouldProcess(message: NetworkMessage): boolean;
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}
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```
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### 4. Serialization Strategies (`src/serialization/`)
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Implement various serialization strategies to convert between in-memory objects and transmissible formats:
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- **JSON Serializer**: Human-readable, widely compatible
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- **Binary Serializer**: Compact, efficient for large data
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- **Protocol Buffers**: Schema-based, versioning support
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- **MessagePack**: Compact binary format with good performance
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#### Core Features
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- **Format Conversion**: Transform between objects and serialized data
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- **Schema Support**: Enforce data structure where appropriate
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- **Versioning**: Handle format evolution gracefully
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- **Optimization**: Balance between size, speed, and compatibility
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- **Type Safety**: Preserve type information where possible
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#### Implementation Requirements
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- Implement the ISerializer interface for all strategies
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- Support both browser and Node.js environments
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- Handle circular references appropriately
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- Provide schema validation where applicable
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- Include performance optimizations
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#### Edge Cases
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- Handle unsupported data types
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- Manage version mismatches
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- Deal with malformed data
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- Support partial deserialization
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- Handle very large messages
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## Middleware System Design
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### Middleware Chain Execution
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The middleware chain should be executed in this sequence:
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1. **Outgoing Messages**:
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- Application generates message
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- Message enters middleware chain
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- Each middleware processes in priority order
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- If any middleware returns null, message is dropped
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- Final processed message is passed to transport layer
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2. **Incoming Messages**:
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- Transport layer receives message
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- Message enters middleware chain
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- Each middleware processes in priority order
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- If any middleware returns null, message is dropped
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- Final processed message is delivered to application
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### Middleware Priority Levels
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Middleware should be organized into standard priority levels:
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1. **Critical (0-99)**: Essential system middleware
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- Security validation
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- Message integrity checks
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- System health filters
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2. **High (100-199)**: Important processing
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- Encryption/decryption
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- Authentication
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- Rate limiting
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3. **Normal (200-299)**: Standard processing
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- Logging
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- Metrics collection
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- Transformations
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4. **Low (300-399)**: Optional enhancements
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- Content enrichment
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- Non-critical validations
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- Debug information
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5. **Background (400+)**: Observability and analysis
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- Performance monitoring
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- Analytics
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- Diagnostic data collection
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### Middleware Configuration
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Middleware should be configurable for flexibility:
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```typescript
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interface MiddlewareConfig {
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// Whether middleware is enabled
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enabled: boolean;
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// Custom middleware options
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options: Record<string, any>;
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// Message filtering criteria
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filters?: {
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types?: string[] | RegExp;
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sources?: string[] | RegExp;
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destinations?: string[] | RegExp;
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properties?: Record<string, any>;
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};
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// Error handling policy
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errorPolicy?: 'continue' | 'stop' | 'retry';
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}
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```
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## Core Middleware Components
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### 1. Logging Middleware
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This middleware logs message details for monitoring and debugging:
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```typescript
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class LoggingMiddleware implements IMiddleware {
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readonly id = 'core:logging';
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readonly priority = 250;
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constructor(private options: {
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logLevel?: LogLevel;
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includeBodies?: boolean;
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bodyMaxSize?: number;
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formatter?: (message: NetworkMessage) => string;
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}) {}
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async processIncoming(message: NetworkMessage): Promise<NetworkMessage> {
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// Log incoming message details
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return message;
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}
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async processOutgoing(message: NetworkMessage): Promise<NetworkMessage> {
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// Log outgoing message details
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return message;
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}
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shouldProcess(message: NetworkMessage): boolean {
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// Determine if this message should be logged
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return true;
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}
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}
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```
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### 2. Validation Middleware
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This middleware ensures messages conform to expected formats:
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```typescript
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class ValidationMiddleware implements IMiddleware {
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readonly id = 'core:validation';
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readonly priority = 50;
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constructor(private options: {
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schemas: Record<string, any>;
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strictMode?: boolean;
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errorHandler?: (error: any, message: NetworkMessage) => void;
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}) {}
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async processIncoming(message: NetworkMessage): Promise<NetworkMessage | null> {
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// Validate incoming message structure
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return message;
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}
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async processOutgoing(message: NetworkMessage): Promise<NetworkMessage | null> {
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// Validate outgoing message structure
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return message;
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}
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shouldProcess(message: NetworkMessage): boolean {
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// Check if we have a schema for this message type
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return this.options.schemas.hasOwnProperty(message.type);
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}
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}
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```
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### 3. Metrics Middleware
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This middleware collects performance metrics:
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```typescript
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class MetricsMiddleware implements IMiddleware {
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readonly id = 'core:metrics';
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readonly priority = 300;
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constructor(private options: {
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trackSizes?: boolean;
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trackTiming?: boolean;
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detailedMetrics?: boolean;
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metricsCallback?: (metrics: MessageMetrics) => void;
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}) {}
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async processIncoming(message: NetworkMessage): Promise<NetworkMessage> {
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// Record incoming message metrics
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return message;
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}
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async processOutgoing(message: NetworkMessage): Promise<NetworkMessage> {
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// Record outgoing message metrics
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return message;
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}
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shouldProcess(message: NetworkMessage): boolean {
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// Usually process all messages
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return true;
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}
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}
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```
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### 4. Transformation Middleware
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This middleware transforms message structure:
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```typescript
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class TransformationMiddleware implements IMiddleware {
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readonly id = 'core:transformation';
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readonly priority = 200;
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constructor(private options: {
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transformations: Record<string, (message: NetworkMessage) => NetworkMessage>;
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}) {}
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async processIncoming(message: NetworkMessage): Promise<NetworkMessage> {
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// Apply transformations to incoming message
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return message;
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}
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async processOutgoing(message: NetworkMessage): Promise<NetworkMessage> {
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// Apply transformations to outgoing message
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return message;
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}
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shouldProcess(message: NetworkMessage): boolean {
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// Check if we have a transformation for this message type
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return this.options.transformations.hasOwnProperty(message.type);
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}
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}
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```
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### 5. Throttling Middleware
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This middleware controls message flow rates:
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```typescript
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class ThrottlingMiddleware implements IMiddleware {
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readonly id = 'core:throttling';
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readonly priority = 150;
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constructor(private options: {
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messagesPerSecond?: number;
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byteLimit?: number;
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burstSize?: number;
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typeSpecificLimits?: Record<string, { messagesPerSecond: number }>;
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}) {}
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async processOutgoing(message: NetworkMessage): Promise<NetworkMessage | null> {
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// Apply rate limiting to outgoing messages
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return message;
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}
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async processIncoming(message: NetworkMessage): Promise<NetworkMessage> {
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// Just pass through incoming messages
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return message;
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}
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shouldProcess(message: NetworkMessage): boolean {
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// Usually only throttle outgoing messages
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return true;
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}
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}
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```
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## Serialization Strategies
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### 1. JSON Serializer
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The JSON serializer provides human-readable serialization:
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```typescript
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class JsonSerializer implements ISerializer {
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constructor(private options: {
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pretty?: boolean;
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replacer?: (key: string, value: any) => any;
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reviver?: (key: string, value: any) => any;
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circularHandling?: 'error' | 'ignore' | 'serialize';
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}) {}
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serialize(message: NetworkMessage): string {
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// Convert message to JSON string
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// Handle circular references
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// Apply replacer function
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return '...';
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}
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deserialize(data: string): NetworkMessage {
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// Parse JSON string to message object
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// Apply reviver function
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return {} as NetworkMessage;
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}
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getContentType(): string {
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return 'application/json';
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}
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}
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```
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### 2. Binary Serializer
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The binary serializer provides efficient binary encoding:
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```typescript
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class BinarySerializer implements ISerializer {
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constructor(private options: {
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compression?: boolean;
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schema?: any;
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serializeBigInt?: boolean;
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}) {}
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serialize(message: NetworkMessage): Uint8Array {
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// Convert message to binary format
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// Apply compression if configured
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return new Uint8Array();
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}
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deserialize(data: Uint8Array): NetworkMessage {
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// Parse binary data to message object
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// Decompress if needed
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return {} as NetworkMessage;
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}
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getContentType(): string {
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return 'application/octet-stream';
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}
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}
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```
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### 3. MessagePack Serializer
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The MessagePack serializer provides compact, efficient serialization:
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```typescript
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class MessagePackSerializer implements ISerializer {
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constructor(private options: {
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useExtensions?: boolean;
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extensionCodecs?: any;
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useBigInt64?: boolean;
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}) {}
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serialize(message: NetworkMessage): Uint8Array {
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// Convert message to MessagePack format
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return new Uint8Array();
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}
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deserialize(data: Uint8Array): NetworkMessage {
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// Parse MessagePack data to message object
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return {} as NetworkMessage;
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}
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getContentType(): string {
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return 'application/x-msgpack';
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}
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}
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```
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## Implementation Details
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### MiddlewareManager
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The MiddlewareManager should implement:
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```typescript
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class MiddlewareManager implements IMiddlewareManager {
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private _middleware: Map<string, IMiddleware> = new Map();
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private _enabledMiddleware: Set<string> = new Set();
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private _sortedMiddleware: IMiddleware[] = [];
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constructor() {
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// Initialize manager
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}
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addMiddleware(middleware: IMiddleware): void {
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// Add middleware to the registry
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// Update sorted middleware array
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// Enable by default
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}
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removeMiddleware(id: string): void {
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// Remove middleware from registry
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// Update sorted middleware array
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}
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async processMessage(message: NetworkMessage, direction: 'incoming' | 'outgoing'): Promise<NetworkMessage | null> {
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// Copy message to prevent mutation issues
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// Get appropriate processor method based on direction
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// Process through middleware chain
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// Return final message or null if dropped
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}
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getMiddlewares(): IMiddleware[] {
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// Return all registered middleware
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}
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setMiddlewareEnabled(id: string, enabled: boolean): void {
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// Enable or disable middleware
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// Update sorted middleware array if needed
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}
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private _sortMiddleware(): void {
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// Sort middleware by priority
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// Filter to only enabled middleware
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}
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}
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```
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### SerializerFactory
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A factory pattern can be used to select the appropriate serializer:
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```typescript
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class SerializerFactory {
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private _serializers: Map<string, ISerializer> = new Map();
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private _defaultSerializer: ISerializer;
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constructor(defaultSerializer?: ISerializer) {
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// Initialize with default (JSON if not specified)
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}
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registerSerializer(contentType: string, serializer: ISerializer): void {
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// Register serializer for content type
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}
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getSerializer(contentType?: string): ISerializer {
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// Return serializer for content type or default
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}
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setDefaultSerializer(contentType: string): void {
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// Set default serializer by content type
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}
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}
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```
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## Testing Strategy
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### Middleware Manager Tests
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1. **Registration Tests**:
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- Test adding middleware
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- Test removing middleware
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- Test duplicate ID handling
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- Test priority ordering
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2. **Processing Tests**:
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- Test message processing chain
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- Test direction-specific processing
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- Test middleware that modifies messages
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- Test middleware that drops messages
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3. **Error Handling Tests**:
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- Test middleware that throws exceptions
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- Test error propagation
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- Test chain recovery after errors
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- Test timeout handling
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### Core Middleware Tests
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1. **Logging Middleware Tests**:
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- Test log output format
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- Test filtering by message type
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- Test body inclusion/exclusion
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- Test custom formatting
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2. **Validation Middleware Tests**:
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- Test schema validation
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- Test handling valid messages
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- Test handling invalid messages
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- Test strict vs. lenient modes
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3. **Other Middleware Tests**:
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- Similar tests for each middleware component
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- Test middleware-specific functionality
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- Test configuration options
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- Test performance characteristics
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### Serializer Tests
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1. **JSON Serializer Tests**:
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- Test basic serialization/deserialization
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- Test handling complex objects
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- Test handling circular references
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- Test custom replacers/revivers
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2. **Binary Serializer Tests**:
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- Test binary format correctness
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- Test compression effectiveness
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- Test handling various data types
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- Test performance characteristics
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3. **Format Compatibility Tests**:
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- Test cross-version compatibility
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- Test partial object serialization
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- Test schema evolution
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- Test with real messages from the system
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## Edge Cases and Considerations
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### 1. Message Transformation Issues
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Handle middleware that transforms messages:
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- Track message changes for debugging
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- Validate transformed messages for consistency
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- Detect transformation loops
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- Support reverting transformations if needed
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### 2. Middleware Performance Impact
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Monitor and optimize middleware performance:
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- Measure processing time per middleware
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- Provide bypass mechanisms for critical paths
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- Support conditional execution based on load
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- Optimize frequently used middleware components
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### 3. Serialization Compatibility
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Ensure serialization works across different environments:
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- Handle browser vs. Node.js differences
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- Support backward/forward compatibility
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- Provide graceful fallbacks for unsupported features
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- Test with real-world message patterns
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### 4. Large Message Handling
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Handle very large messages efficiently:
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- Support streaming serialization/deserialization
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- Implement size limits with configurable policies
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- Provide chunking for large messages
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- Optimize memory usage during processing
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### 5. Error Recovery
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Implement robust error handling:
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- Provide clear error diagnostics
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- Support partial processing where appropriate
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- Include middleware-specific error handling
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- Allow custom error policies
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## Integration Points
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The middleware and serialization systems integrate with:
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1. **NetworkNode**: For message processing
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2. **TransportLayer**: For message serialization
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3. **Plugin System**: For extensibility
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4. **Monitoring**: For performance metrics
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## Performance Considerations
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Optimize middleware and serialization for:
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1. **Processing Efficiency**: Minimize CPU usage per message
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2. **Memory Usage**: Avoid unnecessary copies and allocations
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3. **Scalability**: Maintain performance under increasing load
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4. **Selective Processing**: Skip unnecessary work when possible
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## Success Criteria
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This phase is complete when:
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1. The MiddlewareManager correctly processes messages through the middleware chain
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2. Core middleware components are implemented and working correctly
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3. All serialization strategies are implemented and functional
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4. Middleware priority ordering works as expected
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5. Middleware can be dynamically added, removed, and configured
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6. Serializers correctly handle all supported message formats
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7. Error cases are properly handled
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8. All tests pass with 100% code coverage
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The middleware and serialization systems provide critical infrastructure for message processing and transport, enabling features like logging, validation, and efficient message transmission across different environments and transport mechanisms.
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