feat: Add Backend Platform Websocket service

packages/backend-platform/CHANGELOG.md

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+# Changelog
+
+All notable changes to this project will be documented in this file.
+
+The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
+and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
+
+## [Unreleased]
+
+## [1.0.0] - Initial Release
+
+### Added
+
+- Initial release of @metamask/backend-platform 

packages/backend-platform/LICENSE

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+MIT License
+
+Copyright (c) MetaMask
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.

packages/backend-platform/README.md

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+# `@metamask/backend-platform`
+
+Backend platform utilities and services for MetaMask.
+
+## Installation
+
+`yarn add @metamask/backend-platform`
+
+or
+
+`npm install @metamask/backend-platform`
+
+## Features
+
+- **WebSocket Service**: Robust WebSocket client with automatic reconnection, circuit breaker pattern, and service degradation detection
+- **Type-safe utilities**: Common types and utility functions for backend operations
+- **Service patterns**: Following MetaMask's service architecture guidelines
+
+## Usage
+
+### WebSocket Service
+
+```typescript
+import { WebSocketService, WebSocketState } from '@metamask/backend-platform';
+
+// Create a WebSocket service instance
+const websocketService = new WebSocketService({
+  url: 'wss://your-internal-backend.com/ws',
+  environment: 'production',
+  authToken: 'your-auth-token',
+  connectionTimeout: 15000,
+  pingInterval: 30000,
+  maxReconnectAttempts: 5,
+  policyOptions: {
+    maxRetries: 3,
+    maxConsecutiveFailures: 5,
+    circuitBreakDuration: 60000,
+    degradedThreshold: 3000,
+  },
+});
+
+// Set up event handlers
+websocketService.on('connected', () => {
+  console.log('Connected to WebSocket server');
+});
+
+websocketService.on('message', (message) => {
+  console.log('Received message:', message);
+});
+
+websocketService.on('error', (error) => {
+  console.error('WebSocket error:', error);
+});
+
+// Handle service policy events (recommended approach)
+websocketService.onBreak((data) => {
+  console.warn('Circuit breaker triggered:', data);
+});
+
+websocketService.onDegraded(() => {
+  console.warn('Service is degraded');
+});
+
+websocketService.onRetry((data) => {
+  console.log('Retrying connection:', data);
+});
+
+// Deprecated approach (still supported for backward compatibility)
+const websocketServiceDeprecated = new WebSocketService({
+  url: 'wss://your-internal-backend.com/ws',
+  environment: 'production',
+  // @deprecated - use onBreak() method instead
+  onBreak: () => console.warn('Circuit breaker triggered'),
+  // @deprecated - use onDegraded() method instead  
+  onDegraded: () => console.warn('Service is degraded'),
+});
+
+// Connect and send messages
+async function example() {
+  try {
+    await websocketService.connect();
+
+    const response = await websocketService.send({
+      type: 'getUserAccount',
+      payload: { userId: 'user123' },
+    });
+
+    console.log('Response:', response);
+  } catch (error) {
+    console.error('Error:', error);
+  }
+}
+```
+
+### Utility Functions
+
+```typescript
+import { 
+  createSuccessResponse, 
+  createErrorResponse, 
+  isValidEnvironment 
+} from '@metamask/backend-platform';
+
+// Create standardized responses
+const success = createSuccessResponse({ user: 'data' });
+const error = createErrorResponse('Something went wrong');
+
+// Validate environment strings
+if (isValidEnvironment(process.env.NODE_ENV)) {
+  console.log('Valid environment');
+}
+```
+
+### Types
+
+```typescript
+import type { 
+  BackendConfig, 
+  BackendResponse,
+  WebSocketServiceOptions,
+  WebSocketMessage 
+} from '@metamask/backend-platform';
+
+const config: BackendConfig = {
+  environment: 'development',
+  debug: true,
+};
+
+const response: BackendResponse<string> = {
+  success: true,
+  data: 'Hello world',
+  timestamp: Date.now(),
+};
+```
+
+## Architecture
+
+This package follows MetaMask's service architecture patterns:
+
+- **Service Policy Integration**: Uses `@metamask/controller-utils` for retry logic, circuit breaker pattern, and service degradation detection
+- **Event-driven Architecture**: WebSocket service implements an event emitter pattern for handling connection states and messages
+- **Type Safety**: Comprehensive TypeScript types for all service interactions
+- **Error Handling**: Robust error handling with automatic retries and fallback mechanisms
+
+## WebSocket Service Features
+
+- **Automatic Reconnection**: Configurable reconnection attempts with exponential backoff
+- **Circuit Breaker**: Prevents cascading failures by temporarily stopping requests when service is down
+- **Service Degradation Detection**: Monitors service performance and triggers callbacks when degraded
+- **Authentication**: Built-in support for token-based authentication
+- **Message Correlation**: Automatic correlation of request/response messages
+- **Ping/Pong**: Configurable keep-alive mechanism
+- **Connection State Management**: Comprehensive state tracking and event emission
+
+## API Documentation
+
+For detailed API documentation, please visit [our TypeDoc page](https://metamask.github.io/core/modules/_metamask_backend_platform.html). 

packages/backend-platform/jest.config.js

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+/*
+ * For a detailed explanation regarding each configuration property and type check, visit:
+ * https://jestjs.io/docs/configuration
+ */
+
+const merge = require('deepmerge');
+const path = require('path');
+
+const baseConfig = require('../../tests/jest.config.packages');
+
+const displayName = path.basename(__dirname);
+
+module.exports = merge(baseConfig, {
+  // The display name when running multiple projects
+  displayName,
+
+  // An object that configures minimum threshold enforcement for coverage results
+  coverageThreshold: {
+    global: {
+      branches: 100,
+      functions: 100,
+      lines: 100,
+      statements: 100,
+    },
+  },
+
+  // We rely on `setupFiles` rather than `setupFilesAfterEnv` since we're not
+  // testing with jsdom.
+  setupFiles: ['<rootDir>/../../tests/setup.js'],
+}); 

packages/backend-platform/package.json

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+{
+  "name": "@metamask/backend-platform",
+  "version": "1.0.0",
+  "description": "Backend platform utilities and services for MetaMask",
+  "keywords": [
+    "MetaMask",
+    "Ethereum",
+    "Backend",
+    "Platform"
+  ],
+  "homepage": "https://github.com/MetaMask/core/tree/main/packages/backend-platform#readme",
+  "bugs": {
+    "url": "https://github.com/MetaMask/core/issues"
+  },
+  "repository": {
+    "type": "git",
+    "url": "https://github.com/MetaMask/core.git"
+  },
+  "license": "MIT",
+  "exports": {
+    ".": {
+      "import": {
+        "types": "./dist/index.d.mts",
+        "default": "./dist/index.mjs"
+      },
+      "require": {
+        "types": "./dist/index.d.cts",
+        "default": "./dist/index.cjs"
+      }
+    },
+    "./package.json": "./package.json"
+  },
+  "main": "./dist/index.cjs",
+  "types": "./dist/index.d.cts",
+  "files": [
+    "dist/"
+  ],
+  "scripts": {
+    "build": "ts-bridge --project tsconfig.build.json --verbose --clean --no-references",
+    "build:docs": "typedoc",
+    "changelog:update": "../../scripts/update-changelog.sh @metamask/backend-platform",
+    "changelog:validate": "../../scripts/validate-changelog.sh @metamask/backend-platform",
+    "publish:preview": "yarn npm publish --tag preview",
+    "since-latest-release": "../../scripts/since-latest-release.sh",
+    "test": "NODE_OPTIONS=--experimental-vm-modules jest --reporters=jest-silent-reporter",
+    "test:clean": "NODE_OPTIONS=--experimental-vm-modules jest --clearCache",
+    "test:verbose": "NODE_OPTIONS=--experimental-vm-modules jest --verbose",
+    "test:watch": "NODE_OPTIONS=--experimental-vm-modules jest --watch"
+  },
+  "dependencies": {
+    "@metamask/base-controller": "^8.0.1",
+    "@metamask/controller-utils": "^11.10.0",
+    "@metamask/utils": "^11.2.0"
+  },
+  "devDependencies": {
+    "@metamask/auto-changelog": "^3.4.4",
+    "@types/jest": "^27.4.1",
+    "jest": "^27.5.1",
+    "ts-jest": "^27.1.4",
+    "typedoc": "^0.24.8",
+    "typedoc-plugin-missing-exports": "^2.0.0",
+    "typescript": "~5.2.2"
+  },
+  "engines": {
+    "node": "^18.18 || >=20"
+  },
+  "publishConfig": {
+    "access": "public",
+    "registry": "https://registry.npmjs.org/"
+  }
+}

packages/backend-platform/src/index.ts

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+/**
+ * @metamask/backend-platform
+ *
+ * Backend platform utilities and services for MetaMask.
+ */
+
+// Export types and utilities
+// WebSocket Service - following MetaMask Data Services pattern
+export type {
+  WebSocketServiceOptions,
+  WebSocketMessage,
+  WebSocketConnectionInfo,
+  WebSocketServiceActions,
+  WebSocketServiceConnectAction,
+  WebSocketServiceDisconnectAction,
+  WebSocketServiceSendMessageAction,
+  WebSocketServiceSendRequestAction,
+  WebSocketServiceGetConnectionInfoAction,
+  WebSocketServiceMessenger,
+} from './websocket-service';
+
+export {
+  WebSocketService,
+  WebSocketState,
+  WebSocketEventType,
+} from './websocket-service'; 

packages/backend-platform/src/types.ts

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+/**
+ * Common types for backend platform utilities.
+ */
+
+/**
+ * Base configuration interface for backend services.
+ */
+export interface BackendConfig {
+  /**
+   * The environment the backend is running in.
+   */
+  environment: 'development' | 'staging' | 'production';
+
+  /**
+   * Optional debug mode flag.
+   */
+  debug?: boolean;
+}
+
+/**
+ * Standard response format for backend operations.
+ */
+export interface BackendResponse<T = unknown> {
+  /**
+   * Whether the operation was successful.
+   */
+  success: boolean;
+
+  /**
+   * The response data, if successful.
+   */
+  data?: T;
+
+  /**
+   * Error message, if unsuccessful.
+   */
+  error?: string;
+
+  /**
+   * Timestamp of the response.
+   */
+  timestamp: number;
+}