Real-time and Events

/**
 * Global events channel for real-time functionality
 */
const events: EventsChannel;

interface EventsChannel {
  /**
   * Subscribe to events with an observer
   * @param observer - Observer to handle events
   * @param options - Optional subscription configuration
   * @returns Subscription object for managing the subscription
   */
  subscribe(observer: Observer, options?: EventsOptions): Subscription;
  
  /**
   * Publish an event to the channel
   * @param event - Event data to publish
   * @param options - Optional publish configuration
   * @returns Promise that resolves when event is published
   */
  publish(event: Event, options?: EventsOptions): Promise<any>;
  
  /**
   * Close the channel and all subscriptions
   */
  close(): void;
}

import { events } from "@aws-amplify/api";

// Subscribe to events
const subscription = events.subscribe({
  next: (event) => {
    console.log("Received event:", event);
  },
  error: (error) => {
    console.error("Event error:", error);
  },
  complete: () => {
    console.log("Event stream completed");
  }
});

// Publish an event
await events.publish({
  type: "user-action",
  data: { userId: "123", action: "login" }
});

// Clean up
subscription.unsubscribe();

interface EventsOptions {
  /**
   * Authentication mode for the event operation
   */
  authMode?: GraphQLAuthMode;
  
  /**
   * Custom authentication token
   */
  authToken?: string;
  
  /**
   * Additional headers for the event request
   */
  headers?: Record<string, string>;
  
  /**
   * Event filter criteria
   */
  filter?: EventFilter;
  
  /**
   * Custom user agent details
   */
  userAgentSuffix?: string;
}

interface EventFilter {
  /**
   * Event types to include
   */
  types?: string[];
  
  /**
   * Custom filter function
   */
  predicate?: (event: Event) => boolean;
}

interface Observer {
  /**
   * Handle next event in the stream
   * @param event - The event data
   */
  next: (event: Event) => void;
  
  /**
   * Handle errors in the event stream
   * @param error - The error that occurred
   */
  error?: (error: Error) => void;
  
  /**
   * Handle completion of the event stream
   */
  complete?: () => void;
}

interface Subscription {
  /**
   * Unsubscribe from the event stream
   */
  unsubscribe(): void;
  
  /**
   * Check if subscription is closed
   */
  closed: boolean;
}

/**
 * Constant for connection state change events
 */
const CONNECTION_STATE_CHANGE: string;

/**
 * Enumeration of possible connection states
 */
enum ConnectionState {
  Connected = "Connected",
  ConnectedPendingNetwork = "ConnectedPendingNetwork", 
  ConnectionDisrupted = "ConnectionDisrupted",
  ConnectionDisruptedPendingNetwork = "ConnectionDisruptedPendingNetwork",
  Connecting = "Connecting",
  ConnectedPendingDisconnect = "ConnectedPendingDisconnect",
  Disconnected = "Disconnected",
  ConnectedPendingKeepAlive = "ConnectedPendingKeepAlive"
}

import { events, CONNECTION_STATE_CHANGE, ConnectionState } from "@aws-amplify/api";

// Monitor connection state changes
const connectionSubscription = events.subscribe({
  next: (event) => {
    if (event.type === CONNECTION_STATE_CHANGE) {
      const { connectionState } = event.data;
      
      switch (connectionState) {
        case ConnectionState.Connected:
          console.log("WebSocket connected");
          break;
        case ConnectionState.Disconnected:
          console.log("WebSocket disconnected");
          break;
        case ConnectionState.Connecting:
          console.log("WebSocket connecting...");
          break;
        case ConnectionState.ConnectionDisrupted:
          console.log("Connection disrupted, attempting to reconnect");
          break;
      }
    }
  }
});

interface Event {
  /**
   * Event type identifier
   */
  type: string;
  
  /**
   * Event payload data
   */
  data: any;
  
  /**
   * Event timestamp
   */
  timestamp?: number;
  
  /**
   * Event source identifier
   */
  source?: string;
  
  /**
   * Event correlation ID for tracking
   */
  correlationId?: string;
}

/**
 * Common event types used in the system
 */
interface SystemEventTypes {
  CONNECTION_STATE_CHANGE: "connectionStateChange";
  SUBSCRIPTION_ACK: "subscriptionAck";
  SUBSCRIPTION_ERROR: "subscriptionError"; 
  DATA_EVENT: "dataEvent";
  KEEP_ALIVE: "keepAlive";
}

/**
 * Observable type for real-time data streams
 */
type Observable<T> = {
  subscribe(observer: {
    next: (value: T) => void;
    error?: (error: Error) => void;
    complete?: () => void;
  }): Subscription;
  
  subscribe(
    next: (value: T) => void,
    error?: (error: Error) => void,
    complete?: () => void
  ): Subscription;
};

/**
 * Real-time subscription result
 */
interface SubscriptionResult<T> {
  /**
   * The WebSocket provider managing the connection
   */
  provider: AWSAppSyncRealTimeProvider;
  
  /**
   * The subscription data
   */
  value: GraphQLResult<T>;
}

import { generateClient } from "@aws-amplify/api";

const client = generateClient<Schema>();

// Subscribe to real-time updates
const subscription = client.models.Todo.onCreate().subscribe({
  next: ({ data }) => {
    console.log("New todo created:", data);
  },
  error: (error) => {
    console.error("Subscription error:", error);
  }
});

// Clean up subscription
subscription.unsubscribe();

/**
 * Real-time connection errors
 */
interface ConnectionError extends Error {
  /**
   * Error code for categorization
   */
  code?: string;
  
  /**
   * Connection state when error occurred
   */
  connectionState?: ConnectionState;
  
  /**
   * Whether the error is recoverable
   */
  recoverable?: boolean;
  
  /**
   * Suggested retry delay in milliseconds
   */
  retryDelay?: number;
}

/**
 * Subscription-specific errors
 */
interface SubscriptionError extends Error {
  /**
   * Subscription that failed
   */
  subscription?: string;
  
  /**
   * GraphQL errors if applicable
   */
  graphQLErrors?: GraphQLError[];
  
  /**
   * Network error details
   */
  networkError?: Error;
}