Class InMemoryEventStore

src/utils/InMemoryEventStore.ts:15–92

 * see more details: https://modelcontextprotocol.io/specification/2025-03-26/basic/transports#resumability-and-redelivery.
 */
export class InMemoryEventStore implements EventStore {
  private events: Map<string, { streamId: string; message: JSONRPCMessage }> =
    new Map();

  /**
   * Generates a unique event ID for a given stream ID
   */
  private generateEventId(streamId: string): string {
    return `${streamId}_${Date.now()}_${Math.random().toString(36).substring(2, 10)}`;
  }

  /**
   * Extracts the stream ID from an event ID
   */
  private getStreamIdFromEventId(eventId: string): string {
    const parts = eventId.split('_');
    return parts.length > 0 ? parts[0] : '';
  }

  /**
   * Stores an event with a generated event ID
   * Implements EventStore.storeEvent
   */
  async storeEvent(streamId: string, message: JSONRPCMessage): Promise<string> {
    const eventId = this.generateEventId(streamId);
    this.events.set(eventId, { streamId, message });
    return eventId;
  }

  /**
   * Replays events that occurred after a specific event ID
   * Implements EventStore.replayEventsAfter
   */
  async replayEventsAfter(
    lastEventId: string,
    {
      send,
    }: { send: (eventId: string, message: JSONRPCMessage) => Promise<void> }
  ): Promise<string> {
    if (!lastEventId || !this.events.has(lastEventId)) {
      return '';
    }

    // Extract the stream ID from the event ID
    const streamId = this.getStreamIdFromEventId(lastEventId);
    if (!streamId) {
      return '';
    }

    let foundLastEvent = false;

    // Sort events by eventId for chronological ordering
    const sortedEvents = [...this.events.entries()].sort((a, b) =>
      a[0].localeCompare(b[0])
    );

    for (const [
      eventId,