/**
 * The lifecycle/engagement event types that converge onto a single {@link EmailEvent} shape.
 *
 * The first group (`queued` → `failed`) is emitted by the send pipeline; the rest typically originate
 * from provider webhooks (delivery/engagement signals).
 */
type EmailEventType = "attempt" | "bounced" | "clicked" | "complained" | "deferred" | "delivered" | "failed" | "opened" | "queued" | "sent" | "unsubscribed";
/**
 * A single, provider-agnostic email event. Both internal send-lifecycle signals and normalized
 * webhook events use this shape so a timeline can be reconstructed from one stream.
 */
interface EmailEvent {
  /**
   * Arbitrary structured payload (provider response, bounce sub-type, click URL, …).
   */
  data?: Record<string, unknown>;
  /**
   * A unique id for this event.
   */
  id: string;
  /**
   * The message this event concerns.
   */
  messageId?: string;
  /**
   * The provider that produced (or will produce) the message.
   */
  provider?: string;
  /**
   * The recipient address this event concerns, when applicable.
   */
  recipient?: string;
  /**
   * When the event occurred.
   */
  timestamp: Date;
  /**
   * The kind of event.
   */
  type: EmailEventType;
}
/**
 * A listener invoked for matching {@link EmailEvent}s.
 */
type EmailEventListener = (event: EmailEvent) => void;
/**
 * A persistence backend for {@link EmailEvent}s.
 */
interface EventStore {
  /**
   * Appends an event.
   * @param event The event to store.
   */
  append: (event: EmailEvent) => Promise<void> | void;
  /**
   * Returns the full, time-ordered timeline for a message.
   * @param messageId The message to reconstruct.
   */
  timeline: (messageId: string) => EmailEvent[] | Promise<EmailEvent[]>;
}
type Selector = "*" | EmailEventType;
/**
 * The wildcard selector that subscribes to every event type.
 */
declare const ALL_EVENTS: "*";
/**
 * A tiny synchronous pub/sub bus for {@link EmailEvent}s.
 *
 * Subscribe to a specific {@link EmailEventType} or to {@link ALL_EVENTS} (`"*"`) for every event.
 */
declare class EventBus {
  private readonly listeners;
  /**
   * Subscribes a listener to an event type (or all events).
   * @param type The event type, or `"*"` for all events.
   * @param listener The listener to invoke.
   * @returns An unsubscribe function.
   */
  on(type: Selector, listener: EmailEventListener): () => void;
  /**
   * Subscribes a listener that is removed after its first invocation.
   * @param type The event type, or `"*"` for all events.
   * @param listener The listener to invoke once.
   * @returns An unsubscribe function.
   */
  once(type: Selector, listener: EmailEventListener): () => void;
  /**
   * Removes a previously-added listener.
   * @param type The event type the listener was registered under.
   * @param listener The listener to remove.
   */
  off(type: Selector, listener: EmailEventListener): void;
  /**
   * Emits an event to all matching listeners (type-specific first, then wildcard).
   * @param event The event to dispatch.
   */
  emit(event: EmailEvent): void;
  /**
   * Removes all listeners (optionally for a single type).
   * @param type When provided, only listeners for this type are removed.
   */
  clear(type?: Selector): void;
}
export { ALL_EVENTS as A, EmailEvent as E, EventStore as a, EmailEventListener as b, EmailEventType as c, EventBus as d };