import { AmplitudeAI } from "./client.js";

//#region src/middleware.d.ts

/** A static value or a `(req) => value` resolver for per-request values. */
type ValueOrResolver<T> = T | ((req: unknown) => T | null) | null;
interface MiddlewareOptions {
  amplitudeAI: AmplitudeAI;
  /**
   * Return the authenticated end user for this request (e.g. from your auth
   * middleware's session or a verified token), or `null` for anonymous
   * requests. Do not read it from a request header the client controls:
   * any caller could then send events as any user.
   */
  userIdResolver: (req: unknown) => string | null;
  /**
   * Optional device / anonymous ID for the request (e.g. an Amplitude
   * `device_id` your frontend sends). Lets anonymous traffic be tracked and
   * still emit session-end events when there is no user ID.
   */
  deviceIdResolver?: (req: unknown) => string | null;
  sessionIdResolver?: (req: unknown) => string;
  agentId?: string | null;
  env?: string | null;
  /** Agent code version applied to every request's session. */
  agentVersion?: string | null;
  /** End-customer org for multi-tenant platforms (static or per-request). */
  customerOrgId?: ValueOrResolver<string>;
  /** Segmentation context dict (static or per-request). */
  context?: ValueOrResolver<Record<string, unknown>>;
  /** Group-analytics dict (static or per-request). */
  groups?: ValueOrResolver<Record<string, unknown>>;
  trackSessionEvents?: boolean;
  flushOnResponse?: boolean;
}
interface ExpressLikeRequest {
  headers: Record<string, string | string[] | undefined>;
}
interface ExpressLikeResponse {
  on: (event: string, callback: () => void) => void;
}
/**
 * Creates Express-compatible middleware.
 *
 * Usage (mount after your authentication middleware):
 *   app.use(createAmplitudeAIMiddleware({
 *     amplitudeAI: ai,
 *     userIdResolver: (req) => req.user?.id ?? null,
 *   }));
 *
 * `userIdResolver` must return the authenticated principal, not a value read
 * from a client-supplied header. The trace ID is taken from a valid W3C
 * `traceparent` or a short `x-trace-id` token (letters, digits, `._:-`, up to
 * 64 chars); anything else is ignored and a fresh trace ID is generated.
 */
declare function createAmplitudeAIMiddleware(options: MiddlewareOptions): (req: ExpressLikeRequest, res: ExpressLikeResponse, next: () => void) => void;
//#endregion
export { MiddlewareOptions, createAmplitudeAIMiddleware };
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