/**
* W3C Trace Context propagation for misina. Auto-injects `traceparent`
* and forwards `tracestate` on every outgoing request. Pure JS using
* `crypto.getRandomValues` (Web Crypto, available everywhere).
*
* - L1 spec: https://www.w3.org/TR/trace-context/
* - L2 spec: https://www.w3.org/TR/trace-context-2/
*
* Compose with OpenTelemetry by passing `getCurrentSpan` so misina pulls
* the active span context instead of generating a fresh root.
*
* @example
* ```ts
* import { createMisina } from 'misina'
* import { tracing } from 'misina/tracing'
*
* const api = createMisina({ baseURL, use: [tracing()] })
* await api.get('/users/42') // request gets a fresh traceparent + matching tracestate
*
* // With OpenTelemetry:
* import { trace } from '@opentelemetry/api'
* const api2 = createMisina({
*   baseURL,
*   use: [
*     tracing({
*       getCurrentSpan: () => {
*         const span = trace.getActiveSpan()
*         return span ? { traceId: span.spanContext().traceId, parentId: span.spanContext().spanId } : null
*       },
*     }),
*   ],
* })
* ```
*/
import type { MisinaPlugin } from "../types.mjs";
export interface TracingOptions {
	/**
	* Pull the parent span context from an external tracing system. Return
	* `null` to fall back to a freshly-generated root span. The returned
	* `traceId` must be 32 hex chars; `parentId` 16. `flags` is an integer
	* 0-255; `state` is the W3C tracestate header value.
	*/
	getCurrentSpan?: () => TraceSpanContext | null;
	/**
	* Static or dynamic baggage entries appended to the W3C `Baggage`
	* header. https://www.w3.org/TR/baggage/
	*/
	baggage?: Record<string, string> | (() => Record<string, string>);
	/** Override traceparent flags (default: 01 — sampled). */
	flags?: number;
}
export interface TraceSpanContext {
	traceId: string;
	parentId: string;
	flags?: number;
	state?: string;
}
export declare function tracing(options?: TracingOptions): MisinaPlugin;