/**
 * The span model + exporter seam. Attribute names follow OpenTelemetry HTTP semantic conventions
 * (`http.request.method`, `url.path`, `http.response.status_code`, …) so a span maps cleanly onto an
 * OTel `Span` when bridged - but nothing here depends on the OTel SDK. You supply an
 * {@link ObservationAdapter}
 * (a ~10-line adapter to `@opentelemetry/api`, or the bundled {@link consoleSpanExporter}).
 */
export type SpanStatus = "unset" | "ok" | "error";
export type AttributeValue = string | number | boolean;
/** A non-parent causal relationship to a span in another trace (the OTel `Link` model). */
export interface ObservationLink {
    readonly traceId: string;
    readonly spanId: string;
    readonly attributes?: Readonly<Record<string, AttributeValue>>;
}
/** A completed (or in-flight) server span for one request. */
export interface NifraSpan {
    /** 32-hex W3C trace id - shared across every span/service in the trace. */
    readonly traceId: string;
    /** 16-hex id of this span. */
    readonly spanId: string;
    /** The inbound span's id, if this request continued an upstream trace. */
    readonly parentSpanId?: string;
    /** Whether the trace is sampled (the W3C flag). */
    readonly sampled: boolean;
    /** Span name - `"<METHOD> <path>"`. */
    readonly name: string;
    /** Wall-clock start (epoch ms). */
    readonly startTime: number;
    /** Wall-clock end (epoch ms) - set on completion. */
    endTime?: number;
    /** Duration in ms (monotonic). */
    durationMs?: number;
    status: SpanStatus;
    /** OTel-semantic-convention attributes. */
    readonly attributes: Record<string, AttributeValue>;
    /** Durable/asynchronous parents that are related but are not this span's single trace parent. */
    readonly links?: readonly ObservationLink[];
}
/**
 * Where ended spans go. Implement this to bridge to the OpenTelemetry SDK (map each field onto a
 * real `Span` from a `Tracer`), ship to a collector, or just log. `onStart` is optional (most
 * backends only need the completed span).
 */
export interface ObservationAdapter {
    onStart?(span: NifraSpan): void;
    onEnd(span: NifraSpan): void;
}
/**
 * Fan out lifecycle notifications to several adapters. Each adapter is isolated: an exception in
 * one sink cannot prevent the remaining sinks from observing the span.
 */
export declare function combineObservationAdapters(adapters: readonly ObservationAdapter[]): ObservationAdapter;
/** A no-frills exporter that logs each completed span as one structured line. Useful in dev or as a
 * starting point before wiring a real backend. */
export declare function consoleSpanExporter(log?: (line: string) => void): ObservationAdapter;
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