/**
 * HTTP propagation helpers for Effect tracing context.
 *
 * This module converts Effect `Tracer.Span` values into outbound trace headers
 * and decodes inbound propagation headers into `Tracer.ExternalSpan` parents.
 * HTTP clients use it to continue the current span across outgoing requests, and
 * server middleware uses it to parent request spans from upstream services.
 *
 * **Mental model**
 *
 * Propagation is metadata, not tracing storage. {@link toHeaders} serializes the
 * current span into HTTP headers for the next service. {@link fromHeaders}
 * inspects incoming headers and returns an external parent span when a supported
 * propagation format is present.
 *
 * **Common tasks**
 *
 * - Add outbound propagation headers with {@link toHeaders}
 * - Decode an inbound parent span with {@link fromHeaders}
 * - Use {@link w3c}, {@link b3}, or {@link xb3} directly when an adapter needs a
 *   specific propagation format
 *
 * **Gotchas**
 *
 * - Outbound propagation writes both W3C `traceparent` and compact B3 `b3`
 *   headers
 * - Inbound decoding prefers W3C `traceparent`, then compact B3, then
 *   multi-header B3 (`x-b3-*`)
 * - Header names in `Headers.Headers` are expected to be lowercase
 * - Missing or unsupported trace context decodes to `Option.none`, so callers
 *   should start a new trace when no parent is returned
 *
 * @since 4.0.0
 */
import * as Option from "../../Option.js";
import * as Tracer from "../../Tracer.js";
import * as Headers from "./Headers.js";
/**
 * Encodes a span into HTTP trace propagation headers.
 *
 * **Details**
 *
 * The generated headers include both compact B3 (`b3`) and W3C `traceparent`
 * formats.
 *
 * @category encoding
 * @since 4.0.0
 */
export const toHeaders = span => Headers.fromRecordUnsafe({
  b3: `${span.traceId}-${span.spanId}-${span.sampled ? "1" : "0"}${Option.match(span.parent, {
    onNone: () => "",
    onSome: parent => `-${parent.spanId}`
  })}`,
  traceparent: `00-${span.traceId}-${span.spanId}-${span.sampled ? "01" : "00"}`
});
/**
 * Decodes an external span safely from HTTP trace propagation headers.
 *
 * **Details**
 *
 * W3C `traceparent` is tried first, followed by compact B3 (`b3`) and then
 * multi-header B3 (`x-b3-*`).
 *
 * @category decoding
 * @since 4.0.0
 */
export const fromHeaders = headers => {
  let span = w3c(headers);
  if (Option.isSome(span)) {
    return span;
  }
  span = b3(headers);
  if (Option.isSome(span)) {
    return span;
  }
  return xb3(headers);
};
/**
 * Decodes an external span safely from the compact B3 `b3` header.
 *
 * **Details**
 *
 * Returns `Option.none` when the header is missing or does not contain trace and
 * span identifiers.
 *
 * @category decoding
 * @since 4.0.0
 */
export const b3 = headers => {
  if (!("b3" in headers)) {
    return Option.none();
  }
  const parts = headers["b3"].split("-");
  if (parts.length < 2) {
    return Option.none();
  }
  return Option.some(Tracer.externalSpan({
    traceId: parts[0],
    spanId: parts[1],
    sampled: parts[2] ? parts[2] === "1" : true
  }));
};
/**
 * Decodes an external span safely from multi-header B3 propagation headers.
 *
 * **Details**
 *
 * The decoder reads `x-b3-traceid`, `x-b3-spanid`, and optional `x-b3-sampled`
 * headers.
 *
 * @category decoding
 * @since 4.0.0
 */
export const xb3 = headers => {
  if (!headers["x-b3-traceid"] || !headers["x-b3-spanid"]) {
    return Option.none();
  }
  return Option.some(Tracer.externalSpan({
    traceId: headers["x-b3-traceid"],
    spanId: headers["x-b3-spanid"],
    sampled: headers["x-b3-sampled"] ? headers["x-b3-sampled"] === "1" : true
  }));
};
const w3cTraceId = /^[0-9a-f]{32}$/i;
const w3cSpanId = /^[0-9a-f]{16}$/i;
/**
 * Decodes an external span safely from the W3C `traceparent` header.
 *
 * **Details**
 *
 * Only version `00` headers with valid trace and span identifiers are accepted.
 *
 * @category decoding
 * @since 4.0.0
 */
export const w3c = headers => {
  if (!headers["traceparent"]) {
    return Option.none();
  }
  const parts = headers["traceparent"].split("-");
  if (parts.length !== 4) {
    return Option.none();
  }
  const [version, traceId, spanId, flags] = parts;
  switch (version) {
    case "00":
      {
        if (w3cTraceId.test(traceId) === false || w3cSpanId.test(spanId) === false) {
          return Option.none();
        }
        return Option.some(Tracer.externalSpan({
          traceId,
          spanId,
          sampled: (parseInt(flags, 16) & 1) === 1
        }));
      }
    default:
      {
        return Option.none();
      }
  }
};
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