From 71153d98d505f45c3e31d176b019451056923991 Mon Sep 17 00:00:00 2001
From: Jonathan Bernard <jonathan@jdbernard.com>
Date: Sat, 2 Aug 2025 11:40:37 -0500
Subject: [PATCH] Add utilities for handling the traceparent header (see Trace
 Context W3C standard).

---
 buffoonery.nimble           |  2 +-
 src/buffoonery/apiutils.nim | 34 ++++++++++++++++++++++++++++++++++
 2 files changed, 35 insertions(+), 1 deletion(-)

diff --git a/buffoonery.nimble b/buffoonery.nimble
index 293ef0e..ed71248 100644
--- a/buffoonery.nimble
+++ b/buffoonery.nimble
@@ -1,6 +1,6 @@
 # Package
 
-version       = "0.4.8"
+version       = "0.4.9"
 author        = "Jonathan Bernard"
 description   = "Jonathan's opinionated extensions and auth layer for Jester."
 license       = "MIT"
diff --git a/src/buffoonery/apiutils.nim b/src/buffoonery/apiutils.nim
index 0a7c06b..39f007c 100644
--- a/src/buffoonery/apiutils.nim
+++ b/src/buffoonery/apiutils.nim
@@ -90,6 +90,40 @@ func origin*(req: Request): Option[string] =
   else: none[string]()
 
 
+func traceparent*(req: Request): Option[string] =
+  ## Extract the traceparent from the request headers, if present.
+  if req.headers.contains("traceparent"):
+    return some(req.headers["traceparent"])
+  else:
+    return none[string]()
+
+
+proc makeTraceContextHeaders*(req: Request, traceParentId: string): HttpHeaders =
+  var headers = HttpHeaders(@[])
+
+  if req.headers.contains("traceparent"):
+    # If the traceparent header is present, we should update it with our
+    # parent-id.
+    let traceparentParts = req.headers["traceparent"].split("-")
+    if traceparentParts.len != 4:
+      headers["traceparent"] = "00-$#-$#-00" % [
+        replace($genUUID(), "-", ""), # trace-id
+        traceParentId,                # parent-id
+      ]
+
+    else:
+      headers["traceparent"] = "00-$#-$#-$#" % [
+        traceparentParts[1], # trace-id
+        traceParentId,       # parent-id
+        traceparentParts[3], # flags
+      ]
+
+    if req.headers.contains("tracestate"):
+      headers["tracestate"] = req.headers["tracestate"]
+
+  return headers
+
+
 proc respondWithRawJson*(
     req: Request,
     body: JsonNode,