From 112c7b2e9e4107a7715ac465e58dd4eecfd6bd97 Mon Sep 17 00:00:00 2001
From: Richard Wall <richard.wall@venafi.com>
Date: Wed, 20 Mar 2024 10:24:47 +0000
Subject: [PATCH] An http.RoundTripper which adds the HTTP User-Agent header to
 all requests

This code existed in cert-manager once before and I'm reviving it.
Here's the history:

 * Added:
 https://github.com/cert-manager/cert-manager/pull/422
 * Moved: https://github.com/cert-manager/cert-manager/pull/432
 * Obsoleted: https://github.com/cert-manager/cert-manager/pull/797
 * Deleted: https://github.com/cert-manager/cert-manager/pull/966

Signed-off-by: Richard Wall <richard.wall@venafi.com>
---
 pkg/util/useragent.go | 23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)

diff --git a/pkg/util/useragent.go b/pkg/util/useragent.go
index 34a5a757b..7372031a1 100644
--- a/pkg/util/useragent.go
+++ b/pkg/util/useragent.go
@@ -19,6 +19,7 @@ package util
 import (
 	"bytes"
 	"fmt"
+	"net/http"
 	"strings"
 	"unicode"
 	"unicode/utf8"
@@ -58,3 +59,25 @@ func PrefixFromUserAgent(u string) string {
 	}
 	return buf.String()
 }
+
+// UserAgentRoundTripper implements the http.RoundTripper interface and adds a User-Agent
+// header.
+type userAgentRoundTripper struct {
+	inner     http.RoundTripper
+	userAgent string
+}
+
+// UserAgentRoundTripper returns a RoundTripper that functions identically to
+// the provided 'inner' round tripper, other than also setting a user agent.
+func UserAgentRoundTripper(inner http.RoundTripper, userAgent string) http.RoundTripper {
+	return userAgentRoundTripper{
+		inner:     inner,
+		userAgent: userAgent,
+	}
+}
+
+// RoundTrip implements http.RoundTripper
+func (u userAgentRoundTripper) RoundTrip(req *http.Request) (*http.Response, error) {
+	req.Header.Set("User-Agent", u.userAgent)
+	return u.inner.RoundTrip(req)
+}