✨ Added urlutil package with ShiftPath helper

internal/urlutil/shift_path.go

@@ -0,0 +1,22 @@
+package urlutil
+
+import (
+	"path"
+	"strings"
+)
+
+// ShiftPath splits off the first component of p, which will be cleaned of
+// relative components before processing. head will never contain a slash and
+// tail will always be a rooted path without trailing slash.
+//
+// See: https://blog.merovius.de/posts/2017-06-18-how-not-to-use-an-http-router/
+func ShiftPath(p string) (head, tail string) {
+	p = path.Clean("/" + p)
+
+	i := strings.Index(p[1:], "/") + 1
+	if i <= 0 {
+		return p[1:], "/"
+	}
+
+	return p[1:i], p[i:]
+}

internal/urlutil/shift_path_test.go

@@ -0,0 +1,31 @@
+package urlutil_test
+
+import (
+	"testing"
+
+	"source.toby3d.me/toby3d/auth/internal/urlutil"
+)
+
+func TestShiftPath(t *testing.T) {
+	t.Parallel()
+
+	for in, out := range map[string][2]string{
+		"/":         {"", "/"},
+		"/foo":      {"foo", "/"},
+		"/foo/":     {"foo", "/"},
+		"/foo/bar":  {"foo", "/bar"},
+		"/foo/bar/": {"foo", "/bar"},
+	} {
+		in, out := in, out
+
+		t.Run(in, func(t *testing.T) {
+			t.Parallel()
+
+			head, path := urlutil.ShiftPath(in)
+
+			if out[0] != head || out[1] != path {
+				t.Errorf("ShiftPath(%s) = '%s', '%s', want '%s', '%s'", in, head, path, out[0], out[1])
+			}
+		})
+	}
+}