From d2b41777eea3250250b31c206648e9b77f9cbae7 Mon Sep 17 00:00:00 2001
From: Nicholas Clarke <nick@topos.org.uk>
Date: Wed, 15 Jan 2025 14:34:19 +0100
Subject: [PATCH] Add optics for modifying name and comment

---
 cuddle.cabal                           |  1 +
 src/Codec/CBOR/Cuddle/Huddle/Optics.hs | 24 ++++++++++++++++++++++++
 2 files changed, 25 insertions(+)
 create mode 100644 src/Codec/CBOR/Cuddle/Huddle/Optics.hs

diff --git a/cuddle.cabal b/cuddle.cabal
index 5315b25..3ff1486 100644
--- a/cuddle.cabal
+++ b/cuddle.cabal
@@ -51,6 +51,7 @@ library
     Codec.CBOR.Cuddle.CDDL.Resolve
     Codec.CBOR.Cuddle.Huddle
     Codec.CBOR.Cuddle.Huddle.HuddleM
+    Codec.CBOR.Cuddle.Huddle.Optics
     Codec.CBOR.Cuddle.Parser
     Codec.CBOR.Cuddle.Pretty
 
diff --git a/src/Codec/CBOR/Cuddle/Huddle/Optics.hs b/src/Codec/CBOR/Cuddle/Huddle/Optics.hs
new file mode 100644
index 0000000..45ee0e8
--- /dev/null
+++ b/src/Codec/CBOR/Cuddle/Huddle/Optics.hs
@@ -0,0 +1,24 @@
+-- | Optics for mutating Huddle rules
+module Codec.CBOR.Cuddle.Huddle.Optics (commentL, nameL) where
+
+import Codec.CBOR.Cuddle.Huddle
+import Data.Generics.Product (HasField' (field'))
+import Data.Text qualified as T
+import Optics.Core
+
+mcommentL ::
+  (HasField' "description" a (Maybe T.Text)) =>
+  Lens a a (Maybe T.Text) (Maybe T.Text)
+mcommentL = field' @"description"
+
+-- | Traversal to the comment field of a description. Using this we can for
+--   example set the comment with 'a & commentL .~ "This is a comment"' 
+commentL ::
+  (HasField' "description" a (Maybe T.Text)) =>
+  AffineTraversal a a T.Text T.Text
+commentL = mcommentL % _Just
+
+-- | Lens to the name of a rule (or other named entity). Using this we can
+--   for example append to the name with 'a & nameL %~ (<> "_1")'
+nameL :: Lens (Named a) (Named a) T.Text T.Text
+nameL = field' @"name"