From af3e1f667da4c1c2a6c8c42fa2d44fa25e5b2396 Mon Sep 17 00:00:00 2001
From: Corentin Leruth <corentin.leruth@gmail.com>
Date: Mon, 18 Mar 2024 09:59:38 +0100
Subject: [PATCH 1/2] basic cmarkit to mrkdwn converter

---
 lib/dune                        |  1 +
 lib/mrkdwn.ml                   | 61 +++++++++++++++++++++++++++++++++
 lib_test/mrkdwn/dune            | 11 ++++++
 lib_test/mrkdwn/mrkdwn_of_md.ml |  1 +
 lib_test/mrkdwn/mrkdwn_of_md.t  | 30 ++++++++++++++++
 5 files changed, 104 insertions(+)
 create mode 100644 lib_test/mrkdwn/dune
 create mode 100644 lib_test/mrkdwn/mrkdwn_of_md.ml
 create mode 100644 lib_test/mrkdwn/mrkdwn_of_md.t

diff --git a/lib/dune b/lib/dune
index 349b14c..5fcced5 100644
--- a/lib/dune
+++ b/lib/dune
@@ -5,6 +5,7 @@
   atdgen
   atdgen-runtime
   biniou
+  cmarkit
   cstruct
   devkit
   extlib
diff --git a/lib/mrkdwn.ml b/lib/mrkdwn.ml
index 99a96a9..3c2b2cd 100644
--- a/lib/mrkdwn.ml
+++ b/lib/mrkdwn.ml
@@ -55,3 +55,64 @@ let highlight_mentions get_id_by_slack_name s =
     |> Option.default s
   in
   Re2.replace_exn mention_re s ~f:(fun m -> subst (Re2.Match.get_exn ~sub:(`Index 0) m))
+
+module Cmarkit_slack = struct
+  let renderer =
+    (* https://www.markdownguide.org/tools/slack/#slack-markdown-support-in-posts *)
+    (* https://slack.com/intl/en-gb/help/articles/202288908-Format-your-messages *)
+    let inline c inline =
+      let open Cmarkit in
+      let module C = Cmarkit_renderer.Context in
+      let strong_emphasis c e =
+        let i = Inline.Emphasis.inline e in
+        C.byte c '*';
+        C.inline c i;
+        C.byte c '*'
+      in
+      let emphasis c e =
+        let i = Inline.Emphasis.inline e in
+        C.byte c '_';
+        C.inline c i;
+        C.byte c '_'
+      in
+      let strikethrough c s =
+        let i = Inline.Strikethrough.inline s in
+        C.byte c '~';
+        C.inline c i;
+        C.byte c '~'
+      in
+      let link c l =
+        match Inline.Link.reference l with
+        | `Inline (ld, _) ->
+          begin
+            match Link_definition.dest ld with
+            | None -> C.inline c (Inline.Link.text l)
+            | Some (dest, _) ->
+              C.byte c '<';
+              C.string c dest;
+              C.byte c '|';
+              C.inline c (Inline.Link.text l);
+              C.byte c '>'
+          end;
+          true
+        | _ -> false
+      in
+      match inline with
+      | Inline.Strong_emphasis (e, _) ->
+        strong_emphasis c e;
+        true
+      | Inline.Emphasis (e, _) ->
+        emphasis c e;
+        true
+      | Inline.Ext_strikethrough (s, _) ->
+        strikethrough c s;
+        true
+      | Inline.Link (l, _) -> link c l
+      | _ -> false (* let the default renderer handle that *)
+    in
+    let default_renderer = Cmarkit_commonmark.renderer () in
+    let renderer = Cmarkit_renderer.make ~inline () in
+    Cmarkit_renderer.compose default_renderer renderer
+end
+
+let of_doc = Cmarkit_renderer.doc_to_string Cmarkit_slack.renderer
diff --git a/lib_test/mrkdwn/dune b/lib_test/mrkdwn/dune
new file mode 100644
index 0000000..af6145f
--- /dev/null
+++ b/lib_test/mrkdwn/dune
@@ -0,0 +1,11 @@
+(executable
+ (name mrkdwn_of_md)
+ (libraries slack_lib cmarkit))
+
+(env
+ (_
+  (binaries
+   (./mrkdwn_of_md.exe as mrkdwn_of_md))))
+
+(cram
+ (deps %{bin:mrkdwn_of_md}))
diff --git a/lib_test/mrkdwn/mrkdwn_of_md.ml b/lib_test/mrkdwn/mrkdwn_of_md.ml
new file mode 100644
index 0000000..ef24764
--- /dev/null
+++ b/lib_test/mrkdwn/mrkdwn_of_md.ml
@@ -0,0 +1 @@
+let () = print_string (Cmarkit.Doc.of_string ~strict:false (In_channel.input_all stdin) |> Slack_lib.Mrkdwn.of_doc)
diff --git a/lib_test/mrkdwn/mrkdwn_of_md.t b/lib_test/mrkdwn/mrkdwn_of_md.t
new file mode 100644
index 0000000..4d499af
--- /dev/null
+++ b/lib_test/mrkdwn/mrkdwn_of_md.t
@@ -0,0 +1,30 @@
+bold
+  $ mrkdwn_of_md << "MD"
+  > **bold**
+  > __bold__
+  > MD
+  *bold*
+  *bold*
+
+italic
+  $ mrkdwn_of_md << "MD"
+  > *italic*
+  > _italic_
+  > MD
+  _italic_
+  _italic_
+
+
+strikethrough
+  $ mrkdwn_of_md << "MD"
+  > ~~strike~~
+  > ~strike~
+  > MD
+  ~strike~
+  ~strike~
+
+link
+  $ mrkdwn_of_md << "MD"
+  > [hello](https://google.be)
+  > MD
+  <https://google.be|hello>

From bddd8fd25e4132d394323df2c5cad6b373354ab5 Mon Sep 17 00:00:00 2001
From: Corentin Leruth <corentin.leruth@gmail.com>
Date: Mon, 18 Mar 2024 13:29:37 +0100
Subject: [PATCH 2/2] print headings as bold

---
 lib/mrkdwn.ml                  | 15 ++++++++++++++-
 lib_test/mrkdwn/mrkdwn_of_md.t | 16 ++++++++++++++++
 2 files changed, 30 insertions(+), 1 deletion(-)

diff --git a/lib/mrkdwn.ml b/lib/mrkdwn.ml
index 3c2b2cd..16c1f1f 100644
--- a/lib/mrkdwn.ml
+++ b/lib/mrkdwn.ml
@@ -110,8 +110,21 @@ module Cmarkit_slack = struct
       | Inline.Link (l, _) -> link c l
       | _ -> false (* let the default renderer handle that *)
     in
+    let block c block =
+      let open Cmarkit in
+      let module C = Cmarkit_renderer.Context in
+      match block with
+      | Block.Heading (heading, _) ->
+        let inline = Block.Heading.inline heading in
+        C.byte c '*';
+        C.inline c inline;
+        C.byte c '*';
+        C.byte c '\n';
+        true
+      | _ -> false
+    in
     let default_renderer = Cmarkit_commonmark.renderer () in
-    let renderer = Cmarkit_renderer.make ~inline () in
+    let renderer = Cmarkit_renderer.make ~inline ~block () in
     Cmarkit_renderer.compose default_renderer renderer
 end
 
diff --git a/lib_test/mrkdwn/mrkdwn_of_md.t b/lib_test/mrkdwn/mrkdwn_of_md.t
index 4d499af..ff25f28 100644
--- a/lib_test/mrkdwn/mrkdwn_of_md.t
+++ b/lib_test/mrkdwn/mrkdwn_of_md.t
@@ -28,3 +28,19 @@ link
   > [hello](https://google.be)
   > MD
   <https://google.be|hello>
+
+headings
+  $ mrkdwn_of_md << "MD"
+  > # one
+  > ## two
+  > ### three
+  > #### four
+  > ##### five
+  > ###### six
+  > MD
+  *one*
+  *two*
+  *three*
+  *four*
+  *five*
+  *six*