refactor(xml): move get and next functions to Xml

1 files changed, 19 insertions, 0 deletions

diff --git a/lib/xml.ml b/lib/xml.ml
index 99a388f..25332a5 100644
--- a/lib/xml.ml
+++ b/lib/xml.ml
@@ -1,3 +1,4 @@
+open Lwt.Syntax
 open Markup
 
 exception InvalidStanza of string
@@ -56,3 +57,21 @@ let element_to_string ?(indent = 2) (el : element) =
                            |> tab)
                     ^ "\n</" ^ local_name ^ ">"
   in element_to_string "" el |> String.trim
+
+(** [next stream] is a promise containing a full stanza of the fragments of
+    [stream]. *)
+let next (stream : (signal, async) stream) : (signal, sync) stream Lwt.t =
+  let traverse_stanza depth fragment =
+    let depth = match fragment with
+      | `Start_element _ -> depth + 1
+      | `End_element -> depth - 1
+      | _ -> depth
+    in ([fragment], if depth = 0 then None else Some depth)
+  in transform traverse_stanza 0 stream |> Markup_lwt.load
+
+(** [get stream] is a promise containing a single Xml element of [stream]. *)
+let get (stream : (signal, async) stream) : element Lwt.t =
+  let* signal = next stream
+  in match tree signal with
+     | Some xml -> Lwt.return xml
+     | None -> Lwt.fail (InvalidStanza (signal |> write_xml |> to_string))