add avail-languages header

src/headers.ml

@@ -1,3 +1,8 @@
+let avail_languages_header_value =
+  let pp_avail_languages = Fmt.array ~sep:(Fmt.any ", ") Fmt.string in
+  let s = Fmt.str "%a" pp_avail_languages Assets.supported_lang_arr in
+  s
+
 let select_extension headers =
   let accept = Vif.Headers.get headers "accept" in
   Cohttp.Accept.media_ranges accept

src/mte.ml

@@ -13,6 +13,15 @@
     You should have received a copy of the GNU Affero General Public License
     along with this program.  If not, see <https://www.gnu.org/licenses/>. *)
 
+(* /terms + /privacy
+   - try to find a response with an acceptable mime-type
+   - pick the version in the most preferred language of the user
+   - apply compression if that is allowed by the client
+   - set ETAG header
+   - If it did not change, a "304 Not Modified" response will be returned
+   - A "Taler-Terms-Version" header is generated to indicate the legal version of the terms
+   - When returning a full response (not a "304 Not Modified"),
+     include a "Avail-Languages" header: a comma-separated list of the languages available *)
 module Static = struct
   let select_file headers kind =
     let open Syntax in
@@ -24,23 +33,8 @@ module Static = struct
       Option.to_result ~none:"no acceptable language"
         (Headers.select_language headers)
     in
-    let content = Assets.get_content ~lang ~ext kind in
-    content
+    Assets.get_content ~lang ~ext kind
 
-  (* /terms + /privacy
-
-     - try to find a response with an acceptable mime-type,
-     - then pick the version in the most preferred language of the user,
-     - and finally apply compression if that is allowed by the client
-     - set ETAG header
-     - If it did not change, a "304 Not Modified" response will be returned
-     - A "Taler-Terms-Version" header is generated to indicate the legal version of the terms
-
-     TODO:
-       - When returning a full response (not a "304 Not Modified"), the server
-         should also include a "Avail-Languages" header which includes a
-         comma-separated list of the languages in which the terms of service are available in
-  *)
   let static kind req _server _env =
     let get_ok = function
       | Error e -> Fmt.failwith "TODO handle me, %s" e
@@ -75,6 +69,10 @@ module Static = struct
           Vif.Response.add ~field:"taler-terms-version"
             Config.terms_legal_version
         in
+        let* () =
+          Vif.Response.add ~field:"avail-languages"
+            Headers.avail_languages_header_value
+        in
         (* TODO content-type *)
         let* () =
           Vif.Response.add ~field:"content-type" "html; charset=utf-8"