add api route to send slack unfurl request

Author: yasunariw

lib/api.ml

@@ -10,4 +10,6 @@ end
 
 module type Slack = sig
   val send_notification : ctx:Context.t -> msg:post_message_req -> (unit, string) Result.t Lwt.t
+
+  val send_chat_unfurl : ctx:Context.t -> chat_unfurl_req -> (unit, string) Result.t Lwt.t
 end

lib/api_local.ml

@@ -20,7 +20,15 @@ module Github : Api.Github = struct
     | Ok file -> Lwt.return @@ Ok (Github_j.api_commit_of_string file)
 end
 
+module Slack_base : Api.Slack = struct
+  let send_notification ~ctx:_ ~msg:_ = Lwt.return @@ Error "undefined for local setup"
+
+  let send_chat_unfurl ~ctx:_ _ = Lwt.return @@ Error "undefined for local setup"
+end
+
 module Slack : Api.Slack = struct
+  include Slack_base
+
   let send_notification ~ctx:_ ~msg =
     let json = msg |> Slack_j.string_of_post_message_req |> Yojson.Basic.from_string |> Yojson.Basic.pretty_to_string in
     Stdio.printf "will notify #%s\n" msg.channel;
@@ -29,6 +37,8 @@ module Slack : Api.Slack = struct
 end
 
 module Slack_simple : Api.Slack = struct
+  include Slack_base
+
   let log = Log.from "slack"
 
   let send_notification ~ctx:_ ~(msg : Slack_t.post_message_req) =
@@ -41,6 +51,8 @@ module Slack_simple : Api.Slack = struct
 end
 
 module Slack_json : Api.Slack = struct
+  include Slack_base
+
   let log = Log.from "slack"
 
   let send_notification ~ctx:_ ~(msg : Slack_t.post_message_req) =

lib/api_remote.ml

@@ -81,4 +81,26 @@ module Slack : Api.Slack = struct
         )
       | Error e -> Lwt.return @@ build_query_error url e
       )
+
+  let send_chat_unfurl ~(ctx : Context.t) req =
+    log#info "unfurling Slack links";
+    let secrets = Context.get_secrets_exn ctx in
+    match secrets.slack_access_token with
+    | None -> Lwt.return @@ fmt_error "failed to retrieve Slack access token"
+    | Some access_token ->
+      let data = Slack_j.string_of_chat_unfurl_req req in
+      log#info "%s" data;
+      let url = "https://slack.com/api/chat.unfurl" in
+      let headers = [ bearer_token_header access_token ] in
+      let body = `Raw ("application/json", data) in
+      ( match%lwt http_request ~body ~headers `POST url with
+      | Ok s ->
+        let res = Slack_j.chat_unfurl_res_of_string s in
+        if res.ok then Lwt.return @@ Ok ()
+        else (
+          let msg = Option.value ~default:"an unknown error occurred" res.error in
+          Lwt.return @@ fmt_error "%s\nfailed to unfurl Slack links" msg
+        )
+      | Error e -> Lwt.return @@ fmt_error "error while querying %s: %s\nfailed to unfurl Slack links" url e
+      )
 end