add api routes to retrieve GH issues and PRs

Author: yasunariw

lib/api.ml

@@ -6,6 +6,10 @@ module type Github = sig
   val get_config : ctx:Context.t -> repo:repository -> (Config_t.config, string) Result.t Lwt.t
 
   val get_api_commit : ctx:Context.t -> repo:repository -> sha:string -> (api_commit, string) Result.t Lwt.t
+
+  val get_pull_request : ctx:Context.t -> repo:repository -> number:int -> (pull_request, string) Result.t Lwt.t
+
+  val get_issue : ctx:Context.t -> repo:repository -> number:int -> (issue, string) Result.t Lwt.t
 end
 
 module type Slack = sig

lib/api_local.ml

@@ -18,6 +18,10 @@ module Github : Api.Github = struct
     match get_local_file url with
     | Error e -> Lwt.return @@ fmt_error "error while getting local file: %s\nfailed to get api commit %s" e url
     | Ok file -> Lwt.return @@ Ok (Github_j.api_commit_of_string file)
+
+  let get_pull_request ~ctx:_ ~repo:_ ~number:_ = Lwt.return @@ Error "undefined for local setup"
+
+  let get_issue ~ctx:_ ~repo:_ ~number:_ = Lwt.return @@ Error "undefined for local setup"
 end
 
 module Slack_base : Api.Slack = struct

lib/api_remote.ml

@@ -10,6 +10,12 @@ module Github : Api.Github = struct
   let contents_url ~(repo : Github_t.repository) ~path =
     String.substr_replace_first ~pattern:"{+path}" ~with_:path repo.contents_url
 
+  let pulls_url ~(repo : Github_t.repository) ~number =
+    String.substr_replace_first ~pattern:"{/number}" ~with_:(sprintf "/%d" number) repo.pulls_url
+
+  let issues_url ~(repo : Github_t.repository) ~number =
+    String.substr_replace_first ~pattern:"{/number}" ~with_:(sprintf "/%d" number) repo.issues_url
+
   let build_headers ?token () =
     let headers = [ "Accept: application/vnd.github.v3+json" ] in
     Option.value_map token ~default:headers ~f:(fun v -> sprintf "Authorization: token %s" v :: headers)
@@ -38,13 +44,24 @@ module Github : Api.Github = struct
         @@ fmt_error "unexpected encoding '%s' in Github response\nfailed to get config from file %s" encoding url
       )
 
-  let get_api_commit ~(ctx : Context.t) ~repo ~sha =
+  let get_resource (ctx : Context.t) url =
     let secrets = Context.get_secrets_exn ctx in
-    let url = commits_url ~repo ~sha in
     let headers = build_headers ?token:secrets.gh_token () in
     match%lwt http_request ~headers `GET url with
-    | Ok res -> Lwt.return @@ Ok (Github_j.api_commit_of_string res)
-    | Error e -> Lwt.return @@ fmt_error "error while querying remote: %s\nfailed to get api commit from file %s" e url
+    | Ok res -> Lwt.return @@ Ok res
+    | Error e -> Lwt.return @@ fmt_error "error while querying remote: %s\nfailed to get resource from %s" e url
+
+  let get_api_commit ~(ctx : Context.t) ~repo ~sha =
+    let%lwt res = commits_url ~repo ~sha |> get_resource ctx in
+    Lwt.return @@ Result.map res ~f:Github_j.api_commit_of_string
+
+  let get_pull_request ~(ctx : Context.t) ~repo ~number =
+    let%lwt res = pulls_url ~repo ~number |> get_resource ctx in
+    Lwt.return @@ Result.map res ~f:Github_j.pull_request_of_string
+
+  let get_issue ~(ctx : Context.t) ~repo ~number =
+    let%lwt res = issues_url ~repo ~number |> get_resource ctx in
+    Lwt.return @@ Result.map res ~f:Github_j.issue_of_string
 end
 
 module Slack : Api.Slack = struct