Add endpoint for GET payment by id

api/bin/main.ml

@@ -26,6 +26,21 @@ let post_payments request =
   |> Yojson.Safe.to_string
   |> Dream.json ~status:`Created
 
+let get_payment request =
+  let payment_id = Dream.param request "id" in
+
+  let%lwt payment = Dream.sql request (Payment.find payment_id) in
+
+  match payment with
+  | Some payment ->
+    let response =
+      (fun (id, owner, amount, created_at) -> {id; owner; amount; created_at})
+        payment
+    in
+
+    yojson_of_payment_creation response |> Yojson.Safe.to_string |> Dream.json
+  | None -> Dream.json ~status:`Not_Found ""
+
 let () =
   let postgres_url =
     match Sys.getenv_opt "DATABASE_URL" with
@@ -40,5 +55,6 @@ let () =
   @@ Dream.router
        [
          Dream.get "/" (fun _ -> Dream.html "hello world");
-         Dream.post "/payments/" post_payments;
+         Dream.scope "/payments" []
+           [Dream.post "/" post_payments; Dream.get "/:id/" get_payment];
        ]

api/models/payment.ml

@@ -26,3 +26,15 @@ let create =
       Db.find query (payment.owner, payment.amount, payment.description)
     in
     Caqti_lwt.or_fail result
+
+let find =
+  let query =
+    let open Caqti_request.Infix in
+    (T.string ->? T.(tup4 string string float string))
+      {|
+      SELECT id, owner, amount, created_at FROM payment WHERE id = $1
+      |}
+  in
+  fun (id : string) (module Db : DB) ->
+    let%lwt result = Db.find_opt query id in
+    Caqti_lwt.or_fail result