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(** Testing
    -------
    Component:  Lib_dac_node Data_streamer
    Invocation: dune exec src/lib_dac_node/test/main.exe \
                  -- --file test_data_streamer.ml
    Subject:    Tests for the data streamer component.
*)

let dac_hash_1 = "hash_1"

let dac_hash_2 = "hash_2"

let assert_equal_string expected actual =
  Assert.equal
    ~loc:__LOC__
    ~eq:String.equal
    ~pp:Format.pp_print_string
    expected
    actual

let test_simple_pub_sub () =
  let open Lwt_result_syntax in
  let open Data_streamer in
  let streamer = init () in
  let stream, stopper = handle_subscribe streamer in
  let () = publish streamer dac_hash_1 in
  let*! next = Lwt_stream.next stream in
  let () = Lwt_watcher.shutdown stopper in
  let*! is_empty = Lwt_stream.is_empty stream in
  let () = Assert.assert_true "Expected empty stream." is_empty in
  return @@ assert_equal_string dac_hash_1 next

let test_subscription_time () =
  (* 1. subscriber_1 subscribes to the streamer component.
     2. [dac_hash_1] is published via the streamer component.
     3. subscriber_2 subscribes to the streamer component.
     4. [dac_hash_2] is published via streamer component.

     As such we expect:
     - subscriber_1 first element inside the stream is [dac_hash_1]
       and second one is [dac_hash_2].
     - subscriber_2 first element inside the stream is [dac_hash_2].

     Note that subscriber_2 does not receive [dac_hash_1] as it was published
     before his/her subscription to the streaming component.
  *)
  let open Lwt_result_syntax in
  let open Data_streamer in
  let streamer = init () in
  let stream_1, _stopper_1 = handle_subscribe streamer in
  let () = publish streamer dac_hash_1 in
  let stream_2, _stopper_2 = handle_subscribe streamer in
  let () = publish streamer dac_hash_2 in
  let*! subscriber_1_first = Lwt_stream.next stream_1 in
  let () = assert_equal_string dac_hash_1 subscriber_1_first in
  let*! subscriber_1_second = Lwt_stream.next stream_1 in
  let () = assert_equal_string dac_hash_2 subscriber_1_second in
  let*! subscriber_2_first = Lwt_stream.next stream_2 in
  return @@ assert_equal_string dac_hash_2 subscriber_2_first

let test_closing_subscriber_stream () =
  (* 1. subscriber_1 subscribes to the streamer component.
     2. subscriber_2 subscribes to the streamer component.
     3. subscriber_1's [stream_1] is closed.
     4. [dac_hash_1] is published via streamer component.

     As such we expect:
     - subscriber_1's [stream_1] is empty.
     - subscriber_2 first element inside the stream is [dac_hash_1].
  *)
  let open Lwt_result_syntax in
  let open Data_streamer in
  let streamer = init () in
  let stream_1, stopper_1 = handle_subscribe streamer in
  let stream_2, _stopper_2 = handle_subscribe streamer in
  let () = Lwt_watcher.shutdown stopper_1 in
  let () = publish streamer dac_hash_1 in
  let*! is_empty = Lwt_stream.is_empty stream_1 in
  let () = Assert.assert_true "[stream_1]: expected empty stream." is_empty in
  let*! subscriber_2_first = Lwt_stream.next stream_2 in
  return @@ assert_equal_string dac_hash_1 subscriber_2_first

let tests =
  [
    Tztest.tztest "Simple pub sub" `Quick test_simple_pub_sub;
    Tztest.tztest "Test order of subscription" `Quick test_subscription_time;
    Tztest.tztest
      "Test closing subscriber stream"
      `Quick
      test_closing_subscriber_stream;
  ]

let () =
  Alcotest_lwt.run ~__FILE__ "lib_dac_node" [("Data_streamer.ml", tests)]
  |> Lwt_main.run