(** The examination cap on filtered history walks: that a walk stopped by the
    cap reports truncation, and an exhausted history does not. *)

open Test_helpers

let with_history_repository test =
  with_temp_directory "ogit-walk" (fun root ->
      let name = "project" in
      let path = Filename.concat root name in
      Unix.mkdir path 0o755;
      ignore (git [ "-C"; path; "init"; "-q"; "-b"; "main" ]);
      ignore (git [ "-C"; path; "config"; "user.name"; "Test" ]);
      ignore (git [ "-C"; path; "config"; "user.email"; "t@t.invalid" ]);
      for index = 1 to 8 do
        Out_channel.with_open_text (Filename.concat path "f.txt") (fun ch ->
            Printf.fprintf ch "revision %d\n" index);
        ignore (git [ "-C"; path; "add"; "." ]);
        ignore
          (git [ "-C"; path; "commit"; "-q"; "-m"; Printf.sprintf "c%d" index ])
      done;
      let config = Ogit.Config.{ default with git_project_root = root } in
      let repository =
        match Lwt_main.run (Ogit.Resolvers.open_repository config name) with
        | Ok r -> r
        | Error e -> Alcotest.failf "%a" Ogit.Resolvers.pp_error e
      in
      Fun.protect
        ~finally:(fun () ->
          Lwt_main.run (Ogit.Resolvers.close_repository repository))
        (fun () -> test repository))

let recent_matching ?max_examined repository count predicate =
  match
    Lwt_main.run
      (Ogit.Resolvers.Commit.recent_matching ?max_examined repository count
         predicate)
  with
  | Ok result -> result
  | Error e -> Alcotest.failf "%a" Ogit.Resolvers.pp_error e

let never_matches _ = false

let test_cap_reports_truncation () =
  with_history_repository (fun repository ->
      let commits, truncated =
        recent_matching ~max_examined:3 repository 10 never_matches
      in
      Alcotest.(check int) "no matches" 0 (List.length commits);
      Alcotest.(check bool) "truncated" true truncated)

let test_exhausted_history_is_complete () =
  with_history_repository (fun repository ->
      let commits, truncated =
        recent_matching ~max_examined:100 repository 10 never_matches
      in
      Alcotest.(check int) "no matches" 0 (List.length commits);
      Alcotest.(check bool) "not truncated" false truncated)

let test_cap_keeps_collected_matches () =
  with_history_repository (fun repository ->
      (* Every commit matches; the cap stops the walk after three of eight. *)
      let commits, truncated =
        recent_matching ~max_examined:3 repository 10 (fun _ -> true)
      in
      Alcotest.(check int) "three collected" 3 (List.length commits);
      Alcotest.(check bool) "truncated" true truncated)

let suite =
  ( "commit walk",
    [
      Alcotest.test_case "cap reports truncation" `Slow
        test_cap_reports_truncation;
      Alcotest.test_case "exhausted history is complete" `Slow
        test_exhausted_history_is_complete;
      Alcotest.test_case "cap keeps collected matches" `Slow
        test_cap_keeps_collected_matches;
    ] )