(** Parses a native Hevy CSV export into a {!Workout_import.batch}.

    This is a web-layer adapter: it turns untrusted export text into the
    application's import use case. It does not construct canonical evidence or
    apply Heavy Duty judgment. It never depends on [hito.persistence]. The whole
    export text is retained verbatim through
    {!Hito_app.Workout_import.make_batch}, so provenance survives the parse.

    The adapter enforces the strict native schema. The header must carry all 14
    verified columns, in any order. Rows the adapter cannot promote — warmups,
    non-strength data, unknown set types, malformed fields — become
    {!Workout_import.warning} values, not sets. A row is dropped, never guessed
    at. Rows group into workouts by the exact [(title, start_time, end_time)]
    triple, in first-appearance order. *)

type error =
  | Malformed_csv of { record : int; field : int; detail : string }
      (** The CSV text does not conform to RFC4180. [record] and [field] are
          1-based, as {!Csv.Failure} reports them. *)
  | Missing_column of string
      (** A required column is absent from the header. The first missing column
          in canonical order is reported. *)
  | Empty_file  (** The export has no rows at all, not even a header. *)

val pp_error : Format.formatter -> error -> unit

val parse :
  batch_id:Hito_app.Workout_import.batch_id ->
  fingerprint:string ->
  imported_at:Recovery.timestamp ->
  utc_offset_seconds:int ->
  string ->
  (Hito_app.Workout_import.batch, error) result
(** [parse ~batch_id ~fingerprint ~imported_at ~utc_offset_seconds source]
    parses [source] as a native Hevy export.

    [utc_offset_seconds] is the offset of the wall-clock times in the export.
    Hevy datetimes are local wall time, so UTC seconds = civil seconds - offset.

    Returns [Error Empty_file] for empty input, [Error (Missing_column _)] when
    the header lacks a required column, and [Error (Malformed_csv _)] when the
    CSV text is not well formed. On success the batch retains [source] exactly.
    Rows the adapter cannot use appear in {!Workout_import.batch_warnings} in
    source order. *)