(* emit_csv.ml *)
module T = Template

let escape_field s =
  let needs =
    String.exists (fun c -> c = ',' || c = '"' || c = '\n' || c = '\r') s
  in
  if not needs then s
  else begin
    let b = Buffer.create (String.length s + 8) in
    Buffer.add_char b '"';
    String.iter (fun c -> if c = '"' then Buffer.add_string b "\"\"" else Buffer.add_char b c) s;
    Buffer.add_char b '"';
    Buffer.contents b
  end

let get v k = match v with T.Obj kvs -> List.assoc_opt k kvs | _ -> None
let s v k = match get v k with Some (T.Str x) -> x | _ -> ""

(* [name] is now the single RESOLVED display string (view.ml), not a
   lang-keyed object -- the [name_la]/[name_en] pair this replaces carried
   the kernel's own [Celebration.names], a different, unlocalised source.
   Machine formats still carry [slug] alongside it, so a script keeps the
   stable key and a human reads the name.

   W5 left this deliberately NOT widened with a "second" column, unlike
   [Emit_xml]/[Emit_ics] (each a repeated-element/free-text format that
   grows for free): a CSV's header row is a CONTRACT with every row under
   it (RFC 4180 sec. 2: "each field in the header... should contain the
   same number of fields as the records"), so there is no way to add a
   column only on the days that carry a [Second] reading -- a real
   three-citation day needs either an ALWAYS-present, mostly-empty
   "second" column or genuinely variable-width rows (not CSV). At the
   time, [bin/main.ml]'s [reject_rite_for] refused [--rite] on `emit`
   entirely for any rite but EF, so no [Second] reading could reach this
   module, and this was recorded as the deliberate, disclosed breaking
   change the day OF was admitted here would need -- "a new column, a
   version bump, or a documented trade-off, not a silent one".

   Fix 1 (cli-flags-report, 2026-08-27): that day is this one. The
   "always-present, mostly-empty column" option is taken, gated on
   [rite] (read from [v] itself, exactly as [row]'s own [~rite] already
   is) rather than threaded as a new parameter: EF's [rite = "ef"] keeps
   the ORIGINAL 16-column header and rows, byte for byte -- no [Second]
   reading has ever reached EF's own [citations]
   ({!Rite_ef}'s own [citation_shapes] is still exactly
   [[First; Gospel]]), so [rite = "ef"]'s branch below is provably
   unreachable-different, not merely untested-different. Any OTHER rite
   (OF today) gets a 17th column, "second", spliced between "first" and
   "gospel" -- the same position [Emit_xml]/[Emit_ics] already use for
   it -- reading [s d "second"], which [get]'s own [None -> ""] fallback
   already resolves to the empty string on every day that has no [Second]
   part (a feria, feast or memorial; OLM 1981 Praenotanda n. 66.1/n. 69.1),
   so nothing here needs to know in advance which OF days do carry one. *)
let columns ~rite =
  let base =
    [ "date"; "rite"; "season"; "season_name"; "week"; "slug"; "name"; "weekday"; "rank"; "rank_name";
      "colour"; "colour_name"; "subject"; "first" ]
  in
  let tail = [ "gospel"; "comms" ] in
  if rite = "ef" then base @ tail else base @ [ "second" ] @ tail

let row ~rite d =
  let comms =
    match get d "comms" with
    | Some (T.List l) -> String.concat " " (List.map (fun c -> s c "slug") l)
    | _ -> ""
  in
  let base =
    [ s d "iso"; rite; s d "season"; s d "season_name"; s d "week"; s d "slug"; s d "name";
      s d "weekday"; s d "rank"; s d "rank_name"; s d "colour"; s d "colour_name"; s d "subject";
      s d "first" ]
  in
  let tail = [ s d "gospel"; comms ] in
  let fields = if rite = "ef" then base @ tail else base @ [ s d "second" ] @ tail in
  String.concat "," (List.map escape_field fields)

let year v =
  let rite = s v "rite" in
  let days = match get v "days" with Some (T.List l) -> l | _ -> [] in
  let b = Buffer.create (64 * 400) in
  Buffer.add_string b (String.concat "," (columns ~rite));
  Buffer.add_char b '\n';
  List.iter (fun d -> Buffer.add_string b (row ~rite d); Buffer.add_char b '\n') days;
  Buffer.contents b