(* 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 | _ -> ""
let nested v a b = match get v a with Some inner -> s inner b | None -> ""

let columns =
  [ "date"; "rite"; "season"; "week"; "slug"; "rank"; "colour"; "subject";
    "name_la"; "name_en"; "first"; "gospel"; "comms" ]

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
  String.concat ","
    (List.map escape_field
       [ s d "iso"; rite; s d "season"; s d "week"; s d "slug"; s d "rank";
         s d "colour"; s d "subject"; nested d "name" "la"; nested d "name" "en";
         s d "first"; s d "gospel"; comms ])

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);
  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