(*---------------------------------------------------------------------------
   Copyright (c) 2024 Anil Madhavapeddy. All rights reserved.
   SPDX-License-Identifier: ISC
  ---------------------------------------------------------------------------*)

module Unknown = struct
  type t = (string * Jsont.json) list

  let empty = []
  let is_empty = function [] -> true | _ -> false
end

type t = {
  name : string option;
  url : string option;
  avatar : string option;
  unknown : Unknown.t;
}

let create ?name ?url ?avatar ?(unknown = Unknown.empty) () =
  if name = None && url = None && avatar = None then
    invalid_arg
      "Author.create: at least one field (name, url, or avatar) must be \
       provided";
  { name; url; avatar; unknown }

let name t = t.name
let url t = t.url
let avatar t = t.avatar
let unknown t = t.unknown
let is_valid t = t.name <> None || t.url <> None || t.avatar <> None
let equal a b = a.name = b.name && a.url = b.url && a.avatar = b.avatar

let pp ppf t =
  match (t.name, t.url) with
  | Some name, Some url -> Format.fprintf ppf "%s <%s>" name url
  | Some name, None -> Format.fprintf ppf "%s" name
  | None, Some url -> Format.fprintf ppf "<%s>" url
  | None, None -> (
      match t.avatar with
      | Some avatar -> Format.fprintf ppf "(avatar: %s)" avatar
      | None -> Format.fprintf ppf "(empty author)")

let jsont =
  let kind = "Author" in
  let doc = "An author object with at least one field set" in
  (* Custom mems map for Unknown.t that strips metadata from names *)
  let unknown_mems :
      (Unknown.t, Jsont.json, Jsont.mem list) Jsont.Object.Mems.map =
    let open Jsont.Object.Mems in
    let dec_empty () = [] in
    let dec_add _meta (name : string) value acc =
      ((name, Jsont.Meta.none), value) :: acc
    in
    let dec_finish _meta mems =
      List.rev_map (fun ((name, _meta), value) -> (name, value)) mems
    in
    let enc =
      {
        enc =
          (fun (type acc)
            (f : Jsont.Meta.t -> string -> Jsont.json -> acc -> acc)
            unknown
            (acc : acc)
          ->
            List.fold_left
              (fun acc (name, value) -> f Jsont.Meta.none name value acc)
              acc unknown);
      }
    in
    map ~kind:"Unknown members" Jsont.json ~dec_empty ~dec_add ~dec_finish ~enc
  in
  (* Constructor that matches the jsont object map pattern *)
  let create_obj name url avatar unknown =
    create ?name ?url ?avatar ~unknown ()
  in
  Jsont.Object.map ~kind ~doc create_obj
  |> Jsont.Object.opt_mem "name" Jsont.string ~enc:name
  |> Jsont.Object.opt_mem "url" Jsont.string ~enc:url
  |> Jsont.Object.opt_mem "avatar" Jsont.string ~enc:avatar
  |> Jsont.Object.keep_unknown unknown_mems ~enc:unknown
  |> Jsont.Object.finish