-module(core_automod_settings).
-include("records.hrl").

-export([get/0, update/2, ensure_defaults/0]).

-define(ID, <<"default">>).
-define(DEFAULT_ACTION, flag).
-define(DEFAULT_MATCH, word_boundary).
-define(DEFAULT_THRESHOLD, 3).

-spec get() -> #automod_settings{}.
get() ->
  case catch mnesia:dirty_read(automod_settings, ?ID) of
    [S] -> S;
    [] ->
      case catch ensure_defaults() of
        ok ->
          case catch mnesia:dirty_read(automod_settings, ?ID) of
            [S2] -> S2;
            _ -> default_record(<<>>)
          end;
        _ ->
          default_record(<<>>)
      end;
    {'EXIT', _} ->
      default_record(<<>>);
    _ ->
      default_record(<<>>)
  end.

-spec ensure_defaults() -> ok.
ensure_defaults() ->
  case lists:member(automod_settings, mnesia:system_info(tables)) of
    false ->
      ok;
    true ->
      case mnesia:dirty_read(automod_settings, ?ID) of
        [_] -> ok;
        [] ->
          mnesia:dirty_write(default_record(<<>>)),
          ok
      end
  end.

-spec update(map() | [{atom(), term()}], binary()) ->
  {ok, #automod_settings{}} | {error, term()}.
update(Updates, AdminId) when is_map(Updates) ->
  update(maps:to_list(Updates), AdminId);
update(Updates, AdminId) when is_list(Updates) ->
  Current = get(),
  case apply_updates(Current, Updates) of
    {error, _} = Err -> Err;
    {ok, Next0} ->
      Next = Next0#automod_settings{
        updated_at = calendar:universal_time(),
        updated_by = AdminId
      },
      mnesia:dirty_write(Next),
      {ok, Next}
  end.

default_record(UpdatedBy) ->
  #automod_settings{
    id = ?ID,
    keyword_action = ?DEFAULT_ACTION,
    match_mode = ?DEFAULT_MATCH,
    report_threshold = ?DEFAULT_THRESHOLD,
    updated_at = calendar:universal_time(),
    updated_by = UpdatedBy
  }.

apply_updates(S, []) -> {ok, S};
apply_updates(S, [{keyword_action, A} | Rest])
  when A =:= reject; A =:= flag; A =:= censor ->
  apply_updates(S#automod_settings{keyword_action = A}, Rest);
apply_updates(S, [{match_mode, M} | Rest])
  when M =:= word_boundary; M =:= substring ->
  apply_updates(S#automod_settings{match_mode = M}, Rest);
apply_updates(S, [{report_threshold, N} | Rest])
  when is_integer(N), N >= 1 ->
  apply_updates(S#automod_settings{report_threshold = N}, Rest);
apply_updates(_S, [{Field, _} | _]) ->
  {error, {invalid_field, Field}}.