%%%-------------------------------------------------------------------
%%% @doc Административный обработчик бан-слов.
%%% GET    – список всех слов с пагинацией.
%%% POST   – добавить новое слово.
%%% DELETE – удалить слово по :word.
%%% @end
%%%-------------------------------------------------------------------
-module(admin_handler_banned_words).
-behaviour(cowboy_handler).

-export([init/2]).
-export([trails/0]).

-include("records.hrl").

-spec init(cowboy_req:req(), any()) -> {ok, cowboy_req:req(), any()}.
init(Req, _Opts) ->
  case cowboy_req:method(Req) of
    <<"GET">>    -> list_words(Req);
    <<"POST">>   -> add_word(Req);
    <<"DELETE">> -> delete_word(Req);
    _            -> handler_utils:send_error(Req, 405, <<"Method not allowed">>)
  end.

-spec trails() -> [map()].
trails() ->
  [
    #{  % GET list
      path        => <<"/v1/admin/banned-words">>,
      method      => <<"GET">>,
      description => <<"List all banned words (admin)">>,
      tags        => [<<"Banned Words">>],
      parameters  => [
        #{name => <<"limit">>,  in => <<"query">>, schema => #{type => integer}, description => <<"Page size">>},
        #{name => <<"offset">>, in => <<"query">>, schema => #{type => integer}, description => <<"Offset">>}
      ],
      responses => #{
        200 => #{
          description => <<"Array of banned words">>,
          content => #{<<"application/json">> => #{schema => #{
            type  => array,
            items => banned_word_schema()
          }}}
        }
      }
    },
    #{  % POST add
      path        => <<"/v1/admin/banned-words">>,
      method      => <<"POST">>,
      description => <<"Add a new banned word">>,
      tags        => [<<"Banned Words">>],
      requestBody => #{
        required => true,
        content  => #{<<"application/json">> => #{schema => #{
          type       => object,
          required   => [<<"word">>],
          properties => #{
            word => #{type => string}
          }
        }}}
      },
      responses => #{
        201 => #{description => <<"Word added">>},
        409 => #{description => <<"Word already exists">>}
      }
    },
    #{  % DELETE by word
      path        => <<"/v1/admin/banned-words/:word">>,
      method      => <<"DELETE">>,
      description => <<"Remove a banned word">>,
      tags        => [<<"Banned Words">>],
      parameters  => [
        #{
          name        => <<"word">>,
          in          => <<"path">>,
          description => <<"The word to remove">>,
          required    => true,
          schema      => #{type => string}
        }
      ],
      responses => #{
        200 => #{description => <<"Word removed">>},
        404 => #{description => <<"Word not found">>}
      }
    }
  ].

banned_word_schema() ->
  #{
    type       => object,
    properties => #{
      id        => #{type => string},
      word      => #{type => string},
      added_by  => #{type => string, nullable => true},
      added_at  => #{type => string, format => <<"date-time">>, nullable => true}
    }
  }.

%%% Internal functions

list_words(Req) ->
  case handler_utils:auth_admin(Req) of
    {ok, _AdminId, Req1} ->
      Pagination = handler_utils:parse_pagination_params(Req1),
      %% core_banned_words:list_banned_words() возвращает список, а не {ok, List}
      AllWords = core_banned_words:list_banned_words(),
      BannedWords = lists:sort(AllWords),
      Total = length(BannedWords),
      Page = lists:sublist(BannedWords, maps:get(offset, Pagination) + 1, maps:get(limit, Pagination)),
      Json = [word_to_map(W) || W <- Page],
      ExtraHeaders = pagination_headers(Pagination, Total),
      handler_utils:send_json(Req1, 200, Json, ExtraHeaders);
    {error, Code, Msg, Req1} ->
      handler_utils:send_error(Req1, Code, Msg)
  end.

add_word(Req) ->
  case handler_utils:auth_admin(Req) of
    {ok, AdminId, Req1} ->
      {ok, Body, Req2} = cowboy_req:read_body(Req1),
      try jsx:decode(Body, [return_maps]) of
        #{<<"word">> := Word} ->
          case core_banned_words:add_banned_word(Word, AdminId) of
            {ok, _} ->
              handler_utils:send_json(Req2, 201, #{status => <<"added">>});
            {error, already_exists} ->
              handler_utils:send_error(Req2, 409, <<"Word already exists">>);
            {error, _} ->
              handler_utils:send_error(Req2, 500, <<"Internal server error">>)
          end;
        _ ->
          handler_utils:send_error(Req2, 400, <<"Missing 'word' field">>)
      catch
        _:_ -> handler_utils:send_error(Req1, 400, <<"Invalid JSON">>)
      end;
    {error, Code, Msg, Req1} ->
      handler_utils:send_error(Req1, Code, Msg)
  end.

delete_word(Req) ->
  case handler_utils:auth_admin(Req) of
    {ok, _AdminId, Req1} ->
      Word = cowboy_req:binding(word, Req1),
      case core_banned_words:remove_banned_word(Word) of
        {ok, _} ->
          handler_utils:send_json(Req1, 200, #{status => <<"deleted">>});
        {error, not_found} ->
          handler_utils:send_error(Req1, 404, <<"Word not found">>);
        {error, _} ->
          handler_utils:send_error(Req1, 500, <<"Internal server error">>)
      end;
    {error, Code, Msg, Req1} ->
      handler_utils:send_error(Req1, Code, Msg)
  end.

%% @private Преобразование записи banned_word в JSON-совместимую карту.
word_to_map(W) ->
  #{
    id       => W#banned_word.id,
    word     => W#banned_word.word,
    added_by => W#banned_word.added_by,
    added_at => datetime_to_iso8601(W#banned_word.added_at)
  }.

%% @private Форматирование datetime в ISO8601 строку.
datetime_to_iso8601(undefined) -> undefined;
datetime_to_iso8601({{Year, Month, Day}, {Hour, Minute, Second}}) ->
  iolist_to_binary(io_lib:format("~4..0B-~2..0B-~2..0BT~2..0B:~2..0B:~2..0BZ",
    [Year, Month, Day, Hour, Minute, Second])).

pagination_headers(#{limit := Limit, offset := Offset}, Total) ->
  RangeEnd = min(Offset + Limit - 1, Total - 1),
  #{
    <<"content-range">>                 => iolist_to_binary(io_lib:format("items ~B-~B/~B", [Offset, RangeEnd, Total])),
    <<"x-total-count">>                 => integer_to_binary(Total),
    <<"access-control-expose-headers">> => <<"Content-Range, X-Total-Count">>
  }.