%%%-------------------------------------------------------------------
%%% @doc Административный обработчик списка пользователей.
%%% GET – список пользователей с пагинацией, фильтрацией и сортировкой.
%%% @end
%%%-------------------------------------------------------------------
-module(admin_handler_users).
-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_users(Req);
    _ -> handler_utils:send_error(Req, 405, <<"Method not allowed">>)
  end.

-spec trails() -> [map()].
trails() ->
  [
    #{
      path => <<"/v1/admin/users">>,
      method => <<"GET">>,
      description => <<"List all users (admin)">>,
      tags => [<<"Users">>],
      parameters => [
        #{name => <<"role">>, in => <<"query">>, schema => #{type => string, enum => [<<"user">>, <<"bot">>]}},
        #{name => <<"status">>, in => <<"query">>, schema => #{type => string, enum => [<<"active">>, <<"frozen">>, <<"deleted">>]}},
        #{name => <<"q">>, in => <<"query">>, schema => #{type => string}, description => <<"Search by email or nickname">>},
        #{name => <<"sort">>, in => <<"query">>, schema => #{type => string, enum => [<<"email">>, <<"role">>, <<"created_at">>]}, description => <<"Sort field">>},
        #{name => <<"order">>, in => <<"query">>, schema => #{type => string, enum => [<<"asc">>, <<"desc">>]}, description => <<"Sort direction">>},
        #{name => <<"limit">>, in => <<"query">>, schema => #{type => integer}},
        #{name => <<"offset">>, in => <<"query">>, schema => #{type => integer}}
      ],
      responses => #{
        200 => #{
          description => <<"Array of users">>,
          content => #{<<"application/json">> => #{schema => #{
            type => array,
            items => user_schema()
          }}}
        }
      }
    }
  ].

-spec user_schema() -> map().
user_schema() ->
  #{
    type => object,
    properties => #{
      id => #{type => string},
      email => #{type => string, format => <<"email">>},
      role => #{type => string, enum => [<<"user">>, <<"bot">>]},
      status => #{type => string, enum => [<<"active">>, <<"frozen">>, <<"deleted">>]},
      reason => #{type => string, nullable => true},
      nickname => #{type => string, nullable => true},
      avatar_url => #{type => string, nullable => true},
      timezone => #{type => string, nullable => true},
      language => #{type => string, nullable => true},
      social_links => #{type => array, items => #{type => string}, nullable => true},
      phone => #{type => string, nullable => true},
      preferences => #{type => object, nullable => true},
      last_login => #{type => string, format => <<"date-time">>},
      created_at => #{type => string, format => <<"date-time">>},
      updated_at => #{type => string, format => <<"date-time">>}
    }
  }.

%%%===================================================================
%%% HTTP-методы
%%%===================================================================

%% @doc GET /v1/admin/users – список пользователей.
-spec list_users(cowboy_req:req()) -> {ok, binary(), cowboy_req:req()}.
list_users(Req) ->
  case handler_utils:auth_admin(Req) of
    {ok, _AdminId, Req1} ->
      Filters = parse_user_filters(Req1),
      Pagination = handler_utils:parse_pagination_params(Req1),
      % Передаем параметры сортировки в бизнес-логику
      PaginationWithSort = Pagination#{
        sort => maps:get(sort, Pagination, <<"created_at">>),
        order => maps:get(order, Pagination, <<"desc">>)
      },
      {ok, Total, Users} = logic_user:list_users_admin(Filters, PaginationWithSort),
      Json = [handler_utils:user_to_json(U) || U <- Users],
      ExtraHeaders = handler_utils:pagination_headers(Pagination, Total),
      handler_utils:send_json(Req1, 200, Json, ExtraHeaders);
    {error, Code, Msg, Req1} ->
      handler_utils:send_error(Req1, Code, Msg)
  end.

%%%===================================================================
%%% Вспомогательные функции
%%%===================================================================

%% @private Разбор query-параметров для фильтрации.
-spec parse_user_filters(cowboy_req:req()) -> map().
parse_user_filters(Req) ->
  Qs = cowboy_req:parse_qs(Req),
  RoleBin = proplists:get_value(<<"role">>, Qs),
  StatusBin = proplists:get_value(<<"status">>, Qs),
  #{
    role   => convert_to_atom(RoleBin),
    status => convert_to_atom(StatusBin),
    q      => proplists:get_value(<<"q">>, Qs)
  }.

convert_to_atom(undefined) -> undefined;
convert_to_atom(Bin) when is_binary(Bin) ->
  try binary_to_existing_atom(Bin, utf8)
  catch error:badarg -> Bin
  end.