-module(admin_handler_user_by_id).
-include("records.hrl").
-export([init/2]).
-export([user_to_json/1, convert_updates/1]).

init(Req, Opts) ->
  handle(Req, Opts).

handle(Req, _Opts) ->
  case cowboy_req:method(Req) of
    <<"GET">>    -> get_user(Req);
    <<"PUT">>    -> update_user(Req);
    <<"DELETE">> -> delete_user(Req);
    _            -> send_error(Req, 405, <<"Method not allowed">>)
  end.

get_user(Req) ->
  case handler_auth:authenticate(Req) of
    {ok, AdminId, Req1} ->
      case is_admin(AdminId) of
        true ->
          UserId = cowboy_req:binding(id, Req1),
          case core_user:get_by_id(UserId) of
            {ok, User} when User#user.status =:= deleted ->
              send_error(Req1, 404, <<"User not found">>);
            {ok, User} ->
              send_json(Req1, 200, user_to_json(User));
            {error, not_found} ->
              send_error(Req1, 404, <<"User not found">>)
          end;
        false ->
          send_error(Req1, 403, <<"Admin access required">>)
      end;
    {error, Code, Message, Req1} ->
      send_error(Req1, Code, Message)
  end.

update_user(Req) ->
  case handler_auth:authenticate(Req) of
    {ok, AdminId, Req1} ->
      case is_admin(AdminId) of
        true ->
          UserId = cowboy_req:binding(id, Req1),
          {ok, Body, Req2} = cowboy_req:read_body(Req1),
          try jsx:decode(Body, [return_maps]) of
            Decoded when is_map(Decoded) ->
              Updates = maps:to_list(Decoded),
              Converted = convert_updates(Updates),
              case core_user:update(UserId, Converted) of
                {ok, User} ->
                  send_json(Req2, 200, user_to_json(User));
                {error, not_found} ->
                  send_error(Req2, 404, <<"User not found">>);
                {error, _} ->
                  send_error(Req2, 500, <<"Internal server error">>)
              end;
            _ ->
              send_error(Req2, 400, <<"Invalid JSON">>)
          catch
            _:_ -> send_error(Req2, 400, <<"Invalid JSON format">>)
          end;
        false ->
          send_error(Req1, 403, <<"Admin access required">>)
      end;
    {error, Code, Message, Req1} ->
      send_error(Req1, Code, Message)
  end.

delete_user(Req) ->
  case handler_auth:authenticate(Req) of
    {ok, AdminId, Req1} ->
      case is_admin(AdminId) of
        true ->
          UserId = cowboy_req:binding(id, Req1),
          case core_user:delete(UserId) of
            {ok, _} ->
              send_json(Req1, 200, #{status => <<"deleted">>});
            {error, not_found} ->
              send_error(Req1, 404, <<"User not found">>)
          end;
        false ->
          send_error(Req1, 403, <<"Admin access required">>)
      end;
    {error, Code, Message, Req1} ->
      send_error(Req1, Code, Message)
  end.

is_admin(UserId) ->
  case core_user:get_by_id(UserId) of
    {ok, User} -> User#user.role =:= admin;
    _ -> false
  end.

user_to_json(User) ->
  #{
    id         => User#user.id,
    email      => User#user.email,
    role       => User#user.role,
    status     => User#user.status,
    created_at => datetime_to_iso8601(User#user.created_at),
    updated_at => datetime_to_iso8601(User#user.updated_at)
  }.

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])).

convert_updates(Updates) ->
  lists:map(fun
              ({<<"status">>, Value}) -> {status, binary_to_existing_atom(Value)};
              ({<<"role">>, Value})   -> {role, binary_to_existing_atom(Value)};
              (Other)                 -> Other
            end, Updates).

send_json(Req, Status, Data) ->
  Body = jsx:encode(Data),
  cowboy_req:reply(Status, #{<<"content-type">> => <<"application/json">>}, Body, Req),
  {ok, Body, []}.

send_error(Req, Status, Message) ->
  Body = jsx:encode(#{error => Message}),
  cowboy_req:reply(Status, #{<<"content-type">> => <<"application/json">>}, Body, Req),
  {ok, Body, []}.