nova_error_controller.erl

-module(nova_error_controller).
-export([
         not_found/1,
         server_error/1,
	 status_code/1
        ]).


status_code(Req) ->
    {status, maps:get(resp_status_code, Req, 200)}.

not_found(Req) ->
    %% Check the accept-headers
    Accept = cowboy_req:header(<<"accept">>, Req),
    AcceptList = case Accept of
                     undefined ->
                         [<<"application/json">>];
                     _ ->
                         binary:split(Accept, <<",">>, [global])
                 end,

    case {lists:member(<<"application/json">>, AcceptList),
	  lists:member(<<"text/html">>, AcceptList)} of
        {true, _} ->
            %% Render a json response
            JsonLib = nova:get_env(json_lib, json),
            Json = JsonLib:encode(#{message => "Resource not found"}),
            {status, 404, #{<<"content-type">> => <<"application/json">>}, Json};
	{_, true} ->
            %% Just assume HTML
            Variables = #{status => "Could not find the page you were looking for",
                          title => "404 Not found",
                          message => "We could not find the page you were looking for"},
            {ok, Body} = nova_error_dtl:render(Variables),
            {status, 404, #{<<"content-type">> => <<"text/html">>}, Body};
        _ ->
            {status, 404, #{<<"content-type">> => <<"text/html">>}, <<>>}
    end.

server_error(#{crash_info := #{status_code := StatusCode} = CrashInfo} = Req) ->
    Variables = #{status => maps:get(status, CrashInfo, undefined),
                  title => maps:get(title, CrashInfo, undefined),
                  message => maps:get(message, CrashInfo, undefined),
                  extra_msg => maps:get(extra_msg, CrashInfo, undefined),
                  stacktrace => format_stacktrace(maps:get(stacktrace, CrashInfo, []))},
    case application:get_env(nova, render_error_pages, true) of
        true ->
            case cowboy_req:header(<<"accept">>, Req) of
                <<"application/json">> ->
                    JsonLib = nova:get_env(json_lib, json),
                    Json = JsonLib:encode(Variables),
                    {status, StatusCode, #{<<"content-type">> => <<"application/json">>}, Json};
                <<"text/html">> ->
                    {ok, Body} = nova_error_dtl:render(Variables),
                    {status, StatusCode, #{<<"content-type">> => <<"text/html">>}, Body};
                _ ->
                    {status, StatusCode, #{<<"content-type">> => <<"text/html">>}, <<>>}
            end;
        _ ->
            {status, StatusCode}
    end;
server_error(#{crash_info := #{class := Class, reason := Reason}} = Req) ->
    Stacktrace = maps:get(stacktrace, Req, []),
    Variables = #{status => "Internal Server Error",
                  title => "500 Internal Server Error",
                  message => "Something internal crashed. Please take a look!",
                  extra_msg => io_lib:format("Class: ~p<br /> Reason: ~p", [Class, Reason]),
                  stacktrace => format_stacktrace(Stacktrace)},

    case nova:get_environment() of
        dev ->
            %% We do show a proper error response
            case cowboy_req:header(<<"accept">>, Req) of
                <<"application/json">> ->
                    JsonLib = nova:get_env(json_lib, json),
                    Json = JsonLib:encode(Variables),
                    {status, 500, #{<<"content-type">> => <<"application/json">>}, Json};
                <<"text/html">> ->
                    {ok, Body} = nova_error_dtl:render(Variables),
                    {status, 500, #{<<"content-type">> => <<"text/html">>}, Body};
                _ ->
                    {status, 500, #{<<"content-type">> => <<"text/html">>}, <<>>}
            end;
        _ ->
            {status, 500}
    end.


format_stacktrace(not_enabled) ->
    logger:warning(<<"Stacktrace disabled. If you want to enable stacktraces call nova:stracktrace(true) or update your sys.config - Read more in the docs">>),
    [];
format_stacktrace([]) -> [];
format_stacktrace([{Mod, Func, Arity, TraceOpts}|Tl]) ->
    File = case proplists:get_value(file, TraceOpts) of
                undefined -> undefined;
                F -> list_to_binary(F)
           end,
    Line = proplists:get_value(line, TraceOpts),
    Formated = #{module => erlang:atom_to_binary(Mod, utf8),
                 function => erlang:atom_to_binary(Func, utf8),
                 arity => format_arity(Arity, []),
                 file => File,
                 line => Line},
    [Formated|format_stacktrace(Tl)];
format_stacktrace([Hd|Tl]) ->
    logger:warning(<<"Could not format stacktrace line: ~p">>, [Hd]),
    format_stacktrace(Tl).



format_arity(Arity) when is_pid(Arity) -> list_to_binary(pid_to_list(Arity));
format_arity(Arity) when is_function(Arity) -> <<"fun">>;
format_arity(Arity) -> Arity.

format_arity([], Acc) ->
    Acc;
format_arity([Head, Tail], Acc) ->
    Formated = format_arity(Head),
    format_arity(Tail, [Formated | Acc]);
format_arity(Arity, _) when is_function(Arity)->
    <<"fun">>;
format_arity(Arity, _) ->
    Arity.

-ifdef(TEST).
-compile(export_all).
-endif.