%%------------------------------------------------------------------------------
%% @doc Runtime strategy base functionality module used by the
%% high and low runtime strategies.
%% @private
%% @end
%%------------------------------------------------------------------------------
-module(elector_time_strategy_base).

%%------------------------------------------------------------------------------
%% Exported API
%%------------------------------------------------------------------------------
-export([elect/3]).

%%------------------------------------------------------------------------------
%% Exported functions
%%------------------------------------------------------------------------------
%% @doc Starts the election process.
-spec elect(TimeType :: runtime | wall_clock,
            Direction :: high | low,
            CandidateNodes :: [node()]) ->
               Leader :: elector_strategy_behaviour:leader().
elect(TimeType, Direction, CandidateNodes) ->
    CandidateRefs =
        [{Node, erpc:send_request(Node, fun() -> candidate_data(TimeType) end)}
         || Node <- CandidateNodes],
    CandiateResps = [{Node, erpc:receive_response(Ref)} || {Node, Ref} <- CandidateRefs],
    selected_leader(CandiateResps, Direction).

candidate_data(TimeType) ->
    {Time, _} = erlang:statistics(TimeType),
    Time.

%%------------------------------------------------------------------------------
%% Internal functions
%%------------------------------------------------------------------------------
%% @private
selected_leader(Runtimes, Type) ->
    CompareFn =
        fun (NodeRuntime, {AccNode, _}) when AccNode =:= undefined ->
                NodeRuntime;
            ({Node, Runtime}, {_, AccRuntime}) when Type =:= high andalso Runtime > AccRuntime ->
                {Node, Runtime};
            ({Node, Runtime}, {_, AccRuntime}) when Type =:= low andalso Runtime < AccRuntime ->
                {Node, Runtime};
            (_, Acc) ->
                Acc
        end,

    {Node, _Runtime} = lists:foldl(CompareFn, {undefined, 0}, Runtimes),
    Node.