%%%------------------------------------------------------------------- %%% @author Gary T. Leavens %%% @copyright (C) 2019, Gary T. Leavens %%% @doc %%% %%% @end %%% Created : 19 Nov 2019 by Gary T. Leavens %%%------------------------------------------------------------------- -module(runavginclass). -behaviour(gen_server). -import(gen_server, [call/2]). %% API -export([start_link/0, note/1, average/0]). %% gen_server callbacks -export([init/1, handle_call/3, handle_cast/2, handle_info/2, terminate/2, code_change/3, format_status/2]). -define(SERVER, runavg). % The state is a list of measurements (floats), % with the first 3 elements being the latest ones, so the head of the list % is the latest (most recent) measurement. % Invariant: there are always at least 3 numbers in the state. %%%=================================================================== %%% API %%%=================================================================== %%-------------------------------------------------------------------- %% @doc %% Starts the server %% @end %%-------------------------------------------------------------------- -spec start_link() -> {ok, Pid :: pid()} | {error, Error :: {already_started, pid()}} | {error, Error :: term()} | ignore. start_link() -> gen_server:start_link({local, ?SERVER}, ?MODULE, [], []). %%%=================================================================== %%% gen_server callbacks %%%=================================================================== note(Measurement) -> call(?SERVER, {note, Measurement}). average() -> call(?SERVER, average). %%-------------------------------------------------------------------- %% @private %% @doc %% Initializes the server %% @end %%-------------------------------------------------------------------- -spec init(Args :: term()) -> {ok, State :: term()} | {ok, State :: term(), Timeout :: timeout()} | {ok, State :: term(), hibernate} | {stop, Reason :: term()} | ignore. init([]) -> process_flag(trap_exit, true), {ok, [0.0,0.0,0.0]}. %%-------------------------------------------------------------------- %% @private %% @doc %% Handling call messages %% @end %%-------------------------------------------------------------------- -spec handle_call(Request :: term(), From :: {pid(), term()}, State :: term()) -> {reply, Reply :: term(), NewState :: term()} | {reply, Reply :: term(), NewState :: term(), Timeout :: timeout()} | {reply, Reply :: term(), NewState :: term(), hibernate} | {noreply, NewState :: term()} | {noreply, NewState :: term(), Timeout :: timeout()} | {noreply, NewState :: term(), hibernate} | {stop, Reason :: term(), Reply :: term(), NewState :: term()} | {stop, Reason :: term(), NewState :: term()}. handle_call({note, Measurement}, _From, State) -> Reply = ok, {reply, Reply, [Measurement|State]}; handle_call(average, _From, State) -> Reply = getAverage(State), {reply, Reply, State}. getAverage([One|[Two|[Three|_]]]) -> (One+Two+Three)/3.0. %%-------------------------------------------------------------------- %% @private %% @doc %% Handling cast messages %% @end %%-------------------------------------------------------------------- -spec handle_cast(Request :: term(), State :: term()) -> {noreply, NewState :: term()} | {noreply, NewState :: term(), Timeout :: timeout()} | {noreply, NewState :: term(), hibernate} | {stop, Reason :: term(), NewState :: term()}. handle_cast(_Request, State) -> {noreply, State}. %%-------------------------------------------------------------------- %% @private %% @doc %% Handling all non call/cast messages %% @end %%-------------------------------------------------------------------- -spec handle_info(Info :: timeout() | term(), State :: term()) -> {noreply, NewState :: term()} | {noreply, NewState :: term(), Timeout :: timeout()} | {noreply, NewState :: term(), hibernate} | {stop, Reason :: normal | term(), NewState :: term()}. handle_info(_Info, State) -> {noreply, State}. %%-------------------------------------------------------------------- %% @private %% @doc %% This function is called by a gen_server when it is about to %% terminate. It should be the opposite of Module:init/1 and do any %% necessary cleaning up. When it returns, the gen_server terminates %% with Reason. The return value is ignored. %% @end %%-------------------------------------------------------------------- -spec terminate(Reason :: normal | shutdown | {shutdown, term()} | term(), State :: term()) -> any(). terminate(_Reason, _State) -> ok. %%-------------------------------------------------------------------- %% @private %% @doc %% Convert process state when code is changed %% @end %%-------------------------------------------------------------------- -spec code_change(OldVsn :: term() | {down, term()}, State :: term(), Extra :: term()) -> {ok, NewState :: term()} | {error, Reason :: term()}. code_change(_OldVsn, State, _Extra) -> {ok, State}. %%-------------------------------------------------------------------- %% @private %% @doc %% This function is called for changing the form and appearance %% of gen_server status when it is returned from sys:get_status/1,2 %% or when it appears in termination error logs. %% @end %%-------------------------------------------------------------------- -spec format_status(Opt :: normal | terminate, Status :: list()) -> Status :: term(). format_status(_Opt, Status) -> Status.