From dd51a1d2b2d05192b3d3022f3065b9d2d9f561c1 Mon Sep 17 00:00:00 2001
From: nsensfel <SpamShield0@noot-noot.org>
Date: Wed, 8 Nov 2017 13:18:35 +0100
Subject: Uses "gen_server" behavior for timed cache objects

---
 src/timed_cache_object.erl | 82 ++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 82 insertions(+)
 create mode 100644 src/timed_cache_object.erl

diff --git a/src/timed_cache_object.erl b/src/timed_cache_object.erl
new file mode 100644
index 0000000..1dd4b1a
--- /dev/null
+++ b/src/timed_cache_object.erl
@@ -0,0 +1,82 @@
+-module(timed_cache_object).
+-behavior(gen_server).
+
+%%%% gen_server exports
+-export(
+   [
+      init/1,
+      handle_cast/2,
+      handle_call/3, %% No reply will ever be given.
+      terminate/2,
+      code_change/3,
+      format_status/2,
+      handle_info/2
+   ]
+).
+
+%%%% actual interface
+-export(
+   [
+      fetch/3,
+      invalidate/2
+   ]
+).
+
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+%% LOCAL %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+add_to_cache (DB, ObjectID, Timeout) ->
+   {ok, TimerPID} = gen_server:start(?MODULE, [{DB, ObjectID, Timeout}], []),
+   Data = nothing, %% Do the actual NoSQL Fetch here.
+   ets:insert(DB, {ObjectID, TimerPID, Data}),
+   Data.
+
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+%% EXPORTED %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+%%%% gen_server
+
+init ({DB, ObjectID, Timeout}) ->
+   {ok, {DB, ObjectID, Timeout}}.
+
+handle_call (invalidate, _, State) ->
+   {stop, normal, State};
+handle_call (ping, _, {DB, ObjectID, Timeout}) ->
+   {noreply, {DB, ObjectID, Timeout}, Timeout}.
+
+handle_cast (invalidate, State) ->
+   {stop, normal, State};
+handle_cast (ping, {DB, ObjectID, Timeout}) ->
+   {noreply, {DB, ObjectID, Timeout}, Timeout}.
+
+terminate (_, {DB, ObjectID, _Timeout}) ->
+   ets:delete(DB, ObjectID).
+
+code_change (_, State, _) ->
+   {ok, State}.
+
+format_status (_, [_, State]) ->
+   [{data, [{"State", State}]}].
+
+handle_info(timeout, State) ->
+   {stop, normal, State};
+handle_info(_, {DB, ObjectID, Timeout}) ->
+   {noreply, {DB, ObjectID, Timeout}, Timeout}.
+
+%%%% interface
+fetch (DB, ObjectID, Timeout) ->
+   case ets:lookup(DB, ObjectID) of
+      [] -> add_to_cache(DB, ObjectID, Timeout);
+
+      [{_, TimerPID, Data}] ->
+         gen_server:cast(TimerPID, ping),
+         Data
+   end.
+
+invalidate (DB, ObjectID) ->
+   case ets:lookup(DB, ObjectID) of
+      [] -> ok;
+
+      [{_, TimerPID, _}] ->
+         gen_server:stop(TimerPID)
+   end.
-- 
cgit v1.2.3-70-g09d2