Figuring out how to organize the src folder(s)...

1 files changed, 130 insertions, 0 deletions

diff --git a/src/shared/io/sh_timed_cache.erl b/src/shared/io/sh_timed_cache.erl
new file mode 100644
index 0000000..1839992
--- /dev/null
+++ b/src/shared/io/sh_timed_cache.erl
@@ -0,0 +1,130 @@
+-module(sh_timed_cache).
+-behavior(gen_server).
+
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+%% TYPES %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+%% EXPORTS %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+%%%% '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,
+      update/4,
+      invalidate/3
+   ]
+).
+
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+%% LOCAL FUNCTIONS %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+-spec add_to_cache (atom(), any(), any()) -> any().
+add_to_cache (DB, Owner, ObjectID) ->
+   {ok, TimerPID} = sh_gen_server:start(?MODULE, {DB, {Owner, ObjectID}}, []),
+   {ok, Data} = sh_database:fetch(DB, ObjectID),
+   ets:insert(DB, {{Owner, ObjectID}, TimerPID, Data}),
+   Data.
+
+-spec add_update_to_cache (atom(), any(), any(), any()) -> 'ok'.
+add_update_to_cache (DB, Owner, ObjectID, Data) ->
+   {ok, TimerPID} = gen_server:start(?MODULE, {DB, {Owner, ObjectID}}, []),
+   ets:insert(DB, {{Owner, ObjectID}, TimerPID, Data}),
+   ok.
+
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+%% EXPORTED FUNCTIONS %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+%%%% 'gen_server' functions
+init ({DB, ObjectID}) ->
+   io:format("~nCache entry added: ~p.~n", [{DB, ObjectID}]),
+   {ok, {DB, ObjectID}, sh_timed_caches_manager:get_timeout()}.
+
+handle_call (invalidate, _, State) ->
+   {stop, normal, State};
+handle_call (ping, _, State) ->
+   {noreply, State, sh_timed_caches_manager:get_timeout()}.
+
+handle_cast (invalidate, State) ->
+   {stop, normal, State};
+handle_cast (ping, State) ->
+   {noreply, State, sh_timed_caches_manager:get_timeout()}.
+
+terminate (_, {DB, ObjectID}) ->
+   io:format
+   (
+      "~nCache entry timed out or was invalidated: ~p.~n",
+      [{DB, ObjectID}]
+   ),
+   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}) ->
+   {noreply, {DB, ObjectID}, timed_caches_manager:get_timeout()}.
+
+%%%% Interface Functions
+-spec fetch (atom(), any(), any()) -> any().
+fetch (DB, Owner, ObjectID) ->
+   io:format("~nfetch from cache: ~p.~n", [{DB, {Owner, ObjectID}}]),
+   case ets:lookup(DB, {Owner, ObjectID}) of
+      [] -> add_to_cache(DB, Owner, ObjectID);
+
+      [{_, TimerPID, Data}] ->
+         gen_server:cast(TimerPID, ping),
+         Data
+   end.
+
+-spec update (atom(), any(), any(), any()) -> 'ok'.
+update (DB, Owner, ObjectID, Data) ->
+   io:format("~nUpdating cache: ~p.~n", [{DB, {Owner, ObjectID}}]),
+   case ets:lookup(DB, {Owner, ObjectID}) of
+      [] -> ok;
+
+      [{_OwnerID, TimerPID, _Data}] ->
+         gen_server:stop(TimerPID)
+   end,
+   add_update_to_cache(DB, Owner, ObjectID, Data).
+
+-spec invalidate (atom(), any(), any()) -> 'ok'.
+invalidate (DB, Owner, ObjectID) ->
+   case ets:lookup(DB, {Owner, ObjectID}) of
+      [] ->
+         io:format
+         (
+            "~nInvalidation request on non-stored entry: ~p.~n",
+            [{DB, Owner, ObjectID}]
+         ),
+         ok;
+
+      [{_, TimerPID, _}] ->
+         io:format
+         (
+            "~nInvalidation request on stored entry: ~p.~n",
+            [{DB, Owner, ObjectID}]
+         ),
+         gen_server:stop(TimerPID),
+         ok
+   end.