Grouping unused gen_server callbacks.

[cellular-automata.git] / 001 / src / life_cell.erl

diff --git a/001/src/life_cell.erl b/001/src/life_cell.erl
index 227f673..9f7b171 100644 (file)
--- a/001/src/life_cell.erl
+++ b/001/src/life_cell.erl
@@ -1,4 +1,4 @@
--module(cell).
+-module(life_cell).
 -behaviour(gen_server).
 
 
@@ -15,13 +15,15 @@
         ]).
 
 
--record(state, {id              :: integer()
+-record(state, {cell_id         :: integer()
                ,name            :: string()
                ,cell_state      :: 0 | 1
                ,neighbors       :: list(atom())
                ,live_neighbors  :: integer()
                ,num_neighbors   :: integer()
                ,replies_pending :: integer()
+               ,gen_id          :: integer()
+               ,early_msgs      :: list()
                }).
 
 
@@ -29,7 +31,7 @@
 %% API
 %% ============================================================================
 
-start_link({_ID, Name, _NeighborNames}=Datum) ->
+start_link({_, Name, _}=Datum) ->
     ServerName = {local, Name},
     Args = [Datum],
     Opts = [],
@@ -37,49 +39,73 @@ start_link({_ID, Name, _NeighborNames}=Datum) ->
 
 
 %% ============================================================================
-%% Callbacks
+%% Callbacks (unused)
 %% ============================================================================
 
-init([{ID, Name, NeighborNames}]) ->
-    State = #state{id=ID
-                  ,name=Name
-                  ,cell_state=crypto:rand_uniform(0, 2)
-                  ,neighbors=NeighborNames
-                  ,num_neighbors=length(NeighborNames)
-                  ,live_neighbors=0
-                  ,replies_pending=0
-                  },
-    {ok, State}.
-
+handle_call(_Msg, _From, State)  -> {reply, ok, State}.
+handle_info(_Msg, State)         -> {noreply, State}.
+code_change(_Old, State, _Other) -> {ok, State}.
+terminate(_Reason, State)        -> {ok, State}.
 
-terminate(_Reason, State) ->
-    {ok, State}.
 
+%% ============================================================================
+%% Callbacks
+%% ============================================================================
 
-code_change(_Old, State, _Other) ->
+init([{CellID, Name, NeighborNames}]) ->
+    State = #state{cell_id         = CellID
+                  ,name            = Name
+                  ,cell_state      = crypto:rand_uniform(0, 2)
+                  ,neighbors       = NeighborNames
+                  ,num_neighbors   = length(NeighborNames)
+                  ,live_neighbors  = 0
+                  ,replies_pending = 0
+                  ,early_msgs      = []
+                  },
     {ok, State}.
 
 
-handle_call(_Msg, _From, State) ->
-    {reply, ok, State}.
-
-
-handle_cast(tick,
+handle_cast({next_gen, GenID},
     #state{name=Name
+          ,cell_state=CellState
           ,neighbors=Neighbors
           ,num_neighbors=NumNeighbors
+          ,early_msgs=EarlyMsgs
           }=State) ->
-    ok = cast_all(Neighbors, {request_state, Name}),
-    {noreply, State#state{replies_pending=NumNeighbors}};
 
+    ok = cast_one2all(Neighbors, {state_broadcast, GenID, CellState}),
 
-handle_cast({request_state, Requester}, State) ->
-    ok = gen_server:cast(Requester, {response_state, State#state.cell_state}),
-    {noreply, State};
+    % Put stashed messages back in the mailbox,
+    % now that we're ready to handle them
+    ok = cast_all2one(Name, EarlyMsgs),
+
+    NewState = State#state{replies_pending=NumNeighbors
+                          ,gen_id=GenID
+                          ,early_msgs=[]
+                          },
+
+    {noreply, NewState};
+
+
+%% If we receive 'state_broadcast' before we receive 'next_gen',
+%% stash it until we do.
+%%
+%% Took me a while to realize this, but sometimes it is possible. The more
+%% there're cells, the more likely this is to happen.
+%%
+handle_cast({state_broadcast, ReceivedGenID, _NeighborState}=Msg,
+    #state{gen_id=GenID
+          ,early_msgs=EarlyMsgs
+          }=State) when GenID =/= ReceivedGenID ->
+
+    {noreply, State#state{early_msgs=[Msg|EarlyMsgs]}};
 
 
-handle_cast({response_state, NeighborState},
-    #state{id=ID
+%% Now that we can be sure that this request is for the current generation, we
+%% can handle it
+handle_cast({state_broadcast, GenID, NeighborState},
+    #state{cell_id=CellID
+          ,gen_id=GenID
           ,replies_pending=Pending
           ,cell_state=CellState
           ,live_neighbors=LiveNeighbors
@@ -95,7 +121,7 @@ handle_cast({response_state, NeighborState},
     case NewPending of
         0 ->
             NewCellState = new_state(CellState, NewLiveNeighbors),
-            ok = time:tock(ID, NewCellState),
+            ok = life_time:report_state(CellID, GenID, NewCellState),
 
             {noreply, NewState#state{live_neighbors=0
                                     ,cell_state=NewCellState
@@ -111,18 +137,22 @@ handle_cast(_Msg, State) ->
     {noreply, State}.
 
 
-handle_info(_Msg, State) ->
-    {noreply, State}.
-
-
 %% ============================================================================
 %% Internal
 %% ============================================================================
 
-cast_all([], _) -> ok;
-cast_all([Server | Servers], Msg) ->
+% Cast all messages to one destination
+cast_all2one(_, []) -> ok;
+cast_all2one(Server, [Msg | Msgs]) ->
+    ok = gen_server:cast(Server, Msg),
+    cast_all2one(Server, Msgs).
+
+
+% Cast one message to all destinations
+cast_one2all([], _) -> ok;
+cast_one2all([Server | Servers], Msg) ->
     ok = gen_server:cast(Server, Msg),
-    cast_all(Servers, Msg).
+    cast_one2all(Servers, Msg).
 
 
 new_state(1, LiveNeighbors) when LiveNeighbors  <  2 -> 0;