Converted to OTP app.

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

diff --git a/001/src/cell.erl b/001/src/cell.erl
new file mode 100644 (file)
index 0000000..6090fa0
--- /dev/null
+++ b/001/src/cell.erl
@@ -0,0 +1,136 @@
+-module(cell).
+-behaviour(gen_server).
+
+
+%% API
+-export([start_link/1]).
+
+%% Callbacks
+-export([init/1
+        ,handle_call/3
+        ,handle_cast/2
+        ,handle_info/2
+        ,terminate/2
+        ,code_change/3
+        ]).
+
+
+-record(state, {id              :: integer()
+               ,name            :: string()
+               ,cell_state      :: 0 | 1
+               ,neighbors       :: list(atom())
+               ,live_neighbors  :: integer()
+               ,num_neighbors   :: integer()
+               ,replies_pending :: integer()
+               }).
+
+
+%% ============================================================================
+%% API
+%% ============================================================================
+
+start_link({_ID, Name, _NeighborNames}=Datum) ->
+    ServerName = {local, Name},
+    Args = [Datum],
+    Opts = [],
+    gen_server:start_link(ServerName, ?MODULE, Args, Opts).
+
+
+%% ============================================================================
+%% Callbacks
+%% ============================================================================
+
+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}.
+
+
+terminate(_Reason, State) ->
+    {ok, State}.
+
+
+code_change(_Old, State, _Other) ->
+    {ok, State}.
+
+
+handle_call(_Msg, _From, State) ->
+    {reply, ok, State}.
+
+
+handle_cast(_Msg, State) ->
+    {noreply, State}.
+
+
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+
+handle_info(tick,
+    #state{name=Name
+          ,neighbors=Neighbors
+          ,num_neighbors=NumNeighbors
+          }=State) ->
+
+    ok = send_all(Neighbors, {request_state, Name}),
+    {noreply, State#state{replies_pending=NumNeighbors}};
+
+
+handle_info({request_state, Requester}, State) ->
+    Requester ! {response_state, State#state.cell_state},
+    {noreply, State};
+
+
+handle_info({response_state, NeighborState},
+    #state{id=ID
+          ,replies_pending=Pending
+          ,cell_state=CellState
+          ,live_neighbors=LiveNeighbors
+          }=State) ->
+
+    NewPending = Pending - 1,
+    NewLiveNeighbors = LiveNeighbors + NeighborState,
+
+    NewState = State#state{replies_pending=NewPending
+                          ,live_neighbors=NewLiveNeighbors
+                          },
+
+    case NewPending of
+        0 ->
+            NewCellState = new_state(CellState, NewLiveNeighbors),
+            ok = time:cast({tock, {ID, NewCellState}}),
+
+            {noreply, NewState#state{live_neighbors=0
+                                    ,cell_state=NewCellState
+                                    }};
+
+        _N ->
+            {noreply, NewState}
+    end;
+
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+
+
+handle_info(_Msg, State) ->
+    {noreply, State}.
+
+
+%% ============================================================================
+%% Internal
+%% ============================================================================
+
+send_all([], _) -> ok;
+send_all([PID | PIDs], Msg) ->
+    PID ! Msg,
+    send_all(PIDs, Msg).
+
+
+new_state(1, LiveNeighbors) when LiveNeighbors  <  2 -> 0;
+new_state(1, LiveNeighbors) when LiveNeighbors  <  4 -> 1;
+new_state(1, LiveNeighbors) when LiveNeighbors  >  3 -> 0;
+new_state(0, LiveNeighbors) when LiveNeighbors =:= 3 -> 1;
+new_state(State, _LiveNeighbors) -> State.