001/src/time.erl

   1 -module(time).
   2 -behaviour(gen_server).
   3
   4
   5 %% API
   6 -export([start_link/2
   7         ,cast/1
   8         ]).
   9
  10 %% Callbacks
  11 -export([init/1
  12         ,handle_call/3
  13         ,handle_cast/2
  14         ,handle_info/2
  15         ,terminate/2
  16         ,code_change/3
  17         ]).
  18
  19
  20 -define(INTERVAL, 0).  % In milliseconds
  21
  22 -define(CHAR_DEAD,   32).  % Space
  23 -define(CHAR_ALIVE, 111).  % o
  24 -define(CHAR_BAR,    61).  % =
  25
  26
  27 -record(state, {x               :: integer()
  28                ,cells           :: list(atom())
  29                ,num_cells       :: integer()
  30                ,state_pairs     :: list(tuple(integer(), integer())) | []
  31                ,replies_pending :: integer()
  32                }).
  33
  34
  35 %% ============================================================================
  36 %% API
  37 %% ============================================================================
  38
  39 start_link(X, Cells) ->
  40     ServerName = {local, ?MODULE},
  41     Args = [X, Cells],
  42     Opts = [],
  43     gen_server:start_link(ServerName, ?MODULE, Args, Opts).
  44
  45
  46 cast(Msg) ->
  47     gen_server:cast(?MODULE, Msg).
  48
  49
  50 %% ============================================================================
  51 %% Callbacks
  52 %% ============================================================================
  53
  54 init([X, Cells]) ->
  55     State = #state{x=X
  56                   ,cells=Cells
  57                   ,num_cells=length(Cells)
  58                   ,state_pairs=[]
  59                   ,replies_pending=0
  60                   },
  61     cast(next_tick),
  62     {ok, State}.
  63
  64
  65 terminate(_Reason, State) ->
  66     {ok, State}.
  67
  68
  69 code_change(_Old, State, _Other) ->
  70     {ok, State}.
  71
  72
  73 handle_call(_Msg, _From, State) ->
  74     {reply, ok, State}.
  75
  76
  77 handle_cast(next_tick, #state{cells=Cells, num_cells=NumCells, state_pairs=[]}=State) ->
  78     ok = send_all(Cells, tick),
  79     {noreply, State#state{replies_pending=NumCells}};
  80
  81 handle_cast({tock, {ID, CellState}},
  82     #state{x=X
  83           ,state_pairs=StatePairs
  84           ,replies_pending=RepliesPending
  85           }=State) ->
  86
  87     NewStatePairs = [{ID, CellState} | StatePairs],
  88     NewRepliesPending = RepliesPending - 1,
  89     NewState = State#state{replies_pending=NewRepliesPending},
  90
  91     case NewRepliesPending of
  92         0 ->
  93             SortedStatePairs = lists:sort(NewStatePairs),
  94             StateChars = [state_to_char(S) || {_, S} <- SortedStatePairs],
  95             ok = do_print_bar(X),
  96             ok = do_print_state_chars(X, StateChars),
  97             ok = do_print_bar(X),
  98             ok = timer:sleep(?INTERVAL),
  99             cast(next_tick),
 100             {noreply, NewState#state{state_pairs=[]}};
 101
 102         _N ->
 103             {noreply, NewState#state{state_pairs=NewStatePairs}}
 104     end;
 105
 106 handle_cast(_Msg, State) ->
 107     {noreply, State}.
 108
 109
 110 handle_info(_Msg, State) ->
 111     {noreply, State}.
 112
 113
 114 %% ============================================================================
 115 %% Internal
 116 %% ============================================================================
 117
 118 send_all([], _) -> ok;
 119 send_all([PID | PIDs], Msg) ->
 120     PID ! Msg,
 121     send_all(PIDs, Msg).
 122
 123
 124 state_to_char(0) -> ?CHAR_DEAD;
 125 state_to_char(1) -> ?CHAR_ALIVE.
 126
 127
 128 do_print_state_chars(_, []) -> ok;
 129 do_print_state_chars(X, Chars) ->
 130     {XChars, RestChars} = lists:split(X, Chars),
 131     ok = io:format([XChars, $\n]),
 132     do_print_state_chars(X, RestChars).
 133
 134
 135 do_print_bar(X) ->
 136     io:format("~s~n", [[?CHAR_BAR || _ <- lists:seq(1, X - 1)]]).