--- a/src/rps3.erl	Mon Mar 03 19:46:02 2014 +0900
+++ b/src/rps3.erl	Mon Mar 03 20:00:26 2014 +0900
@@ -8,21 +8,9 @@
 start_link() ->
     gen_server:start_link({local, ?MODULE}, ?MODULE, [], []).
 
-parse_rules([V1,Label,V2|T], #state{hands=Hands, beats=Beats, loses=Loses, why=Why}) ->
-    Acc = #state{
-        hands=[V1|Hands],
-        beats=dict:append(V1, V2, Beats),
-        loses=dict:append(V2, V1, Loses),
-        why=dict:store({V1, V2}, Label, Why)},
-    parse_rules([V2|T], Acc);
-
-parse_rules([_V2], Acc) ->
-    Acc.
-
 init([]) ->
     Text = "scissors cut paper covers rock crushes scissors",
-    Tokens = lists:map(fun list_to_atom/1, string:tokens(Text, " ")),
-    {ok, parse_rules(Tokens, #state{})}.
+    {ok, rps_rules:parse(Text)}.
 
 handle_call(get_hands, _From, State=#state{hands=Hands}) ->
     {reply, Hands, State};
@@ -34,16 +22,7 @@
 % rock, rock, paper     -> paper
 
 handle_call({winning_hand, Hands}, _From, State) ->
-    HSet = sets:from_list(Hands),
-    WHand = sets:fold(
-        fun(Hand, Acc) ->
-            Loses = dict:fetch(Hand, State#state.loses),
-            case sets:is_disjoint(sets:from_list(Loses), HSet) of
-                false -> Acc;
-                true -> Hand
-            end
-        end, undefined, HSet),
-    {reply, WHand, State};
+    {reply, rps_rules:winning_hand(Hands, State), State};
 
 handle_call({why, H1, H2}, _From, State=#state{why=Why}) ->
     {reply, dict:fetch({H1, H2}, Why), State}.

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/rps_rules.erl	Mon Mar 03 20:00:26 2014 +0900
@@ -0,0 +1,36 @@
+-module(rps_rules).
+-export([parse/1, winning_hand/2]).
+
+-record(state, {hands=[], beats=dict:new(), loses=dict:new(), why=dict:new()}).
+
+parse(Text) ->
+    Tokens = lists:map(fun list_to_atom/1, string:tokens(Text, " ")),
+    parse(Tokens, #state{}).
+
+parse([V1,Label,V2|T], #state{hands=Hands, beats=Beats, loses=Loses, why=Why}) ->
+    Acc = #state{
+        hands=[V1|Hands],
+        beats=dict:append(V1, V2, Beats),
+        loses=dict:append(V2, V1, Loses),
+        why=dict:store({V1, V2}, Label, Why)},
+    parse([V2|T], Acc);
+
+parse([_V2], Acc) ->
+    Acc.
+
+% winner for 3 hands is:
+% rock, rock, rock      -> rock
+% rock, paper, scissors -> undefined
+% rock, paper, paper    -> paper
+% rock, rock, paper     -> paper
+
+winning_hand(Hands, State=#state{}) ->
+    HSet = sets:from_list(Hands),
+    sets:fold(
+        fun(Hand, Acc) ->
+            Loses = dict:fetch(Hand, State#state.loses),
+            case sets:is_disjoint(sets:from_list(Loses), HSet) of
+                false -> Acc;
+                true -> Hand
+            end
+        end, undefined, HSet).