From d357b025b6a3229ef60d3528881def7a98d7b075 Mon Sep 17 00:00:00 2001
From: Correl Roush <correl@gmail.com>
Date: Wed, 1 Aug 2012 00:41:43 -0400
Subject: [PATCH] Dai San Gen

---
 src/yaku.erl               | 9 ++++++++-
 test/riichi_yaku_tests.erl | 8 ++++++++
 2 files changed, 16 insertions(+), 1 deletion(-)

diff --git a/src/yaku.erl b/src/yaku.erl
index 81c191e..d7fd17a 100644
--- a/src/yaku.erl
+++ b/src/yaku.erl
@@ -13,7 +13,8 @@
         pinfu/2,
         chiitoitsu/2,
         kokushi_musou/2,
-        ryuu_iisou/2]).
+        ryuu_iisou/2,
+        dai_san_gen/2]).
 
 %% @doc Counts the pons/kans of value tiles in a player's hand.
 %%      Value tiles include all of the dragons, plus the round wind and the player's seat wind.
@@ -92,3 +93,9 @@ ryuu_iisou(#game{}, #player{hand=Hand}) ->
     Greens = sets:from_list([#tile{suit=sou, value=V} || V <- [2,3,4,6,8]] ++ [#tile{suit=dragon, value=green}]),
     Tiles = sets:from_list(riichi_hand:tiles(Hand)),
     sets:is_subset(Tiles, Greens).
+
+%% @doc Returns true for a Big Three Dragons hand
+-spec dai_san_gen(game(), player()) -> boolean().
+dai_san_gen(#game{}, #player{hand=#hand{melds=Melds}}) ->
+    [green, red, white] =:= lists:usort([V || #meld{type=T, tiles=[#tile{suit=dragon, value=V}|_]} <- Melds,
+                                              lists:member(T, [pon, kan])]).
diff --git a/test/riichi_yaku_tests.erl b/test/riichi_yaku_tests.erl
index c53d395..78ed9b1 100644
--- a/test/riichi_yaku_tests.erl
+++ b/test/riichi_yaku_tests.erl
@@ -52,3 +52,11 @@ ryuu_iisou_test() ->
                         #meld{type=pon, tiles=lists:duplicate(3, #tile{suit=sou, value=8})},
                         #meld{type=pair, tiles=lists:duplicate(2, #tile{suit=dragon, value=green})}]},
     ?assert(yaku:ryuu_iisou(#game{}, #player{hand=Hand})).
+
+dai_san_gen_test() ->
+    Hand = #hand{melds=[#meld{type=chii, tiles=[#tile{suit=sou, value=V} || V <- [2,3,4]]},
+                        #meld{type=pon, tiles=lists:duplicate(3, #tile{suit=dragon, value=red})},
+                        #meld{type=pon, tiles=lists:duplicate(3, #tile{suit=dragon, value=green})},
+                        #meld{type=kan, tiles=lists:duplicate(4, #tile{suit=dragon, value=white})},
+                        #meld{type=pair, tiles=lists:duplicate(2, #tile{suit=pin, value=1})}]},
+    ?assert(yaku:dai_san_gen(#game{}, #player{hand=Hand})).