Shuffling

1 files changed, 36 insertions, 0 deletions

diff --git a/server/lib/Cafp/InfiniteDeck.hs b/server/lib/Cafp/InfiniteDeck.hs
new file mode 100644
index 0000000..8772011
--- /dev/null
+++ b/server/lib/Cafp/InfiniteDeck.hs
@@ -0,0 +1,36 @@
+module Cafp.InfiniteDeck
+    ( InfiniteDeck
+    , new
+    , newIO
+    , pop
+    , popN
+    ) where
+
+import           Data.List                 (intercalate)
+import qualified Data.Vector               as V
+import           System.Random             (StdGen, newStdGen)
+import           VectorShuffling.Immutable (shuffle)
+
+newtype InfiniteDeck a = InfiniteDeck [a]
+
+instance Show a => Show (InfiniteDeck a) where
+    show (InfiniteDeck xs) =
+        "[" ++ intercalate ", " (map show $ take 5 xs) ++ "...]"
+
+new :: V.Vector a -> StdGen -> InfiniteDeck a
+new vec gen0
+    | V.null vec = error "Cafp.InfiniteDeck.new: empty vector"
+    | otherwise  = InfiniteDeck (V.toList x ++ xs)
+  where
+    (x, gen1) = shuffle vec gen0
+    InfiniteDeck xs = new vec gen1
+
+newIO :: V.Vector a -> IO (InfiniteDeck a)
+newIO vec = new vec <$> newStdGen
+
+pop :: InfiniteDeck a -> (a, InfiniteDeck a)
+pop (InfiniteDeck [])       = error "Cafp.InfiniteDeck.pop: empty"
+pop (InfiniteDeck (x : xs)) = (x, InfiniteDeck xs)
+
+popN :: Int -> InfiniteDeck a -> ([a], InfiniteDeck a)
+popN n (InfiniteDeck xs) = let (ys, zs) = splitAt n xs in (ys, InfiniteDeck zs)