feat: fix inEOS, add uniqHash + invoke

src/Pipes.Util.purs

@@ -3,17 +3,22 @@ module Pipes.Util where
 import Prelude
 
 import Control.Monad.Maybe.Trans (MaybeT(..), runMaybeT)
-import Control.Monad.Rec.Class (whileJust)
+import Control.Monad.Rec.Class (class MonadRec, forever, whileJust)
 import Control.Monad.ST.Class (liftST)
 import Control.Monad.ST.Ref (STRef)
 import Control.Monad.ST.Ref as STRef
 import Control.Monad.Trans.Class (lift)
 import Data.Array.ST (STArray)
 import Data.Array.ST as Array.ST
+import Data.HashSet as HashSet
+import Data.Hashable (class Hashable, hash)
+import Data.List.NonEmpty (NonEmptyList)
 import Data.Maybe (Maybe(..))
+import Data.Tuple.Nested (type (/\), (/\))
 import Effect.Class (class MonadEffect, liftEffect)
 import Pipes (await, yield)
 import Pipes.Core (Pipe)
+import Pipes.Internal (Proxy(..))
 
 -- | Yields a separator value `sep` between received values
 -- |
@@ -62,3 +67,57 @@ chunked size = do
     when (len >= size) $ lift $ yield =<< Just <$> chunkTake
   yield =<< Just <$> chunkTake
   yield Nothing
+
+-- | Equivalent of unix `uniq`, filtering out duplicate values passed to it.
+-- |
+-- | Uses a `HashSet` of hashes of `a`; for `n` elements `awaited`, this pipe
+-- | will occupy O(n) space, and `yield` in O(1) time.
+uniqHash :: forall a m. Hashable a => MonadEffect m => MonadRec m => Pipe a a m Unit
+uniqHash = do
+  seenHashesST <- liftEffect $ liftST $ STRef.new HashSet.empty
+  forever do
+    a <- await
+    seenHashes <- liftEffect $ liftST $ STRef.read seenHashesST
+    when (not $ HashSet.member (hash a) seenHashes) do
+      void $ liftEffect $ liftST $ STRef.modify (HashSet.insert $ hash a) seenHashesST
+      yield a
+
+-- | The result of a single step forward of a pipe.
+data InvokeResult a b m
+  -- | The pipe `await`ed the value, but did not `yield` a response.
+  = DidNotYield (Pipe a b m Unit)
+  -- | The pipe `await`ed the value, and `yield`ed 1 or more responses.
+  | Yielded (NonEmptyList b /\ Pipe a b m Unit)
+  -- | The pipe `await`ed the value, and exited.
+  | Exited
+
+data IntermediateInvokeResult a b m
+  = IDidNotYield (Pipe a b m Unit)
+  | IYielded (NonEmptyList b /\ Pipe a b m Unit)
+  | IDidNotAwait (Pipe a b m Unit)
+
+-- | Pass a single value to a pipe, returning the result of the pipe's invocation.
+invoke :: forall m a b. Monad m => Pipe a b m Unit -> a -> m (InvokeResult a b m)
+invoke m a =
+  let
+    go :: IntermediateInvokeResult a b m -> m (InvokeResult a b m)
+    go (IYielded (as /\ n)) =
+      case n of
+        Request _ _ -> pure $ Yielded $ as /\ n
+        Respond rep f -> go (IYielded $ (as <> pure rep) /\ f unit)
+        M o -> go =<< IYielded <$> (as /\ _) <$> o
+        Pure _ -> pure Exited
+    go (IDidNotYield n) =
+      case n of
+        Request _ _ -> pure $ DidNotYield n
+        Respond rep f -> go (IYielded $ pure rep /\ f unit)
+        M o -> go =<< IDidNotYield <$> o
+        Pure _ -> pure Exited
+    go (IDidNotAwait n) =
+      case n of
+        Request _ f -> go (IDidNotYield (f a))
+        Respond rep f -> go (IYielded $ pure rep /\ f unit)
+        M o -> go =<< IDidNotAwait <$> o
+        Pure _ -> pure Exited
+  in
+    go (IDidNotAwait m)