fix: more efficiently / less blockingly read?

spago.lock

@@ -15,7 +15,6 @@ workspace:
         - foldable-traversable: ">=6.0.0 <7.0.0"
         - foreign: ">=7.0.0 <8.0.0"
         - foreign-object: ">=4.1.0 <5.0.0"
-        - fork: ">=6.0.0 <7.0.0"
         - integers: ">=6.0.0 <7.0.0"
         - lists: ">=7.0.0 <8.0.0"
         - maybe: ">=6.0.0 <7.0.0"
@@ -61,7 +60,6 @@ workspace:
         - foldable-traversable
         - foreign
         - foreign-object
-        - fork
         - formatters
         - functions
         - functors
@@ -342,12 +340,6 @@ packages:
       - tuples
       - typelevel-prelude
       - unfoldable
-  fork:
-    type: registry
-    version: 6.0.0
-    integrity: sha256-X7u0SuCvFbLbzuNEKLBNuWjmcroqMqit4xEzpQwAP7E=
-    dependencies:
-      - aff
   formatters:
     type: registry
     version: 7.0.0

spago.yaml

@@ -22,7 +22,6 @@ package:
     - foldable-traversable: ">=6.0.0 <7.0.0"
     - foreign: ">=7.0.0 <8.0.0"
     - foreign-object: ">=4.1.0 <5.0.0"
-    - fork: ">=6.0.0 <7.0.0"
     - integers: ">=6.0.0 <7.0.0"
     - lists: ">=7.0.0 <8.0.0"
     - maybe: ">=6.0.0 <7.0.0"
@@ -33,6 +32,7 @@ package:
     - nullable: ">=6.0.0 <7.0.0"
     - numbers: ">=9.0.1 <10.0.0"
     - ordered-collections: ">=3.2.0 <4.0.0"
+    - parallel: ">=6.0.0 <7.0.0"
     - precise-datetime: ">=7.0.0 <8.0.0"
     - prelude: ">=6.0.1 <7.0.0"
     - record: ">=4.0.0 <5.0.0"

src/Node.Stream.CSV.Parse.purs

@@ -5,11 +5,12 @@ import Prelude hiding (join)
 import Control.Alt ((<|>))
 import Control.Monad.Error.Class (liftEither)
 import Control.Monad.Except (runExcept)
-import Control.Monad.Fork.Class (class MonadFork, fork, join)
 import Control.Monad.Maybe.Trans (MaybeT(..), runMaybeT)
-import Control.Monad.Rec.Class (class MonadRec, tailRecM, Step(..), whileJust)
+import Control.Monad.Rec.Class (class MonadRec, whileJust)
 import Control.Monad.ST.Global as ST
 import Control.Monad.Trans.Class (lift)
+import Control.MonadPlus (class Alternative)
+import Control.Parallel (class Parallel, parTraverse_)
 import Data.Array as Array
 import Data.Array.ST as Array.ST
 import Data.Bifunctor (lmap)
@@ -18,13 +19,13 @@ import Data.Either (Either(..))
 import Data.Filterable (filter)
 import Data.Map (Map)
 import Data.Map as Map
-import Data.Maybe (Maybe(..))
-import Data.Newtype (wrap)
+import Data.Maybe (Maybe(..), isNothing)
 import Data.Nullable (Nullable)
 import Data.Nullable as Nullable
-import Data.Traversable (traverse)
+import Data.Traversable (for)
 import Effect (Effect)
-import Effect.Aff (Canceler(..), delay, makeAff)
+import Effect as Effect
+import Effect.Aff (Canceler(..), makeAff)
 import Effect.Aff.Class (class MonadAff, liftAff)
 import Effect.Class (liftEffect)
 import Effect.Exception (error)
@@ -89,7 +90,18 @@ make :: forall @r rl @config @missing @extra. RowToList r rl => ReadCSVRecord r
 make = makeImpl <<< unsafeToForeign <<< Object.union (recordToForeign { columns: false, cast: false, cast_date: false }) <<< recordToForeign
 
 -- | Synchronously parse a CSV string
-parse :: forall @r rl @config missing extra m f. MonadFork f m => MonadAff m => MonadRec m => RowToList r rl => ReadCSVRecord r rl => Union config missing (Config extra) => { | config } -> String -> m (Array { | r })
+parse
+  :: forall @r rl @config missing extra m p
+   . Alternative p
+  => Parallel p m
+  => MonadAff m
+  => MonadRec m
+  => RowToList r rl
+  => ReadCSVRecord r rl
+  => Union config missing (Config extra)
+  => { | config }
+  -> String
+  -> m (Array { | r })
 parse config csv = do
   stream <- liftEffect $ make @r @config @missing @extra config
   void $ liftEffect $ Stream.writeString stream UTF8 csv
@@ -97,21 +109,31 @@ parse config csv = do
   readAll stream
 
 -- | Loop until the stream is closed, invoking the callback with each record as it is parsed.
-foreach :: forall @r rl x m f. MonadFork f m => MonadRec m => MonadAff m => RowToList r rl => ReadCSVRecord r rl => CSVParser r x -> ({ | r } -> m Unit) -> m Unit
+foreach
+  :: forall @r rl x m p
+   . Alternative p
+  => Parallel p m
+  => MonadRec m
+  => MonadAff m
+  => RowToList r rl
+  => ReadCSVRecord r rl
+  => CSVParser r x
+  -> ({ | r } -> m Unit)
+  -> m Unit
 foreach stream cb = whileJust do
   isReadable <- liftEffect $ Stream.readable stream
   liftAff $ when (not isReadable) $ makeAff \res -> do
     stop <- flip (Event.once Stream.readableH) stream $ res $ Right unit
     pure $ Canceler $ const $ liftEffect stop
-  fibers <- flip tailRecM [] \fibers -> do
-    liftAff $ delay $ wrap 0.0
-    r <- liftEffect $ read @r stream
-    case r of
-      Just r' -> do
-        f <- fork (cb r')
-        pure $ Loop $ fibers <> [ f ]
-      Nothing -> pure $ Done fibers
-  void $ traverse join fibers
+
+  recordsST <- liftEffect $ ST.toEffect $ Array.ST.new
+  liftEffect $ Effect.untilE do
+    r <- read @r stream
+    void $ for r $ ST.toEffect <<< flip Array.ST.push recordsST
+    pure $ isNothing r
+  records <- liftEffect $ ST.toEffect $ Array.ST.unsafeFreeze recordsST
+
+  parTraverse_ cb records
   isClosed <- liftEffect $ Stream.closed stream
   pure $ if isClosed then Nothing else Just unit
 
@@ -120,14 +142,28 @@ foreach stream cb = whileJust do
 -- | Returns `Nothing` when either:
 -- | - The internal buffer of parsed records has been exhausted, but there will be more (`Node.Stream.readable` and `Node.Stream.closed` are both `false`)
 -- | - All records have been processed (`Node.Stream.closed` is `true`)
-read :: forall @r rl a. RowToList r rl => ReadCSVRecord r rl => CSVParser r a -> Effect (Maybe { | r })
+read
+  :: forall @r rl a
+   . RowToList r rl
+  => ReadCSVRecord r rl
+  => CSVParser r a
+  -> Effect (Maybe { | r })
 read stream = runMaybeT do
   cols <- MaybeT $ getOrInitColumnsMap stream
   raw :: Array String <- MaybeT $ Nullable.toMaybe <$> readImpl stream
   liftEither $ lmap (error <<< show) $ runExcept $ readCSVRecord @r @rl cols raw
 
 -- | Collect all parsed records into an array
-readAll :: forall @r rl a m f. MonadFork f m => MonadRec m => MonadAff m => RowToList r rl => ReadCSVRecord r rl => CSVParser r a -> m (Array { | r })
+readAll
+  :: forall @r rl a m p
+   . Alternative p
+  => Parallel p m
+  => MonadRec m
+  => MonadAff m
+  => RowToList r rl
+  => ReadCSVRecord r rl
+  => CSVParser r a
+  -> m (Array { | r })
 readAll stream = do
   records <- liftEffect $ ST.toEffect $ Array.ST.new
   foreach stream $ void <<< liftEffect <<< ST.toEffect <<< flip Array.ST.push records