Safe Haskell	Safe-Inferred
Language	Haskell2010

Marconi.Core.Transformer.WithFold

Description

A transformer that allows an indexer to fold incoming events: each new event is the result of a computation between the last result in the indexer and the incoming event.

See Marconi.Core for documentation.

Synopsis

data WithFold m indexer output input
withFold :: output -> (indexer output -> m (Maybe output)) -> (output -> input -> m output) -> indexer output -> WithFold m indexer output input
withFoldPure :: Applicative m => output -> (indexer output -> m (Maybe output)) -> (output -> input -> output) -> indexer output -> WithFold m indexer output input
withFoldMap :: (Monoid output, Applicative m) => (indexer output -> m (Maybe output)) -> (input -> output) -> indexer output -> WithFold m indexer output input
getLastEventAtQueryValue :: (IsSync m event indexer, HasGenesis (Point event), Queryable (ExceptT (QueryError (EventAtQuery a)) m) event (EventAtQuery a) indexer, Ord (Point event), MonadError IndexerError m) => indexer event -> m (Maybe a)
class HasFold m input output indexer where
- fold :: Lens' (indexer input) (output -> input -> m output)

Documentation

data WithFold m indexer output input #

WithFold fold incoming event to produce an output.

Instances

Instances details

(Queryable m output query indexer, Point input ~ Point output) => Queryable m input query (WithFold n indexer output) #
Instance details Defined in Marconi.Core.Transformer.WithFold Methods query :: Point input -> query -> WithFold n indexer output input -> m (Result query) # queryLatest :: query -> WithFold n indexer output input -> m (Result query) #
HasFold m input output (WithFold m indexer output) #
Instance details Defined in Marconi.Core.Transformer.WithFold Methods fold :: Lens' (WithFold m indexer output input) (output -> input -> m output) #
(HasGenesis (Point output), Point input ~ Point output, IsSync m output indexer, IsIndex m output indexer, Ord (Point output)) => IsIndex m input (WithFold m indexer output) #
Instance details Defined in Marconi.Core.Transformer.WithFold Methods index :: Timed (Point input) (Maybe input) -> WithFold m indexer output input -> m (WithFold m indexer output input) # indexAll :: (Eq (Point input), Traversable f) => f (Timed (Point input) (Maybe input)) -> WithFold m indexer output input -> m (WithFold m indexer output input) # indexAllDescending :: (Eq (Point input), Traversable f) => f (Timed (Point input) (Maybe input)) -> WithFold m indexer output input -> m (WithFold m indexer output input) # rollback :: Point input -> WithFold m indexer output input -> m (WithFold m indexer output input) # setLastStablePoint :: Point input -> WithFold m indexer output input -> m (WithFold m indexer output input) #
(Point output ~ Point event, IsSync m output indexer) => IsSync m event (WithFold m indexer output) #
Instance details Defined in Marconi.Core.Transformer.WithFold Methods lastStablePoint :: WithFold m indexer output event -> m (Point event) # lastSyncPoint :: WithFold m indexer output event -> m (Point event) #
(Functor m, Resetable m output indexer, HasGenesis (Point event)) => Resetable m event (WithFold m indexer output) #
Instance details Defined in Marconi.Core.Transformer.WithFold Methods reset :: WithFold m indexer output event -> m (WithFold m indexer output event) #
Closeable m indexer => Closeable m (WithFold m indexer output) #
Instance details Defined in Marconi.Core.Transformer.WithFold Methods close :: WithFold m indexer output event -> m () #
IndexerMapTrans (WithFold m) #
Instance details Defined in Marconi.Core.Transformer.WithFold Methods unwrapMap :: forall (indexer :: Type -> Type) output event. Lens' (WithFold m indexer output event) (indexer output) #

withFold :: output -> (indexer output -> m (Maybe output)) -> (output -> input -> m output) -> indexer output -> WithFold m indexer output input #

A smart constructor for WithFold

withFoldPure :: Applicative m => output -> (indexer output -> m (Maybe output)) -> (output -> input -> output) -> indexer output -> WithFold m indexer output input #

A smart constructor for WithFold

withFoldMap :: (Monoid output, Applicative m) => (indexer output -> m (Maybe output)) -> (input -> output) -> indexer output -> WithFold m indexer output input #

A smart constructor for WithFold

getLastEventAtQueryValue :: (IsSync m event indexer, HasGenesis (Point event), Queryable (ExceptT (QueryError (EventAtQuery a)) m) event (EventAtQuery a) indexer, Ord (Point event), MonadError IndexerError m) => indexer event -> m (Maybe a) #

class HasFold m input output indexer where #

There are few scenarios where you want to modify the fold function but it may happen

Methods

fold :: Lens' (indexer input) (output -> input -> m output) #

Instances

Instances details

HasFold m input output (WithFold m indexer output) #
Instance details Defined in Marconi.Core.Transformer.WithFold Methods fold :: Lens' (WithFold m indexer output input) (output -> input -> m output) #