module Eventful.Aggregate
( Aggregate (..)
, allAggregateStates
, commandStoredAggregate
) where
import Data.Foldable (foldl')
import Data.List (scanl')
import Eventful.Projection
import Eventful.Store.Class
import Eventful.UUID
data Aggregate state event cmd =
Aggregate
{ aggregateCommandHandler :: state -> cmd -> [event]
, aggregateProjection :: Projection state event
}
allAggregateStates
:: Aggregate state event cmd
-> [cmd]
-> [state]
allAggregateStates (Aggregate commandHandler (Projection seed eventHandler)) events =
scanl' go seed events
where
go state command = foldl' eventHandler state $ commandHandler state command
commandStoredAggregate
:: (Monad m)
=> EventStore serialized m
-> Aggregate state serialized cmd
-> UUID
-> cmd
-> m [serialized]
commandStoredAggregate store (Aggregate handler proj) uuid command = do
(latest, vers) <- getLatestProjection store proj uuid
let events = handler latest command
mError <- storeEvents store (ExactVersion vers) uuid events
case mError of
(Just err) -> error $ "TODO: Create aggregate restart logic. " ++ show err
Nothing -> return events