Mixing
eDSL - implement an action that could be used only once in the sequence
3
I'm developing the following eDSL :
import Control.Monad.Free
type CommandHandler
= PersistedCommand -> Maybe AggregateSnapshot -> CommandDirective
data CommandDirective = Reject RejectionReason
| SkipBecauseAlreadyProcessed
| Transact (CommandTransaction ())
type RejectionReason = String
data Action a = PersistEvent Event a
| UpdateSnapshot AggregateSnapshot a
| GetCurrentTime (UTCTime -> a )
| GetNewEventId (EventId -> a) deriving (Functor)
type CommandTransaction a = Free Action a
persistEvent :: Event -> CommandTransaction ()
persistEvent event = Free . PersistEvent event $ Pure ()
updateSnapshot :: AggregateSnapshot -> CommandTransaction ()
updateSnapshot aggregateSnapshot
= Free . UpdateSnapshot aggregateSnapshot $ Pure ()
getNewEventID :: CommandTransaction EventId
getNewEventID = Free $ GetNewEventId Pure
getCurrentTime :: CommandTransaction UTCTime
getCurrentTime = Free $ GetCurrentTime Pure
I would like UpdateSnapshot to be used only once in a sequence not twice as I'm doing now. I could do it with phantom types and then UpdateSnapshot will be the last element of the action chain. But It's kind of semantically wrong and it does not work for 2 actions with the same nature then....
e.g : 2 last updateSnapshot should not be valid :
do
now <- getCurrentTime
eventId <- getNewEventID
persistEvent $ WorkspaceCreated
{ eventId = eventId
, createdOn = now
, workspaceId = workspaceId }
updateSnapshot $ AggregateSnapshot
{ lastOffsetConsumed = 0
, commandsProcessed = Set.fromList [commandId]
, state = AggregateState { aggregateId = workspaceId } }
updateSnapshot $ AggregateSnapshot
{ lastOffsetConsumed = 0
, commandsProcessed = Set.fromList [commandId]
, state = AggregateState { aggregateId = workspaceId } }
haskell dsl free-monad
edited Nov 20 '18 at 9:47
leftaroundabout
79k3117233
asked Nov 19 '18 at 16:13
Nicolas Henin
1,06521433
add a comment |
3
I'm developing the following eDSL :
import Control.Monad.Free
type CommandHandler
= PersistedCommand -> Maybe AggregateSnapshot -> CommandDirective
data CommandDirective = Reject RejectionReason
| SkipBecauseAlreadyProcessed
| Transact (CommandTransaction ())
type RejectionReason = String
data Action a = PersistEvent Event a
| UpdateSnapshot AggregateSnapshot a
| GetCurrentTime (UTCTime -> a )
| GetNewEventId (EventId -> a) deriving (Functor)
type CommandTransaction a = Free Action a
persistEvent :: Event -> CommandTransaction ()
persistEvent event = Free . PersistEvent event $ Pure ()
updateSnapshot :: AggregateSnapshot -> CommandTransaction ()
updateSnapshot aggregateSnapshot
= Free . UpdateSnapshot aggregateSnapshot $ Pure ()
getNewEventID :: CommandTransaction EventId
getNewEventID = Free $ GetNewEventId Pure
getCurrentTime :: CommandTransaction UTCTime
getCurrentTime = Free $ GetCurrentTime Pure
I would like UpdateSnapshot to be used only once in a sequence not twice as I'm doing now. I could do it with phantom types and then UpdateSnapshot will be the last element of the action chain. But It's kind of semantically wrong and it does not work for 2 actions with the same nature then....
e.g : 2 last updateSnapshot should not be valid :
do
now <- getCurrentTime
eventId <- getNewEventID
persistEvent $ WorkspaceCreated
{ eventId = eventId
, createdOn = now
, workspaceId = workspaceId }
updateSnapshot $ AggregateSnapshot
{ lastOffsetConsumed = 0
, commandsProcessed = Set.fromList [commandId]
, state = AggregateState { aggregateId = workspaceId } }
updateSnapshot $ AggregateSnapshot
{ lastOffsetConsumed = 0
, commandsProcessed = Set.fromList [commandId]
, state = AggregateState { aggregateId = workspaceId } }
haskell dsl free-monad
edited Nov 20 '18 at 9:47
leftaroundabout
79k3117233
asked Nov 19 '18 at 16:13
Nicolas Henin
1,06521433
1
What do you mean by "not twice as I'm doing now?" Where are you usingUpdateSnapshot?
– Mark Seemann
Nov 19 '18 at 19:54
I put en example of dsl to show what I meant by using twice UpdateSnapshot
– Nicolas Henin
Nov 19 '18 at 20:26
How about takingUpdateSnapshotout ofActionand make it aFreeTthat you can use to contain the (amputated)CommandTransaction? Most of the functions (persistEvent,getNewEventID, etc.) would returnUpdateSnapshotT CommandTransaction a, butupdateSnapshotwould only returnCommandTransaction. I haven't tried, so it may be a stupid idea...
– Mark Seemann
Nov 19 '18 at 20:33
It's a stupid idea.
– Mark Seemann
Nov 19 '18 at 21:29
Don't be to hard on yourself :-)
– Nicolas Henin
Nov 22 '18 at 10:25
add a comment |
3
3
3
2
I'm developing the following eDSL :
import Control.Monad.Free
type CommandHandler
= PersistedCommand -> Maybe AggregateSnapshot -> CommandDirective
data CommandDirective = Reject RejectionReason
| SkipBecauseAlreadyProcessed
| Transact (CommandTransaction ())
type RejectionReason = String
data Action a = PersistEvent Event a
| UpdateSnapshot AggregateSnapshot a
| GetCurrentTime (UTCTime -> a )
| GetNewEventId (EventId -> a) deriving (Functor)
type CommandTransaction a = Free Action a
persistEvent :: Event -> CommandTransaction ()
persistEvent event = Free . PersistEvent event $ Pure ()
updateSnapshot :: AggregateSnapshot -> CommandTransaction ()
updateSnapshot aggregateSnapshot
= Free . UpdateSnapshot aggregateSnapshot $ Pure ()
getNewEventID :: CommandTransaction EventId
getNewEventID = Free $ GetNewEventId Pure
getCurrentTime :: CommandTransaction UTCTime
getCurrentTime = Free $ GetCurrentTime Pure
I would like UpdateSnapshot to be used only once in a sequence not twice as I'm doing now. I could do it with phantom types and then UpdateSnapshot will be the last element of the action chain. But It's kind of semantically wrong and it does not work for 2 actions with the same nature then....
e.g : 2 last updateSnapshot should not be valid :
do
now <- getCurrentTime
eventId <- getNewEventID
persistEvent $ WorkspaceCreated
{ eventId = eventId
, createdOn = now
, workspaceId = workspaceId }
updateSnapshot $ AggregateSnapshot
{ lastOffsetConsumed = 0
, commandsProcessed = Set.fromList [commandId]
, state = AggregateState { aggregateId = workspaceId } }
updateSnapshot $ AggregateSnapshot
{ lastOffsetConsumed = 0
, commandsProcessed = Set.fromList [commandId]
, state = AggregateState { aggregateId = workspaceId } }
haskell dsl free-monad
edited Nov 20 '18 at 9:47
leftaroundabout
79k3117233
asked Nov 19 '18 at 16:13
Nicolas Henin
1,06521433
I'm developing the following eDSL :
import Control.Monad.Free
type CommandHandler
= PersistedCommand -> Maybe AggregateSnapshot -> CommandDirective
data CommandDirective = Reject RejectionReason
| SkipBecauseAlreadyProcessed
| Transact (CommandTransaction ())
type RejectionReason = String
data Action a = PersistEvent Event a
| UpdateSnapshot AggregateSnapshot a
| GetCurrentTime (UTCTime -> a )
| GetNewEventId (EventId -> a) deriving (Functor)
type CommandTransaction a = Free Action a
persistEvent :: Event -> CommandTransaction ()
persistEvent event = Free . PersistEvent event $ Pure ()
updateSnapshot :: AggregateSnapshot -> CommandTransaction ()
updateSnapshot aggregateSnapshot
= Free . UpdateSnapshot aggregateSnapshot $ Pure ()
getNewEventID :: CommandTransaction EventId
getNewEventID = Free $ GetNewEventId Pure
getCurrentTime :: CommandTransaction UTCTime
getCurrentTime = Free $ GetCurrentTime Pure
I would like UpdateSnapshot to be used only once in a sequence not twice as I'm doing now. I could do it with phantom types and then UpdateSnapshot will be the last element of the action chain. But It's kind of semantically wrong and it does not work for 2 actions with the same nature then....
e.g : 2 last updateSnapshot should not be valid :
do
now <- getCurrentTime
eventId <- getNewEventID
persistEvent $ WorkspaceCreated
{ eventId = eventId
, createdOn = now
, workspaceId = workspaceId }
updateSnapshot $ AggregateSnapshot
{ lastOffsetConsumed = 0
, commandsProcessed = Set.fromList [commandId]
, state = AggregateState { aggregateId = workspaceId } }
updateSnapshot $ AggregateSnapshot
{ lastOffsetConsumed = 0
, commandsProcessed = Set.fromList [commandId]
, state = AggregateState { aggregateId = workspaceId } }
haskell dsl free-monad
haskell dsl free-monad
edited Nov 20 '18 at 9:47
leftaroundabout
79k3117233
asked Nov 19 '18 at 16:13
Nicolas Henin
1,06521433
edited Nov 20 '18 at 9:47
leftaroundabout
79k3117233
asked Nov 19 '18 at 16:13
Nicolas Henin
1,06521433
edited Nov 20 '18 at 9:47
leftaroundabout
79k3117233
edited Nov 20 '18 at 9:47
leftaroundabout
79k3117233
edited Nov 20 '18 at 9:47
leftaroundabout
79k3117233
79k3117233
asked Nov 19 '18 at 16:13
Nicolas Henin
1,06521433
asked Nov 19 '18 at 16:13
Nicolas Henin
1,06521433
asked Nov 19 '18 at 16:13
Nicolas Henin
1,06521433
1,06521433
1
What do you mean by "not twice as I'm doing now?" Where are you usingUpdateSnapshot?
– Mark Seemann
Nov 19 '18 at 19:54
I put en example of dsl to show what I meant by using twice UpdateSnapshot
– Nicolas Henin
Nov 19 '18 at 20:26
How about takingUpdateSnapshotout ofActionand make it aFreeTthat you can use to contain the (amputated)CommandTransaction? Most of the functions (persistEvent,getNewEventID, etc.) would returnUpdateSnapshotT CommandTransaction a, butupdateSnapshotwould only returnCommandTransaction. I haven't tried, so it may be a stupid idea...
– Mark Seemann
Nov 19 '18 at 20:33
It's a stupid idea.
– Mark Seemann
Nov 19 '18 at 21:29
Don't be to hard on yourself :-)
– Nicolas Henin
Nov 22 '18 at 10:25
add a comment |
1
What do you mean by "not twice as I'm doing now?" Where are you usingUpdateSnapshot?
– Mark Seemann
Nov 19 '18 at 19:54
I put en example of dsl to show what I meant by using twice UpdateSnapshot
– Nicolas Henin
Nov 19 '18 at 20:26
How about takingUpdateSnapshotout ofActionand make it aFreeTthat you can use to contain the (amputated)CommandTransaction? Most of the functions (persistEvent,getNewEventID, etc.) would returnUpdateSnapshotT CommandTransaction a, butupdateSnapshotwould only returnCommandTransaction. I haven't tried, so it may be a stupid idea...
– Mark Seemann
Nov 19 '18 at 20:33
It's a stupid idea.
– Mark Seemann
Nov 19 '18 at 21:29
Don't be to hard on yourself :-)
– Nicolas Henin
Nov 22 '18 at 10:25
1
1
What do you mean by "not twice as I'm doing now?" Where are you using
UpdateSnapshot?– Mark Seemann
Nov 19 '18 at 19:54
What do you mean by "not twice as I'm doing now?" Where are you using
UpdateSnapshot?– Mark Seemann
Nov 19 '18 at 19:54
I put en example of dsl to show what I meant by using twice UpdateSnapshot
– Nicolas Henin
Nov 19 '18 at 20:26
I put en example of dsl to show what I meant by using twice UpdateSnapshot
– Nicolas Henin
Nov 19 '18 at 20:26
How about taking
UpdateSnapshot out of Action and make it a FreeT that you can use to contain the (amputated) CommandTransaction? Most of the functions (persistEvent, getNewEventID, etc.) would return UpdateSnapshotT CommandTransaction a, but updateSnapshot would only return CommandTransaction. I haven't tried, so it may be a stupid idea...– Mark Seemann
Nov 19 '18 at 20:33
How about taking
UpdateSnapshot out of Action and make it a FreeT that you can use to contain the (amputated) CommandTransaction? Most of the functions (persistEvent, getNewEventID, etc.) would return UpdateSnapshotT CommandTransaction a, but updateSnapshot would only return CommandTransaction. I haven't tried, so it may be a stupid idea...– Mark Seemann
Nov 19 '18 at 20:33
It's a stupid idea.
– Mark Seemann
Nov 19 '18 at 21:29
It's a stupid idea.
– Mark Seemann
Nov 19 '18 at 21:29
Don't be to hard on yourself :-)
– Nicolas Henin
Nov 22 '18 at 10:25
Don't be to hard on yourself :-)
– Nicolas Henin
Nov 22 '18 at 10:25
add a comment |
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1
What do you mean by "not twice as I'm doing now?" Where are you using
UpdateSnapshot?– Mark Seemann
Nov 19 '18 at 19:54
I put en example of dsl to show what I meant by using twice UpdateSnapshot
– Nicolas Henin
Nov 19 '18 at 20:26
How about taking
UpdateSnapshotout ofActionand make it aFreeTthat you can use to contain the (amputated)CommandTransaction? Most of the functions (persistEvent,getNewEventID, etc.) would returnUpdateSnapshotT CommandTransaction a, butupdateSnapshotwould only returnCommandTransaction. I haven't tried, so it may be a stupid idea...– Mark Seemann
Nov 19 '18 at 20:33
It's a stupid idea.
– Mark Seemann
Nov 19 '18 at 21:29
Don't be to hard on yourself :-)
– Nicolas Henin
Nov 22 '18 at 10:25