phfroidmont/foyer-dsi-assure-2035
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Split EventSourcing

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This commit is contained in:
Paul-Henri Froidmont 2025-11-04 17:55:46 +01:00
parent 49d6b6c8cc
commit 4bd2a1518b
Signed by: phfroidmont
GPG key ID: BE948AFD7E7873BE
6 changed files with 94 additions and 78 deletions
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7
README.md Normal file
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@ -0,0 +1,7 @@
# Scala 3 - ZIO
## Run
```bash
mill api.run
```

59
core/src/lu/foyer/CommandEngine.scala Normal file
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@ -0,0 +1,59 @@
package lu.foyer
import zio.*
import lu.foyer.auth.UserInfo
class CommandEngine[Command, Event, State](
val handlers: List[CommandHandler[Command, Event, State]],
reducer: Reducer[Event, State],
val eventRepo: EventRepository[Event],
val stateRepo: StateRepository[State]):
def handleCommand(command: Command, name: String, entityId: String)
: ZIO[UserInfo, JsonApiError | Throwable, (lu.foyer.Event[Event], lu.foyer.Entity[State])] =
for
handler <- ZIO
.succeed(handlers.find(_.name == name))
.someOrFail(new IllegalArgumentException(s"No handler found for command $name"))
entityOption <- stateRepo.fetchOne(entityId)
(event, newStateOption) <- transition(command, name, entityId, entityOption, handler)
newState <-
ZIO
.succeed(newStateOption)
.someOrFail(new IllegalArgumentException("Reducer cannot resolve state transition"))
newEntity = Entity(entityId, newState, entityOption.map(_.version).getOrElse(1))
_ <-
if entityOption.isEmpty then stateRepo.insert(newEntity.entityId, newEntity)
else stateRepo.update(newEntity.entityId, newEntity)
eventEntity <- Random.nextUUID.map(id => Event(newEntity.entityId, event, id.toString))
_ <- eventRepo.insert(eventEntity.eventId, eventEntity)
yield (eventEntity, newEntity)
private def transition(
command: Command,
name: String,
entityId: String,
entityOption: Option[Entity[State]],
handler: CommandHandler[Command, Event, State]
): ZIO[UserInfo, JsonApiError | Throwable, (Event, Option[State])] = (entityOption, handler) match
case (None, h) if !h.isUpdate =>
h.asInstanceOf[CommandHandlerCreate[Command, Event]]
.onCommand(entityId, command)
.map(event => (event, reducer.reduce(event)))
case (Some(entity), h) if h.isUpdate =>
h.asInstanceOf[CommandHandlerUpdate[Command, Event, State]]
.onCommand(entityId, entity.data, command)
.map(event => (event, reducer.reduce(entity.data, event)))
case (Some(_), h) if !h.isUpdate =>
ZIO.fail(
new IllegalArgumentException(s"State already exists when applying create command $name")
)
case (None, h) if h.isUpdate =>
ZIO.fail(new IllegalArgumentException(s"No state found to apply the update command $name"))
case _ => ZIO.fail(new IllegalArgumentException("Impossible state"))
end CommandEngine
object CommandEngine:
def live[Command: Tag, Event: Tag, State: Tag] =
ZLayer.fromFunction(CommandEngine[Command, Event, State](_, _, _, _))

24
core/src/lu/foyer/CommandHandler.scala Normal file
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@ -0,0 +1,24 @@
package lu.foyer
import zio.*
import zio.schema.Schema
import lu.foyer.auth.UserInfo
trait CommandHandler[+Command, +Event, +State]:
def name: String
def isCreate: Boolean
inline def isUpdate: Boolean = !isCreate
def commandSchema: Schema[?]
trait CommandHandlerCreate[Command: Schema, Event] extends CommandHandler[Command, Event, Nothing]:
def onCommand(entityId: String, command: Command): ZIO[UserInfo, JsonApiError | Throwable, Event]
val isCreate = true
val commandSchema = summon[Schema[Command]]
trait CommandHandlerUpdate[Command: Schema, Event, State]
extends CommandHandler[Command, Event, State]:
def onCommand(entityId: String, state: State, command: Command)
: ZIO[UserInfo, JsonApiError | Throwable, Event]
val isCreate = false
val commandSchema = summon[Schema[Command]]

72
core/src/lu/foyer/EventSourcing.scala
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@ -22,75 +22,3 @@ trait Reducer[Event, State]:
def reduce(state: State, event: Event): Option[State] =
fromState.lift((state, event))
trait CommandHandler[+Command, +Event, +State]:
def name: String
def isCreate: Boolean
inline def isUpdate: Boolean = !isCreate
def commandSchema: Schema[?]
trait CommandHandlerCreate[Command: Schema, Event] extends CommandHandler[Command, Event, Nothing]:
def onCommand(entityId: String, command: Command): ZIO[UserInfo, JsonApiError | Throwable, Event]
val isCreate = true
val commandSchema = summon[Schema[Command]]
trait CommandHandlerUpdate[Command: Schema, Event, State]
extends CommandHandler[Command, Event, State]:
def onCommand(entityId: String, state: State, command: Command)
: ZIO[UserInfo, JsonApiError | Throwable, Event]
val isCreate = false
val commandSchema = summon[Schema[Command]]
class CommandEngine[Command, Event, State](
val handlers: List[CommandHandler[Command, Event, State]],
reducer: Reducer[Event, State],
val eventRepo: EventRepository[Event],
val stateRepo: StateRepository[State]):
def handleCommand(command: Command, name: String, entityId: String)
: ZIO[UserInfo, JsonApiError | Throwable, (lu.foyer.Event[Event], lu.foyer.Entity[State])] =
for
handler <- ZIO
.succeed(handlers.find(_.name == name))
.someOrFail(new IllegalArgumentException(s"No handler found for command $name"))
entityOption <- stateRepo.fetchOne(entityId)
(event, newStateOption) <- transition(command, name, entityId, entityOption, handler)
newState <-
ZIO
.succeed(newStateOption)
.someOrFail(new IllegalArgumentException("Reducer cannot resolve state transition"))
newEntity = Entity(entityId, newState, entityOption.map(_.version).getOrElse(1))
_ <-
if entityOption.isEmpty then stateRepo.insert(newEntity.entityId, newEntity)
else stateRepo.update(newEntity.entityId, newEntity)
eventEntity <- Random.nextUUID.map(id => Event(newEntity.entityId, event, id.toString))
_ <- eventRepo.insert(eventEntity.eventId, eventEntity)
yield (eventEntity, newEntity)
private def transition(
command: Command,
name: String,
entityId: String,
entityOption: Option[Entity[State]],
handler: CommandHandler[Command, Event, State]
): ZIO[UserInfo, JsonApiError | Throwable, (Event, Option[State])] = (entityOption, handler) match
case (None, h) if !h.isUpdate =>
h.asInstanceOf[CommandHandlerCreate[Command, Event]]
.onCommand(entityId, command)
.map(event => (event, reducer.reduce(event)))
case (Some(entity), h) if h.isUpdate =>
h.asInstanceOf[CommandHandlerUpdate[Command, Event, State]]
.onCommand(entityId, entity.data, command)
.map(event => (event, reducer.reduce(entity.data, event)))
case (Some(_), h) if !h.isUpdate =>
ZIO.fail(
new IllegalArgumentException(s"State already exists when applying create command $name")
)
case (None, h) if h.isUpdate =>
ZIO.fail(new IllegalArgumentException(s"No state found to apply the update command $name"))
case _ => ZIO.fail(new IllegalArgumentException("Impossible state"))
end CommandEngine
object CommandEngine:
def live[Command: Tag, Event: Tag, State: Tag] =
ZLayer.fromFunction(CommandEngine[Command, Event, State](_, _, _, _))

5
core/src/lu/foyer/clients/ClientReducer.scala
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@ -3,7 +3,7 @@ package clients
import zio.*
class ClientReducer() extends Reducer[ClientEvent, ClientState]:
object ClientReducer extends Reducer[ClientEvent, ClientState]:
override val fromEmpty =
case e: ClientEvent.Created => ClientState.create(e)
@ -12,5 +12,4 @@ class ClientReducer() extends Reducer[ClientEvent, ClientState]:
case (s: ClientState.Actif, e: ClientEvent.Updated) => s.update(e)
case (s: ClientState.Actif, _: ClientEvent.Disabled) => s.disable()
object ClientReducer:
val live: ULayer[Reducer[ClientEvent, ClientState]] = ZLayer.succeed(ClientReducer())
val live = ZLayer.succeed(ClientReducer)

5
core/src/lu/foyer/contracts/ContractReducer.scala
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@ -3,7 +3,7 @@ package contracts
import zio.*
class ContractReducer() extends Reducer[ContractEvent, ContractState]:
object ContractReducer extends Reducer[ContractEvent, ContractState]:
override val fromEmpty =
case e: ContractEvent.Subscribed => ContractState.subscribe(e)
@ -22,5 +22,4 @@ class ContractReducer() extends Reducer[ContractEvent, ContractState]:
case (s: ContractState.PendingAmendment, _: ContractEvent.Rejected) => s.reject()
case (s: ContractState.PendingAmendment, _: ContractEvent.Terminated) => s.terminate()
object ContractReducer:
val live: ULayer[Reducer[ContractEvent, ContractState]] = ZLayer.succeed(ContractReducer())
val live = ZLayer.succeed(ContractReducer)