feat: move versioning check on the EventStore

eventually-core/src/repository.rs

@@ -12,7 +12,7 @@ use std::fmt::Debug;
 use futures::stream::TryStreamExt;
 
 use crate::aggregate::{Aggregate, AggregateRoot, AggregateRootBuilder};
-use crate::store::{EventStore, Select};
+use crate::store::{EventStore, Expected, Select};
 use crate::versioning::Versioned;
 
 /// Error type returned by the [`Repository`].
@@ -145,11 +145,10 @@ where
 
         if let Some(events) = events_to_commit {
             if !events.is_empty() {
-                // Version is incremented at each events flush.
-                version += 1;
-
-                self.store
-                    .append(root.id().clone(), version, events)
+                // Version is incremented at each events flush by the EventStore.
+                version = self
+                    .store
+                    .append(root.id().clone(), Expected::Exact(version), events)
                     .await
                     .map_err(Error::Store)?;
             }

eventually-core/src/store.rs

@@ -2,13 +2,108 @@
 //!
 //! [`Event`]: ../aggregate/trait.Aggregate.html#associatedtype.Event
 
+use std::ops::Deref;
+
 use futures::future::BoxFuture;
 use futures::stream::BoxStream;
 
 use serde::{Deserialize, Serialize};
 
 use crate::versioning::Versioned;
 
+/// Contains a type-state builder for [`PersistentEvent`] type.
+///
+/// [`PersistentEvent`]: struct.PersistedEvent.html
+pub mod persistent {
+    /// Creates a new [`PersistedEvent`] by wrapping an Event value.
+    ///
+    /// [`PersistentEvent`]: ../struct.PersistedEvent.html
+    pub struct EventBuilder<T> {
+        pub(super) event: T,
+    }
+
+    impl<T> From<T> for EventBuilder<T> {
+        #[inline]
+        fn from(event: T) -> Self {
+            Self { event }
+        }
+    }
+
+    impl<T> EventBuilder<T> {
+        /// Specifies the [`PersistentEvent`] version and moves to the next
+        /// builder state.
+        ///
+        /// [`PersistentEvent`]: ../struct.PersistedEvent.html
+        #[inline]
+        pub fn version(self, value: u32) -> EventBuilderWithVersion<T> {
+            EventBuilderWithVersion {
+                version: value,
+                event: self.event,
+            }
+        }
+
+        /// Specifies the [`PersistentEvent`] sequence number and moves to the next
+        /// builder state.
+        ///
+        /// [`PersistentEvent`]: ../struct.PersistedEvent.html
+        #[inline]
+        pub fn sequence_number(self, value: u32) -> EventBuilderWithSequenceNumber<T> {
+            EventBuilderWithSequenceNumber {
+                sequence_number: value,
+                event: self.event,
+            }
+        }
+    }
+
+    /// Next step in creating a new [`PersistedEvent`] carrying an Event value
+    /// and its version.
+    ///
+    /// [`PersistentEvent`]: ../struct.PersistedEvent.html
+    pub struct EventBuilderWithVersion<T> {
+        version: u32,
+        event: T,
+    }
+
+    impl<T> EventBuilderWithVersion<T> {
+        /// Specifies the [`PersistentEvent`] sequence number and moves to the next
+        /// builder state.
+        ///
+        /// [`PersistentEvent`]: ../struct.PersistedEvent.html
+        #[inline]
+        pub fn sequence_number(self, value: u32) -> super::PersistedEvent<T> {
+            super::PersistedEvent {
+                version: self.version,
+                event: self.event,
+                sequence_number: value,
+            }
+        }
+    }
+
+    /// Next step in creating a new [`PersistedEvent`] carrying an Event value
+    /// and its sequence number.
+    ///
+    /// [`PersistentEvent`]: ../struct.PersistedEvent.html
+    pub struct EventBuilderWithSequenceNumber<T> {
+        sequence_number: u32,
+        event: T,
+    }
+
+    impl<T> EventBuilderWithSequenceNumber<T> {
+        /// Specifies the [`PersistentEvent`] version and moves to the next
+        /// builder state.
+        ///
+        /// [`PersistentEvent`]: ../struct.PersistedEvent.html
+        #[inline]
+        pub fn version(self, value: u32) -> super::PersistedEvent<T> {
+            super::PersistedEvent {
+                version: value,
+                event: self.event,
+                sequence_number: self.sequence_number,
+            }
+        }
+    }
+}
+
 /// An [`Event`] wrapper for events that have been
 /// successfully committed to the [`EventStore`].
 ///
@@ -25,37 +120,28 @@ pub struct PersistedEvent<T> {
     event: T,
 }
 
-impl<T> From<T> for PersistedEvent<T> {
-    #[inline]
-    fn from(event: T) -> Self {
-        Self {
-            event,
-            version: 0,
-            sequence_number: 0,
-        }
-    }
-}
-
 impl<T> Versioned for PersistedEvent<T> {
     #[inline]
     fn version(&self) -> u32 {
         self.version
     }
 }
 
-impl<T> PersistedEvent<T> {
-    /// Updates the event version to the one specified.
-    #[inline]
-    pub fn with_version(mut self, version: u32) -> Self {
-        self.version = version;
-        self
+impl<T> Deref for PersistedEvent<T> {
+    type Target = T;
+
+    fn deref(&self) -> &Self::Target {
+        &self.event
     }
+}
 
-    /// Updates the sequence number version to the one specified.
+impl<T> PersistedEvent<T> {
+    /// Creates a new [`EventBuilder`] from the provided Event value.
+    ///
+    /// [`EventBuilder`]: persistent/struct.EventBuilder.html
     #[inline]
-    pub fn with_sequence_number(mut self, sequence_number: u32) -> Self {
-        self.sequence_number = sequence_number;
-        self
+    pub fn from(event: T) -> persistent::EventBuilder<T> {
+        persistent::EventBuilder { event }
     }
 
     /// Returns the event sequence number.
@@ -93,6 +179,27 @@ pub enum Select {
     From(u32),
 }
 
+/// Specifies the optimistic locking level when performing [`append`] from
+/// an [`EventStore`].
+///
+/// Check out [`append`] documentation for more info.
+///
+/// [`append`]: trait.EventStore.html#method.append
+/// [`EventStore`]: trait.EventStore.html
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum Expected {
+    /// Append events disregarding the current [`Aggregate`] version.
+    ///
+    /// [`Aggregate`]: ../aggregate/trait.Aggregate.html
+    Any,
+
+    /// Append events only if the current version of the [`Aggregate`]
+    /// is the one specified by the value provided here.
+    ///
+    /// [`Aggregate`]: ../aggregate/trait.Aggregate.html
+    Exact(u32),
+}
+
 /// Stream type returned by the [`EventStore::stream`] method.
 ///
 /// [`EventStore::stream`]: trait.EventStore.html#method.stream
@@ -142,7 +249,15 @@ pub trait EventStore {
     /// `append` is a transactional operation: it either appends all the events,
     /// or none at all and returns an [`AppendError`].
     ///
-    /// The desired version for the new [`Event`]s to append must be specified.
+    /// The desired version for the new [`Event`]s to append must be specified
+    /// through an [`Expected`] element.
+    ///
+    /// When using `Expected::Any`, no checks on the current [`Aggregate`]
+    /// values will be performed, disregarding optimistic locking.
+    ///
+    /// When using `Expected::Exact`, the Store will check that the current
+    /// version of the [`Aggregate`] is _exactly_ the one specified.
+    ///
     /// If the version is not the one expected from the Store, implementations
     /// should raise an [`AppendError::Conflict`] error.
     ///
@@ -156,9 +271,9 @@ pub trait EventStore {
     fn append(
         &mut self,
         id: Self::SourceId,
-        version: u32,
+        version: Expected,
         events: Vec<Self::Event>,
-    ) -> BoxFuture<Result<(), Self::Error>>;
+    ) -> BoxFuture<Result<u32, Self::Error>>;
 
     /// Streams a list of [`Event`]s from the `EventStore` back to the application,
     /// by specifying the desired [`SourceId`] and [`Offset`].

eventually-postgres/src/lib.rs

@@ -53,7 +53,7 @@
 
 use std::sync::Arc;
 
-use eventually::store::{AppendError, EventStream, PersistedEvent, Select};
+use eventually::store::{AppendError, EventStream, Expected, PersistedEvent, Select};
 use eventually::{Aggregate, AggregateId};
 
 use futures::future::BoxFuture;
@@ -241,31 +241,34 @@ where
     fn append(
         &mut self,
         id: Self::SourceId,
-        version: u32,
+        version: Expected,
         events: Vec<Self::Event>,
-    ) -> BoxFuture<Result<(), Self::Error>> {
-        let serialized = events
-            .into_iter()
-            .enumerate()
-            .map(|(i, event)| serde_json::to_value(event).map(|value| (i, value)))
-            .collect::<Result<Vec<_>, _>>()
-            .unwrap();
+    ) -> BoxFuture<Result<u32, Self::Error>> {
+        // FIXME(ar3s3ru): this crate needs a new overhaul.
+        unimplemented!("crate needs a new overhaul, after the changes with the EventStore")
 
-        Box::pin(async move {
-            let mut tx = self.client.write().await;
-            let tx = tx.transaction().await.map_err(EventStoreError::from)?;
+        // let serialized = events
+        //     .into_iter()
+        //     .enumerate()
+        //     .map(|(i, event)| serde_json::to_value(event).map(|value| (i, value)))
+        //     .collect::<Result<Vec<_>, _>>()
+        //     .unwrap();
 
-            for (i, event) in serialized {
-                tx.execute(
-                    &*self.append_query,
-                    &[&id.to_string(), &event, &version, &(i as u32)],
-                )
-                .await
-                .map_err(EventStoreError::from)?;
-            }
+        // Box::pin(async move {
+        //     let mut tx = self.client.write().await;
+        //     let tx = tx.transaction().await.map_err(EventStoreError::from)?;
 
-            tx.commit().await.map_err(EventStoreError::from)
-        })
+        //     for (i, event) in serialized {
+        //         tx.execute(
+        //             &*self.append_query,
+        //             &[&id.to_string(), &event, &version, &(i as u32)],
+        //         )
+        //         .await
+        //         .map_err(EventStoreError::from)?;
+        //     }
+
+        //     tx.commit().await.map_err(EventStoreError::from)
+        // })
     }
 
     fn stream(
@@ -292,8 +295,8 @@ where
                     let event: Event = serde_json::from_value(row.get("event")).unwrap();
 
                     PersistedEvent::from(event)
-                        .with_version(row.get("version"))
-                        .with_sequence_number(row.get("offset"))
+                        .version(row.get("version"))
+                        .sequence_number(row.get("offset"))
                 })
                 .map_err(EventStoreError::from)
                 .boxed())