Event backlog (#18)

* Don’t update scoped state while sending events

* Add Package.resolved

* Pass ref

* Event backlog

.gitignore

@@ -8,7 +8,6 @@
 *.perspectivev3
 !default.perspectivev3
 xcuserdata
-profile
 *.moved-aside
 DerivedData
 .idea/
@@ -19,3 +18,4 @@ Carthage/Checkouts/*
 Carthage/Build/*
 /fastlane/report.xml
 /.ruby-version
+*.xcodeproj/project.xcworkspace/xcshareddata/swiftpm/Package.resolved

RedUx/Source/Store.swift

@@ -28,6 +28,9 @@ public final class Store<State, Event, Environment> {
     private let middlewares: [AnyMiddleware<Event, Event, State>]
     private var middlewareTasks: [Task<Void, Error>] = []
 
+    private var eventBacklog: [Event] = []
+    private var isProcessingEvent = false
+
     // MARK: Initialization
 
     /// Construct a Store with state, reducer and environment.
@@ -70,16 +73,30 @@ public final class Store<State, Event, Environment> {
     /// Send an event through the store's reducer.
     /// - Parameter event: The event.
     public func send(_ event: Event) {
-        let eventStream = self.reducer(&self.state, event, self.environment)
+        self.eventBacklog.append(event)
+        guard !self.isProcessingEvent else { return }
 
-        Task {
-            for middleware in self.middlewares {
-                await middleware.execute(event: event, state: { self.state })
-            }
+        self.isProcessingEvent = true
+        var state = self.state
+
+        defer {
+            self.isProcessingEvent = false
+            self.state = state
+        }
+
+        while !self.eventBacklog.isEmpty {
+            let event = self.eventBacklog.removeFirst()
+            let eventStream = self.reducer(&state, event, self.environment)
 
-            guard let eventStream = eventStream else { return }
-            for await event in eventStream {
-                self.send(event)
+            Task { [state] in
+                for middleware in self.middlewares {
+                    await middleware.execute(event: event, state: { state })
+                }
+
+                guard let eventStream = eventStream else { return }
+                for await event in eventStream {
+                    self.send(event)
+                }
             }
         }
     }
@@ -118,8 +135,9 @@ extension Store {
     ) -> Store<ScopedState, ScopedEvent, ScopedEnvironment> {
         let scopedStore = Store<ScopedState, ScopedEvent, ScopedEnvironment>(
             state: toScopedState(self.state),
-            reducer: .init { _, event, _ in
+            reducer: .init { state, event, _ in
                 self.send(fromScopedEvent(event))
+                state = toScopedState(self.state)
                 return .none
             },
             environment: toScopedEnvironment(self.environment),