Async Middleware (#93)

* wip

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* wip

* wip

WildWestOnline/Core/Bang/Sources/Game/GameAction.swift

@@ -5,7 +5,7 @@
 //  Created by Hugues Telolahy on 27/10/2024.
 //
 
-public struct GameAction: Action, Equatable, Codable, Sendable {
+public struct GameAction: Action, Equatable, Codable {
     public var kind: Kind
     public var payload: Payload
 

WildWestOnline/Core/Bang/Sources/Redux/Store.swift

@@ -7,7 +7,6 @@
 
 import Combine
 import Foundation
-import SwiftUI
 // swiftlint:disable private_subject unowned_variable_capture
 
 /// ``Action`` is a plain object that describes what happened.
@@ -22,7 +21,7 @@ public typealias Reducer<State> = (State, Action) throws -> State
 /// ``Middleware`` is a plugin, or a composition of several plugins,
 /// that are assigned to the app global  state pipeline in order to
 /// handle each action received action, to execute side-effects in response, and eventually dispatch more actions
-public typealias Middleware<State> = @Sendable (State, Action) -> Action?
+public typealias Middleware<State> = (State, Action) async -> Action?
 
 /// Namespace for Middlewares
 public enum Middlewares {}
@@ -31,15 +30,13 @@ public enum Middlewares {}
 /// It defines two roles of a "Store":
 /// - receive/distribute `Action`;
 /// - and publish changes of the the current app `State` to possible subscribers.
-public class Store<State: Sendable>: ObservableObject {
+public class Store<State>: ObservableObject, @unchecked Sendable {
     @Published public internal(set) var state: State
     public internal(set) var eventPublisher: PassthroughSubject<Action, Never>
     public internal(set) var errorPublisher: PassthroughSubject<Error, Never>
 
     private let reducer: Reducer<State>
     private let middlewares: [Middleware<State>]
-    private var cancellables: Set<AnyCancellable> = []
-    private let queue = DispatchQueue(label: "store-\(UUID())")
     private var completion: (() -> Void)?
     private var subscribedEffects: Int = 0
     private var completedEffects: Int = 0
@@ -63,36 +60,25 @@ public class Store<State: Sendable>: ObservableObject {
             let newState = try reducer(state, action)
             eventPublisher.send(action)
             state = newState
-            runSideEfects(action, newState: newState)
-        } catch {
-            errorPublisher.send(error)
-            completion?()
-        }
-    }
+            subscribedEffects += middlewares.count
+            Task.detached { [unowned self] in
+                for middleware in middlewares {
+                    let output = await middleware(newState, action)
+                    DispatchQueue.main.async { [unowned self] in
+                        if let output {
+                            dispatch(output)
+                        }
 
-    private func runSideEfects(_ action: Action, newState: State) {
-        middlewares.forEach { middleware in
-            subscribedEffects += 1
-            Deferred {
-                Future<Action?, Never> { promise in
-                    let output = middleware(newState, action)
-                    promise(.success(output))
+                        completedEffects += 1
+                        if completedEffects == subscribedEffects {
+                            completion?()
+                        }
+                    }
                 }
             }
-            .eraseToAnyPublisher()
-            .subscribe(on: queue)
-            .receive(on: DispatchQueue.main)
-            .sink(receiveCompletion: { [unowned self] _ in
-                completedEffects += 1
-                if completedEffects == subscribedEffects {
-                    completion?()
-                }
-            }, receiveValue: { [unowned self] value in
-                if let value {
-                    dispatch(value)
-                }
-            })
-            .store(in: &cancellables)
+        } catch {
+            errorPublisher.send(error)
+            completion?()
         }
     }
 }

WildWestOnline/Core/Bang/Tests/Misc/GameStore+Dispatch.swift

@@ -64,7 +64,7 @@ struct Choice {
     let selectionIndex: Int
 }
 
-private final class ChoicesWrapper: @unchecked Sendable {
+private class ChoicesWrapper {
     var choices: [Choice]
 
     init(choices: [Choice]) {

WildWestOnline/Core/Bang/Tests/SimulationTest.swift

@@ -69,13 +69,16 @@ private extension Middlewares {
     /// Middleare reproducting state according to received event
     static func verifyState(_ prevState: StateWrapper) -> Middleware<GameState> {
         { state, action in
-            guard let nextState = try? GameReducer().reduce(prevState.value, action) else {
-                fatalError("Failed reducing \(action)")
-            }
+            DispatchQueue.main.async {
+                guard let nextState = try? GameReducer().reduce(prevState.value, action) else {
+                    fatalError("Failed reducing \(action)")
+                }
+
+                assert(nextState == state, "Inconsistent state after applying \(action)")
 
-            assert(nextState == state, "Inconsistent state after applying \(action)")
+                prevState.value = nextState
+            }
 
-            prevState.value = nextState
             return nil
         }
     }