From d74cef4de5941a367024d54ee2c680707dafc714 Mon Sep 17 00:00:00 2001
From: Connor Ricks <connor.ricks@gmail.com>
Date: Mon, 12 Feb 2024 17:47:54 -0500
Subject: [PATCH] =?UTF-8?q?=E2=9C=A8=20=20Adds=20SharedState.?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

---
 .../contents.xcworkspacedata                  |   7 +
 .../xcschemes/SharedState.xcscheme            |  71 ++++++++++
 .../xcschemes/swift-nibbles-Package.xcscheme  |  24 ++++
 Package.resolved                              |  14 ++
 Package.swift                                 |   7 +
 Sources/SharedState/SharedState.swift         | 128 ++++++++++++++++++
 Tests/SharedStateTests/SharedState.xctestplan |  25 ++++
 Tests/SharedStateTests/SharedStateTests.swift |  96 +++++++++++++
 Tests/swift-nibbles-Package.xctestplan        |   8 ++
 9 files changed, 380 insertions(+)
 create mode 100644 .swiftpm/xcode/package.xcworkspace/contents.xcworkspacedata
 create mode 100644 .swiftpm/xcode/xcshareddata/xcschemes/SharedState.xcscheme
 create mode 100644 Package.resolved
 create mode 100644 Sources/SharedState/SharedState.swift
 create mode 100644 Tests/SharedStateTests/SharedState.xctestplan
 create mode 100644 Tests/SharedStateTests/SharedStateTests.swift

diff --git a/.swiftpm/xcode/package.xcworkspace/contents.xcworkspacedata b/.swiftpm/xcode/package.xcworkspace/contents.xcworkspacedata
new file mode 100644
index 0000000..919434a
--- /dev/null
+++ b/.swiftpm/xcode/package.xcworkspace/contents.xcworkspacedata
@@ -0,0 +1,7 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<Workspace
+   version = "1.0">
+   <FileRef
+      location = "self:">
+   </FileRef>
+</Workspace>
diff --git a/.swiftpm/xcode/xcshareddata/xcschemes/SharedState.xcscheme b/.swiftpm/xcode/xcshareddata/xcschemes/SharedState.xcscheme
new file mode 100644
index 0000000..49d0303
--- /dev/null
+++ b/.swiftpm/xcode/xcshareddata/xcschemes/SharedState.xcscheme
@@ -0,0 +1,71 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<Scheme
+   LastUpgradeVersion = "1520"
+   version = "1.7">
+   <BuildAction
+      parallelizeBuildables = "YES"
+      buildImplicitDependencies = "YES">
+      <BuildActionEntries>
+         <BuildActionEntry
+            buildForTesting = "YES"
+            buildForRunning = "YES"
+            buildForProfiling = "YES"
+            buildForArchiving = "YES"
+            buildForAnalyzing = "YES">
+            <BuildableReference
+               BuildableIdentifier = "primary"
+               BlueprintIdentifier = "SharedState"
+               BuildableName = "SharedState"
+               BlueprintName = "SharedState"
+               ReferencedContainer = "container:">
+            </BuildableReference>
+         </BuildActionEntry>
+      </BuildActionEntries>
+   </BuildAction>
+   <TestAction
+      buildConfiguration = "Debug"
+      selectedDebuggerIdentifier = "Xcode.DebuggerFoundation.Debugger.LLDB"
+      selectedLauncherIdentifier = "Xcode.DebuggerFoundation.Launcher.LLDB"
+      shouldUseLaunchSchemeArgsEnv = "YES">
+      <TestPlans>
+         <TestPlanReference
+            reference = "container:Tests/SharedStateTests/SharedState.xctestplan"
+            default = "YES">
+         </TestPlanReference>
+      </TestPlans>
+   </TestAction>
+   <LaunchAction
+      buildConfiguration = "Debug"
+      selectedDebuggerIdentifier = "Xcode.DebuggerFoundation.Debugger.LLDB"
+      selectedLauncherIdentifier = "Xcode.DebuggerFoundation.Launcher.LLDB"
+      launchStyle = "0"
+      useCustomWorkingDirectory = "NO"
+      ignoresPersistentStateOnLaunch = "NO"
+      debugDocumentVersioning = "YES"
+      debugServiceExtension = "internal"
+      allowLocationSimulation = "YES">
+   </LaunchAction>
+   <ProfileAction
+      buildConfiguration = "Release"
+      shouldUseLaunchSchemeArgsEnv = "YES"
+      savedToolIdentifier = ""
+      useCustomWorkingDirectory = "NO"
+      debugDocumentVersioning = "YES">
+      <MacroExpansion>
+         <BuildableReference
+            BuildableIdentifier = "primary"
+            BlueprintIdentifier = "SharedState"
+            BuildableName = "SharedState"
+            BlueprintName = "SharedState"
+            ReferencedContainer = "container:">
+         </BuildableReference>
+      </MacroExpansion>
+   </ProfileAction>
+   <AnalyzeAction
+      buildConfiguration = "Debug">
+   </AnalyzeAction>
+   <ArchiveAction
+      buildConfiguration = "Release"
+      revealArchiveInOrganizer = "YES">
+   </ArchiveAction>
+</Scheme>
diff --git a/.swiftpm/xcode/xcshareddata/xcschemes/swift-nibbles-Package.xcscheme b/.swiftpm/xcode/xcshareddata/xcschemes/swift-nibbles-Package.xcscheme
index 563ae5a..5c5a9fd 100644
--- a/.swiftpm/xcode/xcshareddata/xcschemes/swift-nibbles-Package.xcscheme
+++ b/.swiftpm/xcode/xcshareddata/xcschemes/swift-nibbles-Package.xcscheme
@@ -76,6 +76,20 @@
                ReferencedContainer = "container:">
             </BuildableReference>
          </BuildActionEntry>
+         <BuildActionEntry
+            buildForTesting = "YES"
+            buildForRunning = "YES"
+            buildForProfiling = "YES"
+            buildForArchiving = "YES"
+            buildForAnalyzing = "YES">
+            <BuildableReference
+               BuildableIdentifier = "primary"
+               BlueprintIdentifier = "SharedState"
+               BuildableName = "SharedState"
+               BlueprintName = "SharedState"
+               ReferencedContainer = "container:">
+            </BuildableReference>
+         </BuildActionEntry>
       </BuildActionEntries>
    </BuildAction>
    <TestAction
@@ -100,6 +114,16 @@
                ReferencedContainer = "container:">
             </BuildableReference>
          </TestableReference>
+         <TestableReference
+            skipped = "NO">
+            <BuildableReference
+               BuildableIdentifier = "primary"
+               BlueprintIdentifier = "SharedStateTests"
+               BuildableName = "SharedStateTests"
+               BlueprintName = "SharedStateTests"
+               ReferencedContainer = "container:">
+            </BuildableReference>
+         </TestableReference>
       </Testables>
    </TestAction>
    <LaunchAction
diff --git a/Package.resolved b/Package.resolved
new file mode 100644
index 0000000..5ba1171
--- /dev/null
+++ b/Package.resolved
@@ -0,0 +1,14 @@
+{
+  "pins" : [
+    {
+      "identity" : "swift-concurrency-extras",
+      "kind" : "remoteSourceControl",
+      "location" : "https://github.com/pointfreeco/swift-concurrency-extras",
+      "state" : {
+        "revision" : "bb5059bde9022d69ac516803f4f227d8ac967f71",
+        "version" : "1.1.0"
+      }
+    }
+  ],
+  "version" : 2
+}
diff --git a/Package.swift b/Package.swift
index b9fa94c..2aea1e0 100644
--- a/Package.swift
+++ b/Package.swift
@@ -15,9 +15,13 @@ let package = Package(
         .library(name: "Extensions", targets: ["Extensions"]),
         .library(name: "Fuse", targets: ["Fuse"]),
         .library(name: "Identified", targets: ["Identified"]),
+        .library(name: "SharedState", targets: ["SharedState"]),
         .library(name: "Stash", targets: ["Stash"]),
         .plugin(name: "Create TCA Feature", targets: ["Create TCA Feature"])
     ],
+    dependencies: [
+        .package(url: "https://github.com/pointfreeco/swift-concurrency-extras", from: "1.1.0"),
+    ],
     targets: [
         .target(name: "Exchange"),
         .testTarget(name: "ExchangeTests", dependencies: ["Exchange"]),
@@ -31,6 +35,9 @@ let package = Package(
         .target(name: "Identified"),
         .testTarget(name: "IdentifiedTests", dependencies: ["Identified"]),
         
+        .target(name: "SharedState", dependencies: ["Fuse", .product(name: "ConcurrencyExtras", package: "swift-concurrency-extras"),]),
+        .testTarget(name: "SharedStateTests", dependencies: ["SharedState"]),
+        
         .target(name: "Stash"),
         .testTarget(name: "StashTests", dependencies: ["Stash"]),
         
diff --git a/Sources/SharedState/SharedState.swift b/Sources/SharedState/SharedState.swift
new file mode 100644
index 0000000..e9b4f80
--- /dev/null
+++ b/Sources/SharedState/SharedState.swift
@@ -0,0 +1,128 @@
+//
+// MIT License
+//
+// Copyright (c) 2024 Connor Ricks
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to deal
+// in the Software without restriction, including without limitation the rights
+// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+// copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in all
+// copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+// SOFTWARE.
+
+import Combine
+import ConcurrencyExtras
+import Foundation
+import Fuse
+
+public typealias SharedStateUpdateBlock<T> = (_ old: T, _ new: T) async -> Void
+
+
+/// A box that encapsulates an object allowing others to subscribe to and monitor changes to the state.
+///
+/// Useful when you have multiple services or features that wish to subscribe to changes.
+///
+/// Frequently use in PointFree's TCA architecture to subsribe long-running effects to shared state changes.
+///
+/// ```
+/// let settings = SharedState(Settings(theme: .dark), onChange: { old, new in
+///     datastore.saveTheme(new)
+/// })
+///
+/// for await theme in settings {
+///     update(for settings)
+/// }
+/// 
+/// for await theme in settings[stream: \.theme] {
+///     update(for theme)
+/// }
+/// ```
+@dynamicMemberLookup
+public struct SharedState<T: Equatable & Sendable>: @unchecked Sendable {
+    
+    // MARK: Properties
+    
+    private let state: LockIsolated<T>
+    private let subject = PassthroughSubject<T, Never>()
+    private let onChange: SharedStateUpdateBlock<T>?
+    
+    // MARK: Initializers
+    
+    public init(_ value: T, onChange: SharedStateUpdateBlock<T>? = nil) {
+        self.state = LockIsolated(value)
+        self.onChange = onChange
+    }
+    
+    // MARK: Stream
+    
+    public subscript<Value>(dynamicMember keyPath: KeyPath<T, Value>) -> Value {
+        self()[keyPath: keyPath]
+    }
+    
+    public subscript<Value: Equatable>(
+        stream keyPath: KeyPath<T, Value>,
+        bufferingPolicy: AsyncStream<Value>.Continuation.BufferingPolicy = .unbounded
+    ) -> AsyncStream<Value> {
+        
+        return subject
+            .map(keyPath)
+            .filter { state.value[keyPath: keyPath] != $0 }
+            .values(bufferingPolicy: bufferingPolicy)
+            .eraseToStream()
+    }
+    
+    // MARK: Publisher
+    
+    public subscript<Value: Equatable>(
+        publisher keyPath: KeyPath<T, Value>
+    ) -> AnyPublisher<Value, Never> {
+        return subject
+            .map(keyPath)
+            .filter { state.value[keyPath: keyPath] != $0 }
+            .eraseToAnyPublisher()
+    }
+    
+    public var publisher: AnyPublisher<T, Never> {
+        subject.eraseToAnyPublisher()
+    }
+    
+    // MARK: Methods
+    
+    public func callAsFunction() -> T {
+        state.value
+    }
+    
+    private func set(_ newValue: T) async {
+        let oldValue = state.value
+        state.withValue {
+            $0 = newValue
+            subject.send(newValue)
+        }
+        await onChange?(oldValue, newValue)
+    }
+    
+    public func stream(bufferingPolicy: AsyncStream<T>.Continuation.BufferingPolicy = .unbounded) -> AsyncStream<T> {
+        subject
+            .filter { state.value != $0 }
+            .values(bufferingPolicy: bufferingPolicy).eraseToStream()
+    }
+    
+    public func mutate(_ operation: (inout T) async throws -> Void) async rethrows {
+        var value = self()
+        try await operation(&value)
+        await set(value)
+        // Yielding in order to allow subscribers time to react before proceeding onwards.
+        await Task.yield()
+    }
+}
diff --git a/Tests/SharedStateTests/SharedState.xctestplan b/Tests/SharedStateTests/SharedState.xctestplan
new file mode 100644
index 0000000..14393b7
--- /dev/null
+++ b/Tests/SharedStateTests/SharedState.xctestplan
@@ -0,0 +1,25 @@
+{
+  "configurations" : [
+    {
+      "id" : "3AD1685E-93AE-4C99-B1DD-6BFF0C4A1EC1",
+      "name" : "Configuration 1",
+      "options" : {
+
+      }
+    }
+  ],
+  "defaultOptions" : {
+
+  },
+  "testTargets" : [
+    {
+      "parallelizable" : true,
+      "target" : {
+        "containerPath" : "container:",
+        "identifier" : "SharedStateTests",
+        "name" : "SharedStateTests"
+      }
+    }
+  ],
+  "version" : 1
+}
diff --git a/Tests/SharedStateTests/SharedStateTests.swift b/Tests/SharedStateTests/SharedStateTests.swift
new file mode 100644
index 0000000..7143adc
--- /dev/null
+++ b/Tests/SharedStateTests/SharedStateTests.swift
@@ -0,0 +1,96 @@
+// MIT License
+//
+// Copyright (c) 2024 Connor Ricks
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to deal
+// in the Software without restriction, including without limitation the rights
+// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+// copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in all
+// copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+// SOFTWARE.
+
+import ConcurrencyExtras
+@testable import SharedState
+import XCTest
+
+class SharedStateTests: XCTestCase {
+    func test_sharedState_mutate_doesUpdateAndNotify() async throws {
+        struct Container: Equatable { var num: Int }
+        let onChangeExpectation = expectation(description: "Expected onChange to be called.")
+        let publisherExpectation = expectation(description: "Expected publisher to be triggered.")
+        let publisherKeyPathExpectation = expectation(description: "Expected publisher keypath to be triggered.")
+        let streamExpectation = expectation(description: "Expected stream to be triggered.")
+        let streamKeyPathExpectation = expectation(description: "Expected stream keypath to be triggered.")
+        
+        await withMainSerialExecutor {
+            let sharedState = SharedState(Container(num: 10), onChange: { old, new in
+                XCTAssertEqual(old.num, 10)
+                XCTAssertEqual(new.num, 5)
+                onChangeExpectation.fulfill()
+            })
+            
+            // Publisher Subscription
+            let cancellable = sharedState.publisher.sink { container in
+                XCTAssertEqual(container.num, 5)
+                publisherExpectation.fulfill()
+            }
+            
+            // Publisher Keypath Subscription
+            let cancellableKeyPath = sharedState[publisher: \.num].sink { num in
+                XCTAssertEqual(num, 5)
+                publisherKeyPathExpectation.fulfill()
+            }
+            
+            // Streaming Subscription
+            Task {
+                for await container in sharedState.stream(bufferingPolicy: .unbounded) {
+                    XCTAssertEqual(container.num, 5)
+                    streamExpectation.fulfill()
+                    return
+                }
+            }
+            
+            // Streaming Keypath Subscription
+            Task {
+                for await num in sharedState[stream: \.num] {
+                    XCTAssertEqual(num, 5)
+                    streamKeyPathExpectation.fulfill()
+                    return
+                }
+            }
+            
+            XCTAssertEqual(sharedState(), .init(num: 10))
+            XCTAssertEqual(sharedState.num, 10)
+            XCTAssertEqual(sharedState[keyPath: \.num], 10)
+            
+            await sharedState.mutate {
+                await Task.yield()
+                $0.num = 5
+            }
+            
+            XCTAssertEqual(sharedState(), .init(num: 5))
+            XCTAssertEqual(sharedState.num, 5)
+            XCTAssertEqual(sharedState[keyPath: \.num], 5)
+            
+            await fulfillment(of: [
+                onChangeExpectation,
+                publisherExpectation,
+                publisherKeyPathExpectation,
+                streamExpectation,
+                streamKeyPathExpectation,
+            ])
+        }
+    }
+    
+}
diff --git a/Tests/swift-nibbles-Package.xctestplan b/Tests/swift-nibbles-Package.xctestplan
index e0f2386..4e8c409 100644
--- a/Tests/swift-nibbles-Package.xctestplan
+++ b/Tests/swift-nibbles-Package.xctestplan
@@ -53,6 +53,14 @@
         "identifier" : "ExchangeTests",
         "name" : "ExchangeTests"
       }
+    },
+    {
+      "parallelizable" : true,
+      "target" : {
+        "containerPath" : "container:",
+        "identifier" : "SharedStateTests",
+        "name" : "SharedStateTests"
+      }
     }
   ],
   "version" : 1