Unstable Features groundwork

AltStore/AppDelegate.swift

@@ -61,6 +61,8 @@ final class AppDelegate: UIResponder, UIApplicationDelegate {
         // Register default settings before doing anything else.
         UserDefaults.registerDefaults()
         
+        UnstableFeatures.load()
+        
         DatabaseManager.shared.start { (error) in
             if let error = error
             {

AltStore/Unstable Features/UnstableFeatures.swift

@@ -0,0 +1,95 @@
+//
+//  UnstableFeatures.swift
+//  SideStore
+//
+//  Created by naturecodevoid on 5/20/23.
+//  Copyright © 2023 SideStore. All rights reserved.
+//
+
+// I prefixed it with Available to make UnstableFeatures come up first in autocomplete, feel free to rename it if you know a better name
+enum AvailableUnstableFeature: String, CaseIterable {
+    // The value will be the GitHub Issue number. For example, "123" would correspond to https://github.com/SideStore/SideStore/issues/123
+    //
+    // Unstable features must have a GitHub Issue for tracking progress, PRs and feedback/commenting.
+    
+    /// Dummy variant to ensure there is always at least one variant. DO NOT USE!
+    case dummy = "dummy"
+    
+    func availableOutsideDevMode() -> Bool {
+        switch self {
+        // If your unstable feature is stable enough to be used by nightly users who are not alpha testers or developers,
+        // you may want to have it available in the "Unstable Features" menu in Settings (outside of dev mode). To do so, add this:
+        //case .yourFeature: return true
+        
+        default: return false
+        }
+    }
+}
+
+class UnstableFeatures {
+    #if UNSTABLE
+    private static var features: [AvailableUnstableFeature: Bool] = [:]
+    #endif
+    
+    static func load() {
+        #if UNSTABLE
+        
+        if features.count > 0 { return print("It seems unstable features have already been loaded, skipping") }
+        
+        if let rawFeatures = UserDefaults.shared.unstableFeatures,
+           var rawFeatures = try? JSONDecoder().decode([String: Bool].self, from: rawFeatures) {
+            for rawFeature in rawFeatures {
+                if let feature = AvailableUnstableFeature.allCases.first(where: { feature in String(describing: feature) == rawFeature.key }) {
+                    features[feature] = rawFeature.value
+                } else {
+                    print("Unknown unstable feature: \(rawFeature.key) = \(rawFeature.value)")
+                }
+            }
+            save(load: true)
+        } else {
+            print("Setting all unstable features to false since we couldn't load them from UserDefaults (either they were never saved or there was an error decoding JSON)")
+            for feature in AvailableUnstableFeature.allCases {
+                features[feature] = false
+            }
+            save()
+        }
+        
+        #else
+        print("Unstable features are not available on this build")
+        #endif
+    }
+    
+    private static func save(load: Bool = false) {
+        #if UNSTABLE
+        
+        var rawFeatures: [String: Bool] = [:]
+        for feature in features {
+            rawFeatures[String(describing: feature.key)] = feature.value
+        }
+        UserDefaults.shared.unstableFeatures = try! JSONEncoder().encode(rawFeatures)
+        print("\(load ? "Loaded" : "Saved") unstable features: \(String(describing: rawFeatures))")
+        
+        #endif
+    }
+    
+    static func set(_ feature: AvailableUnstableFeature, enabled: Bool) {
+        #if UNSTABLE
+        
+        features[feature] = enabled
+        save()
+        
+        #else
+        // we want this to crash, this function should never be triggered on non-unstable builds
+        fatalError("Tried to set unstable feature \(String(describing: feature)) to \(enabled) on non-unstable build!")
+        #endif
+    }
+    
+    @inline(__always) // hopefully this will help the compiler realize that if statements that use this function should be removed on non-unstable builds
+    static func enabled(_ feature: AvailableUnstableFeature) -> Bool {
+        #if UNSTABLE
+        features[feature] ?? false
+        #else
+        false
+        #endif
+    }
+}