feat: Initialization strategy (#55)

* add the initialization strategy, seprate the memory and storage

* add activate and fetch to the demo app

ConfidenceDemoApp/ConfidenceDemoApp.xcodeproj/project.xcworkspace/xcshareddata/swiftpm/Package.resolved

@@ -3,11 +3,11 @@
     "pins": [
       {
         "package": "OpenFeature",
-        "repositoryURL": "git@github.com:spotify/openfeature-swift-sdk.git",
+        "repositoryURL": "git@github.com:open-feature/swift-sdk.git",
         "state": {
           "branch": null,
-          "revision": "ef8dd46fb9623fc85b0b75788def006f7b59132c",
-          "version": "0.2.5"
+          "revision": "114321e376b3d80e6623c5cbd7e8bcef9c6a86d2",
+          "version": "0.0.2"
         }
       }
     ]

ConfidenceDemoApp/ConfidenceDemoApp/ConfidenceDemoApp.swift

@@ -21,6 +21,7 @@ extension ConfidenceDemoApp {
         }
         let provider = ConfidenceFeatureProvider
             .Builder(credentials: .clientSecret(secret: secret))
+            .with(initializationStrategy: .activateAndFetchAsync)
             .build()
         let ctx = MutableContext(targetingKey: UUID.init().uuidString, structure: MutableStructure())
         OpenFeatureAPI.shared.setProvider(provider: provider, initialContext: ctx)

Sources/ConfidenceProvider/Cache/InMemoryProviderCache.swift

@@ -0,0 +1,67 @@
+import Combine
+import Foundation
+import OpenFeature
+import os
+
+public class InMemoryProviderCache: ProviderCache {
+    private var rwCacheQueue = DispatchQueue(label: "com.confidence.cache.rw", attributes: .concurrent)
+    static let currentVersion = "0.0.1"
+    private let cache: [String: ResolvedValue]
+
+    private var storage: Storage
+    private var curResolveToken: String?
+    private var curEvalContextHash: String?
+
+    init(storage: Storage, cache: [String: ResolvedValue], curResolveToken: String?, curEvalContextHash: String?) {
+        self.storage = storage
+        self.cache = cache
+        self.curResolveToken = curResolveToken
+        self.curEvalContextHash = curEvalContextHash
+    }
+
+    public func getValue(flag: String, ctx: EvaluationContext) throws -> CacheGetValueResult? {
+        if let value = self.cache[flag] {
+            guard let curResolveToken = curResolveToken else {
+                throw ConfidenceError.noResolveTokenFromCache
+            }
+            return .init(
+                resolvedValue: value, needsUpdate: curEvalContextHash != ctx.hash(), resolveToken: curResolveToken)
+        } else {
+            return nil
+        }
+    }
+
+    public static func from(storage: Storage) -> InMemoryProviderCache {
+        do {
+            let storedCache = try storage.load(
+                defaultValue: StoredCacheData(
+                    version: currentVersion, cache: [:], curResolveToken: nil, curEvalContextHash: nil))
+            return InMemoryProviderCache(
+                storage: storage,
+                cache: storedCache.cache,
+                curResolveToken: storedCache.curResolveToken,
+                curEvalContextHash: storedCache.curEvalContextHash)
+        } catch {
+            Logger(subsystem: "com.confidence.cache", category: "storage").error(
+                "Error when trying to load resolver cache, clearing cache: \(error)")
+
+            if case .corruptedCache = error as? ConfidenceError {
+                try? storage.clear()
+            }
+
+            return InMemoryProviderCache(storage: storage, cache: [:], curResolveToken: nil, curEvalContextHash: nil)
+        }
+    }
+}
+
+public struct ResolvedKey: Hashable, Codable {
+    var flag: String
+    var targetingKey: String
+}
+
+struct StoredCacheData: Codable {
+    var version: String
+    var cache: [String: ResolvedValue]
+    var curResolveToken: String?
+    var curEvalContextHash: String?
+}

Sources/ConfidenceProvider/Cache/ProviderCache.swift

@@ -3,8 +3,6 @@ import OpenFeature
 
 public protocol ProviderCache {
     func getValue(flag: String, ctx: EvaluationContext) throws -> CacheGetValueResult?
-
-    func clearAndSetValues(values: [ResolvedValue], ctx: EvaluationContext, resolveToken: String) throws
 }
 
 public struct CacheGetValueResult {