feat: add ability to use cache over bootstrap (#56)

* chore: address feedback

* feat: add ability to use cache over bootstrap

* test: verify cache is used instead of bootstrap

Sources/StatsigOnDeviceEvaluations/Statsig.swift

@@ -443,15 +443,23 @@ extension Statsig {
         _ context: StatsigContext,
         _ value: SynchronousSpecsValue
     ) -> Error? {
-        let (result, error) = parseSpecsValue(value)
+        let (bootstrap, error) = parseSpecsValue(value)
 
-        guard error == nil, let result = result else {
+        guard error == nil, let bootstrap = bootstrap else {
             return error ?? StatsigError.invalidSynchronousSpecs
         }
-
+
+        if context.options?.useNewerCacheValuesOverProvidedValues == true {
+            context.store.loadFromCache(context.sdkKey)
+
+            if bootstrap.response.time < context.store.getSourceInfo().lcut {
+                return nil
+            }
+        }
+
         context.store.setAndCacheValues(
-            response: result.response,
-            responseData: result.raw,
+            response: bootstrap.response,
+            responseData: bootstrap.raw,
             sdkKey: context.sdkKey,
             source: .bootstrap
         )

Sources/StatsigOnDeviceEvaluations/StatsigOptions.swift

@@ -55,7 +55,12 @@ import Foundation
      * Plugin to override SDK evaluations
      */
     @objc public var overrideAdapter: OverrideAdapter?
-
+
+    /**
+     * When bootstrapping (initializeSync or updateSync), set this flag if you would like to use cache values if they are "fresher" then the bootstrap values
+     */
+    @objc public var useNewerCacheValuesOverProvidedValues: Bool = false
+
     public override init() {
         environment = StatsigEnvironment()
     }

Tests/StatsigOnDeviceEvaluationsTestsSwift/SynchronousInitTest.swift

@@ -0,0 +1,77 @@
+import Quick
+import Nimble
+import XCTest
+import StatsigTestUtils
+
+@testable import StatsigOnDeviceEvaluations
+
+func getTestDcsWithTimeField(_ res: String, _ time: Int) -> NSString {
+    var json = TestResources.getJson(res)
+    json["time"] = time
+    return String(data: try! JSONSerialization.data(withJSONObject: json), encoding: .utf8)! as NSString
+}
+
+final class SynchronousInitTest: QuickSpec {
+    override class func spec() {
+        describe("SynchronousInit") {
+            let user = StatsigUser(userID: "a-user")
+
+            func primeCache() {
+                NetworkStubs.clearAllStubs()
+
+                NetworkStubs.stubEndpoint(
+                    endpoint: "download_config_specs",
+                    resource: "RulesetsDownloadConfigsSpecs"
+                )
+
+                let client = Statsig()
+                waitUntil { done in
+                    client.initialize("client-key") { _ in done() }
+                }
+
+                client.shutdown()
+
+                NetworkStubs.clearAllStubs()
+            }
+
+            it("uses cache if newer and useNewerCacheValuesOverProvidedValues is true") {
+                primeCache()
+
+                let opts = StatsigOptions()
+                opts.useNewerCacheValuesOverProvidedValues = true
+
+                let dcs = getTestDcsWithTimeField("EmptyDcs", 123)
+                let client = Statsig()
+                let _ = client.initializeSync("client-key", initialSpecs: dcs, options: opts)
+
+                let gate = client.getFeatureGate("test_public", user)
+                expect(gate.evaluationDetails.reason).to(equal("Cache"))
+            }
+
+            it("uses bootstrap if useNewerCacheValuesOverProvidedValues is false") {
+                primeCache()
+
+                let dcs = getTestDcsWithTimeField("RulesetsDownloadConfigsSpecs", 123)
+                let client = Statsig()
+                let _ = client.initializeSync("client-key", initialSpecs: dcs)
+
+                let gate = client.getFeatureGate("test_public", user)
+                expect(gate.evaluationDetails.reason).to(equal("Bootstrap"))
+            }
+
+            it("uses bootstrap if newer") {
+                primeCache()
+
+                let opts = StatsigOptions()
+                opts.useNewerCacheValuesOverProvidedValues = true
+
+                let dcs = getTestDcsWithTimeField("RulesetsDownloadConfigsSpecs", Int.max)
+                let client = Statsig()
+                let _ = client.initializeSync("client-key", initialSpecs: dcs, options: opts)
+
+                let gate = client.getFeatureGate("test_public", user)
+                expect(gate.evaluationDetails.reason).to(equal("Bootstrap"))
+            }
+        }
+    }
+}

Tests/TestUtils/Resources/EmptyDcs.json

@@ -0,0 +1,20 @@
+{
+    "dynamic_configs": [],
+    "feature_gates": [],
+    "layer_configs": [],
+    "id_lists": {},
+    "layers": {},
+    "has_updates": true,
+    "time": 1697131166636,
+    "company_id": "5NprLGRxV3W28hreG51Z7n",
+    "diagnostics": {
+        "initialize": 1000,
+        "dcs": 1000,
+        "download_config_specs": 1000,
+        "idlist": 100,
+        "get_id_list": 100,
+        "get_id_list_sources": 100,
+        "log": 100,
+        "log_event": 100
+    }
+}