Persistent storage (#359)

Add support for persistent storage
https://docs.statsig.com/server/concepts/persistent_assignment

Kong: https://app.graphite.dev/github/pr/statsig-io/kong/2556
Docs: https://app.graphite.dev/github/pr/statsig-io/docs/1995

src/main/kotlin/com/statsig/sdk/ClientInitializeFormatter.kt

@@ -75,7 +75,7 @@ internal data class ClientConfig(
 
 internal class ClientInitializeFormatter(
     private val specStore: SpecStore,
-    private val evalFun: (ctx: EvaluationContext, config: APIConfig?) -> Unit,
+    private val evalFun: (ctx: EvaluationContext, config: APIConfig) -> Unit,
     private val context: EvaluationContext,
 ) {
     private val user: StatsigUser = context.user
@@ -172,8 +172,8 @@ internal class ClientInitializeFormatter(
         if (delegate != null && delegate != "") {
             val delegateSpec = specStore.getConfig(delegate)
             var delegateContext = context.asNewEvaluation()
-            evalFun(delegateContext, delegateSpec)
             if (delegateSpec != null) {
+                evalFun(delegateContext, delegateSpec)
                 result.allocatedExperimentName = hashName(delegate)
                 result.isUserInExperiment = delegateContext.evaluation.isExperimentGroup
                 result.isExperimentActive = delegateSpec.isActive
@@ -182,6 +182,14 @@ internal class ClientInitializeFormatter(
                 if (delegateContext.evaluation.groupName != null && delegateContext.evaluation.groupName != "") {
                     result.group_name = delegateContext.evaluation.groupName
                 }
+            } else {
+                delegateContext.evaluation = ConfigEvaluation(
+                    evaluationDetails = EvaluationDetails(
+                        this.specStore.getLastUpdateTime(),
+                        this.specStore.getInitTime(),
+                        EvaluationReason.UNRECOGNIZED
+                    )
+                )
             }
         }
 

src/main/kotlin/com/statsig/sdk/ConfigEvaluation.kt

@@ -0,0 +1,62 @@
+package com.statsig.sdk
+
+import com.statsig.sdk.persistent_storage.StickyValues
+
+class ConfigEvaluation(
+    var booleanValue: Boolean = false,
+    var jsonValue: Any? = null,
+    var ruleID: String = Const.EMPTY_STR,
+    var groupName: String? = null,
+    var secondaryExposures: ArrayList<Map<String, String>> = arrayListOf(),
+    var undelegatedSecondaryExposures: ArrayList<Map<String, String>> = arrayListOf(),
+    var explicitParameters: Array<String>? = null,
+    var configDelegate: String? = null,
+    var evaluationDetails: EvaluationDetails? = null,
+    var isExperimentGroup: Boolean = false,
+) {
+    internal var isDelegate: Boolean = false
+
+    fun addSecondaryExposure(exposure: Map<String, String>) {
+        secondaryExposures.add(exposure)
+        if (!isDelegate) {
+            undelegatedSecondaryExposures.add(exposure)
+        }
+    }
+
+    // Used to save to PersistentStorage
+    fun toStickyValues(): StickyValues {
+        return StickyValues(
+            value = this.booleanValue,
+            jsonValue = this.jsonValue,
+            ruleID = this.ruleID,
+            groupName = this.groupName,
+            secondaryExposures = this.secondaryExposures,
+            explicitParameters = this.explicitParameters,
+            configDelegate = this.configDelegate,
+            undelegatedSecondaryExposures = this.undelegatedSecondaryExposures,
+            time = this.evaluationDetails?.configSyncTime ?: Utils.getTimeInMillis(),
+        )
+    }
+
+    companion object {
+        fun fromStickyValues(stickyValues: StickyValues, initTime: Long): ConfigEvaluation {
+            val evalDetail = EvaluationDetails(
+                stickyValues.time,
+                initTime,
+                EvaluationReason.PERSISTED
+            )
+            return ConfigEvaluation(
+                jsonValue = stickyValues.jsonValue,
+                booleanValue = stickyValues.value,
+                ruleID = stickyValues.ruleID,
+                groupName = stickyValues.groupName,
+                secondaryExposures = stickyValues.secondaryExposures,
+                undelegatedSecondaryExposures = stickyValues.undelegatedSecondaryExposures,
+                explicitParameters = stickyValues.explicitParameters,
+                configDelegate = stickyValues.configDelegate,
+                isExperimentGroup = true,
+                evaluationDetails = evalDetail,
+            )
+        }
+    }
+}

src/main/kotlin/com/statsig/sdk/EvaluationContext.kt

@@ -1,11 +1,14 @@
 package com.statsig.sdk
 
+import com.statsig.sdk.persistent_storage.UserPersistedValues
+
 internal class EvaluationContext(
     var user: StatsigUser,
     var evaluation: ConfigEvaluation = ConfigEvaluation(),
     var clientSDKKey: String? = null,
     var hash: HashAlgo = HashAlgo.SHA256,
     var isNested: Boolean = false,
+    var userPersistedValues: UserPersistedValues? = null,
 ) {
     // Overload without default parameters required for Java
     constructor(user: StatsigUser) : this(user, ConfigEvaluation())
@@ -16,6 +19,7 @@ internal class EvaluationContext(
         clientSDKKey = ctx.clientSDKKey,
         hash = ctx.hash,
         isNested = ctx.isNested,
+        userPersistedValues = ctx.userPersistedValues
     )
 
     internal fun asDelegate(): EvaluationContext {
@@ -26,7 +30,7 @@ internal class EvaluationContext(
 
     internal fun asNested(): EvaluationContext {
         var context = EvaluationContext(this)
-        context.isNested = isNested
+        context.isNested = true
         return context
     }
 

src/main/kotlin/com/statsig/sdk/EvaluationDetails.kt

@@ -26,4 +26,5 @@ enum class EvaluationReason(val reason: String) {
     DATA_ADAPTER("DataAdapter"),
     UNSUPPORTED("Unsupported"),
     DEFAULT("Default"),
+    PERSISTED("Persisted"),
 }