Migrate variantManager to remote config (#3758)

Task/Issue URL: https://app.asana.com/0/0/1205644869911729/f

### Description
This PR introduces the capability to download experiment variants from
remote config, replacing the previous hardcoding approach. Additionally,
it includes a refactoring of the old `getVariant()` method, which
previously served as both a setter and a getter for user variants, into
separate setter and getter methods for improved clarity and
maintainability.

### Steps to test this PR

_Replace `PRIVACY_REMOTE_CONFIG_URL` endpoint for
https://www.jsonblob.com/api/1164161108453220352 so you can edit remote
variants for each test_

_Experiment Variants Allocation_
- In remote config add "ma/weight 1.0/ no filters", "mb/weight 1.0/no
filters", "mc/weight 1.0/no filters"
- Fresh install from branch
- [x] Check any of the 3 variants is allocated to the user

_Experiment Variants with weight 0.0_
- In remote config add "ma/weight 0.0/ no filters" & "mb/weight 0.0/no
filters"
- Fresh install from branch
- [x] Check default variant is allocated (_empty string_)

_Experiment Variants with matching locale filter_
- In remote config add "ma/weight 1.0/ locale ["en_US"]" & "mb/weight
1.0/filters: locale ["en_US"]""
- Set your device to English (United States)
- Fresh install from branch
- [x] Check any of the variants have been allocated

_Experiment Variants without matching locale filter_
- Set your device language to English (United States)
- In remote config add "ma/weight 1.0/ locale ["de_DE"]" & "mb/weight
1.0/filters: locale ["de_DE"]""
- Fresh install from branch
- [x] Check default variant is allocated (_empty string_)

_Experiment Variants Update - Disable experiment_
- Make sure you have already a variant allocated (_"ma"_ or _"mb"_)
- In remote config change weight to 0.0 "ma/weight 0.0/no filters" &
"mb/weight 0.0/no filters"
- Install from branch
- [x] Check variant is still allocated to the user

_Experiment Variants Update - Remove experiment_
- Make sure you have already a variant allocated (_"ma"_ or _"mb"_)
- In remote config remove variant allocated to the user
- Install from branch
- [x] Check user variant is updated to default variant (_empty string_)

_Experiment Variants Update - Add new experiment_
- Make sure you have already the default variant allocated (_empty
string_)
- In remote config add a new experiment with variants "md/weight 1.0/ no
filters" & "me/weight 1.0/no filters"
- Install from branch
- [x] Check user variant is not updated (ℹ️ experiments work for new
installs only)

_getVariantKey() should NOT update variant value_
- Install from branch
- Perform an action which would call 'getVariantKey()' -> _e.g._ Send
any pixel
- [x] Check we only get the variant and no setting the value like we
used to do


### No UI changes

---------

Co-authored-by: Cris Barreiro <cbarreiro@duckduckgo.com>
Co-authored-by: Aitor Viana <aitorvs@gmail.com>

anvil/anvil-compiler/src/main/java/com/duckduckgo/anvil/compiler/ContributesRemoteFeatureCodeGenerator.kt

@@ -106,13 +106,17 @@ class ContributesRemoteFeatureCodeGenerator : CodeGenerator {
                                     .build(),
                             )
                             .addParameter("appBuildConfig", appBuildConfig.asClassName(module))
+                            .addParameter("variantManager", variantManager.asClassName(module))
                             .addCode(
                                 """
                             return %T.Builder()
                                 .store(toggleStore)
                                 .appVersionProvider({ appBuildConfig.versionCode })
                                 .flavorNameProvider({ appBuildConfig.flavor.name })
                                 .featureName(%S)
+                                .appVariantProvider({ appBuildConfig.variantName })
+                                // save empty variants will force the default variant to be set
+                                .forceDefaultVariantProvider({ variantManager.saveVariants(emptyList()) })
                                 .build()
                                 .create(%T::class.java)
                                 """.trimIndent(),
@@ -256,6 +260,7 @@ class ContributesRemoteFeatureCodeGenerator : CodeGenerator {
                             )
                             .addParameter("feature", dagger.Lazy::class.asClassName().parameterizedBy(boundType.asClassName()))
                             .addParameter("appBuildConfig", appBuildConfig.asClassName(module))
+                            .addParameter("variantManager", variantManager.asClassName(module))
                             .addParameter("context", context.asClassName(module))
                             .build(),
                     )
@@ -289,6 +294,11 @@ class ContributesRemoteFeatureCodeGenerator : CodeGenerator {
                             .initializer("appBuildConfig")
                             .build(),
                     )
+                    .addProperty(
+                        PropertySpec.builder("variantManager", variantManager.asClassName(module), KModifier.PRIVATE)
+                            .initializer("variantManager")
+                            .build(),
+                    )
                     .addProperty(
                         PropertySpec.builder("context", context.asClassName(module), KModifier.PRIVATE)
                             .initializer("context")
@@ -309,6 +319,7 @@ class ContributesRemoteFeatureCodeGenerator : CodeGenerator {
                     .addFunction(createInvokeMethod(boundType))
                     .addType(createJsonRolloutDataClass(generatedPackage, module))
                     .addType(createJsonRolloutStepDataClass(generatedPackage, module))
+                    .addType(createJsonToggleTargetDataClass(generatedPackage, module))
                     .addType(createJsonToggleDataClass(generatedPackage, module))
                     .addType(createJsonFeatureDataClass(generatedPackage, module))
                     .addType(createJsonExceptionDataClass(generatedPackage, module))
@@ -416,6 +427,7 @@ class ContributesRemoteFeatureCodeGenerator : CodeGenerator {
                             remoteEnableState = isEnabled,
                             enable = isEnabled,
                             minSupportedVersion = feature.minSupportedVersion,
+                            targets = emptyList(),
                         )
                     )
         
@@ -432,13 +444,19 @@ class ContributesRemoteFeatureCodeGenerator : CodeGenerator {
                                 
                                 val previousRolloutStep = previousState?.rolloutStep 
                                 val newStateValue = (jsonToggle.state == "enabled" || (appBuildConfig.flavor == %T && jsonToggle.state == "internal"))
+                                val targets = jsonToggle?.targets?.map { target ->
+                                    Toggle.State.Target(
+                                        variantKey = target.variantKey,
+                                    )
+                                } ?: emptyList()
                                 this.feature.get().invokeMethod(subfeature.key).setEnabled(
                                     Toggle.State(
                                         remoteEnableState = newStateValue,
                                         enable = previousStateValue,
                                         minSupportedVersion = jsonToggle.minSupportedVersion?.toInt(),
                                         rollout = jsonToggle?.rollout?.steps?.map { it.percent },
                                         rolloutStep = previousRolloutStep,
+                                        targets = targets,
                                     ),
                                 )
                             } catch(e: Throwable) {
@@ -613,6 +631,22 @@ class ContributesRemoteFeatureCodeGenerator : CodeGenerator {
             .build()
     }
 
+    private fun createJsonToggleTargetDataClass(
+        generatedPackage: String,
+        module: ModuleDescriptor,
+    ): TypeSpec {
+        return TypeSpec.classBuilder(FqName("$generatedPackage.JsonToggleTarget").asClassName(module))
+            .addModifiers(KModifier.PRIVATE)
+            .addModifiers(KModifier.DATA)
+            .primaryConstructor(
+                FunSpec.constructorBuilder()
+                    .addParameter("variantKey", String::class.asClassName())
+                    .build(),
+            )
+            .addProperty(PropertySpec.builder("variantKey", String::class.asClassName()).initializer("variantKey").build())
+            .build()
+    }
+
     private fun createJsonToggleDataClass(
         generatedPackage: String,
         module: ModuleDescriptor,
@@ -634,6 +668,10 @@ class ContributesRemoteFeatureCodeGenerator : CodeGenerator {
                         "rollout",
                         FqName("JsonToggleRollout").asClassName(module).copy(nullable = true),
                     )
+                    .addParameter(
+                        "targets",
+                        List::class.asClassName().parameterizedBy(FqName("JsonToggleTarget").asClassName(module)),
+                    )
                     .build(),
             )
             .addProperty(
@@ -654,6 +692,12 @@ class ContributesRemoteFeatureCodeGenerator : CodeGenerator {
                     .initializer("rollout")
                     .build(),
             )
+            .addProperty(
+                PropertySpec
+                    .builder("targets", List::class.asClassName().parameterizedBy(FqName("JsonToggleTarget").asClassName(module)))
+                    .initializer("targets")
+                    .build(),
+            )
             .build()
     }
 
@@ -944,6 +988,7 @@ class ContributesRemoteFeatureCodeGenerator : CodeGenerator {
         private val context = FqName("android.content.Context")
         private val privacyFeaturePlugin = FqName("com.duckduckgo.privacy.config.api.PrivacyFeaturePlugin")
         private val appBuildConfig = FqName("com.duckduckgo.appbuildconfig.api.AppBuildConfig")
+        private val variantManager = FqName("com.duckduckgo.experiments.api.VariantManager")
         private val buildFlavorInternal = FqName("com.duckduckgo.appbuildconfig.api.BuildFlavor.INTERNAL")
         private val moshi = FqName("com.squareup.moshi.Moshi")
         private val jsonObjectAdapter = FqName("JSONObjectAdapter")

app-build-config/app-build-config-api/src/main/java/com/duckduckgo/appbuildconfig/api/AppBuildConfig.kt

@@ -32,6 +32,11 @@ interface AppBuildConfig {
     val model: String
     val deviceLocale: Locale
     val isDefaultVariantForced: Boolean
+
+    /**
+     * You should call [variantName] in a background thread
+     */
+    val variantName: String?
 }
 
 enum class BuildFlavor {

app/build.gradle

@@ -187,6 +187,8 @@ dependencies {
     implementation project(':app-build-config-api')
     implementation project(':browser-api')
     implementation project(':statistics')
+    implementation project(':experiments-api')
+    implementation project(':experiments-impl')
     implementation project(':common-utils')
     implementation project(':app-store')
     implementation project(':common-ui')

app/src/androidTest/java/com/duckduckgo/app/integration/AtbIntegrationTest.kt

@@ -19,17 +19,19 @@ package com.duckduckgo.app.integration
 import androidx.test.filters.LargeTest
 import androidx.test.platform.app.InstrumentationRegistry
 import com.duckduckgo.app.getDaggerComponent
-import com.duckduckgo.app.statistics.Variant
-import com.duckduckgo.app.statistics.VariantManager
 import com.duckduckgo.app.statistics.api.RefreshRetentionAtbPlugin
 import com.duckduckgo.app.statistics.api.StatisticsRequester
 import com.duckduckgo.app.statistics.api.StatisticsService
 import com.duckduckgo.app.statistics.model.Atb
 import com.duckduckgo.app.statistics.store.StatisticsDataStore
 import com.duckduckgo.app.statistics.store.StatisticsSharedPreferences
 import com.duckduckgo.autofill.api.email.EmailManager
+import com.duckduckgo.common.test.CoroutineTestRule
 import com.duckduckgo.common.test.InstantSchedulersRule
 import com.duckduckgo.common.utils.plugins.PluginPoint
+import com.duckduckgo.experiments.api.VariantManager
+import kotlinx.coroutines.ExperimentalCoroutinesApi
+import kotlinx.coroutines.test.TestScope
 import org.junit.Assert.*
 import org.junit.Before
 import org.junit.Rule
@@ -44,6 +46,7 @@ import org.mockito.kotlin.whenever
  * Would normally have separate tests for each assertion, but these tests are relatively expensive to run.
  */
 @LargeTest
+@ExperimentalCoroutinesApi
 class AtbIntegrationTest {
 
     private lateinit var mockVariantManager: VariantManager
@@ -55,21 +58,32 @@ class AtbIntegrationTest {
     @get:Rule
     val schedulers = InstantSchedulersRule()
 
+    @get:Rule
+    val coroutineTestRule: CoroutineTestRule = CoroutineTestRule()
+
     @Before
     fun before() {
         mockVariantManager = mock()
         statisticsStore = StatisticsSharedPreferences(InstrumentationRegistry.getInstrumentation().targetContext)
         statisticsStore.clearAtb()
 
-        whenever(mockVariantManager.getVariant()).thenReturn(Variant("ma", 100.0, filterBy = { true }))
+        whenever(mockVariantManager.getVariantKey()).thenReturn("ma")
         service = getDaggerComponent().retrofit().create(StatisticsService::class.java)
 
         val plugins = object : PluginPoint<RefreshRetentionAtbPlugin> {
             override fun getPlugins(): Collection<RefreshRetentionAtbPlugin> {
                 return listOf()
             }
         }
-        testee = StatisticsRequester(statisticsStore, service, mockVariantManager, plugins, emailManager)
+        testee = StatisticsRequester(
+            statisticsStore,
+            service,
+            mockVariantManager,
+            plugins,
+            emailManager,
+            TestScope(),
+            coroutineTestRule.testDispatcherProvider,
+        )
     }
 
     @Test

app/src/androidTest/java/com/duckduckgo/app/notification/NotificationRegistrarTest.kt

@@ -22,18 +22,22 @@ import com.duckduckgo.app.notification.model.NotificationPlugin
 import com.duckduckgo.app.notification.model.SchedulableNotificationPlugin
 import com.duckduckgo.app.pixels.AppPixelName
 import com.duckduckgo.app.settings.db.SettingsDataStore
-import com.duckduckgo.app.statistics.VariantManager
-import com.duckduckgo.app.statistics.VariantManager.Companion.DEFAULT_VARIANT
 import com.duckduckgo.app.statistics.pixels.Pixel
 import com.duckduckgo.appbuildconfig.api.AppBuildConfig
 import com.duckduckgo.common.test.CoroutineTestRule
 import com.duckduckgo.common.utils.plugins.PluginPoint
+import com.duckduckgo.experiments.api.VariantManager
 import kotlinx.coroutines.ExperimentalCoroutinesApi
 import kotlinx.coroutines.test.TestScope
 import org.junit.Before
 import org.junit.Rule
 import org.junit.Test
-import org.mockito.kotlin.*
+import org.mockito.kotlin.any
+import org.mockito.kotlin.eq
+import org.mockito.kotlin.mock
+import org.mockito.kotlin.never
+import org.mockito.kotlin.verify
+import org.mockito.kotlin.whenever
 
 @ExperimentalCoroutinesApi
 class NotificationRegistrarTest {
@@ -54,7 +58,7 @@ class NotificationRegistrarTest {
 
     @Before
     fun before() {
-        whenever(mockVariantManager.getVariant(any())).thenReturn(DEFAULT_VARIANT)
+        whenever(mockVariantManager.getVariantKey()).thenReturn("DEFAULT_VARIANT")
         whenever(appBuildConfig.sdkInt).thenReturn(30)
         testee = NotificationRegistrar(
             TestScope(),

app/src/androidTest/java/com/duckduckgo/app/statistics/api/RxPixelSenderTest.kt

@@ -21,8 +21,6 @@ import androidx.lifecycle.LifecycleOwner
 import androidx.room.Room
 import androidx.test.platform.app.InstrumentationRegistry
 import com.duckduckgo.app.global.db.AppDatabase
-import com.duckduckgo.app.statistics.Variant
-import com.duckduckgo.app.statistics.VariantManager
 import com.duckduckgo.app.statistics.api.RxPixelSenderTest.TestPixels.TEST
 import com.duckduckgo.app.statistics.config.StatisticsLibraryConfig
 import com.duckduckgo.app.statistics.model.Atb
@@ -32,6 +30,7 @@ import com.duckduckgo.app.statistics.store.PendingPixelDao
 import com.duckduckgo.app.statistics.store.StatisticsDataStore
 import com.duckduckgo.common.test.InstantSchedulersRule
 import com.duckduckgo.common.utils.device.DeviceInfo
+import com.duckduckgo.experiments.api.VariantManager
 import io.reactivex.Completable
 import java.util.concurrent.TimeoutException
 import org.junit.After
@@ -46,11 +45,9 @@ import org.mockito.kotlin.*
 class RxPixelSenderTest {
 
     @get:Rule
-    @Suppress("unused")
     var instantTaskExecutorRule = InstantTaskExecutorRule()
 
     @get:Rule
-    @Suppress("unused")
     val schedulers = InstantSchedulersRule()
 
     @Mock
@@ -98,7 +95,7 @@ class RxPixelSenderTest {
     fun whenPixelFiredThenPixelServiceCalledWithCorrectAtbAndVariant() {
         givenPixelApiSucceeds()
         givenAtbVariant(Atb("atb"))
-        givenVariant(Variant("variant", filterBy = { true }))
+        givenVariant("variant")
         givenFormFactor(DeviceInfo.FormFactor.PHONE)
 
         testee.sendPixel(TEST.pixelName, emptyMap(), emptyMap())
@@ -130,7 +127,7 @@ class RxPixelSenderTest {
     fun whenPixelFiredWithAdditionalParametersThenPixelServiceCalledWithDefaultAndAdditionalParameters() {
         givenPixelApiSucceeds()
         givenAtbVariant(Atb("atb"))
-        givenVariant(Variant("variant", filterBy = { true }))
+        givenVariant("variant")
         givenFormFactor(DeviceInfo.FormFactor.PHONE)
         givenAppVersion("1.0.0")
 
@@ -145,7 +142,7 @@ class RxPixelSenderTest {
     fun whenPixelFiredWithoutAdditionalParametersThenPixelServiceCalledWithOnlyDefaultParameters() {
         givenPixelApiSucceeds()
         givenAtbVariant(Atb("atb"))
-        givenVariant(Variant("variant", filterBy = { true }))
+        givenVariant("variant")
         givenFormFactor(DeviceInfo.FormFactor.PHONE)
         givenAppVersion("1.0.0")
 
@@ -158,7 +155,7 @@ class RxPixelSenderTest {
     @Test
     fun whenPixelEnqueuedWitAdditionalParametersThenPixelEnqueuedWithParameters() {
         givenAtbVariant(Atb("atb"))
-        givenVariant(Variant("variant", filterBy = { true }))
+        givenVariant("variant")
         givenFormFactor(DeviceInfo.FormFactor.PHONE)
         givenAppVersion("1.0.0")
         val params = mapOf("param1" to "value1", "param2" to "value2")
@@ -183,7 +180,7 @@ class RxPixelSenderTest {
     @Test
     fun whenPixelEnqueuedWithoutAdditionalParametersThenPixelEnqueuedWithOnlyDefaultParameters() {
         givenAtbVariant(Atb("atb"))
-        givenVariant(Variant("variant", filterBy = { true }))
+        givenVariant("variant")
         givenFormFactor(DeviceInfo.FormFactor.PHONE)
         givenAppVersion("1.0.0")
 
@@ -304,8 +301,8 @@ class RxPixelSenderTest {
         whenever(api.fire(any(), any(), any(), any(), any(), any())).thenReturn(Completable.complete())
     }
 
-    private fun givenVariant(variant: Variant) {
-        whenever(mockVariantManager.getVariant()).thenReturn(variant)
+    private fun givenVariant(variantKey: String) {
+        whenever(mockVariantManager.getVariantKey()).thenReturn(variantKey)
     }
 
     private fun givenAtbVariant(atb: Atb) {