Add ExPlat implementation to :experimentation module

experimentation/build.gradle

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+plugins {
+    id 'com.android.library'
+    id 'org.jetbrains.kotlin.android'
+}
+
+repositories {
+    google()
+    maven {
+        url 'https://a8c-libs.s3.amazonaws.com/android'
+        content {
+            includeGroup "org.wordpress"
+            includeGroup "org.wordpress.fluxc"
+            includeGroup "org.wordpress.wellsql"
+        }
+    }
+}
+
+android {
+    compileSdkVersion 30
+
+    defaultConfig {
+        minSdkVersion 21
+        targetSdkVersion 30
+        versionCode 1
+        versionName "1.0"
+    }
+    compileOptions {
+        sourceCompatibility JavaVersion.VERSION_1_8
+        targetCompatibility JavaVersion.VERSION_1_8
+    }
+    lintOptions {
+        warningsAsErrors true
+        warning 'GradleDependency'
+    }
+}
+
+dependencies {
+    // Coroutines
+    implementation "org.jetbrains.kotlinx:kotlinx-coroutines-core:1.4.2"
+
+    //FluxC
+    implementation "org.wordpress:fluxc:1.36.0"
+
+    //WordPress utils
+    implementation "org.wordpress:utils:2.3.0"
+
+    testImplementation "org.jetbrains.kotlinx:kotlinx-coroutines-test:1.4.2"
+    testImplementation 'junit:junit:4.13.2'
+    testImplementation 'org.assertj:assertj-core:3.19.0'
+    testImplementation 'org.mockito.kotlin:mockito-kotlin:2.2.11'
+    testImplementation 'org.mockito:mockito-inline:3.8.0'
+}

experimentation/src/main/AndroidManifest.xml

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+<?xml version="1.0" encoding="utf-8"?>
+<manifest xmlns:android="http://schemas.android.com/apk/res/android"
+    package="com.automattic.android.experimentation">
+
+</manifest>

experimentation/src/main/java/com/automattic/android/experimentation/ExPlat.kt

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+package com.automattic.android.experimentation
+
+import com.automattic.android.experimentation.ExPlat.RefreshStrategy.ALWAYS
+import com.automattic.android.experimentation.ExPlat.RefreshStrategy.IF_STALE
+import com.automattic.android.experimentation.ExPlat.RefreshStrategy.NEVER
+import kotlinx.coroutines.CoroutineScope
+import kotlinx.coroutines.launch
+import org.wordpress.android.fluxc.model.experiments.Assignments
+import org.wordpress.android.fluxc.model.experiments.Variation
+import org.wordpress.android.fluxc.model.experiments.Variation.Control
+import org.wordpress.android.fluxc.store.ExperimentStore
+import org.wordpress.android.fluxc.store.ExperimentStore.Platform
+import org.wordpress.android.fluxc.utils.AppLogWrapper
+import org.wordpress.android.util.AppLog.T
+
+class ExPlat(
+    private val platform: Platform,
+    private val experiments: Set<Experiment>,
+    private val experimentStore: ExperimentStore,
+    private val appLogWrapper: AppLogWrapper,
+    private val coroutineScope: CoroutineScope,
+    private val isDebug: Boolean
+) {
+    private val activeVariations = mutableMapOf<String, Variation>()
+    private val experimentNames: List<String> by lazy { experiments.map { it.name } }
+
+    fun refreshIfNeeded() {
+        refresh(refreshStrategy = IF_STALE)
+    }
+
+    fun forceRefresh() {
+        refresh(refreshStrategy = ALWAYS)
+    }
+
+    fun clear() {
+        appLogWrapper.d(T.API, "ExPlat: clearing cached assignments and active variations")
+        activeVariations.clear()
+        experimentStore.clearCachedAssignments()
+    }
+
+    /**
+     * This returns the current active [Variation] for the provided [Experiment].
+     *
+     * If no active [Variation] is found, we can assume this is the first time this method is being
+     * called for the provided [Experiment] during the current session. In this case, the [Variation]
+     * is returned from the cached [Assignments] and then set as active. If the cached [Assignments]
+     * is stale and [shouldRefreshIfStale] is `true`, then new [Assignments] are fetched and their
+     * variations are going to be returned by this method on the next session.
+     *
+     * If the provided [Experiment] was not included in [experiments], then [Control] is returned.
+     * If [isDebug] is `true`, an [IllegalArgumentException] is thrown instead.
+     */
+    internal fun getVariation(experimentName: String, shouldRefreshIfStale: Boolean): Variation {
+        if (!experimentNames.contains(experimentName)) {
+            val message = "ExPlat: experiment not found: \"${experimentName}\"! " +
+                "Make sure to include it in the set provided via constructor."
+            appLogWrapper.e(T.API, message)
+            if (isDebug) throw IllegalArgumentException(message) else return Control
+        }
+        return activeVariations.getOrPut(experimentName) {
+            getAssignments(if (shouldRefreshIfStale) IF_STALE else NEVER)
+                .getVariationForExperiment(experimentName)
+        }
+    }
+
+    private fun refresh(refreshStrategy: RefreshStrategy) {
+        if (experimentNames.isNotEmpty()) {
+            getAssignments(refreshStrategy)
+        }
+    }
+
+    private fun getAssignments(refreshStrategy: RefreshStrategy): Assignments {
+        val cachedAssignments = experimentStore.getCachedAssignments() ?: Assignments()
+        if (refreshStrategy == ALWAYS || (refreshStrategy == IF_STALE && cachedAssignments.isStale())) {
+            coroutineScope.launch { fetchAssignments() }
+        }
+        return cachedAssignments
+    }
+
+    private suspend fun fetchAssignments() = experimentStore.fetchAssignments(platform, experimentNames).also {
+        if (it.isError) {
+            appLogWrapper.d(T.API, "ExPlat: fetching assignments failed with result: ${it.error}")
+        } else {
+            appLogWrapper.d(T.API, "ExPlat: fetching assignments successful with result: ${it.assignments}")
+        }
+    }
+
+    private enum class RefreshStrategy { ALWAYS, IF_STALE, NEVER }
+}

experimentation/src/main/java/com/automattic/android/experimentation/Experiment.kt

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+package com.automattic.android.experimentation
+
+import org.wordpress.android.fluxc.model.experiments.Variation
+
+open class Experiment(
+    val name: String,
+    private val exPlat: ExPlat
+) {
+    @Suppress("unused")
+    @JvmOverloads
+    fun getVariation(shouldRefreshIfStale: Boolean = false): Variation {
+        return exPlat.getVariation(
+            experimentName = name,
+            shouldRefreshIfStale = shouldRefreshIfStale
+        )
+    }
+}