Add in-app reviews for play flavor

Signed-off-by: William Brawner <me@wbrawner.com>

app/build.gradle

@@ -125,6 +125,7 @@ dependencies {
     implementation 'com.commonsware.cwac:anddown:0.3.0'
     playImplementation 'com.android.billingclient:billing:3.0.0'
     playImplementation 'com.google.firebase:firebase-core:17.5.0'
+    playImplementation 'com.google.android.play:core-ktx:1.8.1'
     implementation "androidx.core:core-ktx:1.3.1"
     implementation 'androidx.browser:browser:1.2.0'
     implementation "org.jetbrains.kotlin:kotlin-stdlib-jdk7:$kotlin_version"

app/src/free/java/com/wbrawner/simplemarkdown/utility/ReviewHelper.kt

@@ -0,0 +1,15 @@
+package com.wbrawner.simplemarkdown.utility
+
+import android.app.Activity
+import android.content.Context
+import androidx.preference.PreferenceManager
+import com.google.android.play.core.review.ReviewManagerFactory
+import kotlin.coroutines.resume
+import kotlin.coroutines.suspendCoroutine
+
+object ReviewHelper {
+    // No review library for F-droid, so this is a no-op
+    fun init(application: Application, errorHandler: ErrorHandler) {
+        Log.w("ReviewHelper", "ReviewHelper not enabled for free builds")
+    }
+}

app/src/main/java/com/wbrawner/simplemarkdown/MarkdownApplication.kt

@@ -5,6 +5,7 @@ import android.content.Context
 import android.os.StrictMode
 import com.wbrawner.simplemarkdown.utility.AcraErrorHandler
 import com.wbrawner.simplemarkdown.utility.ErrorHandler
+import com.wbrawner.simplemarkdown.utility.ReviewHelper
 
 class MarkdownApplication : Application() {
     val errorHandler: ErrorHandler by lazy {
@@ -23,6 +24,7 @@ class MarkdownApplication : Application() {
                     .build())
         }
         super.onCreate()
+        ReviewHelper.init(this, errorHandler)
     }
 
     override fun attachBaseContext(base: Context?) {

app/src/play/java/com/wbrawner/simplemarkdown/utility/ReviewHelper.kt

@@ -0,0 +1,122 @@
+package com.wbrawner.simplemarkdown.utility
+
+import android.app.Activity
+import android.app.Application
+import android.content.SharedPreferences
+import android.os.Bundle
+import android.os.SystemClock
+import android.util.Log
+import androidx.core.content.edit
+import androidx.preference.PreferenceManager
+import com.google.android.play.core.review.ReviewManager
+import com.google.android.play.core.review.ReviewManagerFactory
+import com.wbrawner.simplemarkdown.view.activity.MainActivity
+
+private const val KEY_TIME_IN_APP = "timeInApp"
+
+// Prompt user to review after they've used the app for 30 minutes
+private const val TIME_TO_PROMPT = 1000L * 60 * 30
+
+/**
+ * A simple attempt at a non-intrusive way of prompting long-time users of the app to leave a
+ * review. It works by registering itself as one of the [Application.ActivityLifecycleCallbacks] to
+ * keep track of the current activity, which is needed to launch the review flow, along with the
+ * time the activity is started to estimate how long the user has been active.
+ */
+object ReviewHelper : Application.ActivityLifecycleCallbacks {
+    private lateinit var application: Application
+    private lateinit var reviewManager: ReviewManager
+    private lateinit var sharedPreferences: SharedPreferences
+    private lateinit var errorHandler: ErrorHandler
+    private var currentActivity: Activity? = null
+    private var activityCount = 0
+        set(value) {
+            field = if (value < 0) {
+                0
+            } else {
+                value
+            }
+        }
+    private var activeTime = 0L
+
+    fun init(
+            application: Application,
+            errorHandler: ErrorHandler,
+            sharedPreferences: SharedPreferences = PreferenceManager.getDefaultSharedPreferences(application),
+            reviewManager: ReviewManager = ReviewManagerFactory.create(application)
+    ) {
+        this.application = application
+        this.errorHandler = errorHandler
+        this.sharedPreferences = sharedPreferences
+        this.reviewManager = reviewManager
+        if (sharedPreferences.getLong(KEY_TIME_IN_APP, 0L) == -1L) {
+            // We've already prompted the user for the review so let's not be annoying about it
+            Log.i("ReviewHelper", "User already prompted for review, not configuring ReviewHelper")
+            return
+        }
+        application.registerActivityLifecycleCallbacks(this)
+    }
+
+    override fun onActivityCreated(activity: Activity, savedInstanceState: Bundle?) {
+        // No op
+    }
+
+    override fun onActivityStarted(activity: Activity) {
+        currentActivity = activity
+        if (activityCount++ == 0) {
+            activeTime = SystemClock.elapsedRealtime()
+        }
+        if (activity !is MainActivity || sharedPreferences.getLong(KEY_TIME_IN_APP, 0L) < TIME_TO_PROMPT) {
+            // Not ready to prompt just yet
+            Log.v("ReviewHelper", "Not ready to prompt user for review yet")
+            return
+        }
+        Log.v("ReviewHelper", "Prompting user for review")
+        reviewManager.requestReviewFlow().addOnCompleteListener { request ->
+            if (!request.isSuccessful) {
+                val exception = request.exception
+                        ?: RuntimeException("Failed to request review")
+                Log.e("ReviewHelper", "Failed to prompt user for review", exception)
+                errorHandler.reportException(exception)
+                return@addOnCompleteListener
+            }
+
+            reviewManager.launchReviewFlow(activity, request.result).addOnCompleteListener { _ ->
+                // According to the docs, this may or may not have actually been shown. Either
+                // way, it's not a critical piece of functionality for the app so I'm not
+                // worried about it failing silently. Link for reference:
+                // https://developer.android.com/guide/playcore/in-app-review/kotlin-java#launch-review-flow
+                Log.v("ReviewHelper", "User finished review, ending activity watch")
+                application.unregisterActivityLifecycleCallbacks(this)
+                sharedPreferences.edit {
+                    putLong(KEY_TIME_IN_APP, -1L)
+                }
+            }
+        }
+    }
+
+    override fun onActivityResumed(activity: Activity) {
+        // No op
+    }
+
+    override fun onActivityPaused(activity: Activity) {
+        // No op
+    }
+
+    override fun onActivityStopped(activity: Activity) {
+        currentActivity = null
+        if (--activityCount == 0) {
+            sharedPreferences.edit {
+                putLong(KEY_TIME_IN_APP, SystemClock.elapsedRealtime() - activeTime)
+            }
+        }
+    }
+
+    override fun onActivitySaveInstanceState(activity: Activity, outState: Bundle) {
+        // No op
+    }
+
+    override fun onActivityDestroyed(activity: Activity) {
+        // No op
+    }
+}