Issue mozilla-mobile#60: Generate versionCode for releases dynamically.

app/build.gradle

@@ -15,14 +15,16 @@ android {
         minSdkVersion rootProject.ext.build['minSdkVersion']
         targetSdkVersion rootProject.ext.build['targetSdkVersion']
         versionCode 1
-        versionName "1.0"
+        versionName AppVersion.versionName
 
         testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
     }
 
     buildTypes {
         release {
             minifyEnabled false
+            shrinkResources false
+
             proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
         }
     }
@@ -66,6 +68,33 @@ android {
     }
 }
 
+android.applicationVariants.all { variant ->
+    def buildType = variant.buildType.name
+
+    if (buildType == "release") {
+        def versionCode = AppVersion.baseVersionCode
+
+        // The Google Play Store does not allow multiple APKs for the same app that all have the
+        // same version code. Therefore we need to have different version codes for our ARM and x86
+        // builds.
+
+        // Our x86 builds need a higher version code to avoid installing ARM builds on an x86 device
+        // with ARM compatibility mode. In addition to that aarch64 builds should be preferred over
+        // ARM builds if suitable: x86 (+2) > aarch64 (+1) > arm.
+
+        // Note: This assumes that we do not need to release more often than every 2 minutes!
+        //       Otherwise this will create version code conflicts.
+
+        if (variant.flavorName.contains("X86")) {
+            versionCode = versionCode + 2
+        } else if (variant.flavorName.contains("Aarch64")) {
+            versionCode = versionCode + 1
+        }
+
+        variant.outputs.all { output -> setVersionCodeOverride(versionCode) }
+    }
+}
+
 repositories {
     ////////////////////////////////////////////////////////////////////////////////////////////
     // GeckoView Nightly

buildSrc/build.gradle.kts

@@ -0,0 +1,8 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+plugins {
+    `kotlin-dsl`
+}
+

buildSrc/src/main/java/AppVersion.kt

@@ -0,0 +1,56 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+import java.text.SimpleDateFormat
+import java.util.Date
+import java.util.Locale
+
+// The first Nightly releases of Fenix  will ship in 2018 so we are using this as the base year for
+// our version code.
+private const val BASE_YEAR = 18
+
+object AppVersion {
+    /**
+     * The version number shown to users.
+     */
+    val versionName = "1.0"
+
+    /**
+     * Internal version number used for release builds.
+     */
+    val baseVersionCode: Int
+
+    init {
+        // This code generates our base "unique" version code for release builds.
+        //
+        // The result of the version code generation depends on the timezone. We assume that this
+        // code will only be used  for release versions and running on our build servers with a
+        // fixed timezone.
+        //
+        // The version code is composed like: yDDDHHmm
+        //  * y   = Double digit year, with 18 subtracted: 2018 -> 18 -> 0 or 2019 -> 19 -> 1
+        //  * DDD = Day of the year, pad with zeros if needed: September 6th -> 249
+        //  * HH  = Hour in day (00-23)
+        //  * mm  = Minute in hour
+        //
+        // For September 10th, 2018, 5:04pm am this will generate the versionCode: 2531704 (0-253-1704).
+
+        val today = Date()
+
+        // We use the current year (double digit) and subtract the base year (see above). This value
+        // will start counting at 0 and increment by one every year.
+        val year = (SimpleDateFormat("yy", Locale.US).format(today).toInt() - BASE_YEAR).toString()
+
+        // We use the day in the Year (e.g. 248) as opposed to month + day (0510) because it's one
+        // digit shorter. If needed we pad with zeros (e.g. 25 -> 025)
+        val day = String.format("%03d", SimpleDateFormat("D", Locale.US).format(today).toInt())
+
+        // We append the hour in day (24h) and minute in hour (7:26 pm -> 1926). We do not append
+        // seconds. This assumes that we do not need to build multiple release(!) builds the same
+        // minute.
+        val time = SimpleDateFormat("HHmm", Locale.US).format(today)
+
+        baseVersionCode = (year + day + time).toInt()
+    }
+}