Issue #6: Implement code for evaluating experiment configuration and …

…bucketing users

Closes #6: Implment code for evaluating experiment configuration and bucketing users

fretboard/src/main/java/mozilla/components/service/fretboard/DeviceUuidFactory.kt

@@ -0,0 +1,29 @@
+/* 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/. */
+
+package mozilla.components.service.fretboard
+
+import android.content.Context
+import java.util.UUID
+
+internal class DeviceUuidFactory(context: Context) {
+    val uuid by lazy {
+        val preferences = context
+            .getSharedPreferences(PREFS_FILE, Context.MODE_PRIVATE)
+        val prefUuid = preferences.getString(PREF_UUID_KEY, null)
+
+        if (prefUuid != null) {
+            UUID.fromString(prefUuid)
+        } else {
+            val uuid = UUID.randomUUID()
+            preferences.edit().putString(PREF_UUID_KEY, uuid.toString()).apply()
+            uuid
+        }
+    }
+
+    companion object {
+        private const val PREFS_FILE = "mozilla.components.service.fretboard"
+        private const val PREF_UUID_KEY = "device_uuid"
+    }
+}

fretboard/src/main/java/mozilla/components/service/fretboard/Experiment.kt

@@ -20,7 +20,11 @@ data class Experiment(
     data class Matcher(
         val language: String? = null,
         val appId: String? = null,
-        val regions: List<String>? = null
+        val regions: List<String>? = null,
+        val version: String? = null,
+        val manufacturer: String? = null,
+        val device: String? = null,
+        val country: String? = null
     )
 
     data class Bucket(

fretboard/src/main/java/mozilla/components/service/fretboard/ExperimentDescriptor.kt

@@ -0,0 +1,7 @@
+/* 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/. */
+
+package mozilla.components.service.fretboard
+
+data class ExperimentDescriptor(val id: String)

fretboard/src/main/java/mozilla/components/service/fretboard/ExperimentEvaluator.kt

@@ -0,0 +1,66 @@
+/* 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/. */
+
+package mozilla.components.service.fretboard
+
+import android.content.Context
+import android.os.Build
+import android.text.TextUtils
+import java.util.Locale
+import java.util.zip.CRC32
+
+internal class ExperimentEvaluator {
+    fun evaluate(
+        context: Context,
+        experimentDescriptor: ExperimentDescriptor,
+        experiments: List<Experiment>,
+        userBucket: Int = getUserBucket(context)
+    ): Boolean {
+        val experiment = experiments.firstOrNull { it.id == experimentDescriptor.id } ?: return false
+        return isInBucket(userBucket, experiment) && matches(context, experiment)
+    }
+
+    private fun matches(context: Context, experiment: Experiment): Boolean {
+        if (experiment.match != null) {
+            val region = Locale.getDefault().isO3Country
+            val matchesRegion = !(experiment.match.regions != null &&
+                                        experiment.match.regions.isNotEmpty() &&
+                                        experiment.match.regions.none { it == region })
+            val appVersion = context.packageManager.getPackageInfo(context.packageName, 0).versionName
+            return matchesRegion &&
+                matchesExperiment(experiment.match.appId, context.packageName) &&
+                matchesExperiment(experiment.match.language, Locale.getDefault().isO3Language) &&
+                matchesExperiment(experiment.match.country, Locale.getDefault().isO3Country) &&
+                matchesExperiment(experiment.match.version, appVersion) &&
+                matchesExperiment(experiment.match.manufacturer, Build.MANUFACTURER) &&
+                matchesExperiment(experiment.match.device, Build.DEVICE)
+        }
+        return true
+    }
+
+    private fun matchesExperiment(experimentValue: String?, deviceValue: String): Boolean {
+        return !(experimentValue != null &&
+            !TextUtils.isEmpty(experimentValue) &&
+            !deviceValue.matches(experimentValue.toRegex()))
+    }
+
+    private fun isInBucket(userBucket: Int, experiment: Experiment): Boolean {
+        return !(experiment.bucket?.min == null ||
+            userBucket < experiment.bucket.min ||
+            experiment.bucket.max == null ||
+            userBucket >= experiment.bucket.max)
+    }
+
+    private fun getUserBucket(context: Context): Int {
+        val uuid = DeviceUuidFactory(context).uuid.toString()
+        val crc = CRC32()
+        crc.update(uuid.toByteArray())
+        val checksum = crc.value
+        return (checksum % MAX_BUCKET).toInt()
+    }
+
+    companion object {
+        private const val MAX_BUCKET = 100L
+    }
+}

fretboard/src/main/java/mozilla/components/service/fretboard/Fretboard.kt

@@ -16,6 +16,7 @@ class Fretboard(
 ) {
     private var experiments: List<Experiment> = listOf()
     private var experimentsLoaded: Boolean = false
+    private val evaluator = ExperimentEvaluator()
 
     /**
      * Loads experiments from local storage

fretboard/src/main/java/mozilla/components/service/fretboard/JSONExperimentParser.kt

@@ -22,7 +22,14 @@ class JSONExperimentParser {
         val matchObject: JSONObject? = jsonObject.optJSONObject(MATCH_KEY)
         val regions: List<String>? = matchObject?.optJSONArray(REGIONS_KEY)?.toList()
         val matcher = if (matchObject != null) {
-            Experiment.Matcher(matchObject.tryGetString(LANG_KEY), matchObject.tryGetString(APP_ID_KEY), regions)
+            Experiment.Matcher(
+                matchObject.tryGetString(LANG_KEY),
+                matchObject.tryGetString(APP_ID_KEY),
+                regions,
+                matchObject.tryGetString(VERSION_KEY),
+                matchObject.tryGetString(MANUFACTURER_KEY),
+                matchObject.tryGetString(DEVICE_KEY),
+                matchObject.tryGetString(COUNTRY_KEY))
         } else null
         val bucket = if (bucketsObject != null) {
             Experiment.Bucket(bucketsObject.tryGetInt(MAX_KEY), bucketsObject.tryGetInt(MIN_KEY))
@@ -107,6 +114,10 @@ class JSONExperimentParser {
         private const val REGIONS_KEY = "regions"
         private const val LANG_KEY = "lang"
         private const val APP_ID_KEY = "appId"
+        private const val VERSION_KEY = "version"
+        private const val MANUFACTURER_KEY = "manufacturer"
+        private const val DEVICE_KEY = "device"
+        private const val COUNTRY_KEY = "country"
         private const val MAX_KEY = "max"
         private const val MIN_KEY = "min"
         private const val ID_KEY = "id"

fretboard/src/test/java/mozilla/components/service/fretboard/DeviceUuidFactoryTest.kt

@@ -0,0 +1,49 @@
+/* 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/. */
+
+package mozilla.components.service.fretboard
+
+import android.content.Context
+import android.content.SharedPreferences
+import org.junit.Assert.assertEquals
+import org.junit.Assert.assertTrue
+import org.junit.Test
+import org.junit.runner.RunWith
+import org.mockito.ArgumentMatchers
+import org.mockito.ArgumentMatchers.any
+import org.mockito.ArgumentMatchers.anyInt
+import org.mockito.ArgumentMatchers.anyString
+import org.mockito.ArgumentMatchers.eq
+import org.mockito.Mockito.`when`
+import org.mockito.Mockito.mock
+import org.mockito.Mockito.verify
+import org.robolectric.RobolectricTestRunner
+import java.util.UUID
+
+@RunWith(RobolectricTestRunner::class)
+class DeviceUuidFactoryTest {
+    @Test
+    fun testUuidNoPreference() {
+        val context = mock(Context::class.java)
+        val sharedPreferences = mock(SharedPreferences::class.java)
+        val editor = mock(SharedPreferences.Editor::class.java)
+        `when`(editor.putString(anyString(), any())).thenReturn(editor)
+        `when`(sharedPreferences.edit()).thenReturn(editor)
+        `when`(sharedPreferences.getString(eq("device_uuid"), ArgumentMatchers.any())).thenReturn(null)
+        `when`(context.getSharedPreferences(anyString(), anyInt())).thenReturn(sharedPreferences)
+        val uuid = DeviceUuidFactory(context).uuid
+        assertTrue(uuid is UUID)
+        verify(editor).putString("device_uuid", uuid.toString())
+    }
+
+    @Test
+    fun testUuidSavedInPreferences() {
+        val savedUuid = "99111a0f-ca5d-4de1-913a-daba905c53b2"
+        val context = mock(Context::class.java)
+        val sharedPreferences = mock(SharedPreferences::class.java)
+        `when`(sharedPreferences.getString(eq("device_uuid"), any())).thenReturn(savedUuid)
+        `when`(context.getSharedPreferences(anyString(), anyInt())).thenReturn(sharedPreferences)
+        assertEquals(savedUuid, DeviceUuidFactory(context).uuid.toString())
+    }
+}