[fenix] For https://github.com/mozilla-mobile/fenix/issues/975: Adds telemetry for settings toggles (https://github.com/mozilla-mobile/fenix/pull/1896)

* For https://github.com/mozilla-mobile/fenix/issues/975: Adds telemetry for settings toggles

* For https://github.com/mozilla-mobile/fenix/issues/975: Uses failable constructor

CHANGELOG.md

@@ -38,6 +38,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - #1312 - Added a missing edit action for bookmark selections
 - #974 - Added telemetry for bookmarks
 - #113 - Added QR code scanner
+- #975 - Added telemetry for preference switches
 
 ### Changed
 - #1429 - Updated site permissions ui for MVP

app/metrics.yaml

@@ -580,3 +580,23 @@ custom_tab:
     notification_emails:
     - fenix-core@mozilla.com
     expires: "2020-03-01"
+
+preferences:
+  preference_toggled:
+    type: event
+    description: >
+      A user toggled a preference switch in settings
+    extra_keys:
+      preference_key:
+        description: "The preference key for the switch preference the user toggled. We currently track: leakcanary,
+        make_default_browser, show_search_suggestions, show_visited_sites_bookmarks, remote_debugging, telemetry,
+        tracking_protection"
+      enabled:
+        description: "Whether or not the preference is *now* enabled"
+    bugs:
+    - 975
+    data_reviews:
+    - https://github.com/mozilla-mobile/fenix/pull/1896
+    notification_emails:
+    - fenix-core@mozilla.com
+    expires: "2020-03-01"

app/src/main/java/org/mozilla/fenix/components/metrics/Metrics.kt

@@ -3,6 +3,7 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 package org.mozilla.fenix.components.metrics
 
+import android.content.Context
 import mozilla.components.browser.search.SearchEngine
 import mozilla.components.support.base.Component
 import mozilla.components.support.base.facts.Fact
@@ -10,6 +11,8 @@ import mozilla.components.support.base.facts.FactProcessor
 import mozilla.components.support.base.facts.Facts
 import mozilla.components.support.base.log.logger.Logger
 import org.mozilla.fenix.BuildConfig
+import org.mozilla.fenix.R
+import java.lang.IllegalArgumentException
 
 sealed class Event {
 
@@ -72,6 +75,29 @@ sealed class Event {
     object CustomTabsMenuOpened : Event()
     object UriOpened : Event()
 
+    data class PreferenceToggled(val preferenceKey: String, val enabled: Boolean, val context: Context) : Event() {
+        private val switchPreferenceTelemetryAllowList = listOf(
+            context.getString(R.string.pref_key_leakcanary),
+            context.getString(R.string.pref_key_make_default_browser),
+            context.getString(R.string.pref_key_show_search_suggestions),
+            context.getString(R.string.pref_key_show_visited_sites_bookmarks),
+            context.getString(R.string.pref_key_remote_debugging),
+            context.getString(R.string.pref_key_telemetry),
+            context.getString(R.string.pref_key_tracking_protection)
+        )
+
+        override val extras: Map<String, String>?
+            get() = mapOf(
+                "preferenceKey" to preferenceKey,
+                "enabled" to enabled.toString()
+            )
+
+        init {
+            // If the event is not in the allow list, we don't want to track it
+            if (!switchPreferenceTelemetryAllowList.contains(preferenceKey)) { throw IllegalArgumentException() }
+        }
+    }
+
     // Interaction Events
     data class SearchBarTapped(val source: Source) : Event() {
         enum class Source { HOME, BROWSER }

app/src/main/java/org/mozilla/fenix/settings/SettingsFragment.kt

@@ -48,6 +48,8 @@ import org.mozilla.fenix.R.string.pref_key_account
 import org.mozilla.fenix.R.string.pref_key_account_category
 import org.mozilla.fenix.R.string.pref_key_search_engine_settings
 import org.mozilla.fenix.R.string.pref_key_tracking_protection_settings
+import org.mozilla.fenix.components.metrics.Event
+import org.mozilla.fenix.ext.components
 import org.mozilla.fenix.utils.ItsNotBrokenSnack
 
 @SuppressWarnings("TooManyFunctions")
@@ -60,6 +62,17 @@ class SettingsFragment : PreferenceFragmentCompat(), CoroutineScope, AccountObse
         super.onCreate(savedInstanceState)
         job = Job()
         updateSignInVisibility()
+
+        preferenceManager.sharedPreferences.registerOnSharedPreferenceChangeListener { sharedPreferences, key ->
+            try {
+                context?.let {
+                    it.components.analytics.metrics.track(Event.PreferenceToggled
+                    (key, sharedPreferences.getBoolean(key, false), it))
+                }
+            } catch (e: IllegalArgumentException) {
+                // The event is not tracked
+            }
+        }
     }
 
     override fun onCreatePreferences(savedInstanceState: Bundle?, rootKey: String?) {