android: PR suggestions for syspolicyHandler (#308)

Updates tailscale/corp#18202

Signed-off-by: Percy Wegmann <percy@tailscale.com>

android/src/main/java/com/tailscale/ipn/App.kt

@@ -15,7 +15,6 @@ import android.content.ContentResolver
 import android.content.ContentValues
 import android.content.Context
 import android.content.Intent
-import android.content.RestrictionsManager
 import android.content.SharedPreferences
 import android.content.pm.PackageInfo
 import android.content.pm.PackageManager
@@ -38,10 +37,7 @@ import androidx.core.app.NotificationCompat
 import androidx.core.app.NotificationManagerCompat
 import androidx.security.crypto.EncryptedSharedPreferences
 import androidx.security.crypto.MasterKey
-import com.tailscale.ipn.mdm.AlwaysNeverUserDecidesMDMSetting
-import com.tailscale.ipn.mdm.BooleanMDMSetting
-import com.tailscale.ipn.mdm.ShowHideMDMSetting
-import com.tailscale.ipn.mdm.StringMDMSetting
+import com.tailscale.ipn.mdm.MDMSettings
 import com.tailscale.ipn.ui.localapi.Client
 import com.tailscale.ipn.ui.localapi.Request
 import com.tailscale.ipn.ui.model.Ipn
@@ -459,29 +455,15 @@ class App : Application(), libtailscale.AppContext {
 
   @Throws(IOException::class, GeneralSecurityException::class)
   override fun getSyspolicyBooleanValue(key: String): Boolean {
-    val manager = getSystemService(Context.RESTRICTIONS_SERVICE) as RestrictionsManager
-    return BooleanMDMSetting(key, key).getFrom(manager.applicationRestrictions, this)
+    return getSyspolicyStringValue(key) == "true"
   }
 
   @Throws(IOException::class, GeneralSecurityException::class)
   override fun getSyspolicyStringValue(key: String): String {
-    val manager = getSystemService(Context.RESTRICTIONS_SERVICE) as RestrictionsManager
-
-    val alwaysNeverSetting = AlwaysNeverUserDecidesMDMSetting(key, key, false)
-    val showHideSetting = ShowHideMDMSetting(key, key, false)
-    val stringSetting = StringMDMSetting(key, key, false)
-
-    return when {
-      alwaysNeverSetting.keyExists(key) ->
-          alwaysNeverSetting.getFrom(manager.applicationRestrictions, this).value
-      showHideSetting.keyExists(key) ->
-          showHideSetting.getFrom(manager.applicationRestrictions, this).value
-      stringSetting.keyExists(key) ->
-          stringSetting.getFrom(manager.applicationRestrictions, this) ?: ""
-      else -> {
-        Log.d("MDM", "$key is not defined on Android. Returning empty.")
-        ""
-      }
-    }
+    return MDMSettings.allSettingsByKey[key]?.flow?.value?.toString()
+        ?: run {
+          Log.d("MDM", "$key is not defined on Android. Returning empty.")
+          ""
+        }
   }
 }

android/src/main/java/com/tailscale/ipn/mdm/MDMSettings.kt

@@ -57,6 +57,8 @@ object MDMSettings {
         .map { it.call(MDMSettings) as MDMSetting<*> }
   }
 
+  val allSettingsByKey by lazy { allSettings.associateBy { it.key } }
+
   fun update(app: App, restrictionsManager: RestrictionsManager?) {
     val bundle = restrictionsManager?.applicationRestrictions
     allSettings.forEach { it.setFrom(bundle, app) }

android/src/main/java/com/tailscale/ipn/mdm/MDMSettingsDefinitions.kt

@@ -4,32 +4,14 @@
 package com.tailscale.ipn.mdm
 
 import android.os.Bundle
-import android.util.Log
 import com.tailscale.ipn.App
 import com.tailscale.ipn.ui.util.set
 import kotlinx.coroutines.flow.MutableStateFlow
 import kotlinx.coroutines.flow.StateFlow
 
-// Don't keep track of the key if shouldRegisterKey is false - shouldRegisterKey should be false when creating an MDMSetting to check whether a key has been registered with that setting.
-abstract class MDMSetting<T>(defaultValue: T, val key: String, val localizedTitle: String, private val shouldRegisterKey: Boolean = true) {
-  private val keys = mutableSetOf<String>()
-
-    init {
-      if (shouldRegisterKey) { registerKey(key)
-    }
-  }
+abstract class MDMSetting<T>(defaultValue: T, val key: String, val localizedTitle: String) {
   val flow: StateFlow<T> = MutableStateFlow<T>(defaultValue)
 
-  private fun registerKey(key: String) {
-    if (!keyExists(key)) {
-        keys.add(key)
-    }
-}
-
-fun keyExists(key: String): Boolean {
-    return keys.contains(key)
-}
-
   fun setFrom(bundle: Bundle?, app: App) {
     val v = getFrom(bundle, app)
     flow.set(v)
@@ -44,8 +26,8 @@ class BooleanMDMSetting(key: String, localizedTitle: String) :
       bundle?.getBoolean(key) ?: app.getEncryptedPrefs().getBoolean(key, false)
 }
 
-class StringMDMSetting(key: String, localizedTitle: String, shouldRegisterKey: Boolean = true) :
-    MDMSetting<String?>(null, key, localizedTitle, shouldRegisterKey) {
+class StringMDMSetting(key: String, localizedTitle: String) :
+    MDMSetting<String?>(null, key, localizedTitle) {
   override fun getFrom(bundle: Bundle?, app: App) =
       bundle?.getString(key) ?: app.getEncryptedPrefs().getString(key, null)
 }
@@ -57,8 +39,8 @@ class StringArrayListMDMSetting(key: String, localizedTitle: String) :
           ?: app.getEncryptedPrefs().getStringSet(key, HashSet<String>())?.toList()
 }
 
-class AlwaysNeverUserDecidesMDMSetting(key: String, localizedTitle: String, shouldRegisterKey: Boolean = true) :
-    MDMSetting<AlwaysNeverUserDecides>(AlwaysNeverUserDecides.UserDecides, key, localizedTitle, shouldRegisterKey) {
+class AlwaysNeverUserDecidesMDMSetting(key: String, localizedTitle: String) :
+    MDMSetting<AlwaysNeverUserDecides>(AlwaysNeverUserDecides.UserDecides, key, localizedTitle) {
   override fun getFrom(bundle: Bundle?, app: App): AlwaysNeverUserDecides {
     val storedString =
         bundle?.getString(key)
@@ -78,8 +60,8 @@ class AlwaysNeverUserDecidesMDMSetting(key: String, localizedTitle: String, shou
   }
 }
 
-class ShowHideMDMSetting(key: String, localizedTitle: String, shouldRegisterKey: Boolean = true) :
-    MDMSetting<ShowHide>(ShowHide.Show, key, localizedTitle, shouldRegisterKey) {
+class ShowHideMDMSetting(key: String, localizedTitle: String) :
+    MDMSetting<ShowHide>(ShowHide.Show, key, localizedTitle) {
   override fun getFrom(bundle: Bundle?, app: App): ShowHide {
     val storedString =
         bundle?.getString(key)