android: make ExitNodePickerViewModel reactive

Updates tailscale/corp#18202

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

android/src/main/java/com/tailscale/ipn/ui/model/TailCfg.kt

@@ -75,6 +75,10 @@ class Tailcfg {
     ) {
         val isAdmin: Boolean
             get() = (Capabilities ?: emptyList()).contains("https://tailscale.com/cap/is-admin")
+
+        // isExitNode reproduces the Go logic in local.go peerStatusFromNode
+        val isExitNode: Boolean =
+            AllowedIPs?.contains("0.0.0.0/0") ?: false && AllowedIPs?.contains("::/0") ?: false
     }
 
     @Serializable

android/src/main/java/com/tailscale/ipn/ui/viewModel/ExitNodePickerViewModel.kt

@@ -4,17 +4,20 @@
 
 package com.tailscale.ipn.ui.viewModel
 
-import android.util.Log
 import androidx.lifecycle.ViewModel
 import androidx.lifecycle.ViewModelProvider
 import androidx.lifecycle.viewModelScope
 import com.tailscale.ipn.ui.localapi.Client
 import com.tailscale.ipn.ui.model.Ipn
 import com.tailscale.ipn.ui.model.StableNodeID
+import com.tailscale.ipn.ui.notifier.Notifier
 import com.tailscale.ipn.ui.util.LoadingIndicator
 import com.tailscale.ipn.ui.util.set
 import kotlinx.coroutines.flow.MutableStateFlow
 import kotlinx.coroutines.flow.StateFlow
+import kotlinx.coroutines.flow.combine
+import kotlinx.coroutines.flow.stateIn
+import kotlinx.coroutines.launch
 import java.util.TreeMap
 
 data class ExitNodePickerNav(
@@ -52,22 +55,22 @@ class ExitNodePickerViewModel(private val nav: ExitNodePickerNav) : IpnViewModel
     val anyActive: StateFlow<Boolean> = MutableStateFlow(false)
 
     init {
-        Client(viewModelScope).status { result ->
-            result.onFailure {
-                Log.e(TAG, "getStatus: ${it.message}")
-            }.onSuccess {
-                it.Peer?.values?.let { peers ->
-                    val allNodes = peers.filter { it.ExitNodeOption }.map {
+        viewModelScope.launch {
+            Notifier.netmap.combine(Notifier.prefs) { netmap, prefs -> Pair(netmap, prefs) }
+                .stateIn(viewModelScope).collect { (netmap, prefs) ->
+                    val exitNodeId = prefs?.ExitNodeID
+                    netmap?.Peers?.let { peers ->
+                        val allNodes = peers.filter { it.isExitNode }.map {
                             ExitNode(
-                            id = it.ID,
-                            label = it.DNSName,
-                            online = it.Online,
-                            selected = it.ExitNode,
-                            mullvad = it.DNSName.endsWith(".mullvad.ts.net."),
-                            priority = it.Location?.Priority ?: 0,
-                            countryCode = it.Location?.CountryCode ?: "",
-                            country = it.Location?.Country ?: "",
-                            city = it.Location?.City ?: "",
+                                id = it.StableID,
+                                label = it.Name,
+                                online = it.Online ?: false,
+                                selected = it.StableID == exitNodeId,
+                                mullvad = it.Name.endsWith(".mullvad.ts.net."),
+                                priority = it.Hostinfo?.Location?.Priority ?: 0,
+                                countryCode = it.Hostinfo?.Location?.CountryCode ?: "",
+                                country = it.Hostinfo?.Location?.Country ?: "",
+                                city = it.Hostinfo?.Location?.City ?: "",
                             )
                         }