feat(native): the app needs TREK 5.1.3 on the server and checks a remembered one once after the update

The fixes that keep the app's sign-in in the app live in the server's UI,
so an updated app on a 5.1.2 server still ended in the browser. The server now
reports nativeApi 2 and the app refuses anything below it, naming 5.1.3.

A server the app remembers from before is not loaded unchecked: the first
launch after the update shows the address screen filled in with it, says why
and checks it right away. A server that is new enough loads again with its
session; an older one gets the update hint.

client/android/app/src/main/java/com/liketrek/trek/MainActivity.java

@@ -26,6 +26,7 @@ public class MainActivity extends BridgeActivity {
         // runs and on its own origin. BridgeActivity reads `config` while it
         // builds the bridge inside super.onCreate().
         boolean restarting = TrekServerStore.consumeRestart(this);
+        TrekServerStore.recheckAfterUpdate(this);
         String server = TrekServerStore.getUrl(this);
         boolean onServer = server != null && !TrekServerStore.consumeShellOnce(this);
         config = TrekServerStore.configFor(this, onServer ? server : null, restarting);

client/android/app/src/main/java/com/liketrek/trek/TrekServerStore.java

@@ -22,6 +22,16 @@ final class TrekServerStore {
 
     private static final String PREFS = "trek_shell";
     private static final String KEY_URL = "server_url";
+    private static final String KEY_PREVIOUS_URL = "previous_server_url";
+    private static final String KEY_SERVER_CHECK = "server_check";
+
+    /**
+     * The server API this build needs (MIN_NATIVE_API in serverAddress.ts). A
+     * server remembered under a lower value is checked once more: the first
+     * launch after an update that raised it puts the address screen back up,
+     * filled in with that server (getPreviousUrl). Raise both together.
+     */
+    private static final int SERVER_CHECK = 2;
     private static final String KEY_SIGN_IN_HOSTS = "sign_in_hosts";
     private static final String KEY_SHELL_ONCE = "shell_once";
     private static final String KEY_RESTART = "restart";
@@ -56,6 +66,21 @@ final class TrekServerStore {
         return prefs(context).getString(KEY_URL, null);
     }
 
+    /** Runs before the bridge is built, so a server picked under an older minimum is not loaded unchecked. */
+    static void recheckAfterUpdate(Context context) {
+        SharedPreferences prefs = prefs(context);
+        if (prefs.getInt(KEY_SERVER_CHECK, 0) >= SERVER_CHECK) return;
+        String server = getUrl(context);
+        SharedPreferences.Editor editor = prefs.edit().putInt(KEY_SERVER_CHECK, SERVER_CHECK);
+        if (server != null) editor.remove(KEY_URL).remove(KEY_SIGN_IN_HOSTS).putString(KEY_PREVIOUS_URL, server);
+        editor.commit();
+    }
+
+    /** The server an update asked to check again, until a server is set. */
+    static String getPreviousUrl(Context context) {
+        return prefs(context).getString(KEY_PREVIOUS_URL, null);
+    }
+
     /** Remembers the server; its sign-in hosts go with it and are replaced or dropped too. */
     static void setUrl(Context context, String url) {
         setServer(context, url, null);
@@ -66,7 +91,7 @@ final class TrekServerStore {
         if (url == null) {
             editor.remove(KEY_URL);
         } else {
-            editor.putString(KEY_URL, url);
+            editor.putString(KEY_URL, url).remove(KEY_PREVIOUS_URL);
         }
         if (signInHosts == null || signInHosts.isEmpty()) {
             editor.remove(KEY_SIGN_IN_HOSTS);

client/android/app/src/main/java/com/liketrek/trek/TrekShellPlugin.java

@@ -310,8 +310,10 @@ public class TrekShellPlugin extends Plugin {
     @PluginMethod
     public void getServer(PluginCall call) {
         String url = TrekServerStore.getUrl(getContext());
+        String previous = TrekServerStore.getPreviousUrl(getContext());
         JSObject result = new JSObject();
         result.put("url", url == null ? JSONObject.NULL : url);
+        result.put("previousUrl", previous == null ? JSONObject.NULL : previous);
         call.resolve(result);
     }