From bce263a928ec60d52de2dd8ec2cdc0e5935f1388 Mon Sep 17 00:00:00 2001
From: Cory McWilliams <cory@unprompted.com>
Date: Sun, 29 Sep 2024 00:17:38 -0400
Subject: [PATCH] android: Use FileObserver, which is actually compatible with
 api level 24 which we claim to support.

---
 .../tildefriends/TildeFriendsActivity.java    | 100 +++++++-----------
 1 file changed, 40 insertions(+), 60 deletions(-)

diff --git a/src/android/com/unprompted/tildefriends/TildeFriendsActivity.java b/src/android/com/unprompted/tildefriends/TildeFriendsActivity.java
index 160a1da2..aa62cf76 100644
--- a/src/android/com/unprompted/tildefriends/TildeFriendsActivity.java
+++ b/src/android/com/unprompted/tildefriends/TildeFriendsActivity.java
@@ -11,6 +11,7 @@ import android.net.ConnectivityManager;
 import android.net.Uri;
 import android.os.Bundle;
 import android.os.Environment;
+import android.os.FileObserver;
 import android.os.IBinder;
 import android.os.Parcel;
 import android.os.ParcelFileDescriptor;
@@ -42,12 +43,6 @@ import java.io.File;
 import java.io.FileOutputStream;
 import java.io.FileReader;
 import java.io.OutputStream;
-import java.nio.file.FileSystems;
-import java.nio.file.Paths;
-import java.nio.file.StandardWatchEventKinds;
-import java.nio.file.WatchEvent;
-import java.nio.file.WatchKey;
-import java.nio.file.WatchService;
 import java.util.concurrent.TimeUnit;
 
 public class TildeFriendsActivity extends Activity {
@@ -55,9 +50,9 @@ public class TildeFriendsActivity extends Activity {
 	TildeFriendsWebView web_view;
 	String base_url;
 	String port_file_path;
-	Thread thread;
 	Thread server_thread;
 	ServiceConnection service_connection;
+	FileObserver observer;
 
 	private ValueCallback<Uri[]> upload_message;
 	private final static int FILECHOOSER_RESULT = 1;
@@ -95,57 +90,9 @@ public class TildeFriendsActivity extends Activity {
 
 		TildeFriendsActivity activity = this;
 
-		thread = new Thread(new Runnable() {
-			@Override
-			public void run() {
-				Log.w("tildefriends", "Watching for changes in: " + getFilesDir().toString());
-				try {
-					WatchService watcher = FileSystems.getDefault().newWatchService();
-					Paths.get(getFilesDir().toString()).register(
-						watcher,
-						StandardWatchEventKinds.ENTRY_CREATE,
-						StandardWatchEventKinds.ENTRY_MODIFY);
-					while (true) {
-						WatchKey key = watcher.poll(100, TimeUnit.MILLISECONDS);
-						boolean attempt_it = true;
-						if (key != null)
-						{
-							attempt_it = false;
-							for (WatchEvent event : key.pollEvents()) {
-								if (event.context().toString().equals("port.txt")) {
-									Log.w("tildefriends", "Observed file write: " + event.context().toString());
-									attempt_it = true;
-								}
-							}
-						}
-						if (attempt_it) {
-							int port = read_port(port_file_path);
-							if (port >= 0) {
-								base_url = "http://127.0.0.1:" + String.valueOf(port) + "/";
-								activity.runOnUiThread(() -> {
-									activity.hide_status();
-									web_view.loadUrl(base_url);
-								});
-								break;
-							} else {
-								activity.runOnUiThread(() -> {
-									activity.set_status("Waiting to connect...");
-								});
-							}
-						}
-						if (key != null && !key.reset()) {
-							Log.w("tildefriends", "watcher is no longer valid");
-							break;
-						}
-					}
-				} catch (java.io.IOException e) {
-					Log.w("tildefriends", "IOException: " + e.toString());
-				} catch (InterruptedException e) {
-					Log.w("tildefriends", "InterruptedException: " + e.toString());
-				}
-			}
-		});
-		thread.start();
+		Log.w("tildefriends", "Watching for changes in: " + getFilesDir().toString());
+		observer = make_file_observer(getFilesDir().toString(), port_file_path);
+		observer.startWatching();
 
 		set_status("Starting server...");
 		server_thread = new Thread(new Runnable() {
@@ -393,11 +340,14 @@ public class TildeFriendsActivity extends Activity {
 
 	private int read_port(String path) {
 		try (BufferedReader reader = new BufferedReader(new FileReader(path))) {
-			return Integer.parseInt(reader.readLine());
+			String line = reader.readLine();
+			if (line != null) {
+				return Integer.parseInt(line);
+			}
 		} catch (NumberFormatException e) {
 			e.printStackTrace();
 		} catch (java.io.FileNotFoundException e) {
-			e.printStackTrace();
+			Log.w("tildefriends", "Port file does not yet exist.");
 		} catch (java.io.IOException e) {
 			e.printStackTrace();
 		}
@@ -462,6 +412,36 @@ public class TildeFriendsActivity extends Activity {
 		}
 	}
 
+	private void check_port_file(String path) {
+		int port = read_port(port_file_path);
+		if (port >= 0) {
+			base_url = "http://127.0.0.1:" + String.valueOf(port) + "/";
+			runOnUiThread(() -> {
+				hide_status();
+				web_view.loadUrl(base_url);
+			});
+			observer = null;
+		} else {
+			runOnUiThread(() -> {
+				set_status("Waiting to connect...");
+			});
+		}
+	}
+
+	@SuppressWarnings("deprecation")
+	private FileObserver make_file_observer(String dir, String path) {
+		FileObserver file_observer = new FileObserver(dir, FileObserver.ALL_EVENTS) {
+			@Override
+			public void onEvent(int event, String file) {
+				if (observer != null) {
+					check_port_file(path);
+				}
+			}
+		};
+		check_port_file(path);
+		return file_observer;
+	}
+
 	@SuppressWarnings("deprecation")
 	private void set_database_path()
 	{