Improve action bar loading bar for server start

VelocityCore/Persistent/src/de/steamwar/persistent/Subserver.java

@@ -22,6 +22,7 @@ package de.steamwar.persistent;
 import com.velocitypowered.api.proxy.Player;
 import com.velocitypowered.api.proxy.server.RegisteredServer;
 import com.velocitypowered.api.proxy.server.ServerInfo;
+import com.velocitypowered.api.scheduler.ScheduledTask;
 import lombok.Getter;
 import net.kyori.adventure.text.Component;
 import net.kyori.adventure.text.format.NamedTextColor;
@@ -32,7 +33,10 @@ import java.util.HashMap;
 import java.util.LinkedList;
 import java.util.List;
 import java.util.Map;
+import java.util.concurrent.CopyOnWriteArrayList;
 import java.util.concurrent.TimeUnit;
+import java.util.regex.Matcher;
+import java.util.regex.Pattern;
 import java.util.function.Consumer;
 import java.util.function.Predicate;
 import java.util.logging.Level;
@@ -98,7 +102,13 @@ public class Subserver {
     @Getter
     private boolean started;
 
-    private final List<Player> cachedPlayers = new LinkedList<>();
+    private static final int MAX_PROGRESS = 10;
+    private static final Pattern PLUGIN_COUNT = Pattern.compile("Bukkit plugins \\((\\d+)\\)");
+
+    private final List<Player> cachedPlayers = new CopyOnWriteArrayList<>();
+    private volatile int progress = 0;
+    private int pluginCount = 0;
+    private int enabledPlugins = 0;
     @Getter
     private final Map<Player, String> tablistNames = new HashMap<>();
 
@@ -127,7 +137,7 @@ public class Subserver {
 
     public void sendPlayer(Player p) {
         if (!started) {
-            p.sendActionBar(generateBar(0));
+            p.sendActionBar(generateBar(progress));
             cachedPlayers.add(p);
         } else {
             p.createConnectionRequest(registeredServer).connect();
@@ -245,32 +255,33 @@ public class Subserver {
 
     private void run() {
         Exception ex = null;
+        try {
+            ScheduledTask refresh = Persistent.getInstance().getProxy().getScheduler()
+                    .buildTask(Persistent.getInstance(), () -> sendProgress(progress))
+                    .repeat(2, TimeUnit.SECONDS).schedule();
+
             try {
                 if (checkpoint) {
                     start(process.getErrorStream(), line -> line.contains("Restore finished successfully."));
                     start(process.getInputStream(), line -> line.contains("Checkpoint restored"));
                     Thread.sleep(100);
                 } else {
-                sendProgress(0);
                     start(process.getInputStream(), line -> {
-                    if (line.contains("Loading libraries, please wait")) {
-                        sendProgress(2);
-                    } else if (line.contains("Starting Minecraft server on")) {
-                        sendProgress(5);
-                    } else if (line.contains("Preparing start region")) {
-                        sendProgress(8);
-                    }
+                        updateProgress(line);
                         return line.contains("Done (");
                     });
                 }
 
                 if (!started) return;
 
-            sendProgress(10);
+                setProgress(MAX_PROGRESS);
                 for (Player cachedPlayer : cachedPlayers) {
                     sendPlayer(cachedPlayer);
                 }
                 cachedPlayers.clear();
+            } finally {
+                refresh.cancel();
+            }
 
             process.waitFor();
         } catch (IOException e) {
@@ -285,6 +296,39 @@ public class Subserver {
         }
     }
 
+    private void updateProgress(String line) {
+        if (line.startsWith("Loading Paper")) {
+            setProgress(1);
+        } else if (line.startsWith("Bukkit plugins (")) {
+            Matcher matcher = PLUGIN_COUNT.matcher(line);
+            if (matcher.find()) pluginCount = Integer.parseInt(matcher.group(1));
+        } else if (line.startsWith("Starting minecraft server version")) {
+            setProgress(2);
+        } else if (line.contains("Starting Minecraft server on")) {
+            setProgress(3);
+        } else if (line.contains("libraries... please wait")) {
+            setProgress(4);
+        } else if (line.startsWith("Loading server plugin")) {
+            setProgress(5);
+        } else if (line.startsWith("Preparing level")) {
+            setProgress(6);
+        } else if (line.startsWith("Preparing start region")) {
+            setProgress(7);
+        } else if (line.startsWith("Enabling ")) {
+            enabledPlugins++;
+            // 7 -> 9 over all plugins, 9 is reached with the last plugin
+            setProgress(7 + (pluginCount > 0 ? Math.min(2, 2 * enabledPlugins / pluginCount) : 0));
+        } else if (line.startsWith("Done preparing level")) {
+            setProgress(9);
+        }
+    }
+
+    private void setProgress(int newProgress) {
+        if (newProgress <= progress) return;
+        progress = newProgress;
+        sendProgress(newProgress);
+    }
+
     private Component generateBar(int progress) {
         return Component.text("⬛".repeat(Math.max(0, progress))).color(NamedTextColor.YELLOW)
                 .append(Component.text("⬛".repeat(Math.max(0, 10 - progress))).color(NamedTextColor.DARK_GRAY));