fancydialogs: Enhance dialog viewer management

Add viewer tracking and handle player join/quit/death events

plugins/fancydialogs/fd-api/src/main/java/com/fancyinnovations/fancydialogs/api/Dialog.java

@@ -2,22 +2,39 @@ package com.fancyinnovations.fancydialogs.api;
 
 import com.fancyinnovations.fancydialogs.api.data.DialogData;
 import org.bukkit.entity.Player;
+import org.jetbrains.annotations.ApiStatus;
+
+import java.util.Set;
+import java.util.UUID;
+import java.util.concurrent.ConcurrentHashMap;
 
 public abstract class Dialog {
 
     protected String id;
     protected DialogData data;
+    protected Set<UUID> viewers;
 
     public Dialog(String id, DialogData data) {
         this.id = id;
         this.data = data;
+        this.viewers = ConcurrentHashMap.newKeySet();
     }
 
     public Dialog() {
     }
 
+    /**
+     * Opens the dialog for the specified player.
+     *
+     * @param player the player to open the dialog for
+     */
     abstract public void open(Player player);
 
+    /**
+     * Closes the dialog for the specified player.
+     *
+     * @param player the player to close the dialog for
+     */
     abstract public void close(Player player);
 
     public String getId() {
@@ -27,4 +44,55 @@ public abstract class Dialog {
     public DialogData getData() {
         return data;
     }
+
+    /**
+     * @return a set of UUIDs of players who have this dialog opened
+     */
+    public Set<UUID> getViewers() {
+        return Set.copyOf(viewers);
+    }
+
+    /**
+     * Checks if the dialog is opened for a specific player by UUID.
+     *
+     * @param uuid of the player to check
+     * @return true if the dialog is opened for the player, false otherwise
+     */
+    public boolean isOpenedFor(UUID uuid) {
+        if (uuid == null) {
+            return false;
+        }
+
+        return viewers.contains(uuid);
+    }
+
+    /***
+     * Checks if the dialog is opened for a specific player.
+     *
+     * @param player the player to check
+     * @return true if the dialog is opened for the player, false otherwise
+     */
+    public boolean isOpenedFor(Player player) {
+        if (player == null) {
+            return false;
+        }
+
+        return isOpenedFor(player.getUniqueId());
+    }
+
+    @ApiStatus.Internal
+    public void addViewer(Player player) {
+        if (player == null) {
+            return;
+        }
+        viewers.add(player.getUniqueId());
+    }
+
+    @ApiStatus.Internal
+    public void removeViewer(Player player) {
+        if (player == null) {
+            return;
+        }
+        viewers.remove(player.getUniqueId());
+    }
 }