AsyncTabCompleteEvent

Let plugins be able to control tab completion of commands and chat async.

This will be useful for frameworks like ACF so we can define async safe completion handlers,
and avoid going to main for tab completions.

Especially useful if you need to query a database in order to obtain the results for tab
completion, such as offline players.

Also adds isCommand and getLocation to the sync TabCompleteEvent

Co-authored-by: Aikar <aikar@aikar.co>

paper-server/src/main/java/org/bukkit/craftbukkit/CraftServer.java

@@ -2297,7 +2297,7 @@ public final class CraftServer implements Server {
             offers = this.tabCompleteChat(player, message);
         }
 
-        TabCompleteEvent tabEvent = new TabCompleteEvent(player, message, offers);
+        TabCompleteEvent tabEvent = new TabCompleteEvent(player, message, offers, message.startsWith("/") || forceCommand, pos != null ? io.papermc.paper.util.MCUtil.toLocation(((CraftWorld) player.getWorld()).getHandle(), BlockPos.containing(pos)) : null); // Paper - AsyncTabCompleteEvent
         this.getPluginManager().callEvent(tabEvent);
 
         return tabEvent.isCancelled() ? Collections.EMPTY_LIST : tabEvent.getCompletions();

paper-server/src/main/java/org/bukkit/craftbukkit/command/ConsoleCommandCompleter.java

@@ -28,6 +28,61 @@ public class ConsoleCommandCompleter implements Completer {
     public void complete(LineReader reader, ParsedLine line, List<Candidate> candidates) {
         final CraftServer server = this.server.server;
         final String buffer = "/" + line.line();
+        // Async Tab Complete
+        final com.destroystokyo.paper.event.server.AsyncTabCompleteEvent event =
+            new com.destroystokyo.paper.event.server.AsyncTabCompleteEvent(server.getConsoleSender(), buffer, true, null);
+        event.callEvent();
+        final List<com.destroystokyo.paper.event.server.AsyncTabCompleteEvent.Completion> completions = event.isCancelled() ? com.google.common.collect.ImmutableList.of() : event.completions();
+
+        if (event.isCancelled() || event.isHandled()) {
+            // Still fire sync event with the provided completions, if someone is listening
+            if (!event.isCancelled() && TabCompleteEvent.getHandlerList().getRegisteredListeners().length > 0) {
+                List<com.destroystokyo.paper.event.server.AsyncTabCompleteEvent.Completion> finalCompletions = new java.util.ArrayList<>(completions);
+                Waitable<List<String>> syncCompletions = new Waitable<List<String>>() {
+                    @Override
+                    protected List<String> evaluate() {
+                        org.bukkit.event.server.TabCompleteEvent syncEvent = new org.bukkit.event.server.TabCompleteEvent(server.getConsoleSender(), buffer,
+                            finalCompletions.stream()
+                                .map(com.destroystokyo.paper.event.server.AsyncTabCompleteEvent.Completion::suggestion)
+                                .collect(java.util.stream.Collectors.toList()));
+                        return syncEvent.callEvent() ? syncEvent.getCompletions() : com.google.common.collect.ImmutableList.of();
+                    }
+                };
+                server.getServer().processQueue.add(syncCompletions);
+                try {
+                    final List<String> legacyCompletions = syncCompletions.get();
+                    completions.removeIf(it -> !legacyCompletions.contains(it.suggestion())); // remove any suggestions that were removed
+                    // add any new suggestions
+                    for (final String completion : legacyCompletions) {
+                        if (notNewSuggestion(completions, completion)) {
+                            continue;
+                        }
+                        completions.add(com.destroystokyo.paper.event.server.AsyncTabCompleteEvent.Completion.completion(completion));
+                    }
+                } catch (InterruptedException | ExecutionException e1) {
+                    e1.printStackTrace();
+                }
+            }
+
+            if (!completions.isEmpty()) {
+                for (final com.destroystokyo.paper.event.server.AsyncTabCompleteEvent.Completion completion : completions) {
+                    if (completion.suggestion().isEmpty()) {
+                        continue;
+                    }
+                    candidates.add(new Candidate(
+                        completion.suggestion(),
+                        completion.suggestion(),
+                        null,
+                        io.papermc.paper.adventure.PaperAdventure.PLAIN.serializeOr(completion.tooltip(), null),
+                        null,
+                        null,
+                        false
+                    ));
+                }
+            }
+            return;
+        }
+
         // Paper end
         Waitable<List<String>> waitable = new Waitable<List<String>>() {
             @Override
@@ -73,4 +128,15 @@ public class ConsoleCommandCompleter implements Completer {
             Thread.currentThread().interrupt();
         }
     }
+
+    // Paper start
+    private boolean notNewSuggestion(final List<com.destroystokyo.paper.event.server.AsyncTabCompleteEvent.Completion> completions, final String completion) {
+        for (final com.destroystokyo.paper.event.server.AsyncTabCompleteEvent.Completion it : completions) {
+            if (it.suggestion().equals(completion)) {
+                return true;
+            }
+        }
+        return false;
+    }
+    // Paper end
 }