Add tab completion to Geyser standalone

bootstrap/standalone/src/main/java/org/geysermc/geyser/platform/standalone/GeyserStandaloneLogger.java

@@ -33,10 +33,24 @@ import org.geysermc.geyser.GeyserImpl;
 import org.geysermc.geyser.GeyserLogger;
 import org.geysermc.geyser.command.GeyserCommandSource;
 import org.geysermc.geyser.text.ChatColor;
+import org.jline.reader.Candidate;
+import org.jline.reader.LineReader;
+import org.jline.reader.LineReaderBuilder;
 
 @Slf4j
 public class GeyserStandaloneLogger extends SimpleTerminalConsole implements GeyserLogger, GeyserCommandSource {
 
+    @Override
+    protected LineReader buildReader(LineReaderBuilder builder) {
+        builder.completer((reader, line, candidates) -> {
+            var suggestions = GeyserImpl.getInstance().commandRegistry().suggestionsFor(this, line.line());
+            for (var suggestion : suggestions.list()) {
+                candidates.add(new Candidate(suggestion.suggestion()));
+            }
+        });
+        return super.buildReader(builder);
+    }
+
     @Override
     protected boolean isRunning() {
         return !GeyserImpl.getInstance().isShuttingDown();

core/src/main/java/org/geysermc/geyser/command/CommandRegistry.java

@@ -68,6 +68,8 @@ import org.incendo.cloud.parser.standard.EnumParser;
 import org.incendo.cloud.parser.standard.IntegerParser;
 import org.incendo.cloud.parser.standard.LiteralParser;
 import org.incendo.cloud.parser.standard.StringArrayParser;
+import org.incendo.cloud.suggestion.Suggestion;
+import org.incendo.cloud.suggestion.Suggestions;
 
 import java.util.ArrayList;
 import java.util.Collection;
@@ -320,6 +322,10 @@ public class CommandRegistry implements EventRegistrar {
         cloud.commandExecutor().executeCommand(source, command);
     }
 
+    public Suggestions<GeyserCommandSource, ? extends Suggestion> suggestionsFor(GeyserCommandSource source, String input) {
+        return cloud.suggestionFactory().suggestImmediately(source, input);
+    }
+
     public void export(GeyserSession session, List<CommandData> bedrockCommands, Set<String> knownAliases) {
         cloud.commandTree().rootNodes().forEach(commandTree -> {
             var command = commandTree.command();