Add CommandExecuteEvent

api/src/main/java/com/velocitypowered/api/command/CommandManager.java

@@ -35,10 +35,21 @@ public interface CommandManager {
 
   /**
    * Attempts to execute a command from the specified {@code cmdLine}.
+   * CommandExecuteEvent will not called
    *
    * @param source the command's source
    * @param cmdLine the command to run
    * @return true if the command was found and executed, false if it was not
    */
   boolean execute(CommandSource source, String cmdLine);
+
+  /**
+   * Attempts to execute a command from the specified {@code cmdLine}.
+   *
+   * @param source the command's source
+   * @param cmdLine the command to run
+   * @param callEvent will CommandExecuteEvent called or not
+   * @return true if the command was found and executed, false if it was not
+   */
+  boolean execute(CommandSource source, String cmdLine, boolean callEvent);
 }

api/src/main/java/com/velocitypowered/api/event/command/CommandExecuteEvent.java

@@ -0,0 +1,143 @@
+package com.velocitypowered.api.event.command;
+
+import com.google.common.base.Preconditions;
+import com.velocitypowered.api.command.CommandSource;
+import com.velocitypowered.api.event.ResultedEvent;
+import com.velocitypowered.api.event.command.CommandExecuteEvent.CommandResult;
+import java.util.Optional;
+import org.checkerframework.checker.nullness.qual.NonNull;
+import org.checkerframework.checker.nullness.qual.Nullable;
+
+/**
+ * This event is fired when a player types in a chat message.
+ */
+public final class CommandExecuteEvent implements ResultedEvent<CommandResult> {
+
+  private final CommandSource commandSource;
+  private final String command;
+  private CommandResult result;
+
+  /**
+   * Constructs a PlayerChatEvent.
+   * @param commandSource the source executing the command
+   * @param command the command being executed without first slash
+   */
+  public CommandExecuteEvent(CommandSource commandSource, String command) {
+    this.commandSource = Preconditions.checkNotNull(commandSource, "commandSource");
+    this.command = Preconditions.checkNotNull(command, "command");
+    this.result = CommandResult.allowed();
+  }
+
+  public CommandSource getCommandSource() {
+    return commandSource;
+  }
+
+  /**
+   * Gets the original command being executed without first slash.
+   * @return the original command being executed
+   */
+  public String getCommand() {
+    return command;
+  }
+
+  @Override
+  public CommandResult getResult() {
+    return result;
+  }
+
+  @Override
+  public void setResult(CommandResult result) {
+    this.result = Preconditions.checkNotNull(result, "result");
+  }
+
+  @Override
+  public String toString() {
+    return "PlayerCommmandEvent{"
+        + "commandSource=" + commandSource
+        + ", command=" + command
+        + ", result=" + result
+        + '}';
+  }
+
+  /**
+   * Represents the result of the {@link CommandExecuteEvent}.
+   */
+  public static final class CommandResult implements Result {
+
+    private static final CommandResult ALLOWED = new CommandResult(true, false,null);
+    private static final CommandResult DENIED = new CommandResult(false, false,null);
+    private static final CommandResult FORWARD_TO_SERVER = new CommandResult(false, true, null);
+
+    private @Nullable String command;
+    private final boolean status;
+    private final boolean forward;
+
+    private CommandResult(boolean status, boolean forward, @Nullable String command) {
+      this.status = status;
+      this.forward = forward;
+      this.command = command;
+    }
+
+    public Optional<String> getCommand() {
+      return Optional.ofNullable(command);
+    }
+
+    public boolean isForwardToServer() {
+      return forward;
+    }
+
+    @Override
+    public boolean isAllowed() {
+      return status;
+    }
+
+    @Override
+    public String toString() {
+      return status ? "allowed" : "denied";
+    }
+
+    /**
+     * Allows the command to be sent, without modification.
+     * @return the allowed result
+     */
+    public static CommandResult allowed() {
+      return ALLOWED;
+    }
+
+    /**
+     * Prevents the command from being executed.
+     * @return the denied result
+     */
+    public static CommandResult denied() {
+      return DENIED;
+    }
+
+    /**
+     * Prevents the command from being executed, but forward command to server.
+     * @return the forward result
+     */
+    public static CommandResult forwardToServer() {
+      return FORWARD_TO_SERVER;
+    }
+
+    /**
+     * Prevents the command from being executed on proxy, but forward command to server.
+     * @param newCommand the command without first slash to use instead
+     * @return a result with a new command being forwarded to server
+     */
+    public static CommandResult forwardToServer(@NonNull String newCommand) {
+      Preconditions.checkNotNull(newCommand, "newCommand");
+      return new CommandResult(false, true, newCommand);
+    }
+
+    /**
+     * Allows the command to be executed, but silently replaced old command with another.
+     * @param newCommand the command to use instead without first slash
+     * @return a result with a new command
+     */
+    public static CommandResult command(@NonNull String newCommand) {
+      Preconditions.checkNotNull(newCommand, "newCommand");
+      return new CommandResult(true, false, newCommand);
+    }
+  }
+}

api/src/main/java/com/velocitypowered/api/event/player/PlayerChatEvent.java

@@ -70,6 +70,10 @@ public final class PlayerChatEvent implements ResultedEvent<PlayerChatEvent.Chat
       this.message = message;
     }
 
+    public Optional<String> getMessage() {
+      return Optional.ofNullable(message);
+    }
+
     @Override
     public boolean isAllowed() {
       return status;
@@ -96,10 +100,6 @@ public final class PlayerChatEvent implements ResultedEvent<PlayerChatEvent.Chat
       return DENIED;
     }
 
-    public Optional<String> getMessage() {
-      return Optional.ofNullable(message);
-    }
-
     /**
      * Allows the message to be sent, but silently replaced with another.
      * @param message the message to use instead
@@ -110,6 +110,4 @@ public final class PlayerChatEvent implements ResultedEvent<PlayerChatEvent.Chat
       return new ChatResult(true, message);
     }
   }
-
-
 }

proxy/src/main/java/com/velocitypowered/proxy/VelocityServer.java

@@ -95,7 +95,7 @@ public class VelocityServer implements ProxyServer {
   private @MonotonicNonNull VelocityConfiguration configuration;
   private @MonotonicNonNull KeyPair serverKeyPair;
   private final ServerMap servers;
-  private final VelocityCommandManager commandManager = new VelocityCommandManager();
+  private final VelocityCommandManager commandManager;
   private final AtomicBoolean shutdownInProgress = new AtomicBoolean(false);
   private boolean shutdown = false;
   private final VelocityPluginManager pluginManager;
@@ -111,6 +111,7 @@ public class VelocityServer implements ProxyServer {
   VelocityServer(final ProxyOptions options) {
     pluginManager = new VelocityPluginManager(this);
     eventManager = new VelocityEventManager(pluginManager);
+    commandManager = new VelocityCommandManager(eventManager);
     scheduler = new VelocityScheduler(pluginManager);
     console = new VelocityConsole(this);
     cm = new ConnectionManager(this);

proxy/src/main/java/com/velocitypowered/proxy/command/VelocityCommandManager.java

@@ -7,16 +7,26 @@ import com.velocitypowered.api.command.Command;
 import com.velocitypowered.api.command.CommandManager;
 import com.velocitypowered.api.command.CommandSource;
 import com.velocitypowered.api.command.RawCommand;
+import com.velocitypowered.api.event.EventManager;
+import com.velocitypowered.api.event.command.CommandExecuteEvent;
+import com.velocitypowered.api.event.command.CommandExecuteEvent.CommandResult;
+
 import java.util.Arrays;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Locale;
 import java.util.Map;
 import java.util.Set;
+import java.util.concurrent.CompletableFuture;
 
 public class VelocityCommandManager implements CommandManager {
 
   private final Map<String, RawCommand> commands = new HashMap<>();
+  private final EventManager eventManager;
+
+  public VelocityCommandManager(EventManager eventManager) {
+    this.eventManager = eventManager;
+  }
 
   @Override
   @Deprecated
@@ -47,11 +57,39 @@ public class VelocityCommandManager implements CommandManager {
     this.commands.remove(alias.toLowerCase(Locale.ENGLISH));
   }
 
+  /**
+   * Calls CommandExecuteEvent.
+   * @param source the command's source
+   * @param cmd the command
+   * @return CompletableFuture of event
+   */
+  public CompletableFuture<CommandExecuteEvent> callCommandEvent(CommandSource source, String cmd) {
+    Preconditions.checkNotNull(source, "invoker");
+    Preconditions.checkNotNull(cmd, "cmd");
+    return eventManager.fire(new CommandExecuteEvent(source, cmd));
+  }
+
   @Override
   public boolean execute(CommandSource source, String cmdLine) {
     Preconditions.checkNotNull(source, "invoker");
     Preconditions.checkNotNull(cmdLine, "cmdLine");
 
+    return execute(source, cmdLine, false);
+  }
+
+  @Override
+  public boolean execute(CommandSource source, String cmdLine, boolean callEvent) {
+    Preconditions.checkNotNull(source, "invoker");
+    Preconditions.checkNotNull(cmdLine, "cmdLine");
+
+    if (callEvent) {
+      CommandExecuteEvent event = callCommandEvent(source, cmdLine).join();
+      CommandResult commandResult = event.getResult();
+      if (commandResult.isForwardToServer() || !commandResult.isAllowed()) {
+        return false;
+      }
+      cmdLine = commandResult.getCommand().orElse(event.getCommand());
+    }
     String alias = cmdLine;
     String args = "";
     int firstSpace = cmdLine.indexOf(' ');

proxy/src/main/java/com/velocitypowered/proxy/connection/client/ClientPlaySessionHandler.java

@@ -4,6 +4,7 @@ import static com.velocitypowered.api.network.ProtocolVersion.MINECRAFT_1_13;
 import static com.velocitypowered.api.network.ProtocolVersion.MINECRAFT_1_8;
 import static com.velocitypowered.proxy.protocol.util.PluginMessageUtil.constructChannelsPacket;
 
+import com.velocitypowered.api.event.command.CommandExecuteEvent;
 import com.velocitypowered.api.event.connection.PluginMessageEvent;
 import com.velocitypowered.api.event.player.PlayerChatEvent;
 import com.velocitypowered.api.event.player.PlayerResourcePackStatusEvent;
@@ -123,17 +124,32 @@ public class ClientPlaySessionHandler implements MinecraftSessionHandler {
 
     String msg = packet.getMessage();
     if (msg.startsWith("/")) {
-      try {
-        if (!server.getCommandManager().execute(player, msg.substring(1))) {
-          return false;
-        }
-      } catch (Exception e) {
-        logger.info("Exception occurred while running command for {}", player.getUsername(),
-                e);
-        player.sendMessage(
-            TextComponent.of("An error occurred while running this command.", TextColor.RED));
-        return true;
-      }
+
+      server.getCommandManager().callCommandEvent(player, msg.substring(1))
+          .thenAcceptAsync(event -> {
+            CommandExecuteEvent.CommandResult commandResult = event.getResult();
+            if (commandResult.isAllowed()) {
+              Optional<String> eventCommand = event.getResult().getCommand();
+              String command = eventCommand.orElse(event.getCommand());
+
+              if (commandResult.isForwardToServer()) {
+                smc.write(Chat.createServerbound(command));
+                return;
+              }
+
+              try {
+                if (!server.getCommandManager().execute(player, command)) {
+                  smc.write(Chat.createServerbound(command));
+                }
+              } catch (Exception e) {
+                logger.info("Exception occurred while running command for {}", player.getUsername(),
+                    e);
+                player.sendMessage(
+                    TextComponent.of("An error occurred while running this command.",
+                        TextColor.RED));
+              }
+            }
+          });
     } else {
       PlayerChatEvent event = new PlayerChatEvent(player, msg);
       server.getEventManager().fire(event)

proxy/src/main/java/com/velocitypowered/proxy/console/VelocityConsole.java

@@ -91,7 +91,7 @@ public final class VelocityConsole extends SimpleTerminalConsole implements Cons
   @Override
   protected void runCommand(String command) {
     try {
-      if (!this.server.getCommandManager().execute(this, command)) {
+      if (!this.server.getCommandManager().execute(this, command, true)) {
         sendMessage(TextComponent.of("Command not found.", TextColor.RED));
       }
     } catch (Exception e) {