LibChess: Add the ucinewgame command

This command is sent from the GUI to tell the engine that the next
position will be from a different game.

Userland/Libraries/LibChess/UCICommand.cpp

@@ -348,4 +348,17 @@ ErrorOr<String> QuitCommand::to_string() const
     return "quit\n"_short_string;
 }
 
+ErrorOr<NonnullOwnPtr<UCINewGameCommand>> UCINewGameCommand::from_string(StringView command)
+{
+    auto tokens = command.split_view(' ');
+    VERIFY(tokens[0] == "ucinewgame");
+    VERIFY(tokens.size() == 1);
+    return adopt_nonnull_own_or_enomem(new (nothrow) UCINewGameCommand);
+}
+
+ErrorOr<String> UCINewGameCommand::to_string() const
+{
+    return "ucinewgame\n"_string;
+}
+
 }

Userland/Libraries/LibChess/UCICommand.h

@@ -281,4 +281,16 @@ public:
     virtual ErrorOr<String> to_string() const override;
 };
 
+class UCINewGameCommand : public Command {
+public:
+    explicit UCINewGameCommand()
+        : Command(Command::Type::UCINewGame)
+    {
+    }
+
+    static ErrorOr<NonnullOwnPtr<UCINewGameCommand>> from_string(StringView command);
+
+    virtual ErrorOr<String> to_string() const override;
+};
+
 }

Userland/Libraries/LibChess/UCIEndpoint.cpp

@@ -56,6 +56,8 @@ void Endpoint::event(Core::Event& event)
         return handle_info(static_cast<InfoCommand const&>(event));
     case Command::Type::Quit:
         return handle_quit();
+    case Command::Type::UCINewGame:
+        return handle_ucinewgame();
     default:
         Object::event(event);
         break;
@@ -115,6 +117,8 @@ NonnullOwnPtr<Command> Endpoint::read_command()
         return InfoCommand::from_string(line).release_value_but_fixme_should_propagate_errors();
     } else if (line.starts_with("quit"sv)) {
         return QuitCommand::from_string(line).release_value_but_fixme_should_propagate_errors();
+    } else if (line.starts_with("ucinewgame"sv)) {
+        return UCINewGameCommand::from_string(line).release_value_but_fixme_should_propagate_errors();
     }
 
     dbgln("command line: {}", line);

Userland/Libraries/LibChess/UCIEndpoint.h

@@ -31,6 +31,7 @@ public:
     virtual void handle_bestmove(BestMoveCommand const&) { }
     virtual void handle_info(InfoCommand const&) { }
     virtual void handle_quit() { }
+    virtual void handle_ucinewgame() { }
     virtual void handle_unexpected_eof() { }
 
     void send_command(Command const&);