src/game/java/net/minecraft/server/commands/GameModeCommand.java

package net.minecraft.server.commands;

import com.mojang.brigadier.CommandDispatcher;
import com.mojang.brigadier.context.CommandContext;
import java.util.Collection;
import java.util.Collections;
import net.minecraft.commands.CommandSourceStack;
import net.minecraft.commands.Commands;
import net.minecraft.commands.arguments.EntityArgument;
import net.minecraft.commands.arguments.GameModeArgument;
import net.minecraft.network.chat.Component;
import net.minecraft.server.level.ServerPlayer;
import net.minecraft.world.level.GameRules;
import net.minecraft.world.level.GameType;

public class GameModeCommand {
    public static final int PERMISSION_LEVEL = 2;

    public static void register(CommandDispatcher<CommandSourceStack> p_137730_) {
        p_137730_.register(
            Commands.literal("gamemode")
                .requires(p_137736_ -> p_137736_.hasPermission(2))
                .then(
                    Commands.argument("gamemode", GameModeArgument.gameMode())
                        .executes(
                            p_258228_ -> setMode(
                                    p_258228_, Collections.singleton(p_258228_.getSource().getPlayerOrException()), GameModeArgument.getGameMode(p_258228_, "gamemode")
                                )
                        )
                        .then(
                            Commands.argument("target", EntityArgument.players())
                                .executes(
                                    p_258229_ -> setMode(
                                            p_258229_, EntityArgument.getPlayers(p_258229_, "target"), GameModeArgument.getGameMode(p_258229_, "gamemode")
                                        )
                                )
                        )
                )
        );
    }

    private static void logGamemodeChange(CommandSourceStack p_137738_, ServerPlayer p_137739_, GameType p_137740_) {
        Component component = Component.translatable("gameMode." + p_137740_.getName());
        if (p_137738_.getEntity() == p_137739_) {
            p_137738_.sendSuccess(() -> Component.translatable("commands.gamemode.success.self", component), true);
        } else {
            if (p_137738_.getLevel().getGameRules().getBoolean(GameRules.RULE_SENDCOMMANDFEEDBACK)) {
                p_137739_.sendSystemMessage(Component.translatable("gameMode.changed", component));
            }

            p_137738_.sendSuccess(() -> Component.translatable("commands.gamemode.success.other", p_137739_.getDisplayName(), component), true);
        }
    }

    private static int setMode(CommandContext<CommandSourceStack> p_137732_, Collection<ServerPlayer> p_137733_, GameType p_137734_) {
        int i = 0;

        for (ServerPlayer serverplayer : p_137733_) {
            if (serverplayer.setGameMode(p_137734_)) {
                logGamemodeChange(p_137732_.getSource(), serverplayer, p_137734_);
                i++;
            }
        }

        return i;
    }
}