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

package net.minecraft.server.commands;

import com.mojang.brigadier.CommandDispatcher;
import com.mojang.brigadier.builder.LiteralArgumentBuilder;
import com.mojang.brigadier.context.CommandContext;
import com.mojang.brigadier.exceptions.CommandSyntaxException;
import com.mojang.brigadier.exceptions.DynamicCommandExceptionType;
import net.minecraft.commands.CommandSourceStack;
import net.minecraft.commands.Commands;
import net.minecraft.network.chat.Component;
import net.minecraft.server.MinecraftServer;
import net.minecraft.world.Difficulty;

public class DifficultyCommand {
    private static final DynamicCommandExceptionType ERROR_ALREADY_DIFFICULT = new DynamicCommandExceptionType(
        p_308648_ -> Component.translatableEscape("commands.difficulty.failure", p_308648_)
    );

    public static void register(CommandDispatcher<CommandSourceStack> p_136939_) {
        LiteralArgumentBuilder<CommandSourceStack> literalargumentbuilder = Commands.literal("difficulty");

        for (Difficulty difficulty : Difficulty.values()) {
            literalargumentbuilder.then(Commands.literal(difficulty.getKey()).executes(p_136937_ -> setDifficulty(p_136937_.getSource(), difficulty)));
        }

        p_136939_.register(literalargumentbuilder.requires(p_136943_ -> p_136943_.hasPermission(2)).executes(p_374871_ -> {
            Difficulty difficulty1 = p_374871_.getSource().getLevel().getDifficulty();
            p_374871_.getSource().sendSuccess(() -> Component.translatable("commands.difficulty.query", difficulty1.getDisplayName()), false);
            return difficulty1.getId();
        }));
    }

    public static int setDifficulty(CommandSourceStack p_136945_, Difficulty p_136946_) throws CommandSyntaxException {
        MinecraftServer minecraftserver = p_136945_.getServer();
        if (minecraftserver.getWorldData().getDifficulty() == p_136946_) {
            throw ERROR_ALREADY_DIFFICULT.create(p_136946_.getKey());
        } else {
            minecraftserver.setDifficulty(p_136946_, true);
            p_136945_.sendSuccess(() -> Component.translatable("commands.difficulty.success", p_136946_.getDisplayName()), true);
            return 0;
        }
    }
}