works"!!

ChatHudMixin.java

package exonihility.client.mixin;


import com.google.common.collect.Lists;
import exonihility.client.util.time.Timestamp;
import net.minecraft.client.font.TextRenderer;
import net.minecraft.client.gui.hud.ChatHud;
import net.minecraft.client.gui.hud.MessageIndicator;
import net.minecraft.client.util.ChatMessages;
import net.minecraft.client.util.TextCollector;
import net.minecraft.network.message.MessageSignatureData;
import net.minecraft.network.message.MessageType;
import net.minecraft.text.*;
import net.minecraft.util.Language;
import net.minecraft.util.collection.ArrayListDeque;
import org.spongepowered.asm.mixin.Mixin;
import org.spongepowered.asm.mixin.Unique;
import org.spongepowered.asm.mixin.injection.At;
import org.spongepowered.asm.mixin.injection.Inject;
import org.spongepowered.asm.mixin.injection.ModifyVariable;
import org.spongepowered.asm.mixin.injection.callback.CallbackInfo;
import org.spongepowered.asm.mixin.injection.callback.CallbackInfoReturnable;

import java.util.List;
import java.util.Optional;
import java.util.UUID;

@Mixin(ChatHud.class)
public abstract class ChatHudMixin {

    @ModifyVariable(method = "addMessage(Lnet/minecraft/text/Text;)V", at = @At("HEAD"), argsOnly = true)
        private Text onAddMessage(Text message) {
         return Timestamp.addToMessage(message);
        }
    @ModifyVariable(at = @At("HEAD"),
            method = "addMessage(Lnet/minecraft/text/Text;Lnet/minecraft/network/message/MessageSignatureData;Lnet/minecraft/client/gui/hud/MessageIndicator;)V",
            argsOnly = true)
    public Text addMessage(Text message) {
        return (message);
    }
    // This injects into the addMessage method of ChatHud, which handles adding messages to the chat.
    @Inject(method = "addMessage(Lnet/minecraft/text/Text;Lnet/minecraft/network/message/MessageSignatureData;Lnet/minecraft/client/gui/hud/MessageIndicator;)V", at = @At("HEAD"))
    private void onAddMessage(Text message, MessageSignatureData signatureData, MessageIndicator indicator, CallbackInfo ci) {
        if (message instanceof MutableText mutableText) {
            // Extract the main message content without player name
            String mainMessage = extractMainMessage(mutableText);

            // Create a new style with a click event to copy the main message and a hover event with instructions.
            Style style = mutableText.getStyle().withClickEvent(
                    new ClickEvent(ClickEvent.Action.COPY_TO_CLIPBOARD, mainMessage)
            ).withHoverEvent(
                    new HoverEvent(HoverEvent.Action.SHOW_TEXT, Text.literal("Click to copy this message"))
            );

            // Apply the new style to the text.
            mutableText.setStyle(style);
        }
    }

    // Helper method to extract the main message, excluding the player name
    private String extractMainMessage(MutableText mutableText) {
        String fullText = mutableText.getString(); // Get the entire message as a string

        // Regex pattern to match typical player name format <PlayerName>
        String pattern = "^<[^>]+>\\s*"; // Matches patterns like "<PlayerName> " at the start of the string

        // Replace the player name with an empty string, leaving only the message content
        return fullText.replaceFirst(pattern, "").trim();
    }

}