Simple GiveawayBot using JDA

GiveawayBot.java

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package giveawaybot;

import java.io.File;
import java.util.LinkedList;
import java.util.List;
import javax.security.auth.login.LoginException;
import net.dv8tion.jda.core.AccountType;
import net.dv8tion.jda.core.JDABuilder;
import net.dv8tion.jda.core.Permission;
import net.dv8tion.jda.core.entities.Icon;
import net.dv8tion.jda.core.entities.Message;
import net.dv8tion.jda.core.entities.User;
import net.dv8tion.jda.core.events.message.guild.GuildMessageReceivedEvent;
import net.dv8tion.jda.core.exceptions.RateLimitedException;
import net.dv8tion.jda.core.hooks.ListenerAdapter;
import net.dv8tion.jda.core.utils.PermissionUtil;

/**
 *
 * @author John Grosh (john.a.grosh@gmail.com)
 */
public class GiveawayBot extends ListenerAdapter {

    
    
    @Override
    public void onGuildMessageReceived(GuildMessageReceivedEvent event) {
        if(event.getMessage().getRawContent().equals("!ghelp"))
        {
            event.getChannel().sendMessage("<:yay:294906617378504704> GiveawayBot help: <:yay:294906617378504704>\n"
                    + "`!ghelp` - this message\n"
                    + "`!gstart <seconds> [item]` - starts a giveway. Ex: `!gstart 180` for a 3 minute giveaway\n"
                    + "`!greroll <messageid>` - rerolls a winner for the giveaway on the provided message\n\n"
                    + "Commands require Manage Server permission to use\n"
                    + "Don't include <> nor []; <> means required, [] means optional").queue();
        }
        else if(event.getMessage().getRawContent().startsWith("!gstart"))
        {
            if(!PermissionUtil.checkPermission(event.getGuild(), event.getMember(), Permission.MANAGE_SERVER))
            {
                event.getChannel().sendMessage("You must have Manage Server perms to use this!").queue();
                return;
            }
            String str = event.getMessage().getRawContent().substring(7).trim();
            String[] parts = str.split("\\s+",2);
            try{
                int sec = Integer.parseInt(parts[0]);
                event.getChannel().sendMessage("<:yay:294906617378504704>  **GIVEAWAY!**  <:yay:294906617378504704>\n"+(parts.length>1 ? "\u25AB*`"+parts[1]+"`*\u25AB\n" : "")+"React with \uD83C\uDF89 to enter!").queue(m -> {
                    m.addReaction("\uD83C\uDF89").queue();
                    new Giveaway(sec,m,parts.length>1 ? parts[1] : null).start();
                });
                event.getMessage().delete().queue();
            } catch(NumberFormatException ex)
            {
                event.getChannel().sendMessage("Could not parse seconds from `"+parts[0]+"`").queue();
            }
        }
        else if(event.getMessage().getRawContent().startsWith("!greroll"))
        {
            if(!PermissionUtil.checkPermission(event.getGuild(), event.getMember(), Permission.MANAGE_SERVER))
            {
                event.getChannel().sendMessage("You must have Manage Server perms to use this!").queue();
                return;
            }
            String id = event.getMessage().getRawContent().substring(8).trim();
            if(!id.matches("\\d{17,22}"))
            {
                event.getChannel().sendMessage("Invalid message id").queue();
                return;
            }
            Message m = event.getChannel().getMessageById(id).complete();
            if(m==null)
            {
                event.getChannel().sendMessage("Message not found!").queue();
                return;
            }
            m.getReactions()
                .stream().filter(mr -> mr.getEmote().getName().equals("\uD83C\uDF89"))
                .findAny().ifPresent(mr -> {
                    List<User> users = new LinkedList<>(mr.getUsers().complete());
                    users.remove(m.getJDA().getSelfUser());
                    String uid = users.get((int)(Math.random()*users.size())).getId();
                    event.getChannel().sendMessage("Congratulations to <@"+uid+">! You won the reroll!").queue();
                });
        }
        else if(event.getAuthor().getId().equals("OWNERID"))
        {
            if(event.getMessage().getRawContent().startsWith("!say"))
                event.getChannel().sendMessage(event.getMessage().getRawContent().substring(4).trim()).queue();
            else if(event.getMessage().getRawContent().startsWith("!ava"))
            {
                String loc = event.getMessage().getRawContent().substring(4).trim();
                try{
                    event.getJDA().getSelfUser().getManager().setAvatar(Icon.from(new File(loc))).complete();
                    event.getChannel().sendMessage("Updated!").queue();
                }catch(Exception ex){
                    event.getChannel().sendMessage("Error: "+ex).queue();
                }
            }
        }
    }
    
    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) throws LoginException, IllegalArgumentException, RateLimitedException {
        new JDABuilder(AccountType.BOT).setToken("REDACTED")
                .addListener(new GiveawayBot())
                .buildAsync();
    }
    
    public class Giveaway {
        
        int seconds;
        Message message;
        String item;
        public Giveaway(int time, Message message, String item)
        {
            seconds = time;
            this.message = message;
            this.item = item;
        }
        
        public void start()
        {
            new Thread(){
                @Override
                public void run() {
                    while(seconds>5)
                    {
                        message.editMessage("<:yay:294906617378504704>  **GIVEAWAY!**  <:yay:294906617378504704>\n"+(item!=null ? "\u25AB*`"+item+"`*\u25AB\n" : "")+"React with \uD83C\uDF89 to enter!\nTime remaining: "+secondsToTime(seconds)).queue();
                        seconds-=5;
                        try{Thread.sleep(5000);}catch(Exception e){}
                    }
                    while(seconds>0)
                    {
                        message.editMessage("<:yay:294906617378504704> **G I V E A W A Y!** <:yay:294906617378504704>\nLAST CHANCE TO ENTER!!!\n"+(item!=null ? "\u25AB*`"+item+"`*\u25AB\n" : "")+"React with \uD83C\uDF89 to enter!\nTime remaining: "+secondsToTime(seconds)).queue();
                        seconds--;
                        try{Thread.sleep(1000);}catch(Exception e){}
                    }
                    message.getChannel().getMessageById(message.getId()).complete().getReactions()
                            .stream().filter(mr -> mr.getEmote().getName().equals("\uD83C\uDF89"))
                            .findAny().ifPresent(mr -> {
                                List<User> users = new LinkedList<>(mr.getUsers().complete());
                                users.remove(message.getJDA().getSelfUser());
                                String id = users.get((int)(Math.random()*users.size())).getId();
                                message.editMessage("<:yay:294906617378504704> **GIVEAWAY ENDED!** <:yay:294906617378504704>\n"+(item!=null ? "\u25AB*`"+item+"`*\u25AB\n" : "")+"\nWinner: <@"+id+"> \uD83C\uDF89").queue();
                                message.getChannel().sendMessage("Congratulations to <@"+id+">! You won"+(item==null ? "" : " the "+item)+"!").queue();
                            });
                }
            }.start();
        }
    }
    
    public static String secondsToTime(long timeseconds)
    {
        StringBuilder builder = new StringBuilder();
        int years = (int)(timeseconds / (60*60*24*365));
        if(years>0)
        {
            builder.append("**").append(years).append("** years, ");
            timeseconds = timeseconds % (60*60*24*365);
        }
        int weeks = (int)(timeseconds / (60*60*24*365));
        if(weeks>0)
        {
            builder.append("**").append(weeks).append("** weeks, ");
            timeseconds = timeseconds % (60*60*24*7);
        }
        int days = (int)(timeseconds / (60*60*24));
        if(days>0)
        {
            builder.append("**").append(days).append("** days, ");
            timeseconds = timeseconds % (60*60*24);
        }
        int hours = (int)(timeseconds / (60*60));
        if(hours>0)
        {
            builder.append("**").append(hours).append("** hours, ");
            timeseconds = timeseconds % (60*60);
        }
        int minutes = (int)(timeseconds / (60));
        if(minutes>0)
        {
            builder.append("**").append(minutes).append("** minutes, ");
            timeseconds = timeseconds % (60);
        }
        if(timeseconds>0)
            builder.append("**").append(timeseconds).append("** seconds");
        String str = builder.toString();
        if(str.endsWith(", "))
            str = str.substring(0,str.length()-2);
        if(str.equals(""))
            str="**No time**";
        return str;
    }
}