Create new Purge command.

.gitignore

@@ -158,3 +158,4 @@ logviewer/types.d.ts
 logviewer/pnpm-lock.yaml
 logviewer/webpack.config.js
 logviewer/webpack.generated.js
+.DS_Store

application/src/main/java/org/togetherjava/tjbot/commands/Commands.java

@@ -5,6 +5,7 @@
 import org.togetherjava.tjbot.commands.basic.PingCommand;
 import org.togetherjava.tjbot.commands.basic.VcActivityCommand;
 import org.togetherjava.tjbot.commands.mathcommands.TeXCommand;
+import org.togetherjava.tjbot.commands.moderation.PurgeCommand;
 import org.togetherjava.tjbot.commands.tags.TagCommand;
 import org.togetherjava.tjbot.commands.tags.TagManageCommand;
 import org.togetherjava.tjbot.commands.tags.TagSystem;
@@ -42,6 +43,6 @@ public enum Commands {
         // available.
         return List.of(new PingCommand(), new DatabaseCommand(database), new TeXCommand(),
                 new TagCommand(tagSystem), new TagManageCommand(tagSystem),
-                new TagsCommand(tagSystem), new VcActivityCommand());
+                new TagsCommand(tagSystem), new PurgeCommand(), new VcActivityCommand());
     }
 }

application/src/main/java/org/togetherjava/tjbot/commands/moderation/PurgeCommand.java

@@ -0,0 +1,108 @@
+package org.togetherjava.tjbot.commands.moderation;
+
+import net.dv8tion.jda.api.Permission;
+import net.dv8tion.jda.api.entities.ISnowflake;
+import net.dv8tion.jda.api.entities.Member;
+import net.dv8tion.jda.api.entities.MessageChannel;
+import net.dv8tion.jda.api.entities.TextChannel;
+import net.dv8tion.jda.api.events.interaction.SlashCommandEvent;
+import net.dv8tion.jda.api.interactions.commands.OptionType;
+import org.jetbrains.annotations.NotNull;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import org.togetherjava.tjbot.commands.SlashCommandAdapter;
+import org.togetherjava.tjbot.commands.SlashCommandVisibility;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Objects;
+import java.util.concurrent.locks.ReentrantLock;
+import java.util.function.Consumer;
+import java.util.stream.Collectors;
+
+/**
+ * This command can remove specific messages using their ids. The command requires the user to input
+ * the id of message they want to delete from and the id of the messages they want to delete to.
+ * <p>
+ * The command fails if one of the message id that was given is invalid or the user lacks the
+ * permission to delete messages.
+ */
+public class PurgeCommand extends SlashCommandAdapter {
+    // TODO Test the command
+    private static final Logger logger = LoggerFactory.getLogger(PurgeCommand.class);
+    private static final String FIRST_MESSAGE_ID = "first_message_id";
+    private static final String LAST_MESSAGE_ID = "last_message_id";
+
+
+    public PurgeCommand() {
+        super("purge", "Delete specific messages using there ids.", SlashCommandVisibility.GUILD);
+
+        getData()
+            .addOption(OptionType.NUMBER, FIRST_MESSAGE_ID,
+                    "The id of the message you want to delete from.", true)
+            .addOption(OptionType.NUMBER, LAST_MESSAGE_ID,
+                    "The id of the message you want to delete to.", true);
+    }
+
+    @Override
+    public void onSlashCommand(@NotNull SlashCommandEvent event) {
+        final Member author = event.getMember();
+
+        if (!author.hasPermission(Permission.MESSAGE_MANAGE)) {
+            event.reply("You are missing MESSAGE_MANAGE permission to delete these the message")
+                .setEphemeral(true)
+                .queue();
+            return;
+        }
+
+        final Member bot = Objects.requireNonNull(event.getGuild()).getSelfMember();
+        if (!bot.hasPermission(Permission.MESSAGE_MANAGE)) {
+            event.reply(
+                    "I am missing MESSAGE_MANAGE permission which means I am unable to delete messages in this server.")
+                .setEphemeral(true)
+                .queue();
+
+            logger.error("The bot does not have MESSAGE_MANAGE permission on the server '{}' ",
+                    event.getGuild().getId());
+            return;
+        }
+
+        long firstMessageId = Objects.requireNonNull(event.getOption(FIRST_MESSAGE_ID)).getAsLong();
+        long lastMessageId = Objects.requireNonNull(event.getOption(LAST_MESSAGE_ID)).getAsLong();
+
+        deleteMessagesById(firstMessageId, lastMessageId, event.getMessageChannel(), strings -> {
+
+        });
+    }
+
+    private static void deleteMessagesById(long firstMessageId, long lastMessageId,
+            MessageChannel mc, Consumer<List<String>> cb) {
+        getBetween0(firstMessageId, lastMessageId, mc, new ArrayList<>(), new ReentrantLock(), cb);
+    }
+
+    private static void getBetween0(long firstMessageId, long lastMessageId, MessageChannel mc,
+            List<String> acc, ReentrantLock lock, Consumer<List<String>> cb) {
+        mc.getHistoryBefore(firstMessageId, 100).queue(his -> {
+            try {
+                lock.lock();
+                List<String> collected = his.getRetrievedHistory()
+                    .stream()
+                    .map(ISnowflake::getId)
+                    .collect(Collectors.toList());
+
+                int foundIdx = collected.indexOf(String.valueOf(lastMessageId));
+
+                if (foundIdx != -1) {
+                    acc.addAll(collected.subList(0, foundIdx));
+                    cb.accept(acc);
+                } else {
+                    acc.addAll(collected);
+                    getBetween0(Long.parseLong(collected.get(collected.size() - 1)), lastMessageId,
+                            mc, acc, lock, cb);
+                }
+            } finally {
+                lock.unlock();
+            }
+        });
+    }
+}