Delete scam help threads

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

@@ -98,6 +98,7 @@ public static Collection<Feature> createFeatures(JDA jda, Database database, Con
         // Event receivers
         features.add(new RejoinModerationRoleListener(actionsStore, config));
         features.add(new OnGuildLeaveCloseThreadListener(database));
+        features.add(new UserBannedDeleteRecentThreadsListener(database));
 
         // Message context commands
 

application/src/main/java/org/togetherjava/tjbot/commands/help/UserBannedDeleteRecentThreadsListener.java

@@ -0,0 +1,67 @@
+package org.togetherjava.tjbot.commands.help;
+
+import net.dv8tion.jda.api.entities.User;
+import net.dv8tion.jda.api.events.guild.GuildBanEvent;
+import net.dv8tion.jda.api.hooks.ListenerAdapter;
+import org.jooq.Record1;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import org.togetherjava.tjbot.commands.EventReceiver;
+import org.togetherjava.tjbot.db.Database;
+
+import java.time.Duration;
+import java.time.Instant;
+import java.util.List;
+import java.util.Objects;
+
+import static org.togetherjava.tjbot.db.generated.Tables.HELP_THREADS;
+
+/**
+ * Reacts on users being banned from a guild. It then deletes (not just closes) all their recently
+ * created help threads.
+ * <p>
+ * This for example tackles threads created by scammers, which are otherwise not automatically
+ * cleaned up on ban.
+ */
+public final class UserBannedDeleteRecentThreadsListener extends ListenerAdapter
+        implements EventReceiver {
+    private static final Logger logger =
+            LoggerFactory.getLogger(UserBannedDeleteRecentThreadsListener.class);
+    private static final Duration RECENT_THREAD_DURATION = Duration.ofMinutes(30);
+
+    private final Database database;
+
+    /**
+     * Creates a new instance.
+     *
+     * @param database to find help threads created by the banned user
+     */
+    public UserBannedDeleteRecentThreadsListener(Database database) {
+        this.database = database;
+    }
+
+    @Override
+    public void onGuildBan(GuildBanEvent event) {
+        getUsersRecentHelpThreadIDs(event.getUser()).stream()
+            .map(event.getJDA()::getThreadChannelById)
+            .filter(Objects::nonNull)
+            .forEach(threadChannel -> threadChannel.delete().queue(any -> {
+            }, failure -> logger.warn("Failed to delete thread {} from banned user {}.",
+                    threadChannel.getId(), event.getUser().getId(), failure)));
+    }
+
+    private List<Long> getUsersRecentHelpThreadIDs(User user) {
+        Instant recentThreadThreshold = Instant.now().minus(RECENT_THREAD_DURATION);
+
+        return database
+            .read(context -> context.select(HELP_THREADS.CHANNEL_ID)
+                .from(HELP_THREADS)
+                .where(HELP_THREADS.AUTHOR_ID.eq(user.getIdLong())
+                    .and(HELP_THREADS.CREATED_AT.greaterThan(recentThreadThreshold)))
+                .fetch())
+            .stream()
+            .map(Record1::value1)
+            .toList();
+    }
+}