Fix formatting of code longer than Discord's message limit

src/main/java/net/discordjug/javabot/systems/user_commands/format_code/Code.java

@@ -0,0 +1,74 @@
+package net.discordjug.javabot.systems.user_commands.format_code;
+
+import java.util.ArrayList;
+import java.util.List;
+
+/**
+ * Holds a piece of code and its {@link Language}, and turns it into
+ * Discord-friendly representations that respect Discord's 2000-character limit.
+ */
+public class Code {
+
+	/**
+	 * Maximum characters per chunk. Discord's hard limit per message is 2000;
+	 * the remaining headroom covers the surrounding ```language fences.
+	 */
+	private static final int MAX_SIZE = 1980;
+
+	private final Language language;
+	private final String content;
+
+	/**
+	 * Creates a code block for the given language and content.
+	 *
+	 * @param language the language the code is written in, used for syntax highlighting
+	 * @param content  the raw, already-sanitized code to format
+	 */
+	public Code(Language language, String content) {
+		this.language = language;
+		this.content = content;
+	}
+
+	public String getContent() {
+		return content;
+	}
+
+	/**
+	 * Splits {@link #content} into pieces that each fit within {@link #MAX_SIZE},
+	 * breaking on newlines where possible so lines are not cut in half.
+	 *
+	 * @return the content split into chunks that each fit within the limit
+	 */
+	private List<String> toDiscordChunks() {
+		List<String> chunks = new ArrayList<>();
+		String remaining = content;
+
+		while (remaining.length() > MAX_SIZE) {
+			int split = remaining.lastIndexOf('\n', MAX_SIZE);
+			if (split <= 0) {
+				// No newline in range (or only at the very start) -> hard cut,
+				// guaranteeing progress so this can never infinite-loop.
+				chunks.add(remaining.substring(0, MAX_SIZE));
+				remaining = remaining.substring(MAX_SIZE);
+			} else {
+				chunks.add(remaining.substring(0, split));
+				remaining = remaining.substring(split + 1); // +1 consumes the '\n'
+			}
+		}
+		chunks.add(remaining);
+		return chunks;
+	}
+
+	/**
+	 * Splits the content into chunks that each fit within Discord's character limit and wraps
+	 * every chunk in a language-tagged code block.
+	 *
+	 * @return the formatted code-block messages, one per Discord message
+	 */
+	public List<String> toDiscordMessages() {
+		return toDiscordChunks()
+				.stream()
+				.map(chunk -> String.format("```%s\n%s\n```", language.getDiscordName(), chunk))
+				.toList();
+	}
+}

src/main/java/net/discordjug/javabot/systems/user_commands/format_code/FormatAndIndentCodeMessageContext.java

@@ -1,16 +1,13 @@
 package net.discordjug.javabot.systems.user_commands.format_code;
 
-
 import net.discordjug.javabot.util.IndentationHelper;
 import net.discordjug.javabot.util.StringUtils;
 import net.dv8tion.jda.api.events.interaction.command.MessageContextInteractionEvent;
 import net.dv8tion.jda.api.interactions.InteractionContextType;
 import net.dv8tion.jda.api.interactions.commands.build.Commands;
-
 import org.jetbrains.annotations.NotNull;
 import xyz.dynxsty.dih4jda.interactions.commands.application.ContextCommand;
 
-import java.util.List;
 
 /**
  * <h3>This class represents the "Format and Indent Code" Message Context command.</h3>
@@ -27,9 +24,12 @@ public FormatAndIndentCodeMessageContext() {
 
 	@Override
 	public void execute(@NotNull MessageContextInteractionEvent event) {
-		event.replyFormat("```java\n%s\n```", IndentationHelper.formatIndentation(StringUtils.standardSanitizer().compute(event.getTarget().getContentRaw()), IndentationHelper.IndentationType.TABS))
-				.setAllowedMentions(List.of())
-				.setComponents(FormatCodeCommand.buildActionRow(event.getTarget(), event.getUser().getIdLong()))
-				.queue();
+		String indented = IndentationHelper.formatIndentation(
+				StringUtils.standardSanitizer().compute(event.getTarget().getContentRaw()),
+				IndentationHelper.IndentationType.TABS);
+
+		Code code = new Code(Language.JAVA, indented);
+
+		event.deferReply().queue(_ -> FormatCodeDispatcher.sendCode(code, event, event.getTarget()));
 	}
 }

src/main/java/net/discordjug/javabot/systems/user_commands/format_code/FormatCodeCommand.java

@@ -2,20 +2,15 @@
 
 import xyz.dynxsty.dih4jda.interactions.commands.application.SlashCommand;
 import net.discordjug.javabot.util.*;
-import net.dv8tion.jda.api.components.actionrow.ActionRow;
-import net.dv8tion.jda.api.components.buttons.Button;
 import net.dv8tion.jda.api.entities.Message;
 import net.dv8tion.jda.api.events.interaction.command.SlashCommandInteractionEvent;
 import net.dv8tion.jda.api.interactions.InteractionContextType;
 import net.dv8tion.jda.api.interactions.commands.OptionMapping;
 import net.dv8tion.jda.api.interactions.commands.OptionType;
 import net.dv8tion.jda.api.interactions.commands.build.Commands;
 import net.dv8tion.jda.api.interactions.commands.build.OptionData;
-import org.jetbrains.annotations.Contract;
-import org.jetbrains.annotations.NotNull;
 
-import java.util.Collections;
-import java.util.List;
+import org.jetbrains.annotations.NotNull;
 
 /**
  * <h3>This class represents the /format-code command.</h3>
@@ -29,25 +24,7 @@ public FormatCodeCommand() {
 				.setContexts(InteractionContextType.GUILD)
 				.addOptions(
 						new OptionData(OptionType.STRING, "message-id", "Message to be formatted, last message used if left blank.", false),
-						new OptionData(OptionType.STRING, "format", "The language used to format the code, defaults to Java if left blank.", false)
-								.addChoice("C", "c")
-								.addChoice("C#", "csharp")
-								.addChoice("C++", "cpp")
-								.addChoice("CSS", "css")
-								.addChoice("D", "d")
-								.addChoice("Go", "go")
-								.addChoice("HTML", "html")
-								.addChoice("Java", "java")
-								.addChoice("JavaScript", "js")
-								.addChoice("Kotlin", "kotlin")
-								.addChoice("PHP", "php")
-								.addChoice("Python", "python")
-								.addChoice("Ruby", "ruby")
-								.addChoice("Rust", "rust")
-								.addChoice("SQL", "sql")
-								.addChoice("Swift", "swift")
-								.addChoice("TypeScript", "typescript")
-								.addChoice("XML", "xml"),
+						formatOption(),
 						new OptionData(OptionType.STRING,"auto-indent","The type of indentation applied to the message, does not automatically indent if left blank.",false)
 								.addChoice("Four Spaces","FOUR_SPACES")
 								.addChoice("Two Spaces","TWO_SPACES")
@@ -56,47 +33,66 @@ public FormatCodeCommand() {
 		);
 	}
 
-	@Contract("_ -> new")
-	static @NotNull ActionRow buildActionRow(@NotNull Message target, long requesterId) {
-		return ActionRow.of(InteractionUtils.createDeleteButton(requesterId),
-				Button.link(target.getJumpUrl(), "View Original"));
+	/**
+	 * Builds the {@code format} option, generating one choice per {@link Language} (excluding
+	 * {@link Language#UNKNOWN}) so the enum stays the single source of truth for the language list.
+	 *
+	 * @return the configured {@code format} option
+	 */
+	private static OptionData formatOption() {
+		OptionData option = new OptionData(OptionType.STRING, "format", "The language used to format the code, defaults to Java if left blank.", false);
+		for (Language language : Language.values()) {
+			if (language != Language.UNKNOWN) {                       // UNKNOWN is the fallback, not a real choice
+				option.addChoice(language.getDisplayName(), language.name()); // value = enum name so valueOf() reverses it
+			}
+		}
+		return option;
 	}
 
 	@Override
 	public void execute(@NotNull SlashCommandInteractionEvent event) {
 		OptionMapping idOption = event.getOption("message-id");
-		String format = event.getOption("format", "java", OptionMapping::getAsString);
+		Language language = event.getOption("format", Language.JAVA, o -> Language.fromString(o.getAsString()));
 		String indentation = event.getOption("auto-indent","NULL",OptionMapping::getAsString);
-		event.deferReply().queue();
+
 		if (idOption == null) {
-			event.getChannel().getHistory()
-					.retrievePast(10)
-					.queue(messages -> {
-						Collections.reverse(messages);
-						Message target = messages.stream()
-								.filter(m -> !m.getAuthor().isBot()).findFirst()
-								.orElse(null);
-						if (target != null) {
-							event.getHook().sendMessageFormat("```%s\n%s\n```", format, IndentationHelper.formatIndentation(StringUtils.standardSanitizer().compute(target.getContentRaw()),IndentationHelper.IndentationType.valueOf(indentation)))
-									.setAllowedMentions(List.of())
-									.setComponents(buildActionRow(target, event.getUser().getIdLong()))
-									.queue();
-						} else {
-							Responses.error(event.getHook(), "Could not find message; please specify a message id.").queue();
-						}
-					});
+			event.deferReply().queue(_ -> {
+				event.getChannel().getHistory()
+				.retrievePast(10)
+				.queue(messages -> {
+					Message target = messages.stream()
+							.filter(m -> !m.getAuthor().isBot()).findFirst()
+							.orElse(null);
+					if (target != null) {
+						sendFormattedCode(event, target, language, indentation);
+					} else {
+						Responses.errorWithTitle(event.getHook(), "Message Not Found", "No recent user message could be found. Please specify a message ID.")
+								.queue();
+					}
+				});
+			});
 		} else {
 			if (Checks.isInvalidLongInput(idOption)) {
-				Responses.error(event.getHook(), "Please provide a valid message id!").queue();
+				Responses.errorWithTitle(event, "Invalid Message ID", "Please provide a valid Discord message ID.")
+					.queue();
 				return;
 			}
 			long messageId = idOption.getAsLong();
-			event.getChannel().retrieveMessageById(messageId).queue(
-					target -> event.getHook().sendMessageFormat("```%s\n%s\n```", format, IndentationHelper.formatIndentation(StringUtils.standardSanitizer().compute(target.getContentRaw()), IndentationHelper.IndentationType.valueOf(indentation)))
-							.setAllowedMentions(List.of())
-							.setComponents(buildActionRow(target, event.getUser().getIdLong()))
-							.queue(),
-					e -> Responses.error(event.getHook(), "Could not retrieve message with id: " + messageId).queue());
+			event.deferReply().queue(_ -> {
+				event.getChannel().retrieveMessageById(messageId).queue(
+						target -> sendFormattedCode(event, target, language, indentation),
+						error -> Responses.errorWithTitle(event.getHook(), "Message Not Found", "Could not retrieve the message with ID `" + messageId + "`. Make sure the message exists and is accessible.").queue());
+			});
 		}
 	}
+
+	private void sendFormattedCode(SlashCommandInteractionEvent event, Message target, Language language, String indentation) {
+		String content = IndentationHelper.formatIndentation(
+				StringUtils.standardSanitizer().compute(target.getContentRaw()),
+				IndentationHelper.IndentationType.valueOf(indentation));
+
+		Code code = new Code(language,content);
+
+		FormatCodeDispatcher.sendCode(code, event, target);
+	}
 }

src/main/java/net/discordjug/javabot/systems/user_commands/format_code/FormatCodeDispatcher.java

@@ -0,0 +1,99 @@
+package net.discordjug.javabot.systems.user_commands.format_code;
+
+import net.discordjug.javabot.util.*;
+import net.dv8tion.jda.api.components.actionrow.ActionRow;
+import net.dv8tion.jda.api.components.buttons.Button;
+import net.dv8tion.jda.api.entities.Message;
+import net.dv8tion.jda.api.entities.channel.middleman.MessageChannel;
+import net.dv8tion.jda.api.interactions.commands.CommandInteraction;
+import org.jetbrains.annotations.Contract;
+import org.jetbrains.annotations.NotNull;
+
+import javax.annotation.Nonnull;
+import java.util.List;
+
+/**
+ * Shared sending logic for the code-formatting commands. Replies with the full code as a
+ * downloadable file, then posts it as one or more ordered code-block messages that each respect
+ * Discord's 2000-character limit.
+ */
+class FormatCodeDispatcher {
+
+	/**
+	 * The maximum number of code-block messages to post inline; longer code results in an error.
+	 */
+	private static final int MAX_MESSAGES = 5;
+
+	/**
+	 * Acknowledges the interaction by replying with the full code as a file, then posts the code as
+	 * ordered code-block messages. Replies with an error instead if there is nothing to format.
+	 *
+	 * @param code   the code to send
+	 * @param event  the interaction to reply to
+	 * @param target the original message the code came from, used for the channel and the
+	 *               "View Original" / delete buttons
+	 */
+	public static void sendCode(Code code, @Nonnull CommandInteraction event, Message target){
+		if (code.getContent().isBlank()) {
+			Responses.errorWithTitle(event.getHook(), "404 Code not found","There is no code to format in that message.").queue();
+			return;
+		}
+
+		List<String> messages = code.toDiscordMessages();
+
+		MessageChannel channel = target.getChannel();
+
+		if (messages.size() > MAX_MESSAGES) {
+			Responses.errorWithTitle(event.getHook(), "Output Too Large", "The formatted result is too large to send. Please provide a smaller code snippet or use a paste service instead."
+			).queue();
+			return;
+		}
+
+		Responses.success(event.getHook(), "Success", "The formatted message is being sent to this channel.")
+				.queue(success -> sendChunksInOrder(channel, messages, 0, target,event));
+	}
+
+
+	private static void sendChunksInOrder(MessageChannel channel, List<String> messages, int index, Message target, @Nonnull CommandInteraction event) {
+		if (index >= messages.size()) {
+			return;
+		}
+		var action = channel.sendMessage(messages.get(index))
+				.setAllowedMentions(List.of());
+
+		if (index == messages.size() - 1) {
+			if(index == 0){
+				action.setComponents(buildActionRow(target, event.getUser().getIdLong()));
+			} else {
+				action.setComponents(buildActionRow(target));
+			}
+		}
+
+		action.queue(success ->
+				sendChunksInOrder(channel, messages, index + 1, target, event));
+	}
+
+	/**
+	 * Builds the action row placed on the last code-block message.
+	 *
+	 * @param target      the original message linked by the "View Original" button
+	 * @return an action row containing the "View Original" link button
+	 */
+	@Contract("_ -> new")
+	static @NotNull ActionRow buildActionRow(@NotNull Message target) {
+		return ActionRow.of(Button.link(target.getJumpUrl(), "View Original"));
+	}
+
+	/**
+	 * Builds the action row placed on the file-upload message: a delete button and a "View Original" link.
+	 *
+	 * @param target      the original message linked by the "View Original" button
+	 * @param requesterId the id of the user permitted to delete the message
+	 * @return an action row containing the delete and "View Original" buttons
+	 */
+	@Contract("_,_ -> new")
+	static @NotNull ActionRow buildActionRow(@NotNull Message target, long requesterId) {
+		return ActionRow.of(InteractionUtils.createDeleteButton(requesterId),
+				Button.link(target.getJumpUrl(), "View Original"));
+	}
+}

src/main/java/net/discordjug/javabot/systems/user_commands/format_code/FormatCodeMessageContext.java

@@ -1,14 +1,12 @@
 package net.discordjug.javabot.systems.user_commands.format_code;
 
-import xyz.dynxsty.dih4jda.interactions.commands.application.ContextCommand;
 import net.discordjug.javabot.util.StringUtils;
+import xyz.dynxsty.dih4jda.interactions.commands.application.ContextCommand;
 import net.dv8tion.jda.api.events.interaction.command.MessageContextInteractionEvent;
 import net.dv8tion.jda.api.interactions.InteractionContextType;
 import net.dv8tion.jda.api.interactions.commands.build.Commands;
-
 import org.jetbrains.annotations.NotNull;
 
-import java.util.List;
 
 /**
  * <h3>This class represents the "Format Code" Message Context command.</h3>
@@ -25,9 +23,10 @@ public FormatCodeMessageContext() {
 
 	@Override
 	public void execute(@NotNull MessageContextInteractionEvent event) {
-		event.replyFormat("```java\n%s\n```", StringUtils.standardSanitizer().compute(event.getTarget().getContentRaw()))
-				.setAllowedMentions(List.of())
-				.setComponents(FormatCodeCommand.buildActionRow(event.getTarget(), event.getUser().getIdLong()))
-				.queue();
+		String content = StringUtils.standardSanitizer().compute(event.getTarget().getContentRaw());
+
+		Code code = new Code(Language.JAVA, content);
+
+		event.deferReply().queue(_ -> FormatCodeDispatcher.sendCode(code, event, event.getTarget()));
 	}
 }