Add DiscordRelayEvent to edit relayed Discord->MC messages (#4656)

Implements the event suggested in #4580.

Co-authored-by: MD <1917406+mdcfe@users.noreply.github.com>

EssentialsDiscord/src/main/java/net/essentialsx/api/v2/events/discord/DiscordRelayEvent.java

@@ -0,0 +1,111 @@
+package net.essentialsx.api.v2.events.discord;
+
+import net.essentialsx.api.v2.services.discord.InteractionChannel;
+import net.essentialsx.api.v2.services.discord.InteractionMember;
+import org.bukkit.Bukkit;
+import org.bukkit.event.Cancellable;
+import org.bukkit.event.Event;
+import org.bukkit.event.HandlerList;
+import org.jetbrains.annotations.NotNull;
+
+import java.util.List;
+
+/**
+ * Fired before a message is relayed to Minecraft.
+ * <p>
+ * Note: This event has no guarantee of the thread it is fired on, please use {@link #isAsynchronous()}} to see if this event is off the main Bukkit thread.
+ */
+public class DiscordRelayEvent extends Event implements Cancellable {
+    private static final HandlerList handlers = new HandlerList();
+
+    private final InteractionMember member;
+    private final InteractionChannel channel;
+    private final List<String> groupNames;
+    private final String rawMessage;
+    private String formattedMessage;
+    private boolean cancelled = false;
+
+    /**
+     * @param member            The member that sent the message.
+     * @param channel           The channel the message was sent in.
+     * @param groupNames        The message type keys which will be used to determine which player group the message should be sent to.
+     * @param rawMessage        The raw message sent from Discord.
+     * @param formattedMessage  The formatted message that will be sent to Minecraft.
+     */
+    public DiscordRelayEvent(final InteractionMember member, final InteractionChannel channel, final List<String> groupNames, final String rawMessage, final String formattedMessage) {
+        super(!Bukkit.isPrimaryThread());
+        this.member = member;
+        this.channel = channel;
+        this.groupNames = groupNames;
+        this.rawMessage = rawMessage;
+        this.formattedMessage = formattedMessage;
+    }
+
+    /**
+     * Gets the Discord member that sent the message.
+     * @return The member that sent the message.
+     */
+    public InteractionMember getMember() {
+        return member;
+    }
+
+    /**
+     * Gets the Discord channel the message was sent in.
+     * @return The channel the message was sent in.
+     */
+    public InteractionChannel getChannel() {
+        return channel;
+    }
+
+    /**
+     * Gets the message type group keys.
+     * @return The message type group keys.
+     */
+    public List<String> getGroupNames() {
+        return groupNames;
+    }
+
+    /**
+     * Gets the raw message sent from Discord.
+     * @return The raw message sent from Discord.
+     */
+    public String getRawMessage() {
+        return rawMessage;
+    }
+
+    /**
+     * Gets the formatted message that will be sent to Minecraft.
+     * @return The formatted message.
+     */
+    public String getFormattedMessage() {
+        return formattedMessage;
+    }
+
+    /**
+     * Sets the formatted message that will be sent to Minecraft.
+     * @param formattedMessage The formatted message.
+     */
+    public void setFormattedMessage(final String formattedMessage) {
+        this.formattedMessage = formattedMessage;
+    }
+
+    @Override
+    public boolean isCancelled() {
+        return cancelled;
+    }
+
+    @Override
+    public void setCancelled(boolean cancelled) {
+        this.cancelled = cancelled;
+    }
+
+    @NotNull
+    @Override
+    public HandlerList getHandlers() {
+        return handlers;
+    }
+
+    public static HandlerList getHandlerList() {
+        return handlers;
+    }
+}

EssentialsDiscord/src/main/java/net/essentialsx/discord/listeners/DiscordListener.java

@@ -8,12 +8,17 @@ import net.dv8tion.jda.api.entities.User;
 import net.dv8tion.jda.api.events.message.guild.GuildMessageReceivedEvent;
 import net.dv8tion.jda.api.hooks.ListenerAdapter;
 import net.ess3.api.IUser;
+import net.essentialsx.api.v2.events.discord.DiscordRelayEvent;
 import net.essentialsx.discord.JDADiscordService;
+import net.essentialsx.discord.interactions.InteractionChannelImpl;
+import net.essentialsx.discord.interactions.InteractionMemberImpl;
 import net.essentialsx.discord.util.DiscordUtil;
 import net.essentialsx.discord.util.MessageUtil;
 import org.apache.commons.lang.StringUtils;
+import org.bukkit.Bukkit;
 import org.jetbrains.annotations.NotNull;
 
+import java.util.Collections;
 import java.util.List;
 import java.util.logging.Level;
 import java.util.logging.Logger;
@@ -88,7 +93,7 @@ public class DiscordListener extends ListenerAdapter {
             return;
         }
 
-        final String formattedMessage = EmojiParser.parseToAliases(MessageUtil.formatMessage(plugin.getPlugin().getSettings().getDiscordToMcFormat(),
+        String formattedMessage = EmojiParser.parseToAliases(MessageUtil.formatMessage(plugin.getPlugin().getSettings().getDiscordToMcFormat(),
                 event.getChannel().getName(), user.getName(), user.getDiscriminator(), user.getAsTag(),
                 effectiveName, DiscordUtil.getRoleColorFormat(member), finalMessage, DiscordUtil.getRoleFormat(member)), EmojiParser.FitzpatrickAction.REMOVE);
 
@@ -99,6 +104,18 @@ public class DiscordListener extends ListenerAdapter {
             }
         }
 
+        // Do not create the event specific objects if there are no listeners
+        if (DiscordRelayEvent.getHandlerList().getRegisteredListeners().length != 0) {
+            final DiscordRelayEvent relayEvent = new DiscordRelayEvent(
+                    new InteractionMemberImpl(member), new InteractionChannelImpl(event.getChannel()),
+                    Collections.unmodifiableList(keys), event.getMessage().getContentRaw(), formattedMessage);
+            Bukkit.getPluginManager().callEvent(relayEvent);
+            if (relayEvent.isCancelled()) {
+                return;
+            }
+            formattedMessage = relayEvent.getFormattedMessage();
+        }
+
         for (IUser essUser : plugin.getPlugin().getEss().getOnlineUsers()) {
             for (String group : keys) {
                 final String perm = "essentials.discord.receive." + group;