Send reminder per DM if failing to send in guild

Author: Zabuzard

application/src/main/java/org/togetherjava/tjbot/commands/reminder/RemindRoutine.java

@@ -2,10 +2,10 @@
 
 import net.dv8tion.jda.api.EmbedBuilder;
 import net.dv8tion.jda.api.JDA;
-import net.dv8tion.jda.api.entities.Guild;
-import net.dv8tion.jda.api.entities.MessageEmbed;
-import net.dv8tion.jda.api.entities.TextChannel;
+import net.dv8tion.jda.api.entities.*;
+import net.dv8tion.jda.api.requests.RestAction;
 import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 import org.togetherjava.tjbot.commands.Routine;
@@ -51,46 +51,89 @@ public void runRoutine(@NotNull JDA jda) {
             .where(PENDING_REMINDERS.REMIND_AT.lessOrEqual(now))
             .stream()
             .forEach(pendingReminder -> {
-                sendReminder(jda, pendingReminder.getGuildId(), pendingReminder.getChannelId(),
-                        pendingReminder.getAuthorId(), pendingReminder.getContent(),
-                        pendingReminder.getCreatedAt());
+                sendReminder(jda, pendingReminder.getId(), pendingReminder.getGuildId(),
+                        pendingReminder.getChannelId(), pendingReminder.getAuthorId(),
+                        pendingReminder.getContent(), pendingReminder.getCreatedAt());
                 pendingReminder.delete();
             }));
     }
 
-    private static void sendReminder(@NotNull JDA jda, long guildId, long channelId, long authorId,
-            @NotNull CharSequence content, @NotNull TemporalAccessor createdAt) {
+    private static void sendReminder(@NotNull JDA jda, long id, long guildId, long channelId,
+            long authorId, @NotNull CharSequence content, @NotNull TemporalAccessor createdAt) {
+        RestAction<ReminderRoute> route = computeReminderRoute(jda, guildId, channelId, authorId);
+        sendReminderViaRoute(route, id, content, createdAt);
+    }
+
+    private static RestAction<ReminderRoute> computeReminderRoute(@NotNull JDA jda, long guildId,
+            long channelId, long authorId) {
+        // If guild and channel can still be found, send there
         Guild guild = jda.getGuildById(guildId);
-        if (guild == null) {
-            logger.debug(
-                    "Attempted to send a reminder but the bot is not connected to the guild '{}' anymore, skipping reminder.",
-                    guildId);
-            return;
+        if (guild != null) {
+            TextChannel channel = guild.getTextChannelById(channelId);
+            if (channel != null) {
+                return createGuildReminderRoute(jda, authorId, channel);
+            }
         }
 
-        TextChannel channel = guild.getTextChannelById(channelId);
-        if (channel == null) {
-            logger.debug(
-                    "Attempted to send a reminder but the guild '{}' does not have a channel with id '{}' anymore, skipping reminder.",
-                    guildId, channelId);
-            return;
-        }
+        // Otherwise, attempt to DM the user directly
+        return createDmReminderRoute(jda, authorId);
+    }
 
-        jda.retrieveUserById(authorId).onErrorMap(error -> null).flatMap(author -> {
-            String authorName = author == null ? "Unknown user" : author.getAsTag();
-            String authorIconUrl = author == null ? null : author.getAvatarUrl();
+    private static @NotNull RestAction<ReminderRoute> createGuildReminderRoute(@NotNull JDA jda,
+            long authorId, @NotNull TextChannel channel) {
+        return jda.retrieveUserById(authorId)
+            .onErrorMap(error -> null)
+            .map(author -> new ReminderRoute(channel, author,
+                    author == null ? null : author.getAsMention()));
+    }
 
-            MessageEmbed embed = new EmbedBuilder().setAuthor(authorName, null, authorIconUrl)
-                .setDescription(content)
-                .setFooter("reminder from")
-                .setTimestamp(createdAt)
-                .setColor(AMBIENT_COLOR)
-                .build();
+    private static @NotNull RestAction<ReminderRoute> createDmReminderRoute(@NotNull JDA jda,
+            long authorId) {
+        return jda.openPrivateChannelById(authorId)
+            .onErrorMap(error -> null)
+            .map(channel -> channel == null ? new ReminderRoute(null, null, null)
+                    : new ReminderRoute(channel, channel.getUser(),
+                            "(Sending your reminder directly, because I was unable to"
+                                    + " locate the original channel you wanted it to be send to)"));
+    }
 
-            if (author == null) {
-                return channel.sendMessageEmbeds(embed);
+    private static void sendReminderViaRoute(@NotNull RestAction<ReminderRoute> routeAction,
+            long id, @NotNull CharSequence content, @NotNull TemporalAccessor createdAt) {
+        routeAction.flatMap(route -> {
+            if (route.isUndeliverable()) {
+                throw new IllegalStateException("Route is not deliverable");
             }
-            return channel.sendMessage(author.getAsMention()).setEmbeds(embed);
-        }).queue();
+
+            MessageEmbed embed = createReminderEmbed(content, createdAt, route.target());
+            if (route.description() == null) {
+                return route.channel().sendMessageEmbeds(embed);
+            }
+            return route.channel().sendMessage(route.description()).setEmbeds(embed);
+        }).queue(message -> {
+        }, failure -> logger.warn(
+                "Failed to send a reminder (id '{}'), skipping it. This can be due to a network issue,"
+                        + " but also happen if the bot disconnected from the target guild and the"
+                        + " user has disabled DMs or has been deleted.",
+                id));
+    }
+
+    private static @NotNull MessageEmbed createReminderEmbed(@NotNull CharSequence content,
+            @NotNull TemporalAccessor createdAt, @Nullable User author) {
+        String authorName = author == null ? "Unknown user" : author.getAsTag();
+        String authorIconUrl = author == null ? null : author.getAvatarUrl();
+
+        return new EmbedBuilder().setAuthor(authorName, null, authorIconUrl)
+            .setDescription(content)
+            .setFooter("reminder from")
+            .setTimestamp(createdAt)
+            .setColor(AMBIENT_COLOR)
+            .build();
+    }
+
+    private record ReminderRoute(@Nullable MessageChannel channel, @Nullable User target,
+            @Nullable String description) {
+        boolean isUndeliverable() {
+            return channel == null && target == null;
+        }
     }
 }