Refactor to using paginator

app/src/main/java/musicbot/RecommendationService.java

@@ -16,7 +16,7 @@ import java.util.stream.Collectors;
 
 public class RecommendationService {
 
-  public List<Track> getRecommendations(final String artist, final String genre, final int page) {
+  public List<Track> getRecommendations(final String artist, final String genre) {
 
     if (artist.isEmpty() && genre.isEmpty()) {
       return ImmutableList.of();

app/src/main/java/musicbot/buttonInteractions/MoreGenre.java

@@ -1,6 +1,7 @@
 package musicbot.buttonInteractions;
 
 import musicbot.ButtonInteraction;
+import musicbot.Paginator;
 import musicbot.SpotifyClient;
 import net.dv8tion.jda.api.EmbedBuilder;
 import net.dv8tion.jda.api.events.interaction.component.ButtonInteractionEvent;
@@ -17,31 +18,25 @@ public class MoreGenre implements ButtonInteraction {
   @Override
   public void execute(ButtonInteractionEvent event) {
     final String id = event.getComponent().getId();
-    final String label = event.getComponent().getLabel();
+    final Paginator paginator = new Paginator();
 
     final String[] args = id.split("_");
     event.deferReply().queue();
 
     final int page = Integer.parseInt(args[1]);
-    final int offset = page * 10;
-    final int index = offset + 10;
-    final int nextPage = page + 1;
 
     final SpotifyClient spotifyClient = new SpotifyClient();
     final List<String> genres = spotifyClient.findGenres();
-    final int maxSize = genres.size();
-    final int maxPage = (int) Math.floor(maxSize / 10);
+    final Paginator.PaginatedItems<String> paginatedGenre = paginator.paginate(genres, 10, page);
 
     final EmbedBuilder eb = new EmbedBuilder();
 
-    if (nextPage <= maxPage) {
-      genres.subList(offset, index).forEach(genreItem -> eb.addField(genreItem, "", false));
-
+    paginatedGenre.get().forEach(genreItem -> eb.addField(genreItem, "", false));
+    if (!paginatedGenre.isIsLastPage()) {
       event.getHook().sendMessageEmbeds(eb.build()).addActionRow(
-          Button.primary("genre_" + nextPage, "More")
+          Button.primary("genre_" + paginatedGenre.getNextPageNum(), "More genres")
       ).queue();
     } else {
-      genres.subList(offset, maxSize).forEach(genreItem -> eb.addField(genreItem, "", false));
       event.getHook().sendMessageEmbeds(eb.build()).queue();
     }
   }

app/src/main/java/musicbot/buttonInteractions/MoreRecommendation.java

@@ -1,6 +1,7 @@
 package musicbot.buttonInteractions;
 
 import musicbot.ButtonInteraction;
+import musicbot.Paginator;
 import musicbot.RecommendationService;
 import net.dv8tion.jda.api.EmbedBuilder;
 import net.dv8tion.jda.api.entities.MessageEmbed;
@@ -21,7 +22,6 @@ public class MoreRecommendation implements ButtonInteraction {
   private static final int INCREMENT = 5;
   private static final String ARGS_DELIMITER = "_";
   private static final String ARTIST_GENRE_DELIMITER = "--";
-  private static final int NUM_RECOMMENDATIONS = 5;
 
   @Override
   public String getName() {
@@ -33,20 +33,19 @@ public class MoreRecommendation implements ButtonInteraction {
     event.deferReply().queue();
     final String id = event.getComponent().getId();
     final String[] args = id.split(ARGS_DELIMITER);
+
     final String[] artistGenre = args[1].split(ARTIST_GENRE_DELIMITER);
     final String artist = artistGenre[0];
     final String genre = artistGenre.length < 2 ? "" : artistGenre[1];
-    final int page = Integer.parseInt(args[2]);
-    final int nextPage = page + 1;
-    final int maxIndex = INCREMENT * page;
-    final int baseIndex = maxIndex - INCREMENT;
 
-    final List<Track> tracks = new RecommendationService().getRecommendations(artist, genre, page);
-    final int maxSize = tracks.size();
-    final int maxPage = (int) Math.floor(maxSize / NUM_RECOMMENDATIONS);
+    final int pageNumber = Integer.parseInt(args[2]);
+    final List<Track> tracks = new RecommendationService().getRecommendations(artist, genre);
+
+    final Paginator paginator = new Paginator();
+    final Paginator.PaginatedItems<Track> paginatedTracks = paginator.paginate(tracks, 5, pageNumber);
 
     final EmbedBuilder eb = new EmbedBuilder();
-    final List<Track> trackList = tracks.subList(baseIndex, maxIndex);
+    final List<Track> trackList = paginatedTracks.get();
     if (!trackList.isEmpty()) {
       eb
           .setTitle("More recommendations based on \"" + artist + "\"")
@@ -70,8 +69,8 @@ public class MoreRecommendation implements ButtonInteraction {
         return Button.primary("recommend_" + artists, track.getName());
       }).collect(Collectors.toList());
 
-      if (nextPage <= maxPage) {
-        final String buttonId = "more-recommend_" + artist + "--" + genre + "_" + nextPage;
+      if (!paginatedTracks.isIsLastPage()) {
+        final String buttonId = "more-recommend_" + artist + "--" + genre + "_" + paginatedTracks.getNextPageNum();
 
         event
             .getHook()

app/src/main/java/musicbot/commands/Genres.java

@@ -2,6 +2,7 @@ package musicbot.commands;
 
 import com.google.common.collect.Lists;
 import musicbot.MCommand;
+import musicbot.Paginator;
 import musicbot.SpotifyClient;
 import net.dv8tion.jda.api.EmbedBuilder;
 import net.dv8tion.jda.api.entities.MessageEmbed;
@@ -37,13 +38,15 @@ public class Genres implements MCommand {
     event.deferReply().queue();
     final SpotifyClient spotifyClient = new SpotifyClient();
     final List<String> genres = spotifyClient.findGenres();
+    final Paginator paginator = new Paginator();
 
     final EmbedBuilder eb = new EmbedBuilder();
+    final Paginator.PaginatedItems<String> paginatedGenre = paginator.paginate(genres, 10, 1);
 
-    genres.subList(0, 10).forEach(genre -> eb.addField(genre, "", false));
+    paginatedGenre.get().forEach(genre -> eb.addField(genre, "", false));
 
     event.getHook().sendMessageEmbeds(eb.build()).addActionRow(
-        Button.primary("genre_1", "More")
+        Button.primary("genre_" + paginatedGenre.getNextPageNum(), "More genres")
     ).queue();
   }
 }

app/src/main/java/musicbot/commands/Recommend.java

@@ -1,6 +1,7 @@
 package musicbot.commands;
 
 import musicbot.MCommand;
+import musicbot.Paginator;
 import musicbot.RecommendationService;
 import net.dv8tion.jda.api.EmbedBuilder;
 import net.dv8tion.jda.api.entities.MessageEmbed;
@@ -48,11 +49,12 @@ public class Recommend implements MCommand {
 
     final String artistInput = event.getOption("artist") != null ? event.getOption("artist").getAsString() : "";
     final String genreInput = event.getOption("genre") != null ? event.getOption("genre").getAsString() : "";
-
-    final List<Track> tracks = new RecommendationService().getRecommendations(artistInput, genreInput, 1);
-
+    final List<Track> tracks = new RecommendationService().getRecommendations(artistInput, genreInput);
+    final Paginator paginator = new Paginator();
+    final Paginator.PaginatedItems<Track> paginatedTracks = paginator.paginate(tracks, 5, 1);
     final EmbedBuilder eb = new EmbedBuilder();
-    final List<Track> trackList = tracks.subList(0, 5);
+    final List<Track> trackList = paginatedTracks.get();
+
     if (!trackList.isEmpty()) {
       eb
           .setTitle("Recommendations based on \"" + artistInput + "\"")
@@ -70,16 +72,14 @@ public class Recommend implements MCommand {
       });
 
       final MessageEmbed embed = eb.build();
-
-
       final List<Button> buttons = trackList.stream().map(track -> {
-            final String artists = Arrays.stream(track.getArtists()).map(ArtistSimplified::getName)
-                .collect(Collectors.joining(", "));
+        final String artists = Arrays.stream(track.getArtists()).map(ArtistSimplified::getName)
+            .collect(Collectors.joining(", "));
 
-            return Button.primary("recommend_" + artists, track.getName());
+        return Button.primary("recommend_" + artists, track.getName());
       }).collect(Collectors.toList());
 
-      final String buttonId = "more-recommend_" + artistInput + "--" + genreInput + "_" + "1";
+      final String buttonId = "more-recommend_" + artistInput + "--" + genreInput + "_" + paginatedTracks.getNextPageNum();
 
       event
           .getHook()