api: optimize pagination!!

API/src/main/java/cc/fascinated/common/PaginationBuilder.java

@@ -5,6 +5,7 @@ import lombok.AllArgsConstructor;
 import lombok.Getter;
 
 import java.util.List;
+import java.util.function.Function;
 import java.util.function.Supplier;
 
 /**
@@ -17,10 +18,15 @@ public class PaginationBuilder<T> {
      */
     private int itemsPerPage;
 
+    /**
+     * The total number of items.
+     */
+    private int totalItems;
+
     /**
      * The items to paginate.
      */
-    private List<T> items;
+    private Function<FetchItems, List<T>> items;
 
     /**
      * Sets the number of items per page.
@@ -33,14 +39,25 @@ public class PaginationBuilder<T> {
         return this;
     }
 
+    /**
+     * Sets the total number of items.
+     *
+     * @param totalItems The total number of items.
+     * @return The pagination builder.
+     */
+    public PaginationBuilder<T> totalItems(Supplier<Integer> totalItems) {
+        this.totalItems = totalItems.get();
+        return this;
+    }
+
     /**
      * Sets the items to paginate.
      *
      * @param getItems The items to paginate.
      * @return The pagination builder.
      */
-    public PaginationBuilder<T> fillItems(Supplier<List<T>> getItems) {
+    public PaginationBuilder<T> items(Function<FetchItems, List<T>> getItems) {
-        this.items = getItems.get();
+        this.items = getItems;
         return this;
     }
 
@@ -60,19 +77,39 @@ public class PaginationBuilder<T> {
      * @return The page.
      */
     public Page<T> getPage(int page) {
-        int totalItems = this.items.size();
+        List<T> items = this.items.apply(new FetchItems(page, this.itemsPerPage));
-        int totalPages = (int) Math.ceil((double) totalItems / this.itemsPerPage);
+        int totalPages = (int) Math.ceil((double) this.totalItems / this.itemsPerPage);
 
         if (page < 1 || page > totalPages) {
             throw new BadRequestException("Invalid page number");
         }
-        List<T> items = this.items.subList((page - 1) * this.itemsPerPage, Math.min(page * this.itemsPerPage, totalItems));
         return new Page<>(
                 items,
-                new Page.Metadata(page, totalPages, totalItems)
+                new Page.Metadata(page, totalPages, this.totalItems)
         );
     }
 
+    @AllArgsConstructor
+    @Getter
+    public static class FetchItems {
+        /**
+         * The current page.
+         */
+        private final int currentPage;
+
+        /**
+         * The items per page.
+         */
+        private final int itemsPerPage;
+
+        /**
+         * The amount of items to skip.
+         */
+        public int skipAmount() {
+            return (currentPage - 1) * itemsPerPage;
+        }
+    }
+
     @AllArgsConstructor
     @Getter
     public static class Page<T> {

API/src/main/java/cc/fascinated/model/score/impl/scoresaber/ScoreSaberScoreResponse.java

@@ -31,4 +31,18 @@ public class ScoreSaberScoreResponse extends ScoreSaberScore {
         this.user = user;
         this.leaderboard = leaderboard;
     }
+
+    /**
+     * Creates a new score saber score response.
+     *
+     * @param score the score to create the response from
+     * @param user the user that set the score
+     * @param leaderboard the leaderboard the score was set on
+     * @return the score saber score response
+     */
+    public static ScoreSaberScoreResponse fromScore(ScoreSaberScore score, UserDTO user, Leaderboard leaderboard) {
+        return new ScoreSaberScoreResponse(score.getId(), score.getPlayerId(), score.getPlatform(), score.getPlatformScoreId(), score.getLeaderboardId(),
+                score.getRank(), score.getAccuracy(), score.getPp(), score.getScore(), score.getModifiers(), score.getMisses(), score.getBadCuts(),
+                score.getDeviceInformation(), score.getTimestamp(), score.getWeight(), score.getMultiplier(), score.getMaxCombo(), user, leaderboard);
+    }
 }

API/src/main/java/cc/fascinated/repository/ScoreRepository.java

@@ -24,9 +24,10 @@ public interface ScoreRepository extends MongoRepository<Score, Long> {
     @Aggregation(pipeline = {
             "{ $match: { platform: ?0, pp: { $gt: 0 } } }",
             "{ $sort: { pp: -1 } }",
+            "{ $skip: ?2 }",
             "{ $limit: ?1 }",
     })
-    List<Score> getTopRankedScores(@NonNull Platform.Platforms platform, int amount);
+    List<Score> getTopRankedScores(@NonNull Platform.Platforms platform, int amount, int skip);
 
     /**
      * Gets all the ranked scores from the platform.

API/src/main/java/cc/fascinated/services/ScoreService.java

@@ -80,36 +80,17 @@ public class ScoreService {
      */
     public PaginationBuilder.Page<ScoreSaberScoreResponse> getTopRankedScores(@NonNull Platform.Platforms platform, int pageNumber, boolean scoresOnly) {
         PaginationBuilder<ScoreSaberScoreResponse> builder = new PaginationBuilder<ScoreSaberScoreResponse>().build();
-        builder.itemsPerPage(50);
+        builder.itemsPerPage(15);
-        builder.fillItems(() -> {
+        builder.totalItems(() -> this.scoreRepository.getTotalRankedScores(platform));
-            List<Score> foundScores = this.scoreRepository.getTopRankedScores(platform, 250);
+        builder.items((fetchItems) -> {
+            List<Score> foundScores = this.scoreRepository.getTopRankedScores(platform, fetchItems.getItemsPerPage(), fetchItems.skipAmount());
             List<ScoreSaberScoreResponse> scores = new ArrayList<>();
             for (Score score : foundScores) {
                 ScoreSaberScore scoreSaberScore = (ScoreSaberScore) score;
                 UserDTO user = scoresOnly ? null : userService.getUser(score.getPlayerId()).getAsDTO();
                 Leaderboard leaderboard = scoresOnly ? null : Leaderboard.getFromScoreSaberToken(scoreSaberService.getLeaderboard(score.getLeaderboardId()));
 
-                scores.add(new ScoreSaberScoreResponse(
+                scores.add(ScoreSaberScoreResponse.fromScore(scoreSaberScore, user, leaderboard));
-                        score.getId(),
-                        score.getPlayerId(),
-                        score.getPlatform(),
-                        score.getPlatformScoreId(),
-                        score.getLeaderboardId(),
-                        score.getRank(),
-                        score.getAccuracy(),
-                        score.getPp(),
-                        score.getScore(),
-                        score.getModifiers(),
-                        score.getMisses(),
-                        score.getBadCuts(),
-                        score.getDeviceInformation(),
-                        score.getTimestamp(),
-                        scoreSaberScore.getWeight(),
-                        scoreSaberScore.getMultiplier(),
-                        scoreSaberScore.getMaxCombo(),
-                        user,
-                        leaderboard
-                ));
             }
             return scores;
         });