perf(render): reuse the viewer membership buffer (#84)

Co-authored-by: Arbousier1 <elderli@foxmail.com>

Author: TypeThe0ry

src/main/java/top/ellan/mahjong/table/render/TableRenderSnapshotFactory.java

@@ -4,32 +4,40 @@
 import top.ellan.mahjong.render.TableRenderSubject;
 import top.ellan.mahjong.render.snapshot.TableRenderSnapshot;
 import top.ellan.mahjong.render.snapshot.TableSeatRenderSnapshot;
+import java.util.Collections;
 import java.util.Comparator;
 import java.util.EnumMap;
 import java.util.HashMap;
-import java.util.HashSet;
 import java.util.List;
 import java.util.Map;
 import java.util.Objects;
-import java.util.Set;
 import java.util.UUID;
 import org.bukkit.Location;
 import org.bukkit.entity.Player;
 
 public final class TableRenderSnapshotFactory {
+    private static final Comparator<SerializedViewerId> SERIALIZED_VIEWER_ID_COMPARATOR =
+        Comparator.comparing(SerializedViewerId::serializedId);
+
     public TableRenderSnapshot create(TableRenderSubject session, long version, long cancellationNonce) {
         Location tableCenter = session.center();
         boolean started = session.isStarted();
         List<SerializedViewerId> serializedOnlineViewerIds = session.viewers().stream()
             .map(Player::getUniqueId)
             .distinct()
             .map(viewerId -> new SerializedViewerId(viewerId, viewerId.toString()))
-            .sorted(Comparator.comparing(SerializedViewerId::serializedId))
+            .sorted(SERIALIZED_VIEWER_ID_COMPARATOR)
             .toList();
         List<UUID> onlineViewerIds = serializedOnlineViewerIds.stream()
             .map(SerializedViewerId::id)
             .toList();
-        Set<UUID> onlineViewerIdSet = new HashSet<>(onlineViewerIds);
+        Map<UUID, SerializedViewerId> serializedOnlineViewersById = new HashMap<>(
+            Math.max(16, (int) (serializedOnlineViewerIds.size() / 0.75F) + 1)
+        );
+        for (SerializedViewerId viewer : serializedOnlineViewerIds) {
+            serializedOnlineViewersById.put(viewer.id(), viewer);
+        }
+        StringBuilder viewerMembershipBuffer = this.viewerMembershipBuffer(serializedOnlineViewerIds);
         SeatWind[] seatWinds = SeatWind.values();
         EnumMap<SeatWind, UUID> seatPlayerIds = new EnumMap<>(SeatWind.class);
         for (SeatWind wind : seatWinds) {
@@ -38,13 +46,28 @@ public TableRenderSnapshot create(TableRenderSubject session, long version, long
         Map<UUID, String> viewerMembershipSignatures = new HashMap<>();
         Map<UUID, List<UUID>> viewerIdsExcluding = new HashMap<>();
         for (UUID playerId : seatPlayerIds.values()) {
-            if (viewerMembershipSignatures.containsKey(playerId)
-                || playerId != null && !onlineViewerIdSet.contains(playerId)) {
+            if (viewerMembershipSignatures.containsKey(playerId)) {
+                continue;
+            }
+            SerializedViewerId excludedViewer = playerId == null
+                ? null
+                : serializedOnlineViewersById.get(playerId);
+            if (playerId != null && excludedViewer == null) {
                 continue;
             }
             viewerMembershipSignatures.put(
                 playerId,
-                this.viewerMembershipSignature(serializedOnlineViewerIds, playerId)
+                excludedViewer == null
+                    ? viewerMembershipBuffer.toString()
+                    : this.viewerMembershipSignature(
+                        viewerMembershipBuffer,
+                        excludedViewer,
+                        Collections.binarySearch(
+                            serializedOnlineViewerIds,
+                            excludedViewer,
+                            SERIALIZED_VIEWER_ID_COMPARATOR
+                        )
+                    )
             );
             viewerIdsExcluding.put(
                 playerId,
@@ -59,7 +82,7 @@ public TableRenderSnapshot create(TableRenderSubject session, long version, long
                     session,
                     wind,
                     seatPlayerIds.get(wind),
-                    onlineViewerIdSet,
+                    serializedOnlineViewersById,
                     viewerMembershipSignatures,
                     viewerIdsExcluding
                 )
@@ -131,7 +154,7 @@ private TableSeatRenderSnapshot captureSeatSnapshot(
         TableRenderSubject session,
         SeatWind wind,
         UUID playerId,
-        Set<UUID> onlineViewerIdSet,
+        Map<UUID, SerializedViewerId> serializedOnlineViewersById,
         Map<UUID, String> viewerMembershipSignatures,
         Map<UUID, List<UUID>> viewerIdsExcluding
     ) {
@@ -145,7 +168,7 @@ private TableSeatRenderSnapshot captureSeatSnapshot(
             occupied && session.isRiichi(playerId),
             occupied && session.isReady(playerId),
             occupied && session.isQueuedToLeave(playerId),
-            occupied && onlineViewerIdSet.contains(playerId),
+            occupied && serializedOnlineViewersById.containsKey(playerId),
             viewerMembershipSignatures.getOrDefault(playerId, ""),
             occupied ? session.selectedHandTileIndex(playerId) : -1,
             occupied ? session.selectedHandTileIndices(playerId) : List.of(),
@@ -160,14 +183,25 @@ private TableSeatRenderSnapshot captureSeatSnapshot(
         );
     }
 
-    private String viewerMembershipSignature(List<SerializedViewerId> onlineViewerIds, UUID excludedPlayerId) {
+    private StringBuilder viewerMembershipBuffer(List<SerializedViewerId> onlineViewerIds) {
         StringBuilder builder = new StringBuilder(onlineViewerIds.size() * 36);
         for (SerializedViewerId viewer : onlineViewerIds) {
-            if (!viewer.id().equals(excludedPlayerId)) {
-                builder.append(viewer.serializedId());
-            }
+            builder.append(viewer.serializedId());
         }
-        return builder.toString();
+        return builder;
+    }
+
+    private String viewerMembershipSignature(
+        StringBuilder viewerMembershipBuffer,
+        SerializedViewerId excludedViewer,
+        int excludedViewerIndex
+    ) {
+        String serializedId = excludedViewer.serializedId();
+        int start = excludedViewerIndex * serializedId.length();
+        viewerMembershipBuffer.delete(start, start + serializedId.length());
+        String signature = viewerMembershipBuffer.toString();
+        viewerMembershipBuffer.insert(start, serializedId);
+        return signature;
     }
 
     private List<UUID> viewerIdsExcluding(List<UUID> onlineViewerIds, UUID excludedPlayerId) {