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Adapter for persistence implementations based on key-value stores
There is a newer version: 4.12.20
// Copyright 2015-2024 Nstream, inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package nstream.persist.kv.state;

import java.util.ArrayList;
import swim.collections.BTree;
import swim.collections.HashTrieSet;
import swim.structure.Value;

/**
 * Implementation details for {@link MapState}.
 */
class MapStateInner {

  private final long epoch;
  private final BTree contents;
  private final HashTrieSet tombstones;

  private MapStateInner(long epoch, BTree contents, HashTrieSet tombstones) {
    this.epoch = epoch;
    this.contents = contents;
    this.tombstones = tombstones;
  }

  MapStateInner(BTree contents) {
    this.epoch = 0;
    this.contents = contents;
    this.tombstones = HashTrieSet.empty();
  }

  public MapStateInner updated(Value key, Value value) {
    final var newContents = this.contents.updated(key, value);
    final var newTombstones = this.tombstones.removed(key);
    if (newContents == this.contents && newTombstones == this.tombstones) {
      return this;
    } else {
      return new MapStateInner(this.epoch, newContents, newTombstones);
    }
  }

  public MapStateInner removed(Value key) {
    if (this.tombstones.contains(key)) {
      return this;
    } else {
      final var newContents = this.contents.removed(key);
      final var newTombstones = this.tombstones.added(key);
      return new MapStateInner(this.epoch, newContents, newTombstones);
    }
  }

  public MapStateInner taken(int n, ArrayList removedKeys) {
    final var size = this.contents.size();
    if (n >= size) {
      return this;
    }
    final var removed = this.contents.drop(n);
    final var newContents = this.contents.take(n);
    final var newTombstones = this.tombstones.added(removed.keySet());
    removedKeys.addAll(removed.keySet());
    return new MapStateInner(this.epoch, newContents, newTombstones);
  }

  public MapStateInner dropped(int n, ArrayList removedKeys) {
    if (n == 0) {
      return this;
    }
    final var removed = this.contents.take(n);
    final var newContents = this.contents.drop(n);
    final var newTombstones = this.tombstones.added(removed.keySet());
    removedKeys.addAll(removed.keySet());
    return new MapStateInner(this.epoch, newContents, newTombstones);
  }

  public MapStateInner cleared() {
    return new MapStateInner(this.epoch + 1, BTree.empty(), HashTrieSet.empty());
  }

  public BTree getMap() {
    return this.contents;
  }

  public long getEpoch() {
    return this.epoch;
  }

}