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package io.cloudstate.javasupport.crdt;

import java.util.*;

/** Utility class for helping implement {@link ORMap} based CRDTs. */
abstract class AbstractORMapWrapper extends AbstractMap
    implements Map {

  final ORMap ormap;

  AbstractORMapWrapper(ORMap ormap) {
    this.ormap = ormap;
  }

  abstract V getCrdtValue(C crdt);

  abstract void setCrdtValue(C crdt, V value);

  abstract C getOrUpdateCrdt(K key, V value);

  @Override
  public int size() {
    return ormap.size();
  }

  @Override
  public boolean containsKey(Object key) {
    return ormap.containsKey(key);
  }

  @Override
  public V get(Object key) {
    C crdt = ormap.get(key);
    if (crdt != null) {
      return getCrdtValue(crdt);
    } else {
      return null;
    }
  }

  @Override
  public V put(K key, V value) {
    C existing = ormap.get(key);
    if (existing != null) {
      V old = getCrdtValue(existing);
      setCrdtValue(existing, value);
      return old;
    } else {
      getOrUpdateCrdt(key, value);
      return null;
    }
  }

  @Override
  public V remove(Object key) {
    C old = ormap.remove(key);
    if (old != null) {
      return getCrdtValue(old);
    } else {
      return null;
    }
  }

  @Override
  public void clear() {
    ormap.clear();
  }

  @Override
  public Set keySet() {
    return ormap.keySet();
  }

  @Override
  public Set> entrySet() {
    return new EntrySet();
  }

  private final class MapEntry implements Entry {
    private final Entry entry;

    MapEntry(Entry entry) {
      this.entry = entry;
    }

    @Override
    public K getKey() {
      return entry.getKey();
    }

    @Override
    public V getValue() {
      return getCrdtValue(entry.getValue());
    }

    @Override
    public V setValue(V value) {
      V old = getCrdtValue(entry.getValue());
      setCrdtValue(entry.getValue(), value);
      return old;
    }
  }

  private final class EntrySet extends AbstractSet> implements Set> {
    @Override
    public int size() {
      return ormap.size();
    }

    @Override
    public Iterator> iterator() {
      return new Iterator>() {
        private final Iterator> iter = ormap.entrySet().iterator();

        @Override
        public boolean hasNext() {
          return iter.hasNext();
        }

        @Override
        public Entry next() {
          return new MapEntry(iter.next());
        }

        @Override
        public void remove() {
          iter.remove();
        }
      };
    }

    @Override
    public boolean add(Entry kvEntry) {
      return !kvEntry.getValue().equals(put(kvEntry.getKey(), kvEntry.getValue()));
    }

    @Override
    public void clear() {
      ormap.clear();
    }
  }
}