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/*
 * Copyright 2018 Red Hat, 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 org.jboss.logmanager;

import java.util.AbstractMap;
import java.util.Collection;
import java.util.Collections;
import java.util.Set;
import java.util.concurrent.ConcurrentMap;
import java.util.concurrent.atomic.AtomicReferenceFieldUpdater;

final class CopyOnWriteMap extends AbstractMap implements ConcurrentMap, Cloneable {

    private static final FastCopyHashMap EMPTY = new FastCopyHashMap(32, 0.25f);

    @SuppressWarnings("unchecked")
    private volatile FastCopyHashMap map = EMPTY;

    private static final AtomicReferenceFieldUpdater mapUpdater = AtomicReferenceFieldUpdater.newUpdater(CopyOnWriteMap.class, FastCopyHashMap.class, "map");

    public V get(final Object key) {
        return map.get(key);
    }

    public boolean containsKey(final Object key) {
        return map.containsKey(key);
    }

    public int size() {
        return map.size();
    }

    public boolean containsValue(final Object value) {
        return map.containsValue(value);
    }

    @SuppressWarnings("unchecked")
    public void clear() {
        map = EMPTY;
    }

    public V put(final K key, final V value) {
        FastCopyHashMap oldVal, newVal;
        V result;
        do {
            oldVal = map;
            newVal = oldVal.clone();
            result = newVal.put(key, value);
        } while (! mapUpdater.compareAndSet(this, oldVal, newVal));
        return result;
    }

    public V remove(final Object key) {
        FastCopyHashMap oldVal, newVal;
        V result;
        do {
            oldVal = map;
            if (! oldVal.containsKey(key)) {
                return null;
            }
            newVal = oldVal.clone();
            result = newVal.remove(key);
        } while (! mapUpdater.compareAndSet(this, oldVal, newVal));
        return result;
    }

    @SuppressWarnings("unchecked")
    public CopyOnWriteMap clone() {
        try {
            return (CopyOnWriteMap) super.clone();
        } catch (CloneNotSupportedException e) {
            throw new IllegalStateException();
        }
    }

    public V putIfAbsent(final K key, final V value) {
        FastCopyHashMap oldVal, newVal;
        do {
            oldVal = map;
            if (oldVal.containsKey(key)) {
                return oldVal.get(key);
            }
            newVal = oldVal.clone();
            newVal.put(key, value);
        } while (! mapUpdater.compareAndSet(this, oldVal, newVal));
        return null;
    }

    @SuppressWarnings("unchecked")
    public boolean remove(final Object key, final Object value) {
        FastCopyHashMap oldVal, newVal;
        do {
            oldVal = map;
            if (value == oldVal.get(key) && (value != null || oldVal.containsKey(key))) {
                if (oldVal.size() == 1) {
                    newVal = EMPTY;
                } else {
                    newVal = oldVal.clone();
                    newVal.remove(key);
                }
            } else {
                return false;
            }
        } while (! mapUpdater.compareAndSet(this, oldVal, newVal));
        return true;
    }

    public boolean replace(final K key, final V oldValue, final V newValue) {
        FastCopyHashMap oldVal, newVal;
        do {
            oldVal = map;
            if (oldValue == oldVal.get(key) && (oldValue != null || oldVal.containsKey(key))) {
                newVal = oldVal.clone();
                newVal.put(key, newValue);
            } else {
                return false;
            }
        } while (! mapUpdater.compareAndSet(this, oldVal, newVal));
        return true;
    }

    public V replace(final K key, final V value) {
        FastCopyHashMap oldVal, newVal;
        V result;
        do {
            oldVal = map;
            if (value == oldVal.get(key) && (value != null || oldVal.containsKey(key))) {
                newVal = oldVal.clone();
                result = newVal.put(key, value);
            } else {
                return null;
            }
        } while (! mapUpdater.compareAndSet(this, oldVal, newVal));
        return result;
    }

    public Set keySet() {
        return Collections.unmodifiableSet(map.keySet());
    }

    public Collection values() {
        return Collections.unmodifiableCollection(map.values());
    }

    public Set> entrySet() {
        return Collections.unmodifiableSet(map.entrySet());
    }
}