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/*
 * Copyright 2013 Samppa Saarela
 *
 * 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.javersion.util;

import java.util.AbstractMap;
import java.util.AbstractSet;
import java.util.Iterator;
import java.util.Map;
import java.util.Set;

import javax.annotation.concurrent.NotThreadSafe;

import org.javersion.util.AbstractHashTrie.Node;

@NotThreadSafe
public class MutableHashMap extends AbstractMap implements MutableMap {

    private MMap map;

    private V previousValue;

    private final Merger> defaultMerger = new Merger>() {

        @Override
        public boolean insert(java.util.Map.Entry newEntry) {
            previousValue = null;
            return true;
        }

        @Override
        public boolean merge(java.util.Map.Entry oldEntry, java.util.Map.Entry newEntry) {
            previousValue = oldEntry.getValue();
            return true;
        }

        @Override
        public boolean delete(java.util.Map.Entry oldEntry) {
            previousValue = oldEntry.getValue();
            return true;
        }
    };

    public MutableHashMap() {
        this.map = new MMap();
    }

    public MutableHashMap(int expectedSize) {
        this.map = new MMap(expectedSize);
    }

    MutableHashMap(Node> root, int size) {
        this.map = new MMap(root, size);
    }

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

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

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

    @Override
    public Set> entrySet() {
        return new AbstractSet>() {

            @Override
            public Iterator> iterator() {
                return map.iterator();
            }

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

            // TODO: clear, contains etc
        };
    }

    // TODO: values(), keySet() with spliterator()

    @Override
    public V put(final K key, final V value) {
        map.merge(key, value, defaultMerger);
        return previousValue;
    }

    @Override
    public V remove(final Object key) {
        map.dissoc(key, defaultMerger);
        return previousValue;
    }

    @Override
    public void putAll(final Map m) {
        map.assocAll(m);
    }

    @Override
    public void clear() {
        if (map.size() > 0) {
            map = new MMap();
        }
    }


    @Override
    public Iterator> iterator() {
        return map.iterator();
    }


    @Override
    public void merge(K key, V value, Merger> merger) {
        map.merge(key, value, merger);
    }

    @Override
    public void mergeAll(Map m, Merger> merger) {
        map.mergeAll(m, merger);
    }

    @Override
    public void mergeAll(Iterable> entries, Merger> merger) {
        map.mergeAll(entries, merger);
    }

    @Override
    public PersistentHashMap toPersistentMap() {
        return map.toPersistentMap();
    }


    private static class MMap extends AbstractHashMap> {

        private final Thread owner = Thread.currentThread();

        private UpdateContext>  updateContext;

        private Node> root;

        private int size;

        @SuppressWarnings("unchecked")
        private MMap(int expectedSize) {
            this(expectedSize, EMPTY_NODE, 0);
        }

        @SuppressWarnings("unchecked")
        private MMap() {
            this(EMPTY_NODE, 0);
        }

        private MMap(Node> root, int size) {
            this(32, root, size);
        }

        private MMap(int expectedSize, Node> root, int size) {
            this.updateContext = new UpdateContext>(expectedSize);
            this.root = root;
            this.size = size;
        }

        @Override
        protected Node> root() {
            verifyThread();
            return root;
        }

        @Override
        protected MMap self() {
            return this;
        }

        public PersistentHashMap toPersistentMap() {
            verifyThread();
            updateContext.commit();
            return PersistentHashMap.create(root, size);
        }

        private void verifyThread() {
            if (owner != Thread.currentThread()) {
                throw new IllegalStateException("MutableMap should only be accessed form the thread it was created in.");
            }
        }

        @Override
        public int size() {
            verifyThread();
            return size;
        }

        @SuppressWarnings("unchecked")
        @Override
        protected MMap doReturn(Node> newRoot, int newSize) {
            this.root = (Node>) (newRoot == null ? EMPTY_NODE : newRoot);
            this.size = newSize;
            return this;
        }

        @Override
        protected UpdateContext> updateContext(int expectedUpdates, Merger> merger) {
            verifyThread();
            if (updateContext.isCommitted()) {
                updateContext = new UpdateContext<>(expectedUpdates, merger);
            } else {
                updateContext.merger(merger);
            }
            return updateContext;
        }

        @Override
        protected void commit(UpdateContext updateContext) {
            // Nothing to do here
        }
    }
}