/*
 * The MIT License
 * 
 * Copyright (c) 2004-2010, Sun Microsystems, Inc., Kohsuke Kawaguchi
 * 
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 * 
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 * 
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */
package hudson.util;

import com.thoughtworks.xstream.converters.MarshallingContext;
import com.thoughtworks.xstream.converters.UnmarshallingContext;
import com.thoughtworks.xstream.converters.collections.MapConverter;
import com.thoughtworks.xstream.converters.collections.TreeMapConverter;
import com.thoughtworks.xstream.io.HierarchicalStreamReader;
import com.thoughtworks.xstream.io.HierarchicalStreamWriter;
import com.thoughtworks.xstream.mapper.Mapper;

import java.util.Collection;
import java.util.Collections;
import java.util.Comparator;
import java.util.HashMap;
import java.util.LinkedHashMap;
import java.util.Map;
import java.util.Set;
import java.util.TreeMap;

/**
 * {@link Map} that has copy-on-write semantics.
 *
 * <p>
 * This class is suitable where highly concurrent access is needed, yet
 * the write operation is relatively uncommon.
 *
 * @author Kohsuke Kawaguchi
 */
public abstract class CopyOnWriteMap<K,V> implements Map<K,V> {
    protected volatile Map<K,V> core;
    /**
     * Read-only view of {@link #core}.
     */
    private volatile Map<K,V> view;

    protected CopyOnWriteMap(Map<K,V> core) {
        update(core);
    }

    protected CopyOnWriteMap() {
        update(Collections.emptyMap());
    }

    protected void update(Map<K,V> m) {
        core = m;
        view = Collections.unmodifiableMap(core);
    }

    /**
     * Atomically replaces the entire map by the copy of the specified map.
     */
    public void replaceBy(Map<? extends K, ? extends V> data) {
        Map<K, V> d = copy();
        d.clear();
        d.putAll(data);
        update(d);
    }

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

    @Override
    public boolean isEmpty() {
        return core.isEmpty();
    }

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

    @Override
    public boolean containsValue(Object value) {
        return core.containsValue(value);
    }

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

    @Override
    public synchronized V put(K key, V value) {
        Map<K,V> m = copy();
        V r = m.put(key,value);
        update(m);

        return r;
    }

    @Override
    public synchronized V remove(Object key) {
        Map<K,V> m = copy();
        V r = m.remove(key);
        update(m);

        return r;
    }

    @Override
    public synchronized void putAll(Map<? extends K, ? extends V> t) {
        Map<K,V> m = copy();
        m.putAll(t);
        update(m);
    }

    protected abstract Map<K,V> copy();

    @Override
    public synchronized void clear() {
        update(Collections.emptyMap());
    }

    /**
     * This method will return a read-only {@link Set}.
     */
    @Override
    public Set<K> keySet() {
        return view.keySet();
    }

    /**
     * This method will return a read-only {@link Collection}.
     */
    @Override
    public Collection<V> values() {
        return view.values();
    }

    /**
     * This method will return a read-only {@link Set}.
     */
    @Override
    public Set<Entry<K,V>> entrySet() {
        return view.entrySet();
    }

    @Override public int hashCode() {
        return copy().hashCode();
    }

    @SuppressWarnings("EqualsWhichDoesntCheckParameterClass")
    @Override public boolean equals(Object obj) {
        return copy().equals(obj);
    }

    @Override public String toString() {
        return copy().toString();
    }

    /**
     * {@link CopyOnWriteMap} backed by {@link HashMap}.
     */
    public static final class Hash<K,V> extends CopyOnWriteMap<K,V> {
        public Hash(Map<K,V> core) {
            super(new LinkedHashMap<>(core));
        }

        public Hash() {
        }

        @Override
        protected Map<K,V> copy() {
            return new LinkedHashMap<>(core);
        }

        public static class ConverterImpl extends MapConverter {
            public ConverterImpl(Mapper mapper) {
                super(mapper);
            }

            @Override
            public boolean canConvert(Class type) {
                return type==Hash.class;
            }

            @Override
            public Object unmarshal(HierarchicalStreamReader reader, UnmarshallingContext context) {
                return new Hash((Map) super.unmarshal(reader,context));
            }

            @Override
            public void marshal(Object source, HierarchicalStreamWriter writer, MarshallingContext context) {
                super.marshal(((Hash)source).core,writer,context);
            }
        }
    }

    /**
     * {@link CopyOnWriteMap} backed by {@link TreeMap}.
     */
    public static final class Tree<K,V> extends CopyOnWriteMap<K,V> {
        private final Comparator<K> comparator;

        public Tree(Map<K,V> core, Comparator<K> comparator) {
            this(comparator);
            putAll(core);
        }

        public Tree(Comparator<K> comparator) {
            super(new TreeMap<>(comparator));
            this.comparator = comparator;
        }

        public Tree() {
            this(null);
        }

        @Override
        protected Map<K,V> copy() {
            TreeMap<K,V> m = new TreeMap<>(comparator);
            m.putAll(core);
            return m;
        }

        @Override
        public synchronized void clear() {
            update(new TreeMap<>(comparator));
        }

        public static class ConverterImpl extends TreeMapConverter {
            public ConverterImpl(Mapper mapper) {
                super(mapper);
            }

            @Override
            public boolean canConvert(Class type) {
                return type==Tree.class;
            }

            @Override
            public Object unmarshal(HierarchicalStreamReader reader, UnmarshallingContext context) {
                TreeMap tm = (TreeMap) super.unmarshal(reader,context);
                return new Tree(tm,tm.comparator());
            }

            @Override
            public void marshal(Object source, HierarchicalStreamWriter writer, MarshallingContext context) {
                super.marshal(((Tree)source).core,writer,context);
            }
        }
    }
}
