NestedMap.java

/**
 * Copyright (c) 2013, Redsolution LTD. All rights reserved.
 *
 * This file is part of Xabber project; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License, Version 3.
 *
 * Xabber is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
 * See the GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License,
 * along with this program. If not, see http://www.gnu.org/licenses/.
 */
package com.xabber.android.data.entity;

import java.util.Collection;
import java.util.Collections;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import java.util.NoSuchElementException;

/**
 * Map of map with string value as keys for both maps.
 *
 * @param <T>
 * @author alexander.ivanov
 */
public class NestedMap<T> implements Iterable<NestedMap.Entry<T>> {

    private final Map<String, Map<String, T>> map;

    public NestedMap() {
        map = new HashMap<>();
    }

    /**
     * @return <code>null</code> if there is no such first or second level.
     */
    public T get(String first, String second) {
        Map<String, T> nested = map.get(first);
        if (nested == null)
            return null;
        return nested.get(second);
    }

    /**
     * Puts value. Nested map will be created if necessary.
     */
    synchronized public void put(String first, String second, T value) {
        Map<String, T> nested = map.get(first);
        if (nested == null) {
            nested = new HashMap<>();
            map.put(first, nested);
        }
        nested.put(second, value);
    }

    /**
     * Removes value. Nested map will be removed if necessary.
     */
    synchronized public T remove(String first, String second) {
        Map<String, T> nested = map.get(first);
        if (nested == null)
            return null;
        T value = nested.remove(second);
        if (nested.isEmpty())
            map.remove(first);
        return value;
    }

    /**
     * Removes all information associated with first level.
     */
    synchronized public void clear(String first) {
        map.remove(first);
    }

    /**
     * Removes all information.
     */
    synchronized public void clear() {
        map.clear();
    }

    /**
     * @return Whether there is no values.
     */
    synchronized public boolean isEmpty() {
        return map.isEmpty();
    }

    /**
     * Returns an {@link Iterator} for the elements in this object.
     * <p/>
     * Iterators are designed to be used by only one thread at a time.
     */
    @Override
    public Iterator<Entry<T>> iterator() {
        return new EntryIterator();
    }

    /**
     * Returns nested map.
     *
     * @return empty map if there is no such first level.
     */
    public Map<String, T> getNested(String first) {
        Map<String, T> nested = map.get(first);
        if (nested == null)
            return Collections.emptyMap();
        return Collections.unmodifiableMap(nested);
    }

    /**
     * Collection with values.
     * <p/>
     * ONLY {@link Collection#iterator()} FUNCTION IS SUPPORTED.
     */
    public Collection<T> values() {
        return new Values();
    }

    /**
     * Adds all elements from another {@link NestedMap}.
     */
    public void addAll(NestedMap<T> nestedMap) {
        for (NestedMap.Entry<T> entry : nestedMap)
            put(entry.getFirst(), entry.getSecond(), entry.getValue());
    }

    /**
     * Entry stored in {@link NestedMap}.
     *
     * @param <T>
     * @author alexander.ivanov
     */
    public static class Entry<T> {

        private final String first;
        private final String second;
        private final T value;

        Entry(String first, String second, T value) {
            super();
            this.first = first;
            this.second = second;
            this.value = value;
        }

        public String getFirst() {
            return first;
        }

        public String getSecond() {
            return second;
        }

        public T getValue() {
            return value;
        }

    }

    private class EntryIterator implements Iterator<Entry<T>> {

        private final Iterator<java.util.Map.Entry<String, Map<String, T>>> firstIterator;

        private java.util.Map.Entry<String, Map<String, T>> nested;

        private Iterator<java.util.Map.Entry<String, T>> secondIterator;

        private EntryIterator() {
            firstIterator = map.entrySet().iterator();
            nested = null;
            secondIterator = null;
        }

        @Override
        public boolean hasNext() {
            if (secondIterator != null && secondIterator.hasNext())
                return true;
            while (firstIterator.hasNext()) {
                nested = firstIterator.next();
                secondIterator = nested.getValue().entrySet().iterator();
                if (secondIterator.hasNext()) {
                    return true;
                }
            }
            return false;
        }

        @Override
        public Entry<T> next() throws NoSuchElementException {
            if (!hasNext())
                throw new NoSuchElementException();
            java.util.Map.Entry<String, T> entry = secondIterator.next();
            return new Entry<T>(nested.getKey(), entry.getKey(),
                    entry.getValue());
        }

        @Override
        public void remove() throws IllegalStateException {
            if (secondIterator == null)
                throw new IllegalStateException();
            secondIterator.remove();
            if (nested.getValue().isEmpty())
                firstIterator.remove();
        }

    }

    private class Values implements Collection<T> {

        @Override
        public boolean add(T object) {
            throw new UnsupportedOperationException();
        }

        @Override
        public boolean addAll(Collection<? extends T> arg0) {
            throw new UnsupportedOperationException();
        }

        @Override
        public void clear() {
            throw new UnsupportedOperationException();
        }

        @Override
        public boolean contains(Object object) {
            throw new UnsupportedOperationException();
        }

        @Override
        public boolean containsAll(Collection<?> arg0) {
            throw new UnsupportedOperationException();
        }

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

        @Override
        public Iterator<T> iterator() {
            return new ValuesIterator();
        }

        @Override
        public boolean remove(Object object) {
            throw new UnsupportedOperationException();
        }

        @Override
        public boolean removeAll(Collection<?> arg0) {
            throw new UnsupportedOperationException();
        }

        @Override
        public boolean retainAll(Collection<?> arg0) {
            throw new UnsupportedOperationException();
        }

        @Override
        public int size() {
            throw new UnsupportedOperationException();
        }

        @Override
        public Object[] toArray() {
            throw new UnsupportedOperationException();
        }

        @Override
        public <Type> Type[] toArray(Type[] array) {
            throw new UnsupportedOperationException();
        }

        private class ValuesIterator implements Iterator<T> {

            private final Iterator<Entry<T>> iterator;

            private ValuesIterator() {
                this.iterator = NestedMap.this.iterator();
            }

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

            @Override
            public T next() {
                return iterator.next().getValue();
            }

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

        }

    }

}