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package javax.ws.rs.core;

import java.util.Collection;
import java.util.LinkedList;
import java.util.List;
import java.util.Map;
import java.util.Set;

/**
 * Abstract skeleton implementation of a {@link MultivaluedMap} that is backed
 * by a [key, multi-value] store represented as a {@link Map Map&lt;K, List&lt;V&gt;&gt;}.
 *
 * @param <K> the type of keys maintained by this map.
 * @param <V> the type of mapped values.
 * @author Marek Potociar
 */
public abstract class AbstractMultivaluedMap<K, V> implements MultivaluedMap<K, V> {

    /**
     * Backing store for the [key, multi-value] pairs.
     */
    protected final Map<K, List<V>> store;

    /**
     * Initialize the backing store in the abstract parent multivalued map
     * implementation.
     *
     * @param store the backing {@link Map} to be used as a [key, multi-value]
     *              store. Must not be {@code null}.
     * @throws NullPointerException in case the underlying {@code store} parameter
     *                              is {@code null}.
     */
    public AbstractMultivaluedMap(Map<K, List<V>> store) {
        if (store == null) {
            throw new NullPointerException("Underlying store must not be 'null'.");
        }
        this.store = store;
    }

    /**
     * Set the value for the key to be a one item list consisting of the supplied
     * value. Any existing values will be replaced.
     * <p />
     * NOTE: This implementation ignores {@code null} values; A supplied value
     * of {@code null} is ignored and not added to the purged value list.
     * As a result of such operation, empty value list would  be registered for
     * the supplied key. Overriding implementations may modify this behavior by
     * redefining the {@link #addNull(java.util.List)} method.
     *
     * @param key   the key
     * @param value the single value of the key. If the value is {@code null} it
     *              will be ignored.
     */
    @Override
    public final void putSingle(K key, V value) {
        List<V> values = getValues(key);

        values.clear();
        if (value != null) {
            values.add(value);
        } else {
            addNull(values);
        }
    }

    /**
     * Define the behavior for adding a {@code null} values to the value list.
     * <p />
     * Default implementation is a no-op, i.e. the {@code null} values are ignored.
     * Overriding implementations may modify this behavior by providing their
     * own definitions of this method.
     *
     * @param values value list where the {@code null} value addition is being
     *               requested.
     */
    @SuppressWarnings("UnusedParameters")
    protected void addNull(List<V> values) {
        // do nothing in the default implementation; ignore the null value
    }

    /**
     * Define the behavior for adding a {@code null} values to the first position
     * in the value list.
     * <p />
     * Default implementation is a no-op, i.e. the {@code null} values are ignored.
     * Overriding implementations may modify this behavior by providing their
     * own definitions of this method.
     *
     * @param values value list where the {@code null} value addition is being
     *               requested.
     */
    @SuppressWarnings("UnusedParameters")
    protected void addFirstNull(List<V> values) {
        // do nothing in the default implementation; ignore the null value
    }

    /**
     * Add a value to the current list of values for the supplied key.
     * <p />
     * NOTE: This implementation ignores {@code null} values; A supplied value
     * of {@code null} is ignored and not added to the value list. Overriding
     * implementations may modify this behavior by redefining the
     * {@link #addNull(java.util.List)} method.
     *
     * @param key   the key
     * @param value the value to be added.
     */
    @Override
    public final void add(K key, V value) {
        List<V> values = getValues(key);

        if (value != null) {
            values.add(value);
        } else {
            addNull(values);
        }
    }

    /**
     * Add multiple values to the current list of values for the supplied key. If
     * the supplied array of new values is empty, method returns immediately.
     * Method throws a {@code NullPointerException} if the supplied array of values
     * is {@code null}.
     * <p />
     * NOTE: This implementation ignores {@code null} values; Any of the supplied values
     * of {@code null} is ignored and not added to the value list. Overriding
     * implementations may modify this behavior by redefining the
     * {@link #addNull(java.util.List)} method.
     *
     * @param key       the key.
     * @param newValues the values to be added.
     * @throws NullPointerException if the supplied array of new values is {@code null}.
     */
    @Override
    public final void addAll(K key, V... newValues) {
        if (newValues == null) {
            throw new NullPointerException("Supplied array of values must not be null.");
        }
        if (newValues.length == 0) {
            return;
        }

        List<V> values = getValues(key);

        for (V value : newValues) {
            if (value != null) {
                values.add(value);
            } else {
                addNull(values);
            }
        }
    }

    /**
     * Add all the values from the supplied value list to the current list of
     * values for the supplied key. If the supplied value list is empty, method
     * returns immediately. Method throws a {@code NullPointerException} if the
     * supplied array of values is {@code null}.
     * <p />
     * NOTE: This implementation ignores {@code null} values; Any {@code null} value
     * in the supplied value list is ignored and not added to the value list. Overriding
     * implementations may modify this behavior by redefining the
     * {@link #addNull(java.util.List)} method.
     *
     * @param key       the key.
     * @param valueList the list of values to be added.
     * @throws NullPointerException if the supplied value list is {@code null}.
     */
    @Override
    public final void addAll(K key, List<V> valueList) {
        if (valueList == null) {
            throw new NullPointerException("Supplied list of values must not be null.");
        }
        if (valueList.isEmpty()) {
            return;
        }

        List<V> values = getValues(key);

        for (V value : valueList) {
            if (value != null) {
                values.add(value);
            } else {
                addNull(values);
            }
        }
    }

    @Override
    public final V getFirst(K key) {
        List<V> values = store.get(key);
        if (values != null && values.size() > 0) {
            return values.get(0);
        } else {
            return null;
        }
    }

    /**
     * Add a value to the first position in the current list of values for the
     * supplied key.
     * <p />
     * NOTE: This implementation ignores {@code null} values; A supplied value
     * of {@code null} is ignored and not added to the purged value list. Overriding
     * implementations may modify this behavior by redefining the
     * {@link #addFirstNull(java.util.List)} method.
     *
     * @param key   the key
     * @param value the value to be added.
     */
    @Override
    public final void addFirst(K key, V value) {
        List<V> values = getValues(key);

        if (value != null) {
            values.add(0, value);
        } else {
            addFirstNull(values);
        }
    }

    /**
     * Return a non-null list of values for a given key. The returned list may be
     * empty.
     * <p />
     * If there is no entry for the key in the map, a new empty {@link List}
     * instance is created, registered within the map to hold the values of
     * the key and returned from the method.
     *
     * @param key the key.
     * @return value list registered with the key. The method is guaranteed to never
     *         return {@code null}.
     */
    protected final List<V> getValues(K key) {
        List<V> l = store.get(key);
        if (l == null) {
            l = new LinkedList<V>();
            store.put(key, l);
        }
        return l;
    }

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

    /**
     * {@inheritDoc }
     * <p />
     * This implementation delegates the method call to to the the underlying
     * [key, multi-value] store.
     *
     * @return a hash code value for the underlying [key, multi-value] store.
     */
    @Override
    public int hashCode() {
        return store.hashCode();
    }

    /**
     * {@inheritDoc }
     * <p />
     * This implementation delegates the method call to to the the underlying
     * [key, multi-value] store.
     *
     * @return {@code true} if the specified object is equal to the underlying
     *         [key, multi-value] store, {@code false} otherwise.
     */
    @Override
    @SuppressWarnings("EqualsWhichDoesntCheckParameterClass")
    public boolean equals(Object o) {
        return store.equals(o);
    }

    @Override
    public Collection<List<V>> values() {
        return store.values();
    }

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

    @Override
    public List<V> remove(Object key) {
        return store.remove(key);
    }

    @Override
    public void putAll(Map<? extends K, ? extends List<V>> m) {
        store.putAll(m);
    }

    @Override
    public List<V> put(K key, List<V> value) {
        return store.put(key, value);
    }

    @Override
    public Set<K> keySet() {
        return store.keySet();
    }

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

    @Override
    public List<V> get(Object key) {
        return store.get(key);
    }

    @Override
    public Set<Entry<K, List<V>>> entrySet() {
        return store.entrySet();
    }

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

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

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

    @Override
    public boolean equalsIgnoreValueOrder(MultivaluedMap<K, V> omap) {
        if (this == omap) {
            return true;
        }
        if (!keySet().equals(omap.keySet())) {
            return false;
        }
        for (Entry<K, List<V>> e : entrySet()) {
            List<V> olist = omap.get(e.getKey());
            if (e.getValue().size() != olist.size()) {
                return false;
            }
            for (V v : e.getValue()) {
                if (!olist.contains(v)) {
                    return false;
                }
            }
        }
        return true;
    }
}
