/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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.apache.commons.flatfile;

import java.io.Serializable;
import java.util.AbstractList;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.Iterator;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;

import org.apache.commons.collections4.IteratorUtils;
import org.apache.commons.collections4.Transformer;
import org.apache.commons.lang3.ArrayUtils;
import org.apache.commons.lang3.Validate;

/**
 * Basic implementation of NamedEntityCollection.
 * @version $Revision: 1766123 $ $Date: 2016-10-21 15:40:45 -0500 (Fri, 21 Oct 2016) $
 */
public class EntityMap extends EntityCollectionSupport implements NamedEntityCollection {

    private static final long serialVersionUID = 3162898927743996952L;

    private static class Child implements Serializable {

        /** Serialization version */
        private static final long serialVersionUID = 2347729609002856564L;

        private final String name;
        @SuppressWarnings("PMD.UnusedPrivateField") // false positive; this field is used in EntityMap#clone()
        private final Entity entity;

        /**
         * Create a new Child instance.
         * @param name of child
         * @param entity child
         */
        public Child(String name, Entity entity) {
            this.name = name;
            if (entity == null) {
                throw new IllegalArgumentException();
            }
            this.entity = entity;
        }

    }

    /**
     * Expose the Child list as List<Entity>. This is necessary because we permit nameless children,
     * which we want to account for in a layout but have no need of referencing later.
     */
    private static class ChildrenList extends AbstractList<Entity> implements Serializable {

        private static final long serialVersionUID = -954784669450571284L;

        private static final Transformer<Child, Entity> CHILD_TO_ENTITY = new Transformer<Child, Entity>() {

            public Entity transform(Child input) {
                return input.entity;
            }
        };

        private final List<Child> wrapped;

        /**
         * Create a new {@link ChildrenList} wrapping the specified {@link List}.
         * @param wrapped {@link List}
         */
        private ChildrenList(List<Child> wrapped) {
            super();
            this.wrapped = wrapped;
        }

        /**
         * {@inheritDoc}
         */
        @Override
        public Entity get(int index) {
            return CHILD_TO_ENTITY.transform(wrapped.get(index));
        }

        /**
         * {@inheritDoc}
         */
        @Override
        public Iterator<Entity> iterator() {
            return IteratorUtils.transformedIterator(wrapped.iterator(), CHILD_TO_ENTITY);
        }

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

    }

    /** All children */
    private List<Child> children;

    /** contains mapped children only */
    private Map<String, Entity> childMap;

    private List<Entity> exposeChildrenList;

    /**
     * Add a child.
     * @param name if {@code null} filler element
     * @param child non-null child Entity
     */
    public synchronized void add(String name, Entity child) {
        Validate.notNull(child, "child entity is null");

        if (children == null) {
            children = new ArrayList<Child>();
            exposeChildrenList = new ChildrenList(children);
            childMap = new LinkedHashMap<String, Entity>();
        }
        if (childMap.containsKey(name)) {
            throw new IllegalArgumentException("cannot add > 1 child entity '" + name + "'");
        }
        if (name != null) {
            childMap.put(name, child);
        }
        children.add(new Child(name, child));
    }

    /**
     * Get a map of the children.
     * @return Map<String, Entity>
     */
    public synchronized Map<String, Entity> getChildMap() {
        return childMap == null ? Collections.<String, Entity> emptyMap() : Collections.unmodifiableMap(childMap);
    }

    /**
     * {@inheritDoc}
     */
    public synchronized String[] getChildNames() {
        return childMap == null ? ArrayUtils.EMPTY_STRING_ARRAY
            : childMap.keySet().toArray(new String[childMap.size()]);
    }

    /**
     * {@inheritDoc}
     */
    public Entity getChild(String name) {
        return getChildMap().get(name);
    }

    /**
     * {@inheritDoc}
     */
    public boolean hasChild(String name) {
        return getChildMap().containsKey(name);
    }

    /**
     * {@inheritDoc}
     */
    public synchronized Collection<Entity> getChildren() {
        return children == null ? Collections.<Entity> emptyList() : Collections.unmodifiableList(exposeChildrenList);
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public synchronized EntityMap clone() {
        EntityMap result = (EntityMap) super.clone();
        result.children = null;
        result.childMap = null;
        result.exposeChildrenList = null;
        if (children != null) {
            for (Child child : children) {
                result.add(child.name, child.entity.clone());
            }
        }
        return result;
    }
}