/*
 * 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.wicket.extensions.markup.html.repeater.tree;

import java.util.Set;

import org.apache.wicket.Component;
import org.apache.wicket.IGenericComponent;
import org.apache.wicket.ajax.AjaxRequestTarget;
import org.apache.wicket.core.request.handler.IPartialPageRequestHandler;
import org.apache.wicket.extensions.markup.html.repeater.util.ProviderSubset;
import org.apache.wicket.markup.html.panel.Panel;
import org.apache.wicket.markup.repeater.DefaultItemReuseStrategy;
import org.apache.wicket.markup.repeater.IItemReuseStrategy;
import org.apache.wicket.markup.repeater.Item;
import org.apache.wicket.model.IModel;

/**
 * Abstract base class for {@link NestedTree} and {@link TableTree}. Uses its model for storing the
 * {@link State} of its nodes.
 * 
 * Note that a tree has no notion of a <em>selection</em>. Handling state of nodes besides
 * expanse/collapse is irrelevant to a tree implementation.
 * 
 * @see #newContentComponent(String, IModel)
 * 
 * @author svenmeier
 * @param <T>
 *            the node type
 */
public abstract class AbstractTree<T> extends Panel implements IGenericComponent<Set<T>, AbstractTree<T>>
{
        private static final long serialVersionUID = 1L;

        private ITreeProvider<T> provider;

        private IItemReuseStrategy itemReuseStrategy;

        protected AbstractTree(String id, ITreeProvider<T> provider)
        {
                this(id, provider, null);
        }

        protected AbstractTree(String id, ITreeProvider<T> provider, IModel<? extends Set<T>> state)
        {
                super(id, state);

                if (provider == null)
                {
                        throw new IllegalArgumentException("argument [provider] cannot be null");
                }
                this.provider = provider;
        }

        /**
         * Sets the item reuse strategy. This strategy controls the creation of {@link Item}s.
         * 
         * @see IItemReuseStrategy
         * 
         * @param strategy
         *            item reuse strategy
         * @return this for chaining
         */
        public AbstractTree<T> setItemReuseStrategy(IItemReuseStrategy strategy)
        {
                this.itemReuseStrategy = strategy;

                return this;
        }

        /**
         * @return currently set item reuse strategy. Defaults to <code>DefaultItemReuseStrategy</code>
         *         if none was set.
         * 
         * @see DefaultItemReuseStrategy
         */
        public IItemReuseStrategy getItemReuseStrategy()
        {
                if (itemReuseStrategy == null)
                {
                        return DefaultItemReuseStrategy.getInstance();
                }
                return itemReuseStrategy;
        }

        /**
         * Get the provider of the tree nodes.
         * 
         * @return provider
         */
        public ITreeProvider<T> getProvider()
        {
                return provider;
        }

        /**
         * Delegate to {@link #newModel()} if none is inited in super implementation.
         */
        @Override
        protected IModel<?> initModel()
        {
                IModel<?> model = super.initModel();

                if (model == null)
                {
                        model = newModel();
                }

                return model;
        }

        /**
         * Factory method for a model, by default creates a model containing a {@link ProviderSubset}.
         * Depending on your {@link ITreeProvider}'s model you might consider to provide a custom
         * {@link Set} implementation.
         * <p>
         * Note: The contained {@link Set} has at least to implement {@link Set#add(Object)},
         * {@link Set#remove(Object)} and {@link Set#contains(Object)}.
         * 
         * @return model for this tree
         */
        protected IModel<Set<T>> newModel()
        {
                return new ProviderSubset<>(provider).createModel();
        }

        /**
         * Expand the given node, tries to update the affected branch if the change happens on an
         * {@link AjaxRequestTarget}.
         * 
         * @param t
         *            the node to expand
         * 
         * @see #getModelObject()
         * @see Set#add(Object)
         * @see #updateBranch(Object, IPartialPageRequestHandler)
         */
        public void expand(T t)
        {
                modelChanging();
                getModelObject().add(t);
                modelChanged();

                getRequestCycle().find(IPartialPageRequestHandler.class).ifPresent(
                        target -> updateBranch(t, target)
                );
        }

        /**
         * Collapse the given node, tries to update the affected branch if the change happens on an
         * {@link AjaxRequestTarget}.
         * 
         * @param t
         *            the object to collapse
         * 
         * @see #getModelObject()
         * @see Set#remove(Object)
         * @see #updateBranch(Object, IPartialPageRequestHandler)
         */
        public void collapse(T t)
        {
                modelChanging();
                getModelObject().remove(t);
                modelChanged();

                getRequestCycle().find(IPartialPageRequestHandler.class).ifPresent(
                        target -> updateBranch(t, target)
                );
        }

        /**
         * Get the given node's {@link State}.
         * 
         * @param t
         *            the node to get state for
         * @return state
         * 
         * @see #getModelObject()
         * @see Set#contains(Object)
         */
        public State getState(T t)
        {
                if (getModelObject().contains(t))
                {
                        return State.EXPANDED;
                }
                else
                {
                        return State.COLLAPSED;
                }
        }

        /**
         * Overridden to detach the {@link ITreeProvider}.
         */
        @Override
        protected void onDetach()
        {
                provider.detach();

                super.onDetach();
        }

        /**
         * Create a new component for a node.
         * 
         * @param id
         *            the component id
         * @param model
         *            the model containing the node
         * @return created component
         */
        public Component newNodeComponent(String id, final IModel<T> model)
        {
                return new Node<T>(id, this, model)
                {
                        private static final long serialVersionUID = 1L;

                        @Override
                        protected Component createContent(String id, IModel<T> model)
                        {
                                return AbstractTree.this.newContentComponent(id, model);
                        }
                };
        }

        /**
         * Create a new component for the content of a node.
         * 
         * @param id
         *            the component id
         * @param model
         *            the model containing the node
         * @return created component
         */
        protected abstract Component newContentComponent(String id, IModel<T> model);

        /**
         * Convenience method to update a single branch on an {@link AjaxRequestTarget}. Does nothing if
         * the given node is currently not visible.
         * 
         * @param node
         *            node to update
         * @param target
         *            request target must not be @code null}
         */
        public abstract void updateBranch(T node, IPartialPageRequestHandler target);

        /**
         * Convenience method to update a single node on an {@link AjaxRequestTarget}. Does nothing if
         * the given node is currently not visible.
         * 
         * @param node
         *            node to update
         * @param target
         *            request target must not be @code null}
         */
        public abstract void updateNode(T node, IPartialPageRequestHandler target);

        /**
         * The state of a node.
         */
        public enum State {
                /**
                 * The node is collapsed, i.e. its children are not iterated.
                 */
                COLLAPSED,
                /**
                 * The node is expanded, i.e. its children are iterated.
                 */
                EXPANDED
        }
}