/*
 * 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.markup.repeater;

import java.util.HashSet;
import java.util.Iterator;
import java.util.Set;

import org.apache.wicket.Component;
import org.apache.wicket.DequeueContext;
import org.apache.wicket.DequeueContext.Bookmark;
import org.apache.wicket.MarkupContainer;
import org.apache.wicket.markup.IMarkupFragment;
import org.apache.wicket.markup.html.WebMarkupContainer;
import org.apache.wicket.model.IModel;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * Base class for repeaters. This container renders each of its children using its own markup.
 * 
 * The children are collected using {@link #renderIterator()} method. This class will take care of
 * properly positioning and rewinding its markup stream so before each child renders it points to
 * the beginning of this component. Each child is rendered by a call to
 * {@link #renderChild(Component)}. A typical implementation simply does
 * <code>child.render();</code>.
 *
 * <strong>Note</strong>: the children are added during the render phase (in {@linkplain #beforeRender()} so
 * most of the specializations of this class should not be used as parents of
 * {@link org.apache.wicket.markup.html.form.FormComponent}s in stateless pages because the form components
 * will not be available during the action phase (i.e. at
 * {@link org.apache.wicket.markup.html.form.StatelessForm#onSubmit()}). Use
 * {@link org.apache.wicket.markup.repeater.RepeatingView} in these cases.
 *
 * @author Igor Vaynberg (ivaynberg)
 */
public abstract class AbstractRepeater extends WebMarkupContainer
{
        private static final long serialVersionUID = 1L;

        private static final Logger log = LoggerFactory.getLogger(AbstractRepeater.class);

        /**
         * Constructor
         * 
         * @param id
         */
        public AbstractRepeater(String id)
        {
                super(id);
        }

        /**
         * Constructor
         * 
         * @param id
         * @param model
         */
        public AbstractRepeater(String id, IModel<?> model)
        {
                super(id, model);
        }

        /**
         * Returns an iterator for the collection of child components to be rendered. Users can override
         * this to change order of rendered children.
         * 
         * @return iterator over child components to be rendered
         */
        protected abstract Iterator<? extends Component> renderIterator();

        /**
         * Renders all child items in no specified order
         */
        @Override
        protected final void onRender()
        {
                Iterator<? extends Component> it = renderIterator();
                while (it.hasNext())
                {
                        Component child = it.next();
                        if (child == null)
                        {
                                throw new IllegalStateException(
                                        "The render iterator returned null for a child. Container: " + this.toString() +
                                                "; Iterator=" + it.toString());
                        }
                        renderChild(child);
                }
        }

        /**
         * Render a single child. This method can be overridden to modify how a single child component
         * is rendered.
         * 
         * @param child
         *            Child component to be rendered
         */
        protected void renderChild(final Component child)
        {
                child.render();
        }

        /**
         * @see org.apache.wicket.Component#onBeforeRender()
         */
        @Override
        protected void onBeforeRender()
        {
                onPopulate();

                if (getApplication().usesDevelopmentConfig())
                {
                        Set<String> usedComponentIds = new HashSet<>();
                        Iterator<? extends Component> i = iterator();
                        while (i.hasNext())
                        {
                                Component c = i.next();
                                String componentId = c.getId();
                                if (usedComponentIds.add(componentId) == false)
                                {
                                        log.warn("Repeater '{}' has multiple children with the same component id: '{}'",
                                                        getPageRelativePath(), componentId);
                                        // do not flood the log
                                        break;
                                }
                        }
                }
                super.onBeforeRender();
        }

        /**
         * @see org.apache.wicket.MarkupContainer#getMarkup(org.apache.wicket.Component)
         */
        @Override
        public IMarkupFragment getMarkup(final Component child)
        {
                // each direct child gets the markup of this repeater
                return getMarkup();
        }

        /**
         * Callback to let the repeater know it should populate itself with its items.
         */
        protected abstract void onPopulate();

        @Override
        public void dequeue(DequeueContext dequeue)
        {
                if (size() > 0)
                {
                        // essentially what we do is for every child replace the repeater with the child in
                        // dequeue container stack and run the dequeue on the child. we also take care to reset
                        // the state of the dequeue context after we process every child.

                        Bookmark bookmark = dequeue.save();

                        for (Component child : this)
                        {
                                if (child instanceof MarkupContainer)
                                {
                                        dequeue.popContainer(); // pop the repeater
                                        MarkupContainer container = (MarkupContainer) child;
                                        dequeue.pushContainer(container);
                                        container.dequeue(dequeue);
                                        dequeue.restore(bookmark);
                                }
                        }
                }

                dequeue.skipToCloseTag();

        }
}