/*
 * 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.html.list;

import java.util.List;

import org.apache.wicket.markup.html.navigation.paging.IPageableItems;
import org.apache.wicket.model.IModel;


/**
 * PageableListView is similar to ListView but provides in addition pageable views. A
 * PageableListView holds pageable rows of information. The rows can be re-ordered and deleted,
 * either one at a time or many at a time.
 * 
 * @author Jonathan Locke
 * @param <T>
 *            type of elements contained in the model's list
 */
public abstract class PageableListView<T> extends ListView<T> implements IPageableItems
{
        private static final long serialVersionUID = 1L;

        /** The page to show. */
        private long currentPage;

        /** Number of rows per page of the list view. */
        private long itemsPerPage;

        /**
         * Constructor
         * 
         * @param id
         *            See Component
         * @param model
         *            See Component
         * @param itemsPerPage
         *            Number of rows to show on a page
         */
        public PageableListView(final String id, final IModel<? extends List<T>> model,
                long itemsPerPage)
        {
                super(id, model);
                this.itemsPerPage = itemsPerPage;
        }

        /**
         * Creates a pageable list view having the given number of rows per page that uses the provided
         * object as a simple model.
         * 
         * @param id
         *            See Component
         * @param list
         *            See Component
         * @param itemsPerPage
         *            Number of rows to show on a page
         * @see ListView#ListView(String, List)
         */
        public PageableListView(final String id, final List<T> list, final long itemsPerPage)
        {
                super(id, list);
                this.itemsPerPage = itemsPerPage;
        }

        /**
         * Gets the index of the current page being displayed by this list view.
         * 
         * @return Returns the currentPage.
         */
        @Override
        public final long getCurrentPage()
        {
                // If first cell is out of range, bring page back into range
                while ((currentPage > 0) && ((currentPage * itemsPerPage) >= getItemCount()))
                {
                        currentPage--;
                }

                return currentPage;
        }

        /**
         * Gets the number of pages in this list view.
         * 
         * @return The number of pages in this list view
         */
        @Override
        public final long getPageCount()
        {
                return ((getItemCount() + itemsPerPage) - 1) / itemsPerPage;
        }

        /**
         * Gets the maximum number of rows on each page.
         * 
         * @return the maximum number of rows on each page.
         */
        @Override
        public final long getItemsPerPage()
        {
                return itemsPerPage;
        }

        /**
         * Sets the maximum number of rows on each page.
         * 
         * @param itemsPerPage
         *            the maximum number of rows on each page.
         */
        @Override
        public final void setItemsPerPage(long itemsPerPage)
        {
                if (itemsPerPage < 0)
                {
                        itemsPerPage = 0;
                }

                addStateChange();
                this.itemsPerPage = itemsPerPage;
        }

        /**
         * @return offset of first item
         */
        public long getFirstItemOffset()
        {
                return getCurrentPage() * getItemsPerPage();
        }

        /**
         * @see org.apache.wicket.markup.html.navigation.paging.IPageableItems#getItemCount()
         */
        @Override
        public long getItemCount()
        {
                return getList().size();
        }

        /**
         * @see org.apache.wicket.markup.html.list.ListView#getViewSize()
         */
        @Override
        public int getViewSize()
        {
                if (getDefaultModelObject() != null)
                {
                        super.setStartIndex((int)getFirstItemOffset());
                        super.setViewSize((int)getItemsPerPage());
                }

                return super.getViewSize();
        }

        /**
         * Sets the current page that this list view should show.
         * 
         * @param currentPage
         *            The currentPage to set.
         */
        @Override
        public final void setCurrentPage(long currentPage)
        {
                if (currentPage < 0)
                {
                        currentPage = 0;
                }

                long pageCount = getPageCount();
                if ((currentPage > 0) && (currentPage >= pageCount))
                {
                        currentPage = pageCount - 1;
                }

                addStateChange();
                this.currentPage = currentPage;
        }


        /**
         * Prevent users from accidentally using it.
         * 
         * @see org.apache.wicket.markup.html.list.ListView#setStartIndex(int)
         * @throws UnsupportedOperationException
         *             always
         */
        @Override
        public ListView<T> setStartIndex(int startIndex) throws UnsupportedOperationException
        {
                throw new UnsupportedOperationException(
                        "You must not use setStartIndex() with PageableListView");
        }

        /**
         * Prevent users from accidentally using it.
         * 
         * @param size
         *            the view size
         * @return This
         * @throws UnsupportedOperationException
         *             always
         * @see org.apache.wicket.markup.html.list.ListView#setStartIndex(int)
         */
        @Override
        public ListView<T> setViewSize(int size) throws UnsupportedOperationException
        {
                throw new UnsupportedOperationException(
                        "You must not use setViewSize() with PageableListView");
        }

}