/**
    * This file Copyright (c) 2008-2016 Magnolia International
    * Ltd.  (http://www.magnolia-cms.com). All rights reserved.
    *
    *
    * This file is dual-licensed under both the Magnolia
    * Network Agreement and the GNU General Public License.
    * You may elect to use one or the other of these licenses.
    *
   * This file is distributed in the hope that it will be
   * useful, but AS-IS and WITHOUT ANY WARRANTY; without even the
   * implied warranty of MERCHANTABILITY or FITNESS FOR A
   * PARTICULAR PURPOSE, TITLE, or NONINFRINGEMENT.
   * Redistribution, except as permitted by whichever of the GPL
   * or MNA you select, is prohibited.
   *
   * 1. For the GPL license (GPL), you can redistribute and/or
   * modify this file under the terms of the GNU General
   * Public License, Version 3, as published by the Free Software
   * Foundation.  You should have received a copy of the GNU
   * General Public License, Version 3 along with this program;
   * if not, write to the Free Software Foundation, Inc., 51
   * Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
   *
   * 2. For the Magnolia Network Agreement (MNA), this file
   * and the accompanying materials are made available under the
   * terms of the MNA which accompanies this distribution, and
   * is available at http://www.magnolia-cms.com/mna.html
   *
   * Any modifications to this file must keep this entire header
   * intact.
   *
   */
  package info.magnolia.templating.models.util;
  
  
  import info.magnolia.context.MgnlContext;
  
  import java.util.Collection;
  import java.util.List;
  
  import javax.jcr.Node;
  import javax.jcr.RepositoryException;
  
  import org.apache.commons.lang3.StringEscapeUtils;
  import org.apache.commons.lang3.StringUtils;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  /**
   * Simple class providing pagination.
   */
  public class Pagination {
  
      private static final Logger log = LoggerFactory.getLogger(Pagination.class);
  
      public static final String PARAMETER_CURRENT_PAGE = "currentPage";
  
      public static final String PROPERTY_MAX_RESULTS = "maxResultsPerPage";
      public static final String PROPERTY_POSITION = "position";
  
      public static final String POSITION_TOP = "top";
      public static final String DEFAULT_POSITION = POSITION_TOP;
      public static final int DEFAULT_MAX_RESULTS = 10000;
  
      private int count;
      private String link;
      private int maxResultsPerPage;
      private Collection items;
      private String position;
  
      public Pagination(String link, Collection items, Node content) {
          this.count = items.size();
          this.items = items;
          this.link = link;
  
          getPaginationProperties(content);
      }
  
      protected Pagination() {
      }
  
      protected void setResults(int maxResultsPerPage) {
          this.maxResultsPerPage = maxResultsPerPage;
      }
  
      protected void setCount(int count) {
          this.count = count;
      }
  
      public int getCount() {
          return count;
      }
  
      /**
       * Returns a sub-{@link java.util.List} of all items from offset (see {@link #getOffset()}) to limit (calculated
       * from max results per page and the before mentioned offset).
       */
      public Collection getPageItems() {
         Collection subList = items;
         int offset = getOffset();
         if (count > 0) {
             int limit = maxResultsPerPage + offset;
             if (items.size() < limit) {
                 limit = count;
             }
             subList = ((List) items).subList(offset, limit);
         }
         return subList;
     }
 
     /**
      * Return the current offset.
      */
     protected int getOffset() {
         int offset = ((getCurrentPage() - 1) * maxResultsPerPage);
         if (offset > count) {
             int pages = count / maxResultsPerPage;
             offset = pages * maxResultsPerPage;
         }
         return offset;
     }
 
     /**
      * Returns the current page (according to the GET parameters value, see {@link #PARAMETER_CURRENT_PAGE}, or 1).
      */
     public int getCurrentPage() {
         int currentPage = 1;
         final String currentPageParameter = MgnlContext.getParameter(PARAMETER_CURRENT_PAGE);
         if (currentPageParameter != null && (Integer.parseInt(currentPageParameter) > 1)) {
             currentPage = Integer.parseInt(currentPageParameter);
         }
         return currentPage;
     }
 
     /**
      * Returns a link the n-th page.
      */
     public String getPageLink(int i) {
         final String current = String.format("%s=", PARAMETER_CURRENT_PAGE);
 
         if (this.link.indexOf('?') > 0) {
             final String queryString = StringUtils.substringAfter(this.link, "?");
             final StringBuilder newQueryString = new StringBuilder("?");
             final String[] params = queryString.split("&");
             boolean pageSet = false;
             int count = 0;
 
             for (String param : params) {
                 if (param.startsWith(current)) {
                     newQueryString.append(current).append(i);
                     pageSet = true;
                 } else {
                     newQueryString.append(StringEscapeUtils.escapeHtml4(param)); // Without this escaping possible XSS
                 }
                 count++;
                 if (count < params.length) {
                     newQueryString.append("&");
                 }
             }
 
             if (!pageSet) {
                 if (newQueryString.length() > 1) {
                     newQueryString.append("&");
                 }
                 newQueryString.append(current).append(i);
 
             }
 
             return StringUtils.substringBefore(this.link, "?") + newQueryString.toString();
         } else {
             return this.link + "?" + current + i;
         }
     }
 
     /**
      * Returns the number of pages.
      */
     public int getNumPages() {
         int numPages = count / maxResultsPerPage;
         if ((count % maxResultsPerPage) > 0) {
             numPages++;
         }
         return numPages;
     }
 
     /**
      * Returns the index to be displayed before the current page.
      */
     public int getBeginIndex() {
         if (getCurrentPage() - 2 <= 1) {
             return 1;
         } else {
             return getCurrentPage() - 2;
         }
     }
 
     /**
      * Returns the index to be displayed after the current page.
      */
     public int getEndIndex() {
         if (getCurrentPage() + 2 >= getNumPages()) {
             return getNumPages();
         } else {
             return getCurrentPage() + 2;
         }
     }
 
     /**
      * Returns the current position of the pagination element (see {@link #DEFAULT_POSITION}, {@link #POSITION_TOP}).
      */
     public String getPosition() {
         return position;
     }
 
     /**
      * Tries to retrieve pagination properties from the underlying content {@link javax.jcr.Node}, otherwise will use
      * provided defaults.
      *
      * @see #PROPERTY_MAX_RESULTS
      * @see #PROPERTY_POSITION
      */
     private void getPaginationProperties(final Node content) {
         maxResultsPerPage = DEFAULT_MAX_RESULTS;
         position = DEFAULT_POSITION;
 
         try {
             if (content.hasProperty(PROPERTY_MAX_RESULTS)) {
                 int max = (int) content.getProperty(PROPERTY_MAX_RESULTS).getLong();
                 if (max > 0) {
                     maxResultsPerPage = max;
                 }
             }
 
             if (content.hasProperty(PROPERTY_POSITION)) {
                 position = content.getProperty(PROPERTY_POSITION).getString();
             }
         } catch (RepositoryException e) {
             log.warn("Could not get pagination properties for content [{}]. Using defaults instead.", content, e);
         }
     }
 
 }