CollectionNavigator.java

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/*
 * Turró i Cutiller Foundation. License notice.
 * Copyright (C) 2018 Lluis Turró Cutiller <http://www.turro.org/>
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
 
package org.turro.collections;
 
import java.util.ArrayList;
import java.util.Collection;
import org.turro.elephant.impl.navigation.DefaultNavigatorItem;
import org.turro.html.HTMLHelper;
 
public class CollectionNavigator {
 
  private final HTMLHelper html;
  private final CollectionHtmlIterator iterator;
  private int pageSpan = 4;
  private ArrayList<DefaultNavigatorItem> buttons;
 
  public CollectionNavigator(CollectionHtmlIterator iterator) {
    this.iterator = iterator;
    this.html = iterator.html;
  }
 
  public void setPageSpan(int pageSpan) {
    this.pageSpan = pageSpan;
  }
  
  public void render() {
    int pages = iterator.pages(), 
        current = Math.max(iterator.current(), 0);
    if(pages < current || pages == 1) return;
    html.startTag("div", "class='dao-navigator'");
    html.startTag("ul");
    
    if(current - pageSpan > 1) {
      html.startTag("li");
      html.startAnchor("?page=" + 1, null);
      html.write("1");
      html.endTag("li");
    }
    
    if(current > 1) {
      html.startTag("li");
      html.startAnchor("?page=" + (current), null);
      html.write("&lt&lt");
      html.endTag("li");
    }
    
    for(int i = current - pageSpan; i < current + pageSpan; i++) {
      if(i >= 0 && i < pages) {
        html.startTag("li", current == i ? "class='active'" : null);
        html.startAnchor("?page=" + (i + 1), null);
        html.write((i + 1) + "");
        html.endTag("li");
      }
    }
    
    if(current != pages && pages > pageSpan) {
      html.startTag("li");
      html.startAnchor("?page=" + (current + 2), null);
      html.write("&gt&gt");
      html.endTag("li");
    }
    
    if(current + pageSpan < pages) {
      html.startTag("li");
      html.startAnchor("?page=" + pages, null);
      html.write(pages + "");
      html.endTag("li");
    }
 
    html.endTag("div");
  }
  
  public Collection<DefaultNavigatorItem> pages() {
    if(buttons == null) {
      buttons = new ArrayList<>();
      int pages = iterator.pages(), 
          current = Math.max(iterator.current(), 0);
      if(pages < current || pages == 1) return buttons;
 
      boolean navbut = pages > pageSpan * 2;
      int start = 0, limit = pageSpan * 2;
      
      if(navbut) {
        buttons.add(new DefaultNavigatorItem("1", "?page=" + 1, null, current == 0));
        buttons.add(new DefaultNavigatorItem("&lt;&lt;", "?page=" + (current), null));
        limit -= 4;
        start = Integer.max(1, current - (limit / 2));
        start = Integer.min(start, pages - (limit + 1));
      }
 
      for(int i = start; i < (start + limit) && i < pages; i++) {
        buttons.add(new DefaultNavigatorItem((i + 1) + "", "?page=" + (i + 1), null, current == i));
      }
 
      if(navbut) {
        buttons.add(new DefaultNavigatorItem("&gt;&gt;", "?page=" + (current + 2), null));
        buttons.add(new DefaultNavigatorItem(pages + "", "?page=" + (pages), null, current == pages - 1));
      }
 
    }
    return buttons;
  }
  
}