pagination.js

(function() {
  'use strict';
  
  angular
    .module('githubApp')
    .factory('Pagination', Pagination)

  function Pagination(){
    
    return {
      pages: function(response, base_url){
        var current_page = parseInt(response.headers('Current-Page'));
        var total_pages  = parseInt(response.headers('Total-Pages'));
        var pages = [];

        var first = { css_class: "first",     href: base_url,                                  text: "First" };
        var prev  = { css_class: "prev",      href: paginationURL(base_url, current_page - 1), text: "Previous" };
        var next  = { css_class: "next_page", href: paginationURL(base_url, current_page + 1), text: "Next" };
        var last  = { css_class: "last next", href: paginationURL(base_url, total_pages),      text: "Last" };
        
        function paginationURL(base_url, val){
          if(base_url.indexOf("?") > 0){
            return base_url + '&page=' + val; 
          } else {
            return base_url + '?page=' + val; 
          }
        }  

        // previous link
        if (current_page != 1){
          pages.push(first);
          pages.push(prev);
        }

        // windowed page numbers
        var inner_window = 4;
        var outer_window = 1;
        var window_from  = current_page - inner_window;
        var window_to    = current_page + inner_window;
        var total_pages  = total_pages;
        // adjust lower or upper limit if other is out of bounds
        if (window_to > total_pages){
          window_from -= window_to - total_pages;
          window_to = total_pages;
        }
        if (window_from < 1){
          window_to += 1 - window_from;
          window_from = 1;
          if (window_to > total_pages)
            window_to = total_pages ;
        }
        
        // these are always visible
        var middle = [];
        for(var i=window_from; i<=window_to; i++){ 
          middle.push(i);
        }
        
        // left window
        var left = [];
        if (outer_window + 3 < middle[0]){
          // there's a gap
          for(i=1; i<=(outer_window + 1); i++){ 
            left.push(i); 
          }
          left.push("...");
        }
        else {
          // runs into visible pages
          for(i=1; i<middle[0]; i++){ 
            left.push(i); 
          }
        }
        
        //right window
        var right = [];
        if (total_pages - outer_window - 2 > middle[middle.length - 1]){
          // again, gap
          for(i=(total_pages - outer_window); i<=total_pages; i++){ 
            right.push(i); 
          }
          right.unshift('...');
        }
        else {
          // runs into visible pages
          for(i=middle[middle.length - 1]; i<total_pages; i++){ 
            right.push(i); 
          }
        }
        
        var page_numbers = left.concat(middle).concat(right);

        if (total_pages > 1){
          angular.forEach(page_numbers, function(val){
            if (current_page == val){
              var el = { css_class: "page active", href: paginationURL(base_url, val), text: val };
            }
            else if(val == '...'){
              var el = { css_class: "page gap disabled", href: "#", text: val };
            }
            else {
              var el = { css_class: "page", href: paginationURL(base_url, val), text: val };
            }

            pages.push(el);
          });
          
          // next link
          if (current_page != total_pages){
            pages.push(next);
            pages.push(last);
          }
        }
        return pages;
      }
    }
  }
})();