require 'builder'
module Merb
  module MerbAdmin
    module MainHelper
      def object_title(object)
        object.try(:name) || object.try(:title) || "#{object.class.to_s} ##{object.id}"
      end

      # Given a page count and the current page, we generate a set of pagination
      # links.
      # 
      # * We use an inner and outer window into a list of links. For a set of 
      # 20 pages with the current page being 10:
      # outer_window:
      #   1 2  ..... 19 20
      # inner_window
      #   5 6 7 8 9 10 11 12 13 14
      #
      # This is totally adjustable, or can be turned off by giving the 
      # :inner_window setting a value of nil.
      #
      # * Options
      # :left_cut_label => <em>text_for_cut</em>::
      #    Used when the page numbers need to be cut off to prevent the set of
      #    pagination links from being too long.
      #    Defaults to '&hellip;'
      # :right_cut_label => <em>text_for_cut</em>::
      #    Same as :left_cut_label but for the right side of numbers.
      #    Defaults to '&hellip;'
      # :outer_window => <em>number_of_pages</em>::
      #    Sets the number of pages to include in the outer 'window'
      #    Defaults to 2
      # :inner_window => <em>number_of_pages</em>::
      #    Sets the number of pags to include in the inner 'window'
      #    Defaults to 7
      # :page_param => <em>name_of_page_paramiter</em>
      #    Sets the name of the paramiter the paginator uses to return what
      #    page is being requested.
      #    Defaults to 'page'
      # :url => <em>url_for_links</em>
      #    Provides the base url to use in the page navigation links.
      #    Defaults to ''
      def paginate(current_page, page_count, options = {})
        options.reverse_merge!({
          :left_cut_label  => '&hellip;',
          :right_cut_label => '&hellip;',
          :outer_window    => 2,
          :inner_window    => 7,
          :page_param      => 'page',
          :url             => ''
        })
        url = options.delete :url
        url << (url.include?('?') ? '&' : '?') << options[:page_param]

        pages = { 
          :all => (1..page_count).to_a, 
          :left => [], 
          :center => [], 
          :right => [] 
        }

        # Only worry about using our 'windows' if the page count is less then 
        # our windows combined.
        if options[:inner_window].nil? || ((options[:outer_window] * 2) + options[:inner_window] + 2) >= page_count
          pages[:center] = pages[:all]
        else
          pages[:left] = pages[:all][0, options[:outer_window]]
          pages[:right] = pages[:all][page_count - options[:outer_window], options[:outer_window]]
          pages[:center] = case current_page
          # allow the inner 'window' to shift to right when close to the left edge
          # Ex: 1 2 [3] 4 5 6 7 8 9 ... 20
          when -infinity .. (options[:inner_window] / 2) + 3
            pages[:all][options[:outer_window], options[:inner_window]] +
              [options[:right_cut_label]]
          # allow the inner 'window' to shift left when close to the right edge
          # Ex: 1 2 ... 12 13 14 15 16 [17] 18 19 20
          when (page_count - (options[:inner_window] / 2.0).ceil) - 1 .. infinity
            [options[:left_cut_label]] +
              pages[:all][page_count - options[:inner_window] - options[:outer_window], options[:inner_window]]
          # Display the unshifed window
          # ex: 1 2 ... 5 6 7 [8] 9 10 11 ... 19 20
          else
            [options[:left_cut_label]] +
              pages[:all][current_page - (options[:inner_window] / 2) - 1, options[:inner_window]] +
              [options[:right_cut_label]]
          end
        end

        b = []

        [pages[:left], pages[:center], pages[:right]].each do |p|
          p.each do |page_number|
            case page_number
            when String
              b << page_number
            when current_page
              b << Builder::XmlMarkup.new.span(page_number, :class => "this-page")
            when page_count
              b << Builder::XmlMarkup.new.a(page_number, :class => "end", :href => "#{url}=#{page_number}")
            else
              b << Builder::XmlMarkup.new.a(page_number, :href => "#{url}=#{page_number}")
            end
          end
        end

        b.join(" ")
      end

      private

      def infinity
        1.0 / 0
      end

    end
  end
end