require 'delegate'
module PageUp
  class Pages < SimpleDelegator

    def initialize collection, page, per_page, opts = {}
      @page     = parse page, 1
      @per_page = parse per_page, 25
      @origin   = collection
      @opts     = opts
      super collection[page_range]
    end

    def total_size
      @opts.fetch(:total_size) { @origin.size }
    end

    def pages
      if total_size > 0
        (total_size.to_f / per_page).ceil
      else
        1
      end
    end

    def current_slice
      slice_start..slice_end
    end

    attr_reader :page, :per_page

  private

    def page_range
      current_page...current_page+per_page
    end

    def current_page
      (page-1)*per_page
    end

    def parse value, default
      Integer(value)
    rescue TypeError
      default
    end

    def slice_start
      start = pages - ((page + 2 > pages) ? 4 : 2)
      start > 0 ? start : 1
    end

    def slice_end
      if page + 2 > pages || pages < 5
        pages
      elsif page - 2 <= 0
        5
      else
        page + 2
      end
    end

  end
end