def initialize(config, page, all_posts, num_pages = nil)
@page = page
@per_page = config['paginate'].to_i
@total_pages = num_pages || Pager.calculate_pages(all_posts, @per_page)
if @page > @total_pages
raise RuntimeError, "page number can't be greater than total pages: #{@page} > #{@total_pages}"
end
init = (@page - 1) * @per_page
offset = (init + @per_page - 1) >= all_posts.size ? all_posts.size : (init + @per_page - 1)
@total_posts = all_posts.size
@posts = all_posts[init..offset]
@previous_page = @page != 1 ? @page - 1 : nil
@next_page = @page != @total_pages ? @page + 1 : nil
end