module Gollum
  class Markup

    # Attempt to process the tag as a page link tag.
    #
    # tag       - The String tag contents (the stuff inside the double 
    #             brackets).
    # no_follow - Boolean that determines if rel="nofollow" is added to all
    #             <a> tags.
    #
    # Returns the String HTML if the tag is a valid page link tag or nil
    #   if it is not.
    def process_page_link_tag(tag, no_follow = false)
      parts = tag.split('|')
      name  = parts[0].strip
      cname = @wiki.page_class.cname((parts[1] || parts[0]).strip)
      if pos = cname.index('#')
        extra = cname[pos..-1]
        cname = cname[0..(pos-1)]
      end
      tag = if name =~ %r{^https?://} && parts[1].nil?
        %{<a href="#{name}">#{name}</a>}
      else
        presence    = "absent"
        link_name   = cname
        page = find_page_from_name(cname)
        if page
          presence  = "present"
        end
        link = ::File.join(@wiki.base_path, CGI.escape(link_name))
        %{<a class="internal #{presence}" href="#{link}#{extra}">#{name}</a>}
      end
      if tag && no_follow
        tag.sub! /^<a/, '<a ref="nofollow"'
      end
      tag
    end

    # Find a page from a given cname.  If the page has an anchor (#) and has
    # no match, strip the anchor and try again.
    #
    # cname - The String canonical page name.
    #
    # Returns a Gollum::Page instance if a page is found, or an Array of
    # [Gollum::Page, String extra] if a page without the extra anchor data
    # is found.
    def find_page_from_name(cname)
      if page = @wiki.page(cname, @version)
        return page
      end
    end
  end
end