class SlugTag < Liquid::Tag
  @@page_by_slug = nil

  def initialize(tag_name, text, tokens)
    @text = text.strip
    @template = Liquid::Template.parse(@text)
  end

  def index_slugs(site)
      return if @@page_by_slug

      @@page_by_slug = Hash.new
      Jekyll.logger.info "      Indexing slugs in #{site.pages.length} pages..."

      duplicates = false
      site.pages.each do |p|
          slug = p.data['slug']
          if (slug)
              if @@page_by_slug.has_key?(slug)
                  Jekyll.logger.warn "Duplicate slug '#{slug}' on #{p.url}"
                  duplicates = true
              end

              @@page_by_slug[slug] = p
          end
      end

      if duplicates
          # raise "Duplicate slugs found. Aborting"
      else
          Jekyll.logger.info "      Done. Found #{@@page_by_slug.length} unique slugs."
      end
  end

  def render(context)
      site = context.registers[:site]
      index_slugs site
      slug_overrides = site.config['slug_overrides'] || Hash.new

      @text = @template.render(context)
      page = @@page_by_slug[@text]
      page_url = context.environments.first["page"]["url"]

      if !page && page_url =~ /\.X\//
          root_slug = @text.sub(/.*\.X_(.*)/, '\1')
          page = @@page_by_slug[root_slug]
      end

      if page
          return site.baseurl + page.url.sub('.html', '')
      elsif slug_overrides.has_key? @text
          return site.baseurl + slug_overrides[@text]
      else
          Jekyll.logger.warn "ERROR:", "No page with slug `#{@text}` in #{page_url}. Consider fixing the slug or use normal link."

          at_exit do
              exit 1
          end
      end
  end
end

Liquid::Template.register_tag('slug', SlugTag)