module Plate
  # Methods related to the meta-data of a page
  module MetaHelper
    # Is there a description available for this page?
    def description?
      !page.description.to_s.blank?
    end
    
    # Sanitize keywords output into a comma separated list string
    def keywords      
      page.keywords.join(", ")
    end
    
    # Are there keywords available on this page?
    def keywords?
      page.keywords.length > 0
    end
    
    # Returns a description meta tag if there is a description available for
    # this page.
    def meta_description_tag
      %Q(<meta name="description" content="#{description}">) if description?
    end
    
    # Returns a keywords meta tag if there are keywords for this page.
    def meta_keywords_tag
      %Q(<meta name="keywords" content="#{keywords}">) if keywords?
    end
    
    # Output the standard meta tags (keywords and description) to a page.
    # Omits any tags with blank data.
    # 
    # Optionally pass in a list of which tags to display.
    #
    # @example Show all available meta tags
    #     <%= meta_tags %>
    #
    # @example Show only the keywords tag
    #     <%= meta_tags :keywords %>
    #
    # @example Show both keywords and description (default)
    #
    #     <%= meta_tags :keywords, :description %>
    #
    # @overload meta_tags([tags...], options)
    #   @param [optional, Symbol] tags Pass in any number of symbols to output those tags.
    #   @param [optional, Hash] options Customize display options
    #   @option options [String] :joiner String to use to join together multiple tags.
    def meta_tags(*args)
      options = args.extract_options!
      options = options.reverse_merge({
        :joiner => "\n"
      })
      
      tags = args.length > 0 ? args : %w( description keywords )
      
      result = []
      
      tags.each do |tag|        
        result << self.send("meta_#{tag}_tag") if self.respond_to?("meta_#{tag}_tag")
      end
      
      result.join(options[:joiner]).strip
    end
    
    # Does this page have a title?
    def title?
      !page.title.to_s.blank?
    end
  end
end