Templating ripped out of Sinatra

template.rb

  # Note: ripped out of Sinatra, minus any `setting` calls, and disabling inline templates
  
  # Template rendering methods. Each method takes the name of a template
  # to render as a Symbol and returns a String with the rendered output,
  # as well as an optional hash with additional options.
  #
  # `template` is either the name or path of the template as symbol
  # (Use `:'subdir/myview'` for views in subdirectories), or a string
  # that will be rendered.
  #
  # Possible options are:
  #   :content_type   The content type to use, same arguments as content_type.
  #   :layout         If set to false, no layout is rendered, otherwise
  #                   the specified layout is used (Ignored for `sass` and `less`)
  #   :layout_engine  Engine to use for rendering the layout.
  #   :locals         A hash with local variables that should be available
  #                   in the template
  #   :scope          If set, template is evaluate with the binding of the given
  #                   object rather than the application instance.
  #   :views          Views directory to use.
  module Templates

    def template_cache; @template_cache ||= Tilt::Cache.new; end

    module ContentTyped
      attr_accessor :content_type
    end

    def initialize
      super
      @default_layout = :layout
    end

    def erb(template, options={}, locals={})
      render :erb, template, options, locals
    end

    def haml(template, options={}, locals={})
      render :haml, template, options, locals
    end

    def sass(template, options={}, locals={})
      options.merge! :layout => false, :default_content_type => :css
      render :sass, template, options, locals
    end

    def scss(template, options={}, locals={})
      options.merge! :layout => false, :default_content_type => :css
      render :scss, template, options, locals
    end

    def less(template, options={}, locals={})
      options.merge! :layout => false, :default_content_type => :css
      render :less, template, options, locals
    end

    def builder(template=nil, options={}, locals={}, &block)
      options[:default_content_type] = :xml
      render_ruby(:builder, template, options, locals, &block)
    end

    def liquid(template, options={}, locals={})
      render :liquid, template, options, locals
    end

    def markdown(template, options={}, locals={})
      render :markdown, template, options, locals
    end

    def textile(template, options={}, locals={})
      render :textile, template, options, locals
    end

    def rdoc(template, options={}, locals={})
      render :rdoc, template, options, locals
    end

    def radius(template, options={}, locals={})
      render :radius, template, options, locals
    end

    def markaby(template=nil, options={}, locals={}, &block)
      render_ruby(:mab, template, options, locals, &block)
    end

    def coffee(template, options={}, locals={})
      options.merge! :layout => false, :default_content_type => :js
      render :coffee, template, options, locals
    end

    def nokogiri(template=nil, options={}, locals={}, &block)
      options[:default_content_type] = :xml
      render_ruby(:nokogiri, template, options, locals, &block)
    end

    def slim(template, options={}, locals={})
      render :slim, template, options, locals
    end

    def creole(template, options={}, locals={})
      render :creole, template, options, locals
    end

    # Calls the given block for every possible template file in views,
    # named name.ext, where ext is registered on engine.
    def find_template(views, name, engine)
      yield ::File.join(views, "#{name}.#{@preferred_extension}")
      Tilt.mappings.each do |ext, engines|
        next unless ext != @preferred_extension and engines.include? engine
        yield ::File.join(views, "#{name}.#{ext}")
      end
    end

  private
    # logic shared between builder and nokogiri
    def render_ruby(engine, template, options={}, locals={}, &block)
      options, template = template, nil if template.is_a?(Hash)
      template = Proc.new { block } if template.nil?
      render engine, template, options, locals
    end

    def render(engine, data, options={}, locals={}, &block)
      # merge app-level options
      options[:outvar]           ||= '@_out_buf'

      # extract generic options
      locals          = options.delete(:locals) || {}
      views           = options.delete(:views)  || "./views"
      layout          = options.delete(:layout)
      eat_errors      = layout.nil?
      layout          = @default_layout if layout.nil? or layout == true
      content_type    = options.delete(:content_type)  || options.delete(:default_content_type)
      layout_engine   = options.delete(:layout_engine) || engine
      scope           = options.delete(:scope)         || self

      # compile and render template
      layout_was      = @default_layout
      @default_layout = false
      template        = compile_template(engine, data, options, views)
      output          = template.render(scope, locals, &block)
      @default_layout = layout_was

      # render layout
      if layout
        options = options.merge(:views => views, :layout => false, :eat_errors => eat_errors, :scope => scope)
        catch(:layout_missing) { return render(layout_engine, layout, options, locals) { output } }
      end

      output.extend(ContentTyped).content_type = content_type if content_type
      output
    end

    def compile_template(engine, data, options, views)
      eat_errors = options.delete :eat_errors
      template_cache.fetch engine, data, options do
        template = Tilt[engine]
        raise "Template engine not found: #{engine}" if template.nil?

        case data
        when Symbol
          path = nil
          found = false
          @preferred_extension = engine.to_s
          find_template(views, data, template) do |file|
            path ||= file # keep the initial path rather than the last one
            if found = File.exists?(file)
              path = file
              break
            end
          end
          throw :layout_missing if eat_errors and not found
          template.new(path, 1, options)
        else
          raise ArgumentError, "Sorry, don't know how to render #{data.inspect}."
        end
      end
    end
  end