module Sinatra
  module RenderPlugin
    module RenderHelpers
      # Renders a erb template based on the relative path
      # erb_template 'users/new'
      def erb_template(template_path, options={})
        render_template template_path, options.merge(:template_engine => :erb)
      end

      # Renders a haml template based on the relative path
      # haml_template 'users/new'
      def haml_template(template_path, options={})
        render_template template_path, options.merge(:template_engine => :haml)
      end

      # Renders a template from a file path automatically determining rendering engine
      # render_template 'users/new'
      # options = { :template_engine => 'haml' }
      def render_template(template_path, options={})
        template_engine = options.delete(:template_engine) || resolve_template_engine(template_path)
        render template_engine.to_sym, template_path.to_sym, options
      end

      # Partials implementation which includes collections support
      # partial 'photo/_item', :object => @photo
      # partial 'photo/_item', :collection => @photos
      def partial(template, options={})
        options.reverse_merge!(:locals => {}, :layout => false)
        path = template.to_s.split(File::SEPARATOR)
        object_name = path[-1].to_sym
        path[-1] = "_#{path[-1]}"
        template_path = File.join(path)
        raise 'Partial collection specified but is nil' if options.has_key?(:collection) && options[:collection].nil?
        if collection = options.delete(:collection)
          options.delete(:object)
          counter = 0
          collection.collect do |member|
            counter += 1
            options[:locals].merge!(object_name => member, "#{object_name}_counter".to_sym => counter)
            render_template(template_path, options.merge(:layout => false))
          end.join("\n")
        else
          if member = options.delete(:object)
            options[:locals].merge!(object_name => member)
          end
          render_template(template_path, options.merge(:layout => false))
        end
      end
      alias render_partial partial

      private

        # Returns the template engine (i.e haml) to use for a given template_path
        # resolve_template_engine('users/new') => :haml
        def resolve_template_engine(template_path)
          resolved_template_path = File.join(self.options.views, template_path.to_s + ".*")
          template_file = Dir[resolved_template_path].first
          raise "Template path '#{template_path}' could not be located in views!" unless template_file
          template_engine = File.extname(template_file)[1..-1].to_sym
        end
    end
  end
end