Generate rails-like route helpers for use in javascript land

journey_coffee_generator.rb

class JourneyCoffeeGenerator < Journey::Visitors::Visitor
  def accept node
    @requirements = [[]]
    super.gsub('" + "', '')
  end

  private

  def visit_GROUP node
    @requirements << []
    inner = visit node.left
    requirements = @requirements.pop
    %{(if #{requirements.map { |key| "options.#{key}" }.join " or "} then (#{inner}) else "")}
  end

  def terminal node
    # LITERAL or SLASH or DOT (SYMBOL handled below)
    node.left.to_json
  end

  def binary node
    [visit(node.left), visit(node.right)].join(' + ')
  end

  def nary node
    node.children.map { |c| visit c }.join(' + ')
  end

  def visit_STAR node
    @starred = true
    super.tap do
      @starred = false
    end
  end

  def visit_SYMBOL node
    key = node.to_sym
    @requirements.last << key
    %{(if options.#{key} then encodeURI#{"Component" unless @starred}(options.#{key}.toString()) else "")}
  end
end

routes.js.coffee.erb

# Generate paths from rails route helpers in javascript land
app.routes =
  named:
    <% Rails.application.routes.named_routes.each do |name, route| %>
    <%= name %>: [
      <%= route.parts.to_json %>
      <%= route.defaults.to_json %>
      (options) ->
        <%= JourneyCoffeeGenerator.new.accept(route.path.spec) %>
    ]
    <% end %>

  path_to: (name, params...) ->
    # Grab the named route
    [parts, defaults, generate] = tc.routes.named[name]

    # The params may end with an options hash
    options = (params.pop() if _.isObject(params[params.length - 1])) || {}

    # Other positional parameters are route parts
    _.extend options, _.object(parts.slice(0, params.length), params)

    # Remove any default options, they're superfluous
    delete options[param] if param is defaults[param] for param of options

    # Generate a path
    path = generate(options)

    # Append a query if we have any non-part options
    path += "?" + query if query = $.param(_(options).omit(parts...))

    # Boom!
    path

for name of tc.routes.named
  tc.routes["#{name}_path"] = _.bind(tc.routes.path_to, name)