require 'singleton'

module SimpleNavigation
  
  # Responsible for evaluating and handling the config/navigation.rb file. 
  class Configuration
    include Singleton
    
    attr_accessor :renderer, :selected_class, :autogenerate_item_ids, :id_generator, :auto_highlight
    attr_reader :render_all_levels
    attr_reader :primary_navigation

    class << self

      # Evals the config_file for the given navigation_context inside the specified context (usually a controller or view)
      def eval_config(context, navigation_context = :default)
        SimpleNavigation.controller = extract_controller_from context
        SimpleNavigation.template = SimpleNavigation.controller.instance_variable_get(:@template)
        context_for_eval.instance_eval(SimpleNavigation.config_files[navigation_context])
      end
      
      # Starts processing the configuration
      def run(&block)
        block.call Configuration.instance
      end    

      # Returns the context in which the config file should be evaluated.
      # This is preferably the template, otherwise te controller
      def context_for_eval
        raise 'no context set for evaluation the config file' unless SimpleNavigation.template || SimpleNavigation.controller
        SimpleNavigation.template || SimpleNavigation.controller
      end

      # Extracts a controller from the context.
      def extract_controller_from(context)
        if context.respond_to? :controller
          context.controller
        else
          context
        end
      end
      
    end #class << self
    
    # Sets the config's default-settings
    def initialize
      @renderer = SimpleNavigation::Renderer::List
      @selected_class = 'selected'
      @autogenerate_item_ids = true
      @id_generator = Proc.new {|id| id.to_s }
      @auto_highlight = true
    end
  
    # Adds a deprecation warning when this options is set in the config file
    def render_all_levels=(do_it)
      ActiveSupport::Deprecation.warn("Setting render_all_levels in the config-file has been deprected. Please use render_navigation(:expand_all => true) instead")
      @render_all_levels = do_it
    end
  
    # This is the main method for specifying the navigation items. It can be used in two ways:
    # 
    # 1. Declaratively specify your items in the config/navigation.rb file using a block. It then yields an SimpleNavigation::ItemContainer for adding navigation items.
    # 1. Directly provide your items to the method (e.g. when loading your items from the database). Either specify 
    #
    # ==== Example for block style
    #   config.items do |primary|
    #     primary.item :my_item, 'My item', my_item_path
    #     ...
    #   end
    #
    # ==== To consider when directly providing items
    # * a methodname (as symbol) that returns your items. The method needs to be available in the view (i.e. a helper method)
    # * an object that responds to :items
    # * an enumerable containing your items
    # The items you specify have to fullfill certain requirements. See SimpleNavigation::ItemAdapter for more details.
    #
    def items(items_provider=nil, &block)
      raise 'please specify either items_provider or block, but not both' if (items_provider && block) || (items_provider.nil? && block.nil?)
      @primary_navigation = ItemContainer.new
      if block
        block.call @primary_navigation
      else
        @primary_navigation.items = SimpleNavigation::ItemsProvider.new(items_provider).items
      end
    end
    
    # Returns true if the config_file has already been evaluated.
    def loaded?
      !@primary_navigation.nil?
    end    
    
    def context_for_eval
      self.class.context_for_eval
    end
    
  end  
  
end