module RHNH
  module Magellan
    class Navigator
      attr_reader :pages
      attr_reader :links

      @@_navigator = nil
      
      def initialize
        @state = {}
        @links = {}
        @pages = {}
      end
      
      def self.instance
        if !@@_navigator
          @@_navigator = Navigator.new
        end
        @@_navigator
      end
      
      def self.draw
        @@_navigator = Navigator.new
        yield instance
      end
      
      def get_page_link state, link_name
        link = link_name ? link_name : @links[link_name]
        
        if link.respond_to?('call')    
          page_obj, params = link.call(@pages, state)
        else
          page_obj, params = @pages[link], nil
        end

        [page_obj, params]
      end
      
      def get_url page, link_name = nil, state = {}
        return(@pages[page] ? @pages[page].url : nil) if !link_name 
        state = {} if !state
        page_obj, params = get_page_link(state, @pages[page][link_name]) if @pages[page]
        page_obj, params = get_page_link(state, @links[link_name]) if !page_obj 

        if page_obj
          if params
            if page_obj.url.has_key?(:params)
              ret = page_obj.url.merge({:params => page_obj.url[:params].merge(params)})
            else
              ret = page_obj.url.merge({:params => params})
            end
          else
            ret = page_obj.url
          end
        end
        ret
      end
      
      def add_page page_name, url = nil
        new_page = NavPage.new
        new_page.url = url if url
        yield new_page if block_given?
        @pages[page_name.to_sym] = new_page
      end
      
      def add_link link_name, target_page
        @links[link_name.to_sym] = target_page
      end
    end

    class NavPage
      attr_accessor :url
      
      def initialize
        @links = {}
        @url = {}
      end
      
      def add_link link_name, target_page
        @links[link_name.to_sym] = target_page
      end
      
      def [] key
        @links[key.to_sym]
      end
    end
  end
end