module PageObject
  #
  # Module to facilitate to creating of page objects in step definitions.  You
  # can make the methods below available to all of your step definitions by adding
  # this module to World.  This idea was first discussed in Alister Scott's blog
  # entry http://watirmelon.com/2011/06/07/removing-local-page-references-from-cucumber-steps/.
  #
  # @example Making the PageFactory available to your step definitions
  #   World PageObject::PageFactory
  #
  # @example Visiting a page for the first time in a Scenario
  #   visit_page MyPageObject do |page|
  #     page.name = 'Cheezy'
  #   end
  #
  # @example using a page that has already been visited in a Scenario
  #   on_page MyPageObject do |page|
  #     page.name.should == 'Cheezy'
  #   end
  #
  # If you plan to use the navigate_to method you will need to ensure
  # you setup the possible routes ahead of time.  You must always have
  # a default route in order for this to work.  Here is an example of
  # how you define routes:
  #
  # @example Example routes defined in env.rb
  #   PageObject::PageFactory.routes = {
  #     :default => [[PageOne,:method1], [PageTwoA,:method2], [PageThree,:method3]],
  #     :another_route => [[PageOne,:method1], [PageTwoB,:method2b], [PageThree,:method3]]
  #   }
  # 
  module PageFactory

    #
    # Create and navigate to a page object.  The navigation will only work if the
    # 'page_url' method was call on the page object.
    #
    # @param [PageObject, String] a class that has included the PageObject module or a string containing the name of the class 
    # @param an optional block to be called
    # @return [PageObject] the newly created page object
    #
    def visit_page(page_class, params={:using_params => {}}, &block)
      page_class = class_from_string(page_class) if page_class.is_a? String
      merged = page_class.params.merge(params[:using_params])
      page_class.instance_variable_set("@merged_params", merged) unless merged.empty?
      on_page page_class, true, &block
    end

    # Support 'visit' for readability of usage
    alias_method :visit, :visit_page

    #
    # Create a page object.
    #
    # @param [PageObject, String]  a class that has included the PageObject module or a string containing the name of the class
    # @param [Boolean]  a boolean indicating if the page should be visited?  default is false.
    # @param [block]  an optional block to be called
    # @return [PageObject] the newly created page object
    #
    def on_page(page_class, visit=false, &block)
      page_class = class_from_string(page_class) if page_class.is_a? String
      @current_page = page_class.new(@browser, visit)
      block.call @current_page if block
      @current_page
    end

    # Support 'on' for readability of usage
    alias_method :on, :on_page
    
    #
    # Create a page object if and only if the current page is the same page to be created
    #
    # @param [PageObject, String]  a class that has included the PageObject module or a string containing the name of the class
    # @param [block]  an optional block to be called
    # @return [PageObject] the newly created page object
    #
    def if_page(page_class, &block)
      page_class = class_from_string(page_class) if page_class.is_a? String
      return @current_page unless @current_page.class == page_class
      on_page(page_class, false, &block)
    end

    # Support 'if' for readability of usage
    alias_method :if, :if_page

    #
    # Navigate to a specific page following a predefined path.
    #
    # This method requires a lot of setup.  See the documentation for
    # this class.  Once the setup is complete you can navigate to a
    # page traversing through all other pages along the way.  It will
    # call the method you specified in the routes for each
    # page as it navigates.  Using the example setup defined in the
    # documentation above you can call the method two ways:
    #
    # @example
    #   page.navigate_to(PageThree)  # will use the default path
    #   page.navigate_to(PageThree, :using => :another_route)
    #
    # @param [PageObject]  a class that has included the PageObject
    # module and which has the navigation_method defined
    # @param [Hash] a hash that contains an element with the key
    # :using.  This will be used to lookup the route.  It has a
    # default value of :default.
    # @param [block]  an optional block to be called
    # @return [PageObject] the page you are navigating to
    #
    def navigate_to(page_cls, how = {:using => :default}, &block)
      path = path_for how
      to_index = find_index_for(path, page_cls)-1
      navigate_through_pages(path[0..to_index])
      on_page(page_cls, &block)
    end

    #
    # Same as navigate_to except it will start at the @current_page
    # instead the beginning of the path.
    #
    # @param [PageObject]  a class that has included the PageObject
    # module and which has the navigation_method defined
    # @param [Hash] a hash that contains an element with the key
    # :using.  This will be used to lookup the route.  It has a
    # default value of :default.
    # @param [block]  an optional block to be called
    # @return [PageObject] the page you are navigating to
    #
    def continue_navigation_to(page_cls, how = {:using => :default}, &block)
      path = path_for how
      from_index = find_index_for(path, @current_page.class)+1
      to_index = find_index_for(path, page_cls)-1
      navigate_through_pages(path[from_index..to_index])
      on_page(page_cls, &block)
    end

    private
    
    def class_from_string(str)
      str.split('::').inject(Object) do |mod, class_name|
        mod.const_get(class_name)
      end
    end
    
    def path_for(how)
      path = PageObject::PageFactory.page_object_routes[how[:using]]
      fail("PageFactory route :#{how[:using].to_s} not found") unless path
      path
    end
    
    def navigate_through_pages(pages)
      pages.each do |cls, method|
        page = on_page(cls)
        fail("Navigation method not specified on #{cls}.  Please call the ") unless page.respond_to? method
        page.send method
      end
    end

    def find_index_for(path, item)
      path.each_with_index { |each, index| return index if each[0] == item}
    end

    class << self
      attr_accessor :page_object_routes
      
      def routes=(routes)
        raise("You must provide a :default route for PageFactory routes") unless routes[:default]
        @page_object_routes = routes
      end
    end
  end
end