base.rb

require 'action_controller/request'
require 'action_controller/response'
require 'action_controller/routing'
require 'action_controller/code_generation'
require 'action_controller/url_rewriter'
require 'drb'

module ActionController #:nodoc:
  class ActionControllerError < StandardError #:nodoc:
  end
  class SessionRestoreError < ActionControllerError #:nodoc:
  end
  class MissingTemplate < ActionControllerError #:nodoc:
  end
  class RoutingError < ActionControllerError #:nodoc:
    attr_reader :failures
    def initialize(message, failures=[])
      super(message)
      @failures = failures
    end
  end
  class UnknownController < ActionControllerError #:nodoc:
  end
  class UnknownAction < ActionControllerError #:nodoc:
  end
  class MissingFile < ActionControllerError #:nodoc:
  end
  class DoubleRenderError < ActionControllerError #:nodoc:
    DEFAULT_MESSAGE = "Render and/or redirect were called multiple times in this action. Please note that you may only call render OR redirect, and only once per action. Also note that neither redirect nor render terminate execution of the action, so if you want to exit an action after redirecting, you need to do something like \"redirect_to(...) and return\". Finally, note that to cause a before filter to halt execution of the rest of the filter chain, the filter must return false, explicitly, so \"render(...) and return false\"." 

    def initialize(message=nil)
      super(message || DEFAULT_MESSAGE)
    end
  end

  # Action Controllers are made up of one or more actions that performs its purpose and then either renders a template or
  # redirects to another action. An action is defined as a public method on the controller, which will automatically be 
  # made accessible to the web-server through a mod_rewrite mapping. A sample controller could look like this:
  #
  #   class GuestBookController < ActionController::Base
  #     def index
  #       @entries = Entry.find_all
  #     end
  #     
  #     def sign
  #       Entry.create(@params["entry"])
  #       redirect_to :action => "index"
  #     end
  #   end
  #
  #   GuestBookController.template_root = "templates/"
  #   GuestBookController.process_cgi
  #
  # All actions assume that you want to render a template matching the name of the action at the end of the performance
  # unless you tell it otherwise. The index action complies with this assumption, so after populating the @entries instance
  # variable, the GuestBookController will render "templates/guestbook/index.rhtml".
  #
  # Unlike index, the sign action isn't interested in rendering a template. So after performing its main purpose (creating a 
  # new entry in the guest book), it sheds the rendering assumption and initiates a redirect instead. This redirect works by
  # returning an external "302 Moved" HTTP response that takes the user to the index action.
  #
  # The index and sign represent the two basic action archetypes used in Action Controllers. Get-and-show and do-and-redirect.
  # Most actions are variations of these themes.
  #
  # Also note that it's the final call to <tt>process_cgi</tt> that actually initiates the action performance. It will extract
  # request and response objects from the CGI
  #
  # When Action Pack is used inside of Rails, the template_root is automatically configured and you don't need to call process_cgi
  # yourself.
  #
  # == Requests
  #
  # Requests are processed by the Action Controller framework by extracting the value of the "action" key in the request parameters.
  # This value should hold the name of the action to be performed. Once the action has been identified, the remaining
  # request parameters, the session (if one is available), and the full request with all the http headers are made available to
  # the action through instance variables. Then the action is performed.
  #
  # The full request object is available with the request accessor and is primarily used to query for http headers. These queries
  # are made by accessing the environment hash, like this:
  #
  #   def hello_ip
  #     location = request.env["REMOTE_IP"]
  #     render_text "Hello stranger from #{location}"
  #   end
  #
  # == Parameters
  #
  # All request parameters whether they come from a GET or POST request, or from the URL, are available through the params hash.
  # So an action that was performed through /weblog/list?category=All&limit=5 will include { "category" => "All", "limit" => 5 }
  # in params.
  #
  # It's also possible to construct multi-dimensional parameter hashes by specifying keys using brackets, such as:
  #
  #   <input type="text" name="post[name]" value="david">
  #   <input type="text" name="post[address]" value="hyacintvej">
  #
  # A request stemming from a form holding these inputs will include <tt>{ "post" => { "name" => "david", "address" => "hyacintvej" } }</tt>.
  # If the address input had been named "post[address][street]", the params would have included 
  # <tt>{ "post" => { "address" => { "street" => "hyacintvej" } } }</tt>. There's no limit to the depth of the nesting.
  #
  # == Sessions
  #
  # Sessions allows you to store objects in memory between requests. This is useful for objects that are not yet ready to be persisted,
  # such as a Signup object constructed in a multi-paged process, or objects that don't change much and are needed all the time, such
  # as a User object for a system that requires login. The session should not be used, however, as a cache for objects where it's likely 
  # they could be changed unknowingly. It's usually too much work to keep it all synchronized -- something databases already excel at.
  #
  # You can place objects in the session by using the <tt>session</tt> hash accessor:
  #
  #   session[:person] = Person.authenticate(user_name, password)
  #
  # And retrieved again through the same hash:
  #
  #   Hello #{session[:person]}
  #
  # Any object can be placed in the session (as long as it can be Marshalled). But remember that 1000 active sessions each storing a
  # 50kb object could lead to a 50MB memory overhead. In other words, think carefully about size and caching before resorting to the use
  # of the session.
  #
  # For removing objects from the session, you can either assign a single key to nil, like <tt>session[:person] = nil</tt>, or you can
  # remove the entire session with reset_session.
  #
  # == Responses
  #
  # Each action results in a response, which holds the headers and document to be sent to the user's browser. The actual response
  # object is generated automatically through the use of renders and redirects, so it's normally nothing you'll need to be concerned about.
  #
  # == Renders
  #
  # Action Controller sends content to the user by using one of five rendering methods. The most versatile and common is the rendering
  # of a template. Included in the Action Pack is the Action View, which enables rendering of ERb templates. It's automatically configured.
  # The controller passes objects to the view by assigning instance variables:
  #
  #   def show
  #     @post = Post.find(params[:id])
  #   end
  #
  # Which are then automatically available to the view:
  #
  #   Title: <%= @post.title %>
  #
  # You don't have to rely on the automated rendering. Especially actions that could result in the rendering of different templates will use
  # the manual rendering methods:
  #
  #   def search
  #     @results = Search.find(params[:query])
  #     case @results
  #       when 0 then render :action=> "no_results"
  #       when 1 then render :action=> "show"
  #       when 2..10 then render :action=> "show_many"
  #     end
  #   end
  #
  # Read more about writing ERb and Builder templates in link:classes/ActionView/Base.html.
  #
  # == Redirects
  #
  # Redirecting is what actions that update the model do when they're done. The <tt>save_post</tt> method shouldn't be responsible for also
  # showing the post once it's saved -- that's the job for <tt>show_post</tt>. So once <tt>save_post</tt> has completed its business, it'll
  # redirect to <tt>show_post</tt>. All redirects are external, which means that when the user refreshes his browser, it's not going to save
  # the post again, but rather just show it one more time.
  # 
  # This sounds fairly simple, but the redirection is complicated by the quest for a phenomenon known as "pretty urls". Instead of accepting
  # the dreadful beings that is "weblog_controller?action=show&post_id=5", Action Controller goes out of its way to represent the former as
  # "/weblog/show/5". And this is even the simple case. As an example of a more advanced pretty url consider
  # "/library/books/ISBN/0743536703/show", which can be mapped to books_controller?action=show&type=ISBN&id=0743536703.
  # 
  # Redirects work by rewriting the URL of the current action. So if the show action was called by "/library/books/ISBN/0743536703/show", 
  # we can redirect to an edit action simply by doing <tt>redirect_to(:action => "edit")</tt>, which could throw the user to 
  # "/library/books/ISBN/0743536703/edit". Naturally, you'll need to setup the routes configuration file to point to the proper controller
  # and action in the first place, but once you have, it can be rewritten with ease.
  # 
  # Let's consider a bunch of examples on how to go from "/clients/37signals/basecamp/project/dash" to somewhere else:
  #
  #   redirect_to(:action => "edit") =>
  #     /clients/37signals/basecamp/project/dash
  #   
  #   redirect_to(:client_name => "nextangle", :project_name => "rails") =>
  #     /clients/nextangle/rails/project/dash
  #
  # Those redirects happen under the configuration of:
  #
  #   map.connect 'clients/:client_name/:project_name/:controller/:action'
  #
  # == Calling multiple redirects or renders
  #
  # An action should conclude by a single render or redirect. Attempting to try to do either again will result in a DoubleRenderError:
  #
  #   def do_something
  #     redirect_to :action => "elsewhere"
  #     render :action => "overthere" # raises DoubleRenderError
  #   end
  #
  # If you need to redirect on the condition of something, then be sure to add "and return" to halt execution.
  #
  #   def do_something
  #     redirect_to(:action => "elsewhere") and return if monkeys.nil?
  #     render :action => "overthere" # won't be called unless monkeys is nil
  #   end
  #
  # == Environments
  #
  # Action Controller works out of the box with CGI, FastCGI, and mod_ruby. CGI and mod_ruby controllers are triggered just the same using:
  #
  #   WeblogController.process_cgi
  #
  # FastCGI controllers are triggered using:
  #
  #   FCGI.each_cgi{ |cgi| WeblogController.process_cgi(cgi) }
  class Base
    DEFAULT_RENDER_STATUS_CODE = "200 OK"
  
    # Determines whether the view has access to controller internals @request, @response, @session, and @template.
    # By default, it does.
    @@view_controller_internals = true
    cattr_accessor :view_controller_internals

    # Protected instance variable cache
    @@protected_variables_cache = nil
    cattr_accessor :protected_variables_cache

    # Prepends all the URL-generating helpers from AssetHelper. This makes it possible to easily move javascripts, stylesheets, 
    # and images to a dedicated asset server away from the main web server. Example: 
    #   ActionController::Base.asset_host = "http://assets.example.com"
    @@asset_host = ""
    cattr_accessor :asset_host

    # All requests are considered local by default, so everyone will be exposed to detailed debugging screens on errors.
    # When the application is ready to go public, this should be set to false, and the protected method <tt>local_request?</tt>
    # should instead be implemented in the controller to determine when debugging screens should be shown.
    @@consider_all_requests_local = true
    cattr_accessor :consider_all_requests_local
    
    # Enable or disable the collection of failure information for RoutingErrors.
    # This information can be extremely useful when tweaking custom routes, but is
    # pointless once routes have been tested and verified.
    @@debug_routes = true
    cattr_accessor :debug_routes

    # Controls whether the application is thread-safe, so multi-threaded servers like WEBrick knows whether to apply a mutex
    # around the performance of each action. Action Pack and Active Record are by default thread-safe, but many applications
    # may not be. Turned off by default.
    @@allow_concurrency = false
    cattr_accessor :allow_concurrency

    # Template root determines the base from which template references will be made. So a call to render("test/template")
    # will be converted to "#{template_root}/test/template.rhtml".
    class_inheritable_accessor :template_root

    # The logger is used for generating information on the action run-time (including benchmarking) if available.
    # Can be set to nil for no logging. Compatible with both Ruby's own Logger and Log4r loggers.
    cattr_accessor :logger
    
    # Determines which template class should be used by ActionController.
    cattr_accessor :template_class

    # Turn on +ignore_missing_templates+ if you want to unit test actions without making the associated templates.
    cattr_accessor :ignore_missing_templates

    # Holds the request object that's primarily used to get environment variables through access like
    # <tt>request.env["REQUEST_URI"]</tt>.
    attr_accessor :request
    
    # Holds a hash of all the GET, POST, and Url parameters passed to the action. Accessed like <tt>params["post_id"]</tt>
    # to get the post_id. No type casts are made, so all values are returned as strings.
    attr_accessor :params
    
    # Holds the response object that's primarily used to set additional HTTP headers through access like 
    # <tt>response.headers["Cache-Control"] = "no-cache"</tt>. Can also be used to access the final body HTML after a template
    # has been rendered through response.body -- useful for <tt>after_filter</tt>s that wants to manipulate the output,
    # such as a OutputCompressionFilter.
    attr_accessor :response
    
    # Holds a hash of objects in the session. Accessed like <tt>session[:person]</tt> to get the object tied to the "person"
    # key. The session will hold any type of object as values, but the key should be a string.
    attr_accessor :session
    
    # Holds a hash of header names and values. Accessed like <tt>headers["Cache-Control"]</tt> to get the value of the Cache-Control
    # directive. Values should always be specified as strings.
    attr_accessor :headers
    
    # Holds the hash of variables that are passed on to the template class to be made available to the view. This hash
    # is generated by taking a snapshot of all the instance variables in the current scope just before a template is rendered.
    attr_accessor :assigns

    # Returns the name of the action this controller is processing.
    attr_accessor :action_name

    class << self
      # Factory for the standard create, process loop where the controller is discarded after processing.
      def process(request, response) #:nodoc:
        new.process(request, response)
      end
      
      # Converts the class name from something like "OneModule::TwoModule::NeatController" to "NeatController".
      def controller_class_name
        @controller_class_name ||= name.demodulize
      end

      # Converts the class name from something like "OneModule::TwoModule::NeatController" to "neat".
      def controller_name
        @controller_name ||= controller_class_name.sub(/Controller$/, '').underscore
      end
      
      # Convert the class name from something like "OneModule::TwoModule::NeatController" to "one_module/two_module/neat".
      def controller_path
        unless @controller_path
          components = self.name.to_s.split('::')
          components[-1] = $1 if /^(.*)Controller$/ =~ components.last
          # Accomodate the root Controllers module.
          components.shift if components.first == 'Controllers'
          @controller_path = components.map { |name| name.underscore }.join('/')
        end
        @controller_path
      end

      # Return an array containing the names of public methods that have been marked hidden from the action processor.
      # By default, all methods defined in ActionController::Base and included modules are hidden.
      # More methods can be hidden using +hide_actions+.
      def hidden_actions
        write_inheritable_attribute(:hidden_actions, ActionController::Base.public_instance_methods) unless read_inheritable_attribute(:hidden_actions)
        read_inheritable_attribute(:hidden_actions)
      end

      # Hide each of the given methods from being callable as actions.
      def hide_action(*names)
        write_inheritable_attribute(:hidden_actions, hidden_actions | names.collect {|n| n.to_s})
      end

      # Set the template root to be one directory behind the root dir of the controller. Examples:
      #   /code/weblog/components/admin/users_controller.rb with Admin::UsersController 
      #     will use /code/weblog/components as template root 
      #     and find templates in /code/weblog/components/admin/users/
      #
      #   /code/weblog/components/admin/parties/users_controller.rb with Admin::Parties::UsersController 
      #     will also use /code/weblog/components as template root 
      #     and find templates in /code/weblog/components/admin/parties/users/
      def uses_component_template_root
        path_of_calling_controller = File.dirname(caller[0].split(/:\d+:/).first)
        path_of_controller_root    = path_of_calling_controller.sub(/#{controller_path.split("/")[0..-2]}$/, "") # " (for ruby-mode)
        self.template_root = path_of_controller_root
      end

      # Temporary method for enabling upload progress until it's ready to leave experimental mode
      def enable_upload_progress # :nodoc:
        require 'action_controller/upload_progress'
        include ActionController::UploadProgress
      end
    end

    public
      # Extracts the action_name from the request parameters and performs that action.
      def process(request, response, method = :perform_action, *arguments) #:nodoc:
        initialize_template_class(response)
        assign_shortcuts(request, response)
        initialize_current_url
        @action_name = params['action'] || 'index'
        @variables_added = nil

        log_processing if logger
        send(method, *arguments)
        close_session

        @response
      end

      # Returns a URL that has been rewritten according to the options hash and the defined Routes. 
      # (For doing a complete redirect, use redirect_to).
      #  
      # <tt>url_for</tt> is used to:
      #  
      # All keys given to url_for are forwarded to the Route module save for the following:
      # * <tt>:anchor</tt> -- specifies the anchor name to be appended to the path. For example, 
      #   <tt>url_for :controller => 'posts', :action => 'show', :id => 10, :anchor => 'comments'</tt> 
      #   will produce "/posts/show/10#comments".
      # * <tt>:only_path</tt> --  if true, returns the absolute URL (omitting the protocol, host name, and port)
      # * <tt>:trailing_slash</tt> --  if true, adds a trailing slash, as in "/archive/2005/". Note that this
      #   is currently not recommended since it breaks caching.
      # * <tt>:host</tt> -- overrides the default (current) host if provided
      # * <tt>:protocol</tt> -- overrides the default (current) protocol if provided
      #
      # The URL is generated from the remaining keys in the hash. A URL contains two key parts: the <base> and a query string.
      # Routes composes a query string as the key/value pairs not included in the <base>.
      #
      # The default Routes setup supports a typical Rails path of "controller/action/id" where action and id are optional, with
      # action defaulting to 'index' when not given. Here are some typical url_for statements and their corresponding URLs:
      #  
      #   url_for :controller => 'posts', :action => 'recent' # => 'proto://host.com/posts/recent'
      #   url_for :controller => 'posts', :action => 'index' # => 'proto://host.com/posts'
      #   url_for :controller => 'posts', :action => 'show', :id => 10 # => 'proto://host.com/posts/show/10'
      #
      # When generating a new URL, missing values may be filled in from the current request's parameters. For example,
      # <tt>url_for :action => 'some_action'</tt> will retain the current controller, as expected. This behavior extends to
      # other parameters, including <tt>:controller</tt>, <tt>:id</tt>, and any other parameters that are placed into a Route's
      # path.
      #  
      # The URL helpers such as <tt>url_for</tt> have a limited form of memory: when generating a new URL, they can look for
      # missing values in the current request's parameters. Routes attempts to guess when a value should and should not be
      # taken from the defaults. There are a few simple rules on how this is performed:
      #
      # * If the controller name begins with a slash, no defaults are used: <tt>url_for :controller => '/home'</tt>
      # * If the controller changes, the action will default to index unless provided
      #
      # The final rule is applied while the URL is being generated and is best illustrated by an example. Let us consider the
      # route given by <tt>map.connect 'people/:last/:first/:action', :action => 'bio', :controller => 'people'</tt>.
      #
      # Suppose that the current URL is "people/hh/david/contacts". Let's consider a few different cases URLs which are generated
      # from this page.
      #
      # * <tt>url_for :action => 'bio'</tt> -- During the generation of this URL, default values will be used for the first and
      # last components, and the action shall change. The generated URL will be, "people/hh/david/bio".
      # * <tt>url_for :first => 'davids-little-brother'</tt> This generates the URL 'people/hh/davids-little-brother' -- note
      #   that this URL leaves out the assumed action of 'bio'.
      #
      # However, you might ask why the action from the current request, 'contacts', isn't carried over into the new URL. The
      # answer has to do with the order in which the parameters appear in the generated path. In a nutshell, since the
      # value that appears in the slot for <tt>:first</tt> is not equal to default value for <tt>:first</tt> we stop using
      # defaults. On it's own, this rule can account for much of the typical Rails URL behavior.
      #  
      # Although a convienence, defaults can occasionaly get in your way. In some cases a default persists longer than desired.
      # The default may be cleared by adding <tt>:name => nil</tt> to <tt>url_for</tt>'s options.
      # This is often required when writing form helpers, since the defaults in play may vary greatly depending upon where the
      # helper is used from. The following line will redirect to PostController's default action, regardless of the page it is
      # displayed on:
      #
      #   url_for :controller => 'posts', :action => nil
      #      
      # Instead of passing an options hash, you can also pass a method reference in the form of a symbol. Consider this example:
      #
      #   class WeblogController < ActionController::Base
      #     def update
      #       # do some update
      #       redirect_to :dashboard_url
      #     end
      #     
      #     protected
      #       def dashboard_url
      #         url_for :controller => (@project.active? ? "project" : "account"), :action => "dashboard"
      #       end
      #   end
      def url_for(options = {}, *parameters_for_method_reference) #:doc:
        case options
          when String then options
          when Symbol then send(options, *parameters_for_method_reference)
          when Hash   then @url.rewrite(rewrite_options(options))
        end
      end

      # Converts the class name from something like "OneModule::TwoModule::NeatController" to "NeatController".
      def controller_class_name
        self.class.controller_class_name
      end

      # Converts the class name from something like "OneModule::TwoModule::NeatController" to "neat".
      def controller_name
        self.class.controller_name
      end

    protected
      # Renders the content that'll be returned to the browser as the response body. This can just be as regular text, but is
      # more often the compilation of a template.
      #
      # === Rendering an action
      # 
      # Action rendering is the most common form and the type used automatically by Action Controller when nothing else is
      # specified. By default, actions are rendered within the current layout (if one exists).
      #
      #   # Renders the template for the action "goal" within the current controller
      #   render :action => "goal"
      #
      #   # Renders the template for the action "short_goal" within the current controller,
      #   # but without the current active layout
      #   render :action => "short_goal", :layout => false
      #
      #   # Renders the template for the action "long_goal" within the current controller,
      #   # but with a custom layout
      #   render :action => "long_goal", :layout => "spectacular"
      #
      # _Deprecation_ _notice_: This used to have the signatures <tt>render_action("action", status = 200)</tt>,
      # <tt>render_without_layout("controller/action", status = 200)</tt>, and 
      # <tt>render_with_layout("controller/action", status = 200, layout)</tt>.
      #
      # === Rendering partials
      # 
      # Partial rendering is most commonly used together with Ajax calls that only updates one or a few elements on a page
      # without reloading. Rendering of partials from the controller makes it possible to use the same partial template in
      # both the full-page rendering (by calling it from within the template) and when sub-page updates happen (from the
      # controller action responding to Ajax calls). By default, the current layout is not used.
      #
      #   # Renders the partial located at app/views/controller/_win.r(html|xml)
      #   render :partial => "win"
      #
      #   # Renders the partial with a status code of 500 (internal error)
      #   render :partial => "broken", :status => 500
      #
      #   # Renders the same partial but also makes a local variable available to it
      #   render :partial => "win", :locals => { :name => "david" }
      #
      #   # Renders a collection of the same partial by making each element of @wins available through 
      #   # the local variable "win" as it builds the complete response
      #   render :partial => "win", :collection => @wins
      #
      #   # Renders the same collection of partials, but also renders the win_divider partial in between
      #   # each win partial.
      #   render :partial => "win", :collection => @wins, :spacer_template => "win_divider"
      #
      # _Deprecation_ _notice_: This used to have the signatures 
      # <tt>render_partial(partial_path = default_template_name, object = nil, local_assigns = {})</tt> and
      # <tt>render_partial_collection(partial_name, collection, partial_spacer_template = nil, local_assigns = {})</tt>.
      #
      # === Rendering a file
      # 
      # File rendering works just like action rendering except that it takes a path relative to the template root or an absolute
      # path if use_full_path is passed as true. The current layout is not applied automatically.
      #
      #   # Renders the template located in [TEMPLATE_ROOT]/weblog/show.r(html|xml) (in Rails, app/views/weblog/show.rhtml)
      #   render :file => "weblog/show"
      #
      #   # Renders the template located in /path/to/some/template.r(html|xml)
      #   render :file => "/path/to/some/template", :use_full_path => false
      #
      #   # Renders the same template within the current layout, but with a 404 status code
      #   render :file => "/path/to/some/template", :use_full_path => false, :layout => true, :status => 404
      #
      # _Deprecation_ _notice_: This used to have the signature <tt>render_file(path, status = 200)</tt>
      #
      # === Rendering text
      # 
      # Rendering of text is usually used for tests or for rendering prepared content, such as a cache. By default, text
      # rendering is not done within the active layout.
      #
      #   # Renders the clear text "hello world" with status code 200
      #   render :text => "hello world!"
      #
      #   # Renders the clear text "Explosion!"  with status code 500
      #   render :text => "Explosion!", :status => 500 
      #
      #   # Renders the clear text "Hi there!" within the current active layout (if one exists)
      #   render :text => "Explosion!", :layout => true
      #
      #   # Renders the clear text "Hi there!" within the the layout 
      #   # placed in "app/views/layouts/special.r(html|xml)"
      #   render :text => "Explosion!", :layout => "special"
      #
      # _Deprecation_ _notice_: This used to have the signature <tt>render_text("text", status = 200)</tt>
      #
      # === Rendering an inline template
      #
      # Rendering of an inline template works as a cross between text and action rendering where the source for the template
      # is supplied inline, like text, but its interpreted with ERb or Builder, like action. By default, ERb is used for rendering
      # and the current layout is not used.
      #
      #   # Renders "hello, hello, hello, again"
      #   render :inline => "<%= 'hello, ' * 3 + 'again' %>" 
      #
      #   # Renders "<p>Good seeing you!</p>" using Builder
      #   render :inline => "xml.p { 'Good seeing you!' }", :type => :rxml
      #
      #   # Renders "hello david"
      #   render :inline => "<%= 'hello ' + name %>", :locals => { :name => "david" }
      #
      # _Deprecation_ _notice_: This used to have the signature <tt>render_template(template, status = 200, type = :rhtml)</tt>
      #
      # === Rendering nothing
      #
      # Rendering nothing is often convenient in combination with Ajax calls that perform their effect client-side or
      # when you just want to communicate a status code. Due to a bug in Safari, nothing actually means a single space.
      #
      #   # Renders an empty response with status code 200
      #   render :nothing => true
      #
      #   # Renders an empty response with status code 401 (access denied)
      #   render :nothing => true, :status => 401
      def render(options = nil, deprecated_status = nil) #:doc:
        raise DoubleRenderError, "Can only render or redirect once per action" if performed?

        # Backwards compatibility
        unless options.is_a?(Hash)
          return render_file(options || default_template_name, deprecated_status, true)
        end

        if text = options[:text]
          render_text(text, options[:status])

        else
          if file = options[:file]
            render_file(file, options[:status], options[:use_full_path])

          elsif template = options[:template]
            render_file(template, options[:status], true)
            
          elsif inline = options[:inline]
            render_template(inline, options[:status], options[:type])
            
          elsif action_name = options[:action]
            render_action(action_name, options[:status], options[:layout]) 
            
          elsif partial = options[:partial]
            partial = default_template_name if partial == true
            if collection = options[:collection]
              render_partial_collection(partial, collection, options[:spacer_template], options[:locals], options[:status])
            else
              render_partial(partial, ActionView::Base::ObjectWrapper.new(options[:object]), options[:locals], options[:status])
            end

          elsif options[:nothing]
            # Safari doesn't pass the headers of the return if the response is zero length
            render_text(" ", options[:status])
            
          else
            render_file(default_template_name, options[:status], true)
            
          end
        end
      end

      # Renders according to the same rules as <tt>render</tt>, but returns the result in a string instead
      # of sending it as the response body to the browser.
      def render_to_string(options = nil) #:doc:
        result = render(options)
        erase_render_results
        result
      end    

      def render_action(action_name, status = nil, with_layout = true)
        if with_layout
          render_with_layout(default_template_name(action_name), status)
        else
          render_with_no_layout(default_template_name(action_name), status)
        end
      end

      def render_file(template_path, status = nil, use_full_path = false)
        add_variables_to_assigns
        assert_existance_of_template_file(template_path) if use_full_path
        logger.info("Rendering #{template_path}" + (status ? "(#{status})" : '')) if logger
        render_text(@template.render_file(template_path, use_full_path), status)
      end

      def render_template(template, status = nil, type = :rhtml)
        add_variables_to_assigns
        render_text(@template.render_template(type, template), status)
      end

      def render_text(text = nil, status = nil)
        @performed_render = true
        @response.headers['Status'] = (status || DEFAULT_RENDER_STATUS_CODE).to_s
        @response.body = text
      end

      def render_nothing(status = nil)
        render_text(' ', status)
      end

      def render_partial(partial_path = default_template_name, object = nil, local_assigns = nil, status = nil)
        add_variables_to_assigns
        render_text(@template.render_partial(partial_path, object, local_assigns), status)
      end

      def render_partial_collection(partial_name, collection, partial_spacer_template = nil, local_assigns = nil, status = nil)
        add_variables_to_assigns
        render_text(@template.render_partial_collection(partial_name, collection, partial_spacer_template, local_assigns), status)
      end

      def render_with_layout(template_name = default_template_name, status = nil, layout = nil)
        render_with_a_layout(template_name, status, layout)
      end

      def render_without_layout(template_name = default_template_name, status = nil)
        render_with_no_layout(template_name, status)
      end


      # Clears the rendered results, allowing for another render to be performed.
      def erase_render_results
        @response.body = nil
        @performed_render = false
      end

      # Clears the redirected results from the headers, resetting the status to 200 and returns 
      # the URL that was used to redirect or nil if there was no redirected URL
      # Note that +redirect_to+ will change the body of the response to indicate a redirection.
      # The response body is not reset here, see +erase_render_results+
      def erase_redirect_results
        @performed_redirect = false
        response.redirected_to = nil
        response.redirected_to_method_params = nil
        response.headers['Status'] = DEFAULT_RENDER_STATUS_CODE
        response.headers.delete('location')
      end

      # Erase both render and redirect results
      def erase_results
        erase_render_results
        erase_redirect_results
      end

      def rewrite_options(options)
        if defaults = default_url_options(options)
          defaults.merge(options)
        else
          options
        end
      end
      
      # Overwrite to implement a number of default options that all url_for-based methods will use. The default options should come in
      # the form of a hash, just like the one you would use for url_for directly. Example:
      #
      #   def default_url_options(options)
      #     { :project => @project.active? ? @project.url_name : "unknown" }
      #   end
      #
      # As you can infer from the example, this is mostly useful for situations where you want to centralize dynamic decisions about the
      # urls as they stem from the business domain. Please note that any individual url_for call can always override the defaults set
      # by this method.
      def default_url_options(options) #:doc:
      end
      
      # Redirects the browser to the target specified in +options+. This parameter can take one of three forms:
      #
      # * <tt>Hash</tt>: The URL will be generated by calling url_for with the +options+.
      # * <tt>String starting with protocol:// (like http://)</tt>: Is passed straight through as the target for redirection.
      # * <tt>String not containing a protocol</tt>: The current current protocol and host is prepended to the string.
      # 
      # Examples:
      #   redirect_to :action => "show", :id => 5
      #   redirect_to "http://www.rubyonrails.org"
      #   redirect_to "/images/screenshot.jpg"
      #
      # The redirection happens as a "302 Moved" header.
      def redirect_to(options = {}, *parameters_for_method_reference) #:doc:
        case options
          when %r{^\w+://.*}
            raise DoubleRenderError if performed?
            logger.info("Redirected to #{options}") unless logger.nil?
            response.redirect(options)
            response.redirected_to = options
            @performed_redirect = true

          when String
            redirect_to(request.protocol + request.host_with_port + options)

          else
            if parameters_for_method_reference.empty?
              redirect_to(url_for(options))
              response.redirected_to = options
            else
              redirect_to(url_for(options, *parameters_for_method_reference))
              response.redirected_to, response.redirected_to_method_params = options, parameters_for_method_reference
            end
        end
      end
      
      # Sets a HTTP 1.1 Cache-Control header. Defaults to issuing a "private" instruction, so that
      # intermediate caches shouldn't cache the response.
      #
      # Examples:
      #   expires_in 20.minutes
      #   expires_in 3.hours, :private => false
      #   expires in 3.hours, 'max-stale' => 5.hours, :private => nil, :public => true
      # 
      # This method will overwrite an existing Cache-Control header.
      # See http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html for more possibilities.
      def expires_in(seconds, options = {}) #:doc:
        cache_options = { 'max-age' => seconds, 'private' => true }.symbolize_keys.merge!(options.symbolize_keys)
        cache_options.delete_if { |k,v| v.nil? or v == false }
        cache_control = cache_options.map{ |k,v| v == true ? k.to_s : "#{k.to_s}=#{v.to_s}"}
        @response.headers["Cache-Control"] = cache_control.join(', ')
      end
      
      # Sets a HTTP 1.1 Cache-Control header of "no-cache" so no caching should occur by the browser or
      # intermediate caches (like caching proxy servers).
      def expires_now #:doc:
        @response.headers["Cache-Control"] = "no-cache"
      end

      # Resets the session by clearing out all the objects stored within and initializing a new session object.
      def reset_session #:doc:
        @request.reset_session
        @session = @request.session
        @response.session = @session
      end
    
    private
      def self.view_class
        unless @view_class
          # create a new class based on the default template class and include helper methods
          logger.debug "defining view class for #{name}" if logger
          @view_class = Class.new(ActionView::Base)
          @view_class.send(:include, master_helper_module)
        end
        @view_class
      end

      def self.view_root
        @view_root ||= template_root
      end

      def initialize_template_class(response)
        raise "You must assign a template class through ActionController.template_class= before processing a request" unless @@template_class
        
        response.template = self.class.view_class.new(self.class.view_root, {}, self)
        @performed_render = @performed_redirect = false
      end
    
      def assign_shortcuts(request, response)
        @request, @params, @cookies = request, request.parameters, request.cookies

        @response         = response
        @response.session = request.session

        @session  = @response.session
        @template = @response.template
        @assigns  = @response.template.assigns        
        @headers  = @response.headers
      end
      
      def initialize_current_url
        @url = UrlRewriter.new(@request, @params.clone())
      end

      def log_processing
        logger.info "\n\nProcessing #{controller_class_name}\##{action_name} (for #{request_origin})"
        logger.info "  Parameters: #{@params.inspect}"
      end
    
      def perform_action
        if self.class.action_methods.include?(action_name) || self.class.action_methods.include?('method_missing')
          send(action_name)
          render unless performed?
        elsif template_exists? && template_public?
          render
        else
          raise UnknownAction, "No action responded to #{action_name}", caller
        end
      end
      
      def performed?
        @performed_render || @performed_redirect
      end

      def action_methods
        self.class.action_methods
      end

      def self.action_methods
        @action_methods ||= (public_instance_methods - hidden_actions).inject({}) { |h, k| h[k] = true; h }
      end

      def add_variables_to_assigns
        unless @variables_added
          add_instance_variables_to_assigns
          add_class_variables_to_assigns if view_controller_internals
          @variables_added = true
        end
      end

      def add_instance_variables_to_assigns
        @@protected_variables_cache ||= protected_instance_variables.inject({}) { |h, k| h[k] = true; h }
        instance_variables.each do |var|
          next if @@protected_variables_cache.include?(var)
          @assigns[var[1..-1]] = instance_variable_get(var)
        end
      end

      def add_class_variables_to_assigns
        %w( template_root logger template_class ignore_missing_templates ).each do |cvar|
          @assigns[cvar] = self.send(cvar)
        end
      end

      def protected_instance_variables
        if view_controller_internals
          [ "@assigns", "@performed_redirect", "@performed_render" ]
        else
          [ "@assigns", "@performed_redirect", "@performed_render", "@request", "@response", "@session", "@cookies", "@template" ]
        end
      end


      def request_origin
        "#{@request.remote_ip} at #{Time.now.to_s}"
      end
      
      def complete_request_uri
        request.protocol + request.host + request.request_uri
      end

      def close_session
        @session.close unless @session.nil? || Hash === @session
      end

      
      def template_exists?(template_name = default_template_name)
        @template.file_exists?(template_name)
      end

      def template_public?(template_name = default_template_name)
        @template.file_public?(template_name)
      end

      def assert_existance_of_template_file(template_name)
        unless template_exists?(template_name) || ignore_missing_templates
          full_template_path = @template.send(:full_template_path, template_name, 'rhtml')
          template_type = (template_name =~ /layouts/i) ? 'layout' : 'template'
          raise(MissingTemplate, "Missing #{template_type} #{full_template_path}")
        end
      end

      def default_template_name(default_action_name = action_name)
        "#{self.class.controller_path}/#{default_action_name}"
      end
  end
end