Chris@909: module ActionController
Chris@909:   # === Action Pack pagination for Active Record collections
Chris@909:   #
Chris@909:   # The Pagination module aids in the process of paging large collections of
Chris@909:   # Active Record objects. It offers macro-style automatic fetching of your
Chris@909:   # model for multiple views, or explicit fetching for single actions. And if
Chris@909:   # the magic isn't flexible enough for your needs, you can create your own
Chris@909:   # paginators with a minimal amount of code.
Chris@909:   #
Chris@909:   # The Pagination module can handle as much or as little as you wish. In the
Chris@909:   # controller, have it automatically query your model for pagination; or,
Chris@909:   # if you prefer, create Paginator objects yourself.
Chris@909:   #
Chris@909:   # Pagination is included automatically for all controllers.
Chris@909:   #
Chris@909:   # For help rendering pagination links, see 
Chris@909:   # ActionView::Helpers::PaginationHelper.
Chris@909:   #
Chris@909:   # ==== Automatic pagination for every action in a controller
Chris@909:   #
Chris@909:   #   class PersonController < ApplicationController   
Chris@909:   #     model :person
Chris@909:   #
Chris@909:   #     paginate :people, :order => 'last_name, first_name',
Chris@909:   #              :per_page => 20
Chris@909:   #     
Chris@909:   #     # ...
Chris@909:   #   end
Chris@909:   #
Chris@909:   # Each action in this controller now has access to a <tt>@people</tt>
Chris@909:   # instance variable, which is an ordered collection of model objects for the
Chris@909:   # current page (at most 20, sorted by last name and first name), and a 
Chris@909:   # <tt>@person_pages</tt> Paginator instance. The current page is determined
Chris@909:   # by the <tt>params[:page]</tt> variable.
Chris@909:   #
Chris@909:   # ==== Pagination for a single action
Chris@909:   #
Chris@909:   #   def list
Chris@909:   #     @person_pages, @people =
Chris@909:   #       paginate :people, :order => 'last_name, first_name'
Chris@909:   #   end
Chris@909:   #
Chris@909:   # Like the previous example, but explicitly creates <tt>@person_pages</tt>
Chris@909:   # and <tt>@people</tt> for a single action, and uses the default of 10 items
Chris@909:   # per page.
Chris@909:   #
Chris@909:   # ==== Custom/"classic" pagination 
Chris@909:   #
Chris@909:   #   def list
Chris@909:   #     @person_pages = Paginator.new self, Person.count, 10, params[:page]
Chris@909:   #     @people = Person.find :all, :order => 'last_name, first_name', 
Chris@909:   #                           :limit  =>  @person_pages.items_per_page,
Chris@909:   #                           :offset =>  @person_pages.current.offset
Chris@909:   #   end
Chris@909:   # 
Chris@909:   # Explicitly creates the paginator from the previous example and uses 
Chris@909:   # Paginator#to_sql to retrieve <tt>@people</tt> from the model.
Chris@909:   #
Chris@909:   module Pagination
Chris@909:     unless const_defined?(:OPTIONS)
Chris@909:       # A hash holding options for controllers using macro-style pagination
Chris@909:       OPTIONS = Hash.new
Chris@909:   
Chris@909:       # The default options for pagination
Chris@909:       DEFAULT_OPTIONS = {
Chris@909:         :class_name => nil,
Chris@909:         :singular_name => nil,
Chris@909:         :per_page   => 10,
Chris@909:         :conditions => nil,
Chris@909:         :order_by   => nil,
Chris@909:         :order      => nil,
Chris@909:         :join       => nil,
Chris@909:         :joins      => nil,
Chris@909:         :count      => nil,
Chris@909:         :include    => nil,
Chris@909:         :select     => nil,
Chris@909:         :group      => nil,
Chris@909:         :parameter  => 'page'
Chris@909:       }
Chris@909:     else
Chris@909:       DEFAULT_OPTIONS[:group] = nil
Chris@909:     end
Chris@909:       
Chris@909:     def self.included(base) #:nodoc:
Chris@909:       super
Chris@909:       base.extend(ClassMethods)
Chris@909:     end
Chris@909:   
Chris@909:     def self.validate_options!(collection_id, options, in_action) #:nodoc:
Chris@909:       options.merge!(DEFAULT_OPTIONS) {|key, old, new| old}
Chris@909: 
Chris@909:       valid_options = DEFAULT_OPTIONS.keys
Chris@909:       valid_options << :actions unless in_action
Chris@909:     
Chris@909:       unknown_option_keys = options.keys - valid_options
Chris@909:       raise ActionController::ActionControllerError,
Chris@909:             "Unknown options: #{unknown_option_keys.join(', ')}" unless
Chris@909:               unknown_option_keys.empty?
Chris@909: 
Chris@909:       options[:singular_name] ||= ActiveSupport::Inflector.singularize(collection_id.to_s)
Chris@909:       options[:class_name]  ||= ActiveSupport::Inflector.camelize(options[:singular_name])
Chris@909:     end
Chris@909: 
Chris@909:     # Returns a paginator and a collection of Active Record model instances
Chris@909:     # for the paginator's current page. This is designed to be used in a
Chris@909:     # single action; to automatically paginate multiple actions, consider
Chris@909:     # ClassMethods#paginate.
Chris@909:     #
Chris@909:     # +options+ are:
Chris@909:     # <tt>:singular_name</tt>:: the singular name to use, if it can't be inferred by singularizing the collection name
Chris@909:     # <tt>:class_name</tt>:: the class name to use, if it can't be inferred by
Chris@909:     #                        camelizing the singular name
Chris@909:     # <tt>:per_page</tt>::   the maximum number of items to include in a 
Chris@909:     #                        single page. Defaults to 10
Chris@909:     # <tt>:conditions</tt>:: optional conditions passed to Model.find(:all, *params) and
Chris@909:     #                        Model.count
Chris@909:     # <tt>:order</tt>::      optional order parameter passed to Model.find(:all, *params)
Chris@909:     # <tt>:order_by</tt>::   (deprecated, used :order) optional order parameter passed to Model.find(:all, *params)
Chris@909:     # <tt>:joins</tt>::      optional joins parameter passed to Model.find(:all, *params)
Chris@909:     #                        and Model.count
Chris@909:     # <tt>:join</tt>::       (deprecated, used :joins or :include) optional join parameter passed to Model.find(:all, *params)
Chris@909:     #                        and Model.count
Chris@909:     # <tt>:include</tt>::    optional eager loading parameter passed to Model.find(:all, *params)
Chris@909:     #                        and Model.count
Chris@909:     # <tt>:select</tt>::     :select parameter passed to Model.find(:all, *params)
Chris@909:     #
Chris@909:     # <tt>:count</tt>::      parameter passed as :select option to Model.count(*params)
Chris@909:     #
Chris@909:     # <tt>:group</tt>::     :group parameter passed to Model.find(:all, *params). It forces the use of DISTINCT instead of plain COUNT to come up with the total number of records
Chris@909:     #
Chris@909:     def paginate(collection_id, options={})
Chris@909:       Pagination.validate_options!(collection_id, options, true)
Chris@909:       paginator_and_collection_for(collection_id, options)
Chris@909:     end
Chris@909: 
Chris@909:     # These methods become class methods on any controller 
Chris@909:     module ClassMethods
Chris@909:       # Creates a +before_filter+ which automatically paginates an Active
Chris@909:       # Record model for all actions in a controller (or certain actions if
Chris@909:       # specified with the <tt>:actions</tt> option).
Chris@909:       #
Chris@909:       # +options+ are the same as PaginationHelper#paginate, with the addition 
Chris@909:       # of:
Chris@909:       # <tt>:actions</tt>:: an array of actions for which the pagination is
Chris@909:       #                     active. Defaults to +nil+ (i.e., every action)
Chris@909:       def paginate(collection_id, options={})
Chris@909:         Pagination.validate_options!(collection_id, options, false)
Chris@909:         module_eval do
Chris@909:           before_filter :create_paginators_and_retrieve_collections
Chris@909:           OPTIONS[self] ||= Hash.new
Chris@909:           OPTIONS[self][collection_id] = options
Chris@909:         end
Chris@909:       end
Chris@909:     end
Chris@909: 
Chris@909:     def create_paginators_and_retrieve_collections #:nodoc:
Chris@909:       Pagination::OPTIONS[self.class].each do |collection_id, options|
Chris@909:         next unless options[:actions].include? action_name if
Chris@909:           options[:actions]
Chris@909: 
Chris@909:         paginator, collection = 
Chris@909:           paginator_and_collection_for(collection_id, options)
Chris@909: 
Chris@909:         paginator_name = "@#{options[:singular_name]}_pages"
Chris@909:         self.instance_variable_set(paginator_name, paginator)
Chris@909: 
Chris@909:         collection_name = "@#{collection_id.to_s}"
Chris@909:         self.instance_variable_set(collection_name, collection)     
Chris@909:       end
Chris@909:     end
Chris@909:   
Chris@909:     # Returns the total number of items in the collection to be paginated for
Chris@909:     # the +model+ and given +conditions+. Override this method to implement a
Chris@909:     # custom counter.
Chris@909:     def count_collection_for_pagination(model, options)
Chris@909:       model.count(:conditions => options[:conditions],
Chris@909:                   :joins => options[:join] || options[:joins],
Chris@909:                   :include => options[:include],
Chris@909:                   :select => (options[:group] ? "DISTINCT #{options[:group]}" : options[:count]))
Chris@909:     end
Chris@909:     
Chris@909:     # Returns a collection of items for the given +model+ and +options[conditions]+,
Chris@909:     # ordered by +options[order]+, for the current page in the given +paginator+.
Chris@909:     # Override this method to implement a custom finder.
Chris@909:     def find_collection_for_pagination(model, options, paginator)
Chris@909:       model.find(:all, :conditions => options[:conditions],
Chris@909:                  :order => options[:order_by] || options[:order],
Chris@909:                  :joins => options[:join] || options[:joins], :include => options[:include],
Chris@909:                  :select => options[:select], :limit => options[:per_page],
Chris@909:                  :group => options[:group], :offset => paginator.current.offset)
Chris@909:     end
Chris@909:   
Chris@909:     protected :create_paginators_and_retrieve_collections,
Chris@909:               :count_collection_for_pagination,
Chris@909:               :find_collection_for_pagination
Chris@909: 
Chris@909:     def paginator_and_collection_for(collection_id, options) #:nodoc:
Chris@909:       klass = options[:class_name].constantize
Chris@909:       page  = params[options[:parameter]]
Chris@909:       count = count_collection_for_pagination(klass, options)
Chris@909:       paginator = Paginator.new(self, count, options[:per_page], page)
Chris@909:       collection = find_collection_for_pagination(klass, options, paginator)
Chris@909:     
Chris@909:       return paginator, collection 
Chris@909:     end
Chris@909:       
Chris@909:     private :paginator_and_collection_for
Chris@909: 
Chris@909:     # A class representing a paginator for an Active Record collection.
Chris@909:     class Paginator
Chris@909:       include Enumerable
Chris@909: 
Chris@909:       # Creates a new Paginator on the given +controller+ for a set of items
Chris@909:       # of size +item_count+ and having +items_per_page+ items per page.
Chris@909:       # Raises ArgumentError if items_per_page is out of bounds (i.e., less
Chris@909:       # than or equal to zero). The page CGI parameter for links defaults to
Chris@909:       # "page" and can be overridden with +page_parameter+.
Chris@909:       def initialize(controller, item_count, items_per_page, current_page=1)
Chris@909:         raise ArgumentError, 'must have at least one item per page' if
Chris@909:           items_per_page <= 0
Chris@909: 
Chris@909:         @controller = controller
Chris@909:         @item_count = item_count || 0
Chris@909:         @items_per_page = items_per_page
Chris@909:         @pages = {}
Chris@909:         
Chris@909:         self.current_page = current_page
Chris@909:       end
Chris@909:       attr_reader :controller, :item_count, :items_per_page
Chris@909:       
Chris@909:       # Sets the current page number of this paginator. If +page+ is a Page
Chris@909:       # object, its +number+ attribute is used as the value; if the page does 
Chris@909:       # not belong to this Paginator, an ArgumentError is raised.
Chris@909:       def current_page=(page)
Chris@909:         if page.is_a? Page
Chris@909:           raise ArgumentError, 'Page/Paginator mismatch' unless
Chris@909:             page.paginator == self
Chris@909:         end
Chris@909:         page = page.to_i
Chris@909:         @current_page_number = has_page_number?(page) ? page : 1
Chris@909:       end
Chris@909: 
Chris@909:       # Returns a Page object representing this paginator's current page.
Chris@909:       def current_page
Chris@909:         @current_page ||= self[@current_page_number]
Chris@909:       end
Chris@909:       alias current :current_page
Chris@909: 
Chris@909:       # Returns a new Page representing the first page in this paginator.
Chris@909:       def first_page
Chris@909:         @first_page ||= self[1]
Chris@909:       end
Chris@909:       alias first :first_page
Chris@909: 
Chris@909:       # Returns a new Page representing the last page in this paginator.
Chris@909:       def last_page
Chris@909:         @last_page ||= self[page_count] 
Chris@909:       end
Chris@909:       alias last :last_page
Chris@909: 
Chris@909:       # Returns the number of pages in this paginator.
Chris@909:       def page_count
Chris@909:         @page_count ||= @item_count.zero? ? 1 :
Chris@909:                           (q,r=@item_count.divmod(@items_per_page); r==0? q : q+1)
Chris@909:       end
Chris@909: 
Chris@909:       alias length :page_count
Chris@909: 
Chris@909:       # Returns true if this paginator contains the page of index +number+.
Chris@909:       def has_page_number?(number)
Chris@909:         number >= 1 and number <= page_count
Chris@909:       end
Chris@909: 
Chris@909:       # Returns a new Page representing the page with the given index
Chris@909:       # +number+.
Chris@909:       def [](number)
Chris@909:         @pages[number] ||= Page.new(self, number)
Chris@909:       end
Chris@909: 
Chris@909:       # Successively yields all the paginator's pages to the given block.
Chris@909:       def each(&block)
Chris@909:         page_count.times do |n|
Chris@909:           yield self[n+1]
Chris@909:         end
Chris@909:       end
Chris@909: 
Chris@909:       # A class representing a single page in a paginator.
Chris@909:       class Page
Chris@909:         include Comparable
Chris@909: 
Chris@909:         # Creates a new Page for the given +paginator+ with the index
Chris@909:         # +number+. If +number+ is not in the range of valid page numbers or
Chris@909:         # is not a number at all, it defaults to 1.
Chris@909:         def initialize(paginator, number)
Chris@909:           @paginator = paginator
Chris@909:           @number = number.to_i
Chris@909:           @number = 1 unless @paginator.has_page_number? @number
Chris@909:         end
Chris@909:         attr_reader :paginator, :number
Chris@909:         alias to_i :number
Chris@909: 
Chris@909:         # Compares two Page objects and returns true when they represent the 
Chris@909:         # same page (i.e., their paginators are the same and they have the
Chris@909:         # same page number).
Chris@909:         def ==(page)
Chris@909:           return false if page.nil?
Chris@909:           @paginator == page.paginator and 
Chris@909:             @number == page.number
Chris@909:         end
Chris@909: 
Chris@909:         # Compares two Page objects and returns -1 if the left-hand page comes
Chris@909:         # before the right-hand page, 0 if the pages are equal, and 1 if the
Chris@909:         # left-hand page comes after the right-hand page. Raises ArgumentError
Chris@909:         # if the pages do not belong to the same Paginator object.
Chris@909:         def <=>(page)
Chris@909:           raise ArgumentError unless @paginator == page.paginator
Chris@909:           @number <=> page.number
Chris@909:         end
Chris@909: 
Chris@909:         # Returns the item offset for the first item in this page.
Chris@909:         def offset
Chris@909:           @paginator.items_per_page * (@number - 1)
Chris@909:         end
Chris@909:         
Chris@909:         # Returns the number of the first item displayed.
Chris@909:         def first_item
Chris@909:           offset + 1
Chris@909:         end
Chris@909:         
Chris@909:         # Returns the number of the last item displayed.
Chris@909:         def last_item
Chris@909:           [@paginator.items_per_page * @number, @paginator.item_count].min
Chris@909:         end
Chris@909: 
Chris@909:         # Returns true if this page is the first page in the paginator.
Chris@909:         def first?
Chris@909:           self == @paginator.first
Chris@909:         end
Chris@909: 
Chris@909:         # Returns true if this page is the last page in the paginator.
Chris@909:         def last?
Chris@909:           self == @paginator.last
Chris@909:         end
Chris@909: 
Chris@909:         # Returns a new Page object representing the page just before this
Chris@909:         # page, or nil if this is the first page.
Chris@909:         def previous
Chris@909:           if first? then nil else @paginator[@number - 1] end
Chris@909:         end
Chris@909: 
Chris@909:         # Returns a new Page object representing the page just after this
Chris@909:         # page, or nil if this is the last page.
Chris@909:         def next
Chris@909:           if last? then nil else @paginator[@number + 1] end
Chris@909:         end
Chris@909: 
Chris@909:         # Returns a new Window object for this page with the specified 
Chris@909:         # +padding+.
Chris@909:         def window(padding=2)
Chris@909:           Window.new(self, padding)
Chris@909:         end
Chris@909: 
Chris@909:         # Returns the limit/offset array for this page.
Chris@909:         def to_sql
Chris@909:           [@paginator.items_per_page, offset]
Chris@909:         end
Chris@909:         
Chris@909:         def to_param #:nodoc:
Chris@909:           @number.to_s
Chris@909:         end
Chris@909:       end
Chris@909: 
Chris@909:       # A class for representing ranges around a given page.
Chris@909:       class Window
Chris@909:         # Creates a new Window object for the given +page+ with the specified
Chris@909:         # +padding+.
Chris@909:         def initialize(page, padding=2)
Chris@909:           @paginator = page.paginator
Chris@909:           @page = page
Chris@909:           self.padding = padding
Chris@909:         end
Chris@909:         attr_reader :paginator, :page
Chris@909: 
Chris@909:         # Sets the window's padding (the number of pages on either side of the
Chris@909:         # window page).
Chris@909:         def padding=(padding)
Chris@909:           @padding = padding < 0 ? 0 : padding
Chris@909:           # Find the beginning and end pages of the window
Chris@909:           @first = @paginator.has_page_number?(@page.number - @padding) ?
Chris@909:             @paginator[@page.number - @padding] : @paginator.first
Chris@909:           @last =  @paginator.has_page_number?(@page.number + @padding) ?
Chris@909:             @paginator[@page.number + @padding] : @paginator.last
Chris@909:         end
Chris@909:         attr_reader :padding, :first, :last
Chris@909: 
Chris@909:         # Returns an array of Page objects in the current window.
Chris@909:         def pages
Chris@909:           (@first.number..@last.number).to_a.collect! {|n| @paginator[n]}
Chris@909:         end
Chris@909:         alias to_a :pages
Chris@909:       end
Chris@909:     end
Chris@909: 
Chris@909:   end
Chris@909: end