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