Added pagination support through both a controller and helper add-on #817 [Sam Stephenson]

git-svn-id: http://svn-commit.rubyonrails.org/rails/trunk@949 5ecf4fe2-1ee6-0310-87b1-e25e094e27de

1 files changed, 378 insertions, 0 deletions

diff --git a/actionpack/lib/action_controller/pagination.rb b/actionpack/lib/action_controller/pagination.rb
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+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.
+  #
+  # For help rendering pagination links, see 
+  # ActionView::Helpers::PaginationHelper.
+  #
+  # ==== Automatic pagination for every action in a controller
+  #
+  #   class PersonController < ApplicationController
+  #     helper :pagination     
+  #     model :person
+  #
+  #     paginate :people, :order_by => '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_by => '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 nil, 'last_name, first_name', 
+  #               @person_pages.current.to_sql
+  #   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,
+        :per_page   => 10,
+        :conditions => nil,
+        :order_by   => nil,
+        :join       => nil,
+        :parameter  => 'page'
+      }
+    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>:class_name</tt>:: the class name to use, if it can't be inferred by
+    #                        singularizing the collection 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 and
+    #                        Model.count
+    # <tt>:order_by</tt>::   optional order parameter passed to Model.find_all
+    # <tt>:join</tt>::       optional join parameter passed to Model.find_all
+    #                        and Model.count
+    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 which includes
+    # PaginationHelper.
+    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, conditions)
+      model.count(conditions)
+    end
+  
+    # Returns a collection of items for the given +model+ and +conditions+,
+    # ordered by +order_by+, for the current page in the given +paginator+.
+    # Override this method to implement a custom finder.
+    def find_collection_for_pagination(model, conditions, order_by, join, paginator)
+      model.find_all(conditions, order_by, paginator.current.to_sql, join)
+    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 = eval options[:class_name]
+      page  = @params[options[:parameter]]
+      count = count_collection_for_pagination(klass, options[:conditions])
+
+      paginator = Paginator.new(self, count, options[:per_page], page)
+      
+      collection = find_collection_for_pagination(klass,
+        options[:conditions], options[:order_by], options[:join], 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
+        
+        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 = has_page_number?(page) ? page : 1
+      end
+
+      # Returns a Page object representing this paginator's current page.
+      def current_page
+        self[@current_page]
+      end
+      alias current :current_page
+
+      # Returns a new Page representing the first page in this paginator.
+      def first_page
+        self[1]
+      end
+      alias first :first_page
+
+      # Returns a new Page representing the last page in this paginator.
+      def last_page
+        self[page_count] 
+      end
+      alias last :last_page
+
+      # Returns the number of pages in this paginator.
+      def page_count
+        return 1 if @item_count.zero?
+        (@item_count / @items_per_page.to_f).ceil
+      end
+      alias length :page_count
+
+      # Returns true if this paginator contains the page of index +number+.
+      def has_page_number?(number)
+        return false unless number.is_a? Fixnum
+        number >= 1 and number <= page_count
+      end
+
+      # Returns a new Page representing the page with the given index
+      # +number+.
+      def [](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 Page.new(@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 Page.new(@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.map {|n| @paginator[n]}
+        end
+        alias to_a :pages
+      end
+    end
+
+  end
+end