WillPaginate adapter for paginating CouchPotato views

couch_potato_pagination.rb

# = WillPaginate adapter for CouchPotato views
#
# Pagination for CouchPotato[http://github.com/langalex/couch_potato] views
# compatible with the will_paginate[http://github.com/mislav/will_paginate] gem.
#
# See http://github.com/mislav/will_paginate/blob/rails3/lib/will_paginate/finders/data_mapper.rb
# for example adapter.
#
# Just `require` this file in your code and you'll have the `paginate` method available.
#
# TODO: Research if pagination can be done via "fast pagination" as described in
#       http://books.couchdb.org/relax/reference/recipes#Pagination.
#       We need the "Jump to Page" functionality for WillPaginate.
#
# TODO: Make ordering work (descending=true, have to flip startkey/endkey etc)
# 

require 'rubygems'
require 'will_paginate/finders/base'
require 'couch_potato'

module CouchPotato
  module View
    class BaseViewSpec
      # Allow manipulation of view_parameters
      attr_writer :view_parameters
    end
  end
end

module WillPaginate::Finders
  module CouchPotato
    include WillPaginate::Finders::Base

    # Return WillPaginate collection for the passed CouchPotato view, so you can use the
    # fine-tuned view helper with automatic CSS classes, pagination links, etc.
    #
    # Example:
    # --------
    #
    #   In the controller:
    #
    #   @articles = CouchPotato.database.paginate Article.all, :page => params[:page], :per_page => 50
    #
    #   In the view:
    #
    #   <%= will_paginate @articles %>
    #
    def paginate(spec, options={}, &block)
      options[:page]         ||= 1

      page, per_page, total_entries = wp_parse_options(options)
      
      WillPaginate::Collection.create(page, per_page, total_entries) do |pager|
        query_options = options.except :page, :per_page, :total_entries, :page_params
        wp_query(spec, query_options, pager, &block)
      end
    end

    # Return count of all documents for the passed view.
    #
    # Example:
    # --------
    #
    #   @CouchPotato.database.count Article.all
    #
    def count(spec)
      # FIXME: Why `view_parameters.update ...` does not work?
      spec.view_parameters = spec.view_parameters.merge({ :reduce => true, :include_docs => false })
      view(spec) || 0
    end

  protected
    
    def wp_query(spec, options, pager, &block) #:nodoc

      query_options = { :limit       => pager.per_page,
                        :skip        => pager.offset }

      paginated_spec = spec.dup
      paginated_spec.view_parameters = paginated_spec.view_parameters.merge(query_options)

      collection = view(paginated_spec)

      pager.replace collection

      pager.total_entries = collection.total_rows
    end

  end
end

CouchPotato::Database.send(:include, WillPaginate::Finders::CouchPotato)


if $0 == __FILE__ # Launch `ruby couch_potato_pagination.rb` to run test suite
  require 'test/unit'
  require 'shoulda'

  class CouchPotato::PaginationWithWillPaginate < Test::Unit::TestCase

    class ::Article
      include CouchPotato::Persistence

      property :title
      property :author

      view :all, :key => :title
    end

    def setup
      CouchPotato::Config.database_name = 'couchpotato-pagination-test'
      CouchPotato.couchrest_database.recreate!

      50.times do |i|
        CouchPotato.database.save_document Article.new(:title => "Article #{ '%.3d' % (i+1) }", :author => 'John Smith')
      end
    end

    def teardown
      CouchPotato.couchrest_database.delete!
    end

    context "CouchPotato database" do

      should "have the paginate method" do
        assert_respond_to CouchPotato.database, :paginate
      end

      should "return the count of documents" do
        assert_respond_to CouchPotato.database, :count
        assert_equal 50, CouchPotato.database.count(Article.all)
      end

      should "return zero count when there are no documents" do
        CouchPotato.couchrest_database.recreate!
        assert_equal 0, CouchPotato.database.count(Article.all)
      end

      should "return paginated collection of records" do
        collection = CouchPotato.database.paginate Article.all, :per_page => 20
        assert_respond_to collection, :each
        assert_equal 20, collection.size
      end

      should "raise NoMethodError when paginate method is called with non-existing view" do
        assert_raise(NoMethodError) { CouchPotato.database.paginate Article.krupitzowka }
      end

      should "return default WillPaginate::Collection from paginate method" do
        collection = CouchPotato.database.paginate Article.all
        assert_instance_of WillPaginate::Collection, collection
        assert_equal 30, collection.size
        assert_equal 50, collection.total_entries
      end

      should "allow to set options for paginate method" do
        collection = CouchPotato.database.paginate Article.all, :per_page => 5
        assert_equal 5, collection.size
        assert_equal 50, collection.total_entries
      end
      
    end

    context "When paginating articles, it" do

      should "allow to move in paginated collection" do
        collection = CouchPotato.database.paginate Article.all, :per_page => 5
        assert_equal 'Article 001', collection.first.title

        collection = CouchPotato.database.paginate Article.all, :page => collection.next_page,     :per_page => 5
        assert_equal 'Article 006', collection.first.title

        collection = CouchPotato.database.paginate Article.all, :page => collection.next_page,     :per_page => 5
        assert_equal 'Article 011', collection.first.title

        collection = CouchPotato.database.paginate Article.all, :page => collection.previous_page, :per_page => 5
        assert_equal 'Article 006', collection.first.title

        collection = CouchPotato.database.paginate Article.all, :page => 5, :per_page => 5
        assert_equal 'Article 021', collection.first.title

        collection = CouchPotato.database.paginate Article.all, :page => 11, :per_page => 5
        assert collection.empty?, "#{collection.inspect} should be empty"
        assert collection.out_of_bounds?, "Should be out of bounds"
      end

      should "give total entries" do
        collection = CouchPotato.database.paginate Article.all, :page => 2, :per_page => 5
        assert_equal 50, collection.total_entries
      end

    end

  end
end