Pivotal Tracker Importer for Redmine

pitoval_import.rake

begin
  require 'ruport'
rescue LoadError => err
  warn "Couldn't load ruport gem: #{err}"
end

# ugly Ruport monkey patching to avoid the call of FasterCSV

module Ruport::Data
  class Table
    module FromCSV
      def get_table_from_csv(msg,param,options={},&block) #:nodoc:
        options = {:has_names => true,
                   :csv_options => {} }.merge(options)
        adjust_options_for_fcsv_headers(options)
        table = self.new(options) do |feeder|
          first_line = true
          CSV.send(msg,param,options[:csv_options]) do |row|
            if first_line
              adjust_for_headers(feeder.data,row,options)
              first_line = false
              next if options[:has_names]
            end

            if block
              handle_csv_row_proc(feeder,row,options,block)
            else
              feeder << row
            end
          end
        end
        return table
      end
    end
  end
end




namespace :import do
  desc 'Import tickets from CSV File'
  task :csv => :environment do

    csv_file = Ruport::Data::Table.load(Rails.root.join('db', 'seeds', 'import.csv'), :records => true)

    csv_file.rename_columns({
      'Story'                 => 'subject',
#     'Story Type'            => 'story_type',   ##  Story type is not available without the Backlogs plugin
      'Current State'         => 'state',
      'Description'           => 'description',
      'Estimate'              => 'estimate'
    })
    csv_file.each do |row|
      issue = Issue.new
      story = row.to_hash

      issue.project_id = 1

      case story['story_type']
      when 'chore'
        issue.tracker_id = 4
      when 'bug'
        issue.tracker_id = 1
      when 'feature'
        issue.tracker_id = 2
      else
        issue.tracker_id = nil
      end

      issue.subject = story['subject']
      issue.description = story['description']
#     issue.story_points = story['estimate']
      issue.author = User.first


      case story['state']
      when 'unscheduled'
        issue.status_id = 7
      when 'unstarted'
        issue.status_id = 1
      when 'started'
        issue.status_id = 2
      when 'finished'
        issue.done_ratio = 100
        issue.status_id = 3
      when 'accepted'
        issue.status_id = 5
      else
        issue.status_id = 8
      end

      if issue.save
        print '.'
      else
        print "! #{story.id} - #{issue.errors.first} !"
      end
    end
  end
end

How does this work? I would like to use this, but am fairly new to ruby... Hence, I don't get the 'gist' of this.... :-D

Quick explanation please? Thanks.