daily_planet_export.txt

Merchant  Date  Ends  Deal  Price Value 
Burger King 10/2/2011 10/4/2011 Your way  25  50
McDonalds 10/5/2011   Not really food 22  44
Arbys 10/8/2011 10/10/2011  More burgers  7 14

import.rake

namespace :publisher do
  desc "Import a publisher's data"
  task :import, [:file_path, :publisher_name] => [:environment] do |t, args|
    args.with_defaults(
      file_path: Rails.root.join('script/data/daily_planet_export.txt'),
      publisher_name: 'The Daily Planet'
    )
    file = File.new(args[:file_path])
    publisher = Publisher.find_or_create_by_name(args[:publisher_name])
    PublisherImporter.new(publisher, file).import
  end
end

publisher_importer.rb

class PublisherImporter
  def initialize(publisher, file)
    @publisher = publisher
    @file = file
  end

  def import
    each_row do |row|
      RowScanner.new(row).create_deal(@publisher)
    end
  end

  private

  def each_row
    @file.drop(1).each {|line| yield line.chomp }
  end

  class RowScanner
    def initialize(str)
      @string_scanner = StringScanner.new(str)
    end
    
    def create_deal(publisher)
      advertiser = publisher.advertisers.find_or_create_by_name(scan_words)
      advertiser.deals.create to_hash
    end
    
    private

    def scan_words
      @string_scanner.scan(/\D+/)
    end

    def scan_date
      @string_scanner.scan(/\d{1,2}\/\d{1,2}\/\d{2,4}\s*/)
    end

    def scan_digits
      @string_scanner.scan(/\d+\s*/)
    end
    
    def to_hash
      {
        start_at: scan_date,
        end_at: scan_date,
        description: scan_words,
        price: scan_digits,
        value: scan_digits
      }
    end
  end
end