rails_reporter.rb

class Reporter

  class << self

    def run_example_report(person,start_date,end_date)
      sd_string = start_date.strftime("%Y%m%d")
      ed_string = end_date.strftime("%Y%m%d")
      filename = "#{person.name}_report_for_#{sd_string}_#{ed_string}"
      self.run_report(filename,"EXAMPLE") do |sheet|
        sheet.add_row [person.name]
        sheet.add_row ["Make","Model","Year","VIN"]
        self.process_by_page(Car,"person_id = #{person.id}") do |cars|
          cars.each do |car|
            sheet.add_row [car.make,car.model,car.year,car.vin]
          end
        end
      end
    end

  end

protected
  class << self
    def run_report(file_name,title,header_row = nil)
      name = "#{file_name}_#{DateTime.now.hour}#{DateTime.now.min}.csv"
      path = File.join(OUTPUT_DIRECTORY,name)
      file = File.new(path,"w+");
      writer = CSV::Writer.create(file)
      sheet = CsvSheetWrapper.new(writer)
      sheet.add_row [title]
      sheet.index = 2
      sheet.add_row header_row if header_row
      yield(sheet)
      return name
    end
    
    def process_by_page(model,sql_conditions)
      set = model.find(:all,:conditions=>sql_conditions,:page => {:size => 50})
      keep_going = true
      while keep_going
        yield(set)
        GC.start
        keep_going = set.next_page!
      end
    end
  end

end

class CsvSheetWrapper
  attr_accessor :index
  
  def initialize(csv_writer)
    @sheet = csv_writer
    @index = 0
  end

  def add_row(array)
    @sheet << array
    @index += 1
  end 
  
  def add_lines(count)
    count.times do 
      @sheet << []
    end
    @index += count
  end
end