CSV Summation

#!/usr/bin/ruby
require 'csv'
require 'date'
require 'pathname'

CSV::Converters.update({ force_date: lambda {|f| Date.strptime(f, '%Y/%m/%d') rescue f } })

in_dir = '/home/data'
out_dir = '/home/ranking'
today = Date.today

CSV.open(
  Pathname(out_dir).join((today - 1).strftime('%Y%m%d') + '.csv'), 'w',
  :headers => %w(RANKING USER TOTAL), :write_headers => true
) {|csv|
  Pathname(in_dir).children.select {|e| e.fnmatch('*.csv', File::FNM_CASEFOLD) }
  .map {|e|
    {
      user: e.basename(e.extname).to_s,
      total: CSV.read(
               e,
               :converters => [:force_date, :integer],
               :headers => :first_row,
               :return_headers => false
             ).select {|a| today - a['DATE'] == 1 }
             .inject(0) {|s, a| s += a['DATA1'] + a['DATA2'] }
    }
  }.sort_by {|e| -e[:total] }
  .each_with_index {|e, i| csv << [i + 1, e[:user], e[:total]] }
}