CSV Duplication Remover

#!/usr/bin/ruby -w

require 'csv'
require 'active_support/core_ext'

class Parser

  attr_accessor :input_folder
  attr_accessor :output_folder
  attr_accessor :filename
  attr_accessor :seperator
  attr_accessor :column_names
  attr_accessor :entries
  attr_accessor :output
  attr_accessor :identifier
  attr_accessor :criteria
  attr_accessor :output_columns

  def initialize(filename, identifier, criteria, options = {})
    options.reverse_merge!({
      :input_folder => "../csv/",
      :output_folder => "../output/",
      :output_columns => :all,
    })

    @filename = filename

    @input_folder = options[:input_folder]
    @output_folder = options[:output_folder]

    @identifier = identifier
    @criteria = criteria

    @seperator = ";"

    @output_columns = options[:output_columns]
  end

  def input_path
    input_folder + filename
  end

  def output_path
    output_folder + filename
  end

  def read_csv
    @entries = []
    @output = []

    CSV.open(input_path, 'r', @seperator) do |row|
      @entries << row
    end

    @column_names = entries.delete_at(0)
  end

  def remove_duplicates
    identifier_index = column_names.index(identifier)
    criteria_index = column_names.index(criteria)

    grouped = entries.group_by { |entry| entry[identifier_index] }

    grouped.each do |key, rows|
      values = rows.map { |row| row[criteria_index] }.uniq

      rows.each do |row|
        criteria = row[criteria_index]

        if values.include?(criteria)
          output << filter_row(row)

          values.delete(criteria)
        end
      end
    end
  end

  def filter_row(row)
    return row if output_columns == :all

    output_columns.inject([]) do |filtered_row, column|
      index = column_names.index(column)
      filtered_row << row[index]
    end
  end

  def write_csv
    CSV.open(output_path, "w", seperator) do |csv|
      csv << filter_row(column_names)
      output.each { |row| csv << row }
    end
  end

  def statistic
    size = output.size
    total = entries.size

    criteria_index = column_names.index(criteria)
    criteria_values = entries.map { |row| row[criteria_index] }.uniq

    empty = 0
    empty += output.select { |row| row[criteria_index].blank? }.size

    identifier_per_criteria = criteria_values.inject("") do |string, field|
      hits = output.select { |row| row[criteria_index] == field }.size
      string += "#{field} (#{hits}); "
    end

    puts
    puts "  #total: #{total}"
    puts "  #rows: #{size}"
    puts "  empty: #{empty}"
    puts "  #{column_names[criteria_index]}: #{identifier_per_criteria}\n\n\n"
  end

  def run
    puts "=> #{filename}"
    read_csv

    remove_duplicates

    write_csv

    statistic
  end

end

filenames = ["file1.csv", "file2.csv", "file3.csv"]

identifier = "ID"
criteria = "City"

options = {
  :output_columns => :all,
}

filenames.each do |filename|
  Parser.new(filename, identifier, criteria, options).run
end