csv parser. takes 2 csv files and combines them together to make one without duplicates

csv_parser.rb

require 'csv'

# Handles csv's with varrying total columns
# Does not handle headers yet

# This method serves as initialize method; calls all other methods
# Takes 2 csv files as arguments
# First csv should be original file
# Second should be the updated file
def update_csv(orig_file, new_file)
  orig_file_mapped = parse_orig(orig_file)
  orig_num_columns = orig_file_mapped.first.first.length
  new_file_mapped = parse_new(new_file, orig_num_columns)
  joined_map = join_maps(orig_file_mapped, new_file_mapped)
  csv_formatted = convert_map(joined_map)
  output_file_name = create_output_file_name(new_file)
  write_to_file(csv_formatted, output_file_name)
end

# Takes csv file and maps each row to a key; value is same as key
def parse_orig(file)
  rows_hash = {}
  # Tells Ruby the file is in ISO-8859-1 encoding
  csv_file = File.open(file, "r:ISO-8859-1")
  CSV.parse(csv_file).each { |row| rows_hash[row] = row }
  rows_hash
end

# Takes csv file and sets key to row of length equal to original number of columns
# Value is set to full row
def parse_new(file, columns)
  key_length = columns - 1
  rows_hash = {}
  csv_file = File.open(file, "r:ISO-8859-1")
  CSV.parse(csv_file).each { |row| rows_hash[row[0..key_length]] = row }
  rows_hash
end

# adds row (key) to new_map unless it already exists
def join_maps(orig_map, new_map)
  orig_map.each do |key, value|
    new_map[key] = value unless new_map.has_key?(key)
  end
  new_map
end

def convert_map(mapping)
  csv_format = []
  mapping.each { |key, value| csv_format << value }
  csv_format
end

def create_output_file_name(file_name)
  file_name.gsub!('.csv', '_updated6.csv')
end

def write_to_file(data=[], file_name)
  CSV.open(file_name, "w:UTF-8") do |csv|
    data.each do |row|
      csv << row
    end
  end
end