require 'yaml'

def get_head(informations)
  informations[0].keys.join("\t")
end

def get_content(informations)
  info = ''
  informations.each do |information|
    info << information.values.join("\t") << "\n"
  end
  info
end

def read_yaml(file)
  YAML.load(File.read(file))
end

fail ArgumentError, "Usage: YAML_to_TSV input_file (output_file)\n" if \
                                              ARGV.count == 0 || ARGV.count > 2
fail ArgumentError, "The file is not exist\n" unless File.exist? ARGV[0].to_s

input = read_yaml ARGV[0]
result = get_head(input) << "\n" << get_content(input)
if ARGV.count != 1
  File.open(ARGV[1], 'w') do |file|
    file.puts result
  end
else
  puts result
end