capsule/src/cgi-bin/translate

#!/usr/bin/ruby --disable-all

# A cgi-bin script that translates between languages. It relies on apertium
# being installed on the machine.
#
# CGI works with environment variables. Here are the ones that matter:
#
# PATH_INFO: /<from>/<to>
# QUERY_STRING: Some%20text%20to%20translate
#
# We expect to be called like: /cgi-bin/translate/eng/spa?Food
#
# If we don't have two languages, make it a Not Found error.
# If we don't have a query string to translate, ask for one.

require 'cgi'

LANGUAGE_PAIRS = %w[en-es es-en]

class Object
  def blank?
    nil? || self&.empty?
  end
end

def respond!(code, meta, body = nil)
  STDOUT.print("#{code} #{meta}\r\n")
  STDOUT.print(body) unless body.blank?
  exit 0
end

def ask!(prompt)
  respond!(10, prompt)
end

def ok!(meta, body = nil)
  respond!(20, meta, body)
end

def temp_fail!(meta = 'Temporary Failure')
  respond!(40, meta)
end

def not_found!(meta = 'Not Found')
  respond!(51, meta)
end

def extract_langpair(path)
  return if path.blank? || !path.start_with?('/')

  _, src, dst, *rest = path.split('/')

  return unless rest.empty?

  pair = [src, dst].join('-')
  return unless LANGUAGE_PAIRS.include?(pair)

  pair
end

def extract_text(query)
  return "" if query.blank?

  CGI.unescape(query)
end

LANG_PAIR = extract_langpair(ENV['PATH_INFO'])
not_found! if LANG_PAIR.blank?

TRANSLATE = extract_text(ENV['QUERY_STRING'])

# TODO: we could detect a URL and translate the whole page sometime, perhaps
ask!('Enter text to translate') if TRANSLATE.blank?

require 'open3'

translation, status = Open3.capture2("apertium", LANG_PAIR, stdin_data: TRANSLATE)

temp_fail!("Couldn't get translation") unless status.success?

ok!('text/plain; charset="utf-8"', translation)