module AllFather

While the logic of abstracting stuff to callers has it's benefits, sometimes it's required to identify which instance are we specifically operate on. This method returns the instance currently being operated on and returns one of the TYPE_ constants defined here Implement this unless and absolutely it's necessary and there is no other easy way to do things

Returns¶ ↑

• the call sign of the instance

# File lib/allfather.rb, line 171
def callsign
  raise "Not Implemented. Class #{self.class.name} doesn't implement callsign"
end

Method to infer the language(s) of the caption by inspecting the file depending on the type of the caption file

Returns¶ ↑

• The ISO 639-1 Letter Language codes

# File lib/allfather.rb, line 56
def infer_languages
  raise "Not Implemented. Class #{self.class.name} doesn't implement infer_languages"
end

Method to do basic validations like is this a valid file to even accept for any future transactions

Returns:¶ ↑

true if the file is valid and false otherwise

# File lib/allfather.rb, line 44
def is_valid?
  raise "Not Implemented. Class #{self.class.name} doesn't implement is_valid?"
end

Method to set a translation engine

• translator - Instance of translation engine. Refer to `engines/aws` for example

Raises¶ ↑

• `InvalidInputException` when the argument `translator` is not an instance of Translator class

# File lib/allfather.rb, line 69
def set_translator(translator)
  if translator && !(translator.is_a? Translator)
    raise InvalidInputException.new("Argument is not an instance of Translator")
  end
end

Method to report on the supported transformations. Each implementor is free to return the types to which it can convert itself to

Returns ¶ ↑

• An array of one or more types defined as TYPE_ constants here

# File lib/allfather.rb, line 157
def supported_transformations
  raise "Not Implemented. Class #{self.class.name} doesn't implement supported_transformations"
end

Method to convert from one caption type to other types. If the src_lang is not provided then all source languages will be converted to target types. For example, if a ttml file has “en” and “es” and target_type is vtt and no src_lang is provided 2 vtt files would be created one per language in the source. if a target_lang is provided then one of the lang from source would be picked for creating the output file with target_lang

If no target_lang is provided, no translations are applied. output_file is created using without any need for any language translation services. Hence doesn't incur any cost !!

Note: src_lang makes sense only for caption types that can hold multi lingual captions like dfxp and ttml. For other caption sources this field is ignored

• types - An array of Valid input caption type(s). Refer to `#CaptionType`

• src_lang - can be inferred using infer_language method

• target_lang - Target 2 letter ISO language code to which the source needs to be translated in to.

• output_dir - Output Directory. Generated files would be dumped here

Raises¶ ↑

InvalidInputException shall be raised if

1. The input file doesn't exist or is unreadable or is invalid caption

2. The output dir doesn't exist

3. Invalid lang codes for a given caption type

4. Unsupported type to which conversion is requested for

# File lib/allfather.rb, line 134
def transform_to(types, src_lang, target_lang, output_dir)
  if (types - supported_transformations).size != 0
    raise InvalidInputException.new("Unknown types provided for conversion in input #{types}")
  end
  unless File.directory?(output_dir)
    FileUtils.mkdir_p(output_dir)
  end
  # Basic validations
  if types.include?(TYPE_SCC)
    if target_lang && !target_lang.eql?("en")
      raise InvalidInputException.new("SCC can be generated only in en. #{target_lang} is unsupported")
    end
  end
end

Method to translate the caption from one language to another

• src_lang - can be inferred using infer_language method

• target_lang - Target 2 letter ISO language code to which the source needs to be translated in to.

• output_file - Output file. Can be a fully qualified path or just file name

Raises¶ ↑

InvalidInputException shall be raised if

1. The input file doesn't exist or is unreadable or is invalid caption

2. The output file can't be written

3. The target_lang is not a valid ISO 639-1 Letter Language code

# File lib/allfather.rb, line 89
def translate(src_lang, target_lang, output_file)
  # Check if a non empty output file is present and error out to avoid
  # the danger or overwriting some important file !!
  if File.exists?(output_file) && File.size(output_file) > 0
    raise InvalidInputException.new("Output file #{output_file} is not empty.")
  else
    # Just open the file in writable mode and close it just to ensure that
    # we can write the output file
    File.open(output_file, "w") {|f|
    }
  end
  # Check if the file is writable ?
  unless File.writable?(output_file)
    raise InvalidInputException.new("Output file #{output_file} not writable.")
  end
  # Further checks can be done only in caption specific implementations
  # or translation engine specific implementation
end