gzigzigzeo/google_translate_diff

class GoogleTranslateDiff::Request
  extend Dry::Initializer
  extend Forwardable

  param :values
  param :options

  def_delegators :GoogleTranslateDiff, :api, :cache_store, :rate_limiter
  def_delegators :"GoogleTranslateDiff::Linearizer", :linearize, :restore

  def call
    validate_globals

    return values if from == to || values.empty?

    translation
  end

  private

  def from
    @from ||= options.fetch(:from)
  end

  def to
    @to ||= options.fetch(:to)
  end

  def validate_globals
    raise "Set GoogleTranslateDiff.api before calling ::translate" unless api
    return if cache_store
    raise "Set GoogleTranslateDiff.cache_store before calling ::translate"
  end

  # Extracts flat text array
  # => "Name", "<b>Good</b> boy"
  #
  # #values might be something like { name: "Name", bio: "<b>Good</b> boy" }
  def texts
    @texts ||= linearize(values)
  end

  # Converts each array item to token list
  # => [..., [["<b>", :markup], ["Good", :text], ...]]
  def tokens
    @tokens ||= texts.map do |value|
      GoogleTranslateDiff::Tokenizer.tokenize(value)
    end
  end

  # Extracts text tokens from token list
  # => { ..., "1_1" => "Good", 1_3 => "Boy", ... }
  def text_tokens
    @text_tokens ||= extract_text_tokens.to_h
  end

  def extract_text_tokens
    tokens.each_with_object([]).with_index do |(group, result), group_index|
      group.each_with_index do |(value, type), index|
        result << ["#{group_index}_#{index}", value] if type == :text
      end
    end
  end

  # Extracts values from text tokens
  # => [ ..., "Good", "Boy", ... ]
  def text_tokens_texts
    @text_tokens_texts ||= linearize(text_tokens).map(&:to_s).map(&:strip)
  end

  # Splits things requires translations to per-request chunks
  # (groups less 2k sym)
  # => [[ ..., "Good", "Boy", ... ]]
  def chunks
    @chunks ||= GoogleTranslateDiff::Chunker.new(text_tokens_texts).call
  end

  # Translates/loads from cache values from each chunk
  # => [[ ..., "Horoshiy", "Malchik", ... ]]
  def chunks_translated
    @chunks_translated ||= chunks.map do |chunk|
      cached, missing = cache.cached_and_missing(chunk)
      if missing.empty?
        cached
      else
        cache.store(chunk, cached, call_api(missing))
      end
    end
  end

  # Restores indexes for translated tokens
  # => { ..., "1_1" => "Horoshiy", 1_3 => "Malchik", ... }
  def text_tokens_translated
    @text_tokens_texts_translated ||=
      restore(text_tokens, chunks_translated.flatten)
  end

  # Restores tokens translated + adds same spacing as in source token
  # => [[..., [ "Horoshiy", :text ], ...]]
  # rubocop:disable Metrics/AbcSize
  def tokens_translated
    @tokens_translated ||= tokens.dup.tap do |tokens|
      text_tokens_translated.each do |index, value|
        group_index, index = index.split("_")
        tokens[group_index.to_i][index.to_i][0] =
          restore_spacing(tokens[group_index.to_i][index.to_i][0], value)
      end
    end
  end
  # rubocop:enable Metrics/AbcSize

  def restore_spacing(source_value, value)
    GoogleTranslateDiff::Spacing.restore(source_value, value)
  end

  # Restores texts from tokens
  # [..., "<b>Horoshiy</b> Malchik", ...]
  def texts_translated
    @texts_translated ||= tokens_translated.map do |group|
      group.map { |value, type| type == :text ? value : fix_ascii(value) }.join
    end
  end

  # Final result
  def translation
    @translation ||= restore(values, texts_translated)
  end

  def call_api(values)
    check_rate_limit(values)
    [api.translate(*values, **options)].flatten.map(&:text)
  end

  def cache
    @cache ||= GoogleTranslateDiff::Cache.new(from, to)
  end

  def check_rate_limit(values)
    return if rate_limiter.nil?
    size = values.map(&:size).inject(0) { |sum, x| sum + x }
    rate_limiter.check(size)
  end

  # Markup should not contain control characters
  def fix_ascii(value)
    value.gsub(/[\u0000-\u001F]/, " ")
  end
end