module MetaTags::TextNormalizer

def calculate_limit_left(limit, length, result, separator)
  limit - length - (result.any? ? separator.length : 0)
end

def calculate_title_limits(site_title, title, separator, global_limit)
  # What should we truncate first: site title or page title?
  main_title = MetaTags.config.truncate_site_title_first ? title : [site_title]
  main_length = main_title.map(&:length).sum + ((main_title.size - 1) * separator.length)
  main_limited_length = global_limit
  secondary_limited_length = global_limit - ((main_length > 0) ? main_length + separator.length : 0)
  secondary_limited_length = [0, secondary_limited_length].max
  if MetaTags.config.truncate_site_title_first
    [secondary_limited_length, main_limited_length]
  else
    [main_limited_length, secondary_limited_length]
  end
end

def cleanup_string(string, strip: true)
  return "" if string.nil?
  raise ArgumentError, "Expected a string or an object that implements #to_str" unless string.respond_to?(:to_str)
  s = strip_tags(string.to_str)
  s = s.dup if s.frozen?
  s.gsub!(/\s+/, " ")
  s.strip! if strip
  s
end

def cleanup_strings(strings, strip: true)
  strings = Array(strings).flatten.map! { |s| cleanup_string(s, strip: strip) }
  strings.reject!(&:blank?)
  strings
end

def helpers
  ActionController::Base.helpers
end

def normalize_description(description)
  # description could be another object not a string, but since it probably
  # serves the same purpose we could just as it to convert itself to str
  # and continue from there
  description = cleanup_string(description)
  return "" if description.blank?
  truncate(description, MetaTags.config.description_limit)
end

def normalize_keywords(keywords)
  keywords = cleanup_strings(keywords)
  return "" if keywords.blank?
  keywords.each(&:downcase!) if MetaTags.config.keywords_lowercase
  separator = cleanup_string MetaTags.config.keywords_separator, strip: false
  keywords = truncate_array(keywords, MetaTags.config.keywords_limit, separator)
  safe_join(keywords, separator)
end

def normalize_title(site_title, title, separator, reverse = false)
  clean_title = cleanup_strings(title)
  clean_title.reverse! if reverse
  site_title = cleanup_string(site_title)
  separator = cleanup_string(separator, strip: false)
  # Truncate title and site title
  site_title, clean_title = truncate_title(site_title, clean_title, separator)
  if site_title.present?
    if reverse
      clean_title.push(site_title)
    else
      clean_title.unshift(site_title)
    end
  end
  safe_join(clean_title, separator)
end

def safe_join(array, sep = $OFS)
  helpers.safe_join(array, sep)
end

def strip_tags(string)
  if defined?(Loofah)
    # Instead of strip_tags we will use Loofah to strip tags from now on
    Loofah.fragment(string).text(encode_special_chars: false)
  else
    helpers.strip_tags(string)
  end
end

def truncate(string, limit = nil)
  return string if limit.to_i == 0
  helpers.truncate(
    string,
    length: limit,
    separator: MetaTags.config.truncate_on_natural_separator,
    omission: "",
    escape: true
  )
end

def truncate_array(string_array, limit = nil, separator = "")
  return string_array if limit.nil? || limit <= 0
  length = 0
  result = []
  string_array.each do |string|
    limit_left = calculate_limit_left(limit, length, result, separator)
    if string.length > limit_left
      result << truncate(string, limit_left)
      break string_array
    end
    length += (result.any? ? separator.length : 0) + string.length
    result << string
    # No more strings will fit
    break string_array if length + separator.length >= limit
  end
  result
end

def truncate_title(site_title, title, separator)
  global_limit = MetaTags.config.title_limit.to_i
  if global_limit > 0
    site_title_limited_length, title_limited_length = calculate_title_limits(
      site_title, title, separator, global_limit
    )
    title = (title_limited_length > 0) ? truncate_array(title, title_limited_length, separator) : []
    site_title = (site_title_limited_length > 0) ? truncate(site_title, site_title_limited_length) : nil
  end
  [site_title, title]
end