module FilenameCleaner
  DOT = "."
  class << self
    # Sanitize the any name with or without extension
    #
    # @param [String] name the input string
    # @param [String] sep_char the separator char to be used
    # @param [Boolean] have_extension indicate if the the input file should be
    #                  treated as having extension or not having one
    # @return [String] output string with special chars replaced withe specified string
    def sanitize(name, sep_char = ".", have_extension = false)
      if have_extension
        sanitize_name_with_extension(name, sep_char)
      else
        sanitize_name_without_extension(name, sep_char)
      end
    end

    # Get formatted name for existing file
    #
    # @param [String] filename the input filename
    # @param [Hash<Symbol, Object>] opts the hash value for options to be applied
    #
    # @option opts [String]  :sep_char The separator string
    # @option opts [Boolean] :downcase Convert each word to lower case
    # @option opts [Boolean] :capitalize: Capitalize each word in the name
    def formatted_name(filename, opts = {})
      sep_char = opts[:sep_char] || "."
      sanitized_name = FilenameCleaner.sanitize(filename, sep_char, true)

      # First split the two part so that only name is used!
      basename = File.basename(sanitized_name, ".*")
      extname  = File.extname(sanitized_name)
      if opts[:downcase]
        basename = basename.split(sep_char).map(&:downcase).join(sep_char)
      end
      if opts[:capitalize]
        basename = basename.split(sep_char).map(&:capitalize).join(sep_char)
      end
      "#{basename}#{extname}"
    end

  private

    # Sanitize the any name with or without any extension
    #
    # @param [String] name the input string
    # @param [String] sep_char the separator char to be used
    # @return [String] output string with special chars replaced withe specified string
    def sanitize_name_without_extension(name, sep_char = ".")
      replace_dot(sanitize_with_dot(name), sep_char)
    end

    # Sanitize filename that works with file with extension
    #
    # @param [String] name the input filename with extension
    # @return [String] the output file with special characters replaced
    def sanitize_name_with_extension(name, sep_char = ".")
      extension = File.extname(name)
      name_only = File.basename(name, ".*")
      name_only = replace_dot(sanitize_with_dot(name_only), sep_char)
      "#{name_only}#{extension}"
    end

    # Replace the multiple special characters with a dot string
    #
    # @param [String] input_name input file
    # @return [String] the new name with special characters replaced or removed.
    def sanitize_with_dot(input_name)
      # Don't mutate the input name
      name = input_name.clone

      # Replace any special characters with a dot
      name.gsub!(/[^0-9A-Za-z\-_ ]/, DOT)

      # Replace multiple occurrences of a given character with a dot
      ["-", "_", " "].each do |c|
        name.gsub!(/#{Regexp.quote(c)}+/, DOT)
      end

      # Replace multiple occurrence of dot with one dot
      name.gsub!(/#{Regexp.quote(DOT)}+/, DOT)

      # Remove the last char if it is a dot
      name.gsub!(/\.$/, "") if name[-1] == DOT

      # return the result
      name
    end

    # Replace 'dot' string with a given string if specified
    def replace_dot(string, replace = nil)
      result = string.clone
      result.gsub!(/#{Regexp.quote(DOT)}+/, replace) if replace
      result
    end
  end
end