class Reline::LineEditor

def retrieve_completion_block(set_completion_quote_character = false)
  if Reline.completer_word_break_characters.empty?
    word_break_regexp = nil
  else
    word_break_regexp = /\A[#{Regexp.escape(Reline.completer_word_break_characters)}]/
  end
  if Reline.completer_quote_characters.empty?
    quote_characters_regexp = nil
  else
    quote_characters_regexp = /\A[#{Regexp.escape(Reline.completer_quote_characters)}]/
  end
  before = @line.byteslice(0, @byte_pointer)
  rest = nil
  break_pointer = nil
  quote = nil
  closing_quote = nil
  escaped_quote = nil
  i = 0
  while i < @byte_pointer do
    slice = @line.byteslice(i, @byte_pointer - i)
    unless slice.valid_encoding?
      i += 1
      next
    end
    if quote and slice.start_with?(closing_quote)
      quote = nil
      i += 1
      rest = nil
    elsif quote and slice.start_with?(escaped_quote)
      # skip
      i += 2
    elsif quote_characters_regexp and slice =~ quote_characters_regexp # find new "
      rest = $'
      quote = $&
      closing_quote = /(?!\\)#{Regexp.escape(quote)}/
      escaped_quote = /\\#{Regexp.escape(quote)}/
      i += 1
      break_pointer = i - 1
    elsif word_break_regexp and not quote and slice =~ word_break_regexp
      rest = $'
      i += 1
      before = @line.byteslice(i, @byte_pointer - i)
      break_pointer = i
    else
      i += 1
    end
  end
  postposing = @line.byteslice(@byte_pointer, @line.bytesize - @byte_pointer)
  if rest
    preposing = @line.byteslice(0, break_pointer)
    target = rest
    if set_completion_quote_character and quote
      Reline.core.instance_variable_set(:@completion_quote_character, quote)
      if postposing !~ /(?!\\)#{Regexp.escape(quote)}/ # closing quote
        insert_text(quote)
      end
    end
  else
    preposing = ''
    if break_pointer
      preposing = @line.byteslice(0, break_pointer)
    else
      preposing = ''
    end
    target = before
  end
  if @is_multiline
    lines = whole_lines
    if @line_index > 0
      preposing = lines[0..(@line_index - 1)].join("\n") + "\n" + preposing
    end
    if (lines.size - 1) > @line_index
      postposing = postposing + "\n" + lines[(@line_index + 1)..-1].join("\n")
    end
  end
  [preposing.encode(@encoding), target.encode(@encoding), postposing.encode(@encoding)]
end