class RubyLsp::Document::Scanner

def find_char_position(position)
  # Find the character index for the beginning of the requested line
  until @current_line == position[:line]
    @pos += 1 until LINE_BREAK == @source[@pos]
    @pos += 1
    @current_line += 1
  end
  # The final position is the beginning of the line plus the requested column. If the encoding is UTF-16, we also
  # need to adjust for surrogate pairs
  requested_position = @pos + position[:character]
  if @encoding == Constant::PositionEncodingKind::UTF16
    requested_position -= utf_16_character_position_correction(@pos, requested_position)
  end
  requested_position
end

def initialize(source, encoding)
  @current_line = T.let(0, Integer)
  @pos = T.let(0, Integer)
  @source = T.let(source.codepoints, T::Array[Integer])
  @encoding = encoding
end

def utf_16_character_position_correction(current_position, requested_position)
  utf16_unicode_correction = 0
  until current_position == requested_position
    codepoint = @source[current_position]
    utf16_unicode_correction += 1 if codepoint && codepoint > SURROGATE_PAIR_START
    current_position += 1
  end
  utf16_unicode_correction
end