class NIO::ByteBuffer

def [](index)
  raise ArgumentError, "negative index given" if index < 0
  raise ArgumentError, "specified index exceeds limit" if index >= @limit
  @buffer.bytes[index]
end

def clear
  @buffer   = ("\0" * @capacity).force_encoding(Encoding::BINARY)
  @position = 0
  @limit    = @capacity
  @mark     = nil
  self
end

def compact
  @buffer[0...(@limit - @position)] = @buffer[@position...@limit]
  @position = @limit - @position
  @limit = capacity
  self
end

def each(&block)
  @buffer[0...@limit].each_byte(&block)
end

def flip
  @limit = @position
  @position = 0
  @mark = nil
  self
end

def full?
  remaining.zero?
end

def get(length = remaining)
  raise ArgumentError, "negative length given" if length < 0
  raise UnderflowError, "not enough data in buffer" if length > @limit - @position
  result = @buffer[@position...length]
  @position += length
  result
end

def initialize(capacity)
  raise TypeError, "no implicit conversion of #{capacity.class} to Integer" unless capacity.is_a?(Integer)
  @capacity = capacity
  clear
end

def inspect
  format(
    "#<%s:0x%x @position=%d @limit=%d @capacity=%d>",
    self.class,
    object_id << 1,
    @position,
    @limit,
    @capacity
  )
end

def limit=(new_limit)
  raise ArgumentError, "negative limit given" if new_limit < 0
  raise ArgumentError, "specified limit exceeds capacity" if new_limit > @capacity
  @position = new_limit if @position > new_limit
  @mark = nil if @mark && @mark > new_limit
  @limit = new_limit
end

def mark
  @mark = @position
  self
end

def position=(new_position)
  raise ArgumentError, "negative position given" if new_position < 0
  raise ArgumentError, "specified position exceeds capacity" if new_position > @capacity
  @mark = nil if @mark && @mark > new_position
  @position = new_position
end

def put(str)
  raise TypeError, "expected String, got #{str.class}" unless str.respond_to?(:to_str)
  str = str.to_str
  raise OverflowError, "buffer is full" if str.length > @limit - @position
  @buffer[@position...str.length] = str
  @position += str.length
  self
end

def read_from(io)
  nbytes = @limit - @position
  raise OverflowError, "buffer is full" if nbytes.zero?
  bytes_read = IO.try_convert(io).read_nonblock(nbytes, exception: false)
  return 0 if bytes_read == :wait_readable
  self << bytes_read
  bytes_read.length
end

def remaining
  @limit - @position
end

def reset
  raise MarkUnsetError, "mark has not been set" unless @mark
  @position = @mark
  self
end

def rewind
  @position = 0
  @mark = nil
  self
end

def write_to(io)
  nbytes = @limit - @position
  raise UnderflowError, "no data remaining in buffer" if nbytes.zero?
  bytes_written = IO.try_convert(io).write_nonblock(@buffer[@position...@limit], exception: false)
  return 0 if bytes_written == :wait_writable
  @position += bytes_written
  bytes_written
end