class ZipTricks::FileReader::InflatingReader
  def initialize(from_io, compressed_data_size)
    @io = from_io
    @compressed_data_size = compressed_data_size
    @already_read = 0
    @zlib_inflater = ::Zlib::Inflate.new(-Zlib::MAX_WBITS)
  end

  def extract(n_bytes=nil)
    n_bytes ||= (@compressed_data_size - @already_read)

    return if eof?

    available = @compressed_data_size - @already_read

    return if available.zero?

    n_bytes = available if n_bytes > available

    return '' if n_bytes.zero?

    compressed_chunk = @io.read(n_bytes)
    @already_read += compressed_chunk.bytesize
    @zlib_inflater.inflate(compressed_chunk)
  end

  def eof?
    @zlib_inflater.finished?
  end
end