import tempfile

from digest.digest_tools import content_path


class StoragePaths(object):
  shared_images = 'sharedimages'

  @staticmethod
  def temp_store_handler():
    tmpf = tempfile.TemporaryFile()

    def fn(buf):
      try:
        tmpf.write(buf)
      except IOError:
        pass

    return tmpf, fn

  def image_path(self, storage_uuid):
    return '{0}/{1}/'.format(self.shared_images, storage_uuid)

  def image_json_path(self, storage_uuid):
    base_path = self.image_path(storage_uuid)
    return '{0}json'.format(base_path)

  def v1_image_layer_path(self, storage_uuid):
    base_path = self.image_path(storage_uuid)
    return '{0}layer'.format(base_path)

  def blob_path(self, digest_str):
    return content_path(digest_str)

  def image_file_trie_path(self, storage_uuid):
    base_path = self.image_path(storage_uuid)
    return '{0}files.trie'.format(base_path)

  def image_file_diffs_path(self, storage_uuid):
    base_path = self.image_path(storage_uuid)
    return '{0}diffs.json'.format(base_path)


class BaseStorage(StoragePaths):
  def __init__(self):
    # Set the IO buffer to 64kB
    self.buffer_size = 64 * 1024

  def setup(self):
    """ Called to perform any storage system setup. """
    pass

  def validate(self):
    """ Called to perform any custom storage system validation. """
    pass

  def get_direct_download_url(self, path, expires_in=60, requires_cors=False):
    return None

  def get_direct_upload_url(self, path, mime_type, requires_cors=True):
    return None

  def get_supports_resumable_downloads(self):
    return False

  def get_content(self, path):
    raise NotImplementedError

  def put_content(self, path, content):
    raise NotImplementedError

  def stream_read(self, path):
    raise NotImplementedError

  def stream_read_file(self, path):
    raise NotImplementedError

  def stream_write(self, path, fp, content_type=None, content_encoding=None):
    raise NotImplementedError

  def list_directory(self, path=None):
    raise NotImplementedError

  def exists(self, path):
    raise NotImplementedError

  def remove(self, path):
    raise NotImplementedError

  def get_checksum(self, path):
    raise NotImplementedError

  def stream_write_to_fp(self, in_fp, out_fp, num_bytes=-1):
    """ Copy the specified number of bytes from the input file stream to the output stream. If
        num_bytes < 0 copy until the stream ends.
    """
    bytes_copied = 0
    while bytes_copied < num_bytes or num_bytes == -1:
      size_to_read = min(num_bytes - bytes_copied, self.buffer_size)
      if size_to_read < 0:
        size_to_read = self.buffer_size

      try:
        buf = in_fp.read(size_to_read)
        if not buf:
          break
        out_fp.write(buf)
        bytes_copied += len(buf)
      except IOError:
        break

    return bytes_copied


class InvalidChunkException(RuntimeError):
  pass


class BaseStorageV2(BaseStorage):
  def initiate_chunked_upload(self):
    """ Start a new chunked upload, returning the uuid and any associated storage metadata
    """
    raise NotImplementedError

  def stream_upload_chunk(self, uuid, offset, length, in_fp, storage_metadata):
    """ Upload the specified amount of data from the given file pointer to the chunked destination
        specified, starting at the given offset. Returns the number of bytes uploaded, and a new
        version of the storage_metadata. Raises InvalidChunkException if the offset or length can
        not be accepted.
    """
    raise NotImplementedError

  def complete_chunked_upload(self, uuid, final_path, storage_metadata):
    """ Complete the chunked upload and store the final results in the path indicated.
        Returns nothing.
    """
    raise NotImplementedError

  def cancel_chunked_upload(self, uuid, storage_metadata):
    """ Cancel the chunked upload and clean up any outstanding partially uploaded data.
        Returns nothing.
    """
    raise NotImplementedError