import json

from image.docker.interfaces import ContentRetriever

class ContentRetrieverForTesting(ContentRetriever):
  def __init__(self, digests=None):
    self.digests = digests or {}

  def add_digest(self, digest, content):
    self.digests[digest] = content

  def get_manifest_bytes_with_digest(self, digest):
    return self.digests.get(digest)

  def get_blob_bytes_with_digest(self, digest):
    return self.digests.get(digest)

  @classmethod
  def for_config(cls, config_obj, digest, size, ensure_ascii=True):
    config_str = json.dumps(config_obj, ensure_ascii=ensure_ascii)
    padded_string = config_str + ' ' * (size - len(config_str))
    digests = {}
    digests[digest] = padded_string
    return ContentRetrieverForTesting(digests)


class _CustomEncoder(json.JSONEncoder):
  def encode(self, o):
    encoded = super(_CustomEncoder, self).encode(o)
    if isinstance(o, basestring):
      encoded = encoded.replace('<', '\\u003c')
      encoded = encoded.replace('>', '\\u003e')
      encoded = encoded.replace('&', '\\u0026')
    return encoded


def to_canonical_json(value, ensure_ascii=True, indent=None):
  """ Returns the canonical JSON string form of the given value,
      as per the guidelines in https://github.com/docker/distribution/blob/master/docs/spec/json.md.

      `indent` is allowed only for the purposes of indenting for debugging.
  """
  return json.dumps(value, ensure_ascii=ensure_ascii, sort_keys=True, separators=(',', ':'),
                    cls=_CustomEncoder, indent=indent)