Builds ExportedMetadata object for a given client id and ClientFullInfo.

def GetMetadata(client_id, client_full_info):
  """Builds ExportedMetadata object for a given client id and ClientFullInfo."""

  metadata = ExportedMetadata()

  last_snapshot = None
  if client_full_info.HasField("last_snapshot"):
    last_snapshot = client_full_info.last_snapshot

  metadata.client_urn = client_id
  metadata.client_age = client_full_info.metadata.first_seen

  if last_snapshot is not None:
    kb = client_full_info.last_snapshot.knowledge_base

    metadata.hostname = kb.fqdn
    metadata.os = kb.os
    metadata.uname = last_snapshot.Uname()
    metadata.os_release = last_snapshot.os_release
    metadata.os_version = last_snapshot.os_version
    metadata.usernames = ",".join(user.username for user in kb.users)

    addresses = last_snapshot.GetMacAddresses()
    if addresses:
      metadata.mac_address = last_snapshot.GetMacAddresses().pop()
    metadata.hardware_info = last_snapshot.hardware_info
    metadata.kernel_version = last_snapshot.kernel

    ci = last_snapshot.cloud_instance
    if ci is not None:
      if ci.cloud_type == ci.InstanceType.AMAZON:
        metadata.cloud_instance_type = metadata.CloudInstanceType.AMAZON
        metadata.cloud_instance_id = ci.amazon.instance_id
      elif ci.cloud_type == ci.InstanceType.GOOGLE:
        metadata.cloud_instance_type = metadata.CloudInstanceType.GOOGLE
        metadata.cloud_instance_id = ci.google.unique_id

  system_labels = set()
  user_labels = set()
  for l in client_full_info.labels:
    if l.owner == "GRR":
      system_labels.add(l.name)
    else:
      user_labels.add(l.name)

  metadata.labels = ",".join(sorted(system_labels | user_labels))
  metadata.system_labels = ",".join(sorted(system_labels))
  metadata.user_labels = ",".join(sorted(user_labels))

  return metadata