import logging
import logging.config

from peewee import JOIN, fn, IntegrityError

from app import app
from data.database import (UseThenDisconnect, TagManifest, TagManifestToManifest, Image,
                           db_transaction)
from data.model.tag import populate_manifest
from image.docker.schema1 import (DockerSchema1Manifest, ManifestException, ManifestInterface,
                                  DOCKER_SCHEMA1_SIGNED_MANIFEST_CONTENT_TYPE)
from workers.worker import Worker
from util.log import logfile_path
from util.migrate.allocator import yield_random_entries

logger = logging.getLogger(__name__)

class BrokenManifest(ManifestInterface):
  """ Implementation of the ManifestInterface for "broken" manifests. This allows us to add the
      new manifest row while not adding any additional rows for it.
  """
  def __init__(self, digest, payload):
    self._digest = digest
    self._payload = payload

  @property
  def digest(self):
    return self._digest

  @property
  def media_type(self):
    return DOCKER_SCHEMA1_SIGNED_MANIFEST_CONTENT_TYPE

  @property
  def manifest_dict(self):
    return {}

  @property
  def bytes(self):
    return self._payload

  @property
  def layers(self):
    return []

  @property
  def leaf_layer_v1_image_id(self):
    return None

  @property
  def blob_digests(self):
    return []


class ManifestBackfillWorker(Worker):
  def __init__(self):
    super(ManifestBackfillWorker, self).__init__()
    self.add_operation(self._backfill_manifests, 1)

  def _candidates_to_backfill(self):
    def missing_tmt_query():
      return (TagManifest
              .select()
              .join(TagManifestToManifest, JOIN.LEFT_OUTER)
              .where(TagManifestToManifest.id >> None))

    min_id = (TagManifest
              .select(fn.Min(TagManifest.id))
              .join(TagManifestToManifest, JOIN.LEFT_OUTER)
              .where(TagManifestToManifest.id >> None)
              .scalar())
    max_id = TagManifest.select(fn.Max(TagManifest.id)).scalar()

    iterator = yield_random_entries(
      missing_tmt_query,
      TagManifest.id,
      100,
      max_id,
      min_id,
    )

    return iterator

  def _backfill_manifests(self):
    """ Performs garbage collection on repositories. """
    with UseThenDisconnect(app.config):
      iterator = self._candidates_to_backfill()
      if iterator is None:
        logger.debug('Found no additional images to scan')
        return None

      for candidate, abt, _ in iterator:
        if not backfill_manifest(candidate):
          logger.info('Another worker pre-empted us for manifest: %s', candidate.id)
          abt.set()


def lookup_map_row(tag_manifest):
  try:
    TagManifestToManifest.get(tag_manifest=tag_manifest)
    return True
  except TagManifestToManifest.DoesNotExist:
    return False


def backfill_manifest(tag_manifest):
  logger.info('Backfilling manifest %s', tag_manifest.id)

  # Ensure that a mapping row doesn't already exist. If it does, we've been preempted.
  if lookup_map_row(tag_manifest):
    return False

  # Parse the manifest. If we cannot parse, then we treat the manifest  as broken and just emit it
  # without additional rows or data, as it will eventually not be useful.
  is_broken = False
  try:
    manifest = DockerSchema1Manifest(tag_manifest.json_data, validate=False)
  except ManifestException:
    logger.exception('Exception when trying to parse manifest %s', tag_manifest.id)
    manifest = BrokenManifest(tag_manifest.digest, tag_manifest.json_data)
    is_broken = True

  # Lookup the storages for the digests.
  root_image = tag_manifest.tag.image
  storage_id_map = {root_image.storage.content_checksum: root_image.storage.id}
  for parent_image_id in root_image.ancestor_id_list():
    storage = Image.get(id=parent_image_id).storage
    storage_id_map[storage.content_checksum] = storage.id

  with db_transaction():
    # Re-retrieve the tag manifest to ensure it still exists and we're pointing at the correct tag.
    try:
      tag_manifest = TagManifest.get(id=tag_manifest.id)
    except TagManifest.DoesNotExist:
      return True

    # Create the new-style rows for the manifest.
    manifest_row = populate_manifest(tag_manifest.tag.repository, manifest,
                                     tag_manifest.tag.image, storage_id_map)

    # Create the mapping row. If we find another was created for this tag manifest in the
    # meantime, then we've been preempted.
    try:
      TagManifestToManifest.create(tag_manifest=tag_manifest, manifest=manifest_row,
                                   broken=is_broken)
      return True
    except IntegrityError:
      return False



if __name__ == "__main__":
  logging.config.fileConfig(logfile_path(debug=False), disable_existing_loggers=False)
  worker = ManifestBackfillWorker()
  worker.start()