import logging
import random

from enum import Enum
from datetime import timedelta, datetime
from peewee import Case, JOIN, fn, SQL, IntegrityError
from cachetools import ttl_cache

from data.model import (
  config, DataModelException, tag, db_transaction, storage, permission, _basequery)
from data.database import ( 
  Repository, Namespace, RepositoryTag, Star, Image, ImageStorage, User, Visibility,
  RepositoryPermission, RepositoryActionCount, Role, RepositoryAuthorizedEmail,
  DerivedStorageForImage, Label, db_for_update, get_epoch_timestamp,
  db_random_func, db_concat_func, RepositorySearchScore, RepositoryKind, ApprTag,
  ManifestLegacyImage, Manifest, ManifestChild)
from data.text import prefix_search
from util.itertoolrecipes import take

logger = logging.getLogger(__name__)
SEARCH_FIELDS = Enum("SearchFields", ["name", "description"])


def get_repo_kind_name(repo):
  return Repository.kind.get_name(repo.kind_id)


def get_repository_count():
  return Repository.select().count()


def get_public_repo_visibility():
  return _basequery.get_public_repo_visibility()


def create_repository(namespace, name, creating_user, visibility='private', repo_kind='image',
                      description=None):
  namespace_user = User.get(username=namespace)
  yesterday = datetime.now() - timedelta(days=1)

  with db_transaction():
    repo = Repository.create(name=name, visibility=Repository.visibility.get_id(visibility),
                            namespace_user=namespace_user,
                            kind=Repository.kind.get_id(repo_kind),
                            description=description)

    RepositoryActionCount.create(repository=repo, count=0, date=yesterday)
    RepositorySearchScore.create(repository=repo, score=0)

    # Note: We put the admin create permission under the transaction to ensure it is created.
    if creating_user and not creating_user.organization:
      admin = Role.get(name='admin')
      RepositoryPermission.create(user=creating_user, repository=repo, role=admin)

  # Apply default permissions (only occurs for repositories under organizations)
  if creating_user and not creating_user.organization and creating_user.username != namespace:
    permission.apply_default_permissions(repo, creating_user)

  return repo


def get_repository(namespace_name, repository_name, kind_filter=None):
  try:
    return _basequery.get_existing_repository(namespace_name, repository_name,
                                              kind_filter=kind_filter)
  except Repository.DoesNotExist:
    return None


def get_or_create_repository(namespace, name, creating_user, visibility='private',
                             repo_kind='image'):
  repo = get_repository(namespace, name, repo_kind)
  if repo is None:
    repo = create_repository(namespace, name, creating_user, visibility, repo_kind)
  return repo


def purge_repository(namespace_name, repository_name):
  """ Completely delete all traces of the repository. Will return True upon
      complete success, and False upon partial or total failure. Garbage
      collection is incremental and repeatable, so this return value does
      not need to be checked or responded to.
      """

  try:
    repo = _basequery.get_existing_repository(namespace_name, repository_name)
  except Repository.DoesNotExist:
    return False

  # Delete the repository of all Appr-referenced entries.
  # Note that new-model Tag's must be deleted in *two* passes, as they can reference parent tags,
  # and MySQL is... particular... about such relationships when deleting.
  ApprTag.delete().where(ApprTag.repository == repo, ~(ApprTag.linked_tag >> None)).execute()
  ApprTag.delete().where(ApprTag.repository == repo).execute()

  # Gc to remove the images and storage
  successful_gc = garbage_collect_repo(repo, is_purge=True)
  if not successful_gc:
    return False

  # Delete the rest of the repository metadata
  try:
    fetched = _basequery.get_existing_repository(namespace_name, repository_name)
  except Repository.DoesNotExist:
    return False

  fetched.delete_instance(recursive=True, delete_nullable=False)

  # Run callbacks
  for callback in config.repo_cleanup_callbacks:
    callback(namespace_name, repository_name)

  return True


@ttl_cache(maxsize=1, ttl=600)
def _get_gc_expiration_policies():
  policy_tuples_query = (
    Namespace.select(Namespace.removed_tag_expiration_s).distinct()
    .limit(100)  # This sucks but it's the only way to limit memory
    .tuples())
  return [policy[0] for policy in policy_tuples_query]


def get_random_gc_policy():
  """ Return a single random policy from the database to use when garbage collecting.
  """
  return random.choice(_get_gc_expiration_policies())


def find_repository_with_garbage(limit_to_gc_policy_s):
  expiration_timestamp = get_epoch_timestamp() - limit_to_gc_policy_s

  try:
    candidates = (RepositoryTag.select(RepositoryTag.repository).join(Repository)
                  .join(Namespace, on=(Repository.namespace_user == Namespace.id))
                  .where(~(RepositoryTag.lifetime_end_ts >> None),
                         (RepositoryTag.lifetime_end_ts <= expiration_timestamp),
                         (Namespace.removed_tag_expiration_s == limit_to_gc_policy_s)).limit(500)
                  .distinct().alias('candidates'))

    found = (RepositoryTag.select(candidates.c.repository_id).from_(candidates)
             .order_by(db_random_func()).get())

    if found is None:
      return

    return Repository.get(Repository.id == found.repository_id)
  except RepositoryTag.DoesNotExist:
    return None
  except Repository.DoesNotExist:
    return None


def _all_images_for_gc(repo):
  """ Returns all the images found in the given repository, for the purposes of GC. """
  images = (Image
            .select(Image.id, Image.docker_image_id,
                    ImageStorage.id, ImageStorage.uuid)
            .join(ImageStorage)
            .where(Image.repository == repo))
  return list(images)


def _filter_to_unreferenced(repo, candidates_orphans):
  """ Filters the given candidate orphan images into those unreferenced by any tag or
      other image. """
  def _get_clause(field, candidates):
    if len(candidates) == 1:
      return field == candidates[0]

    return field << candidates

  # Any image directly referenced by a tag that still exists, cannot be GCed.
  direct_referenced = (RepositoryTag
                       .select(RepositoryTag.image)
                       .where(RepositoryTag.repository == repo.id,
                              _get_clause(RepositoryTag.image, candidates_orphans)))

  # Any image which is the parent of another image, cannot be GCed.
  parent_referenced = (Image
                       .select(Image.parent)
                       .where(Image.repository == repo.id,
                              _get_clause(Image.parent, candidates_orphans)))

  referenced_candidates = (direct_referenced | parent_referenced)

  # We desire a few pieces of information from the database from the following
  # query: all of the image ids which are associated with this repository,
  # and the storages which are associated with those images.
  unreferenced_candidates = (Image
                             .select(Image.id, Image.docker_image_id,
                                     ImageStorage.id, ImageStorage.uuid)
                             .join(ImageStorage)
                             .where(_get_clause(Image.id, candidates_orphans),
                                    ~(_get_clause(Image.id, referenced_candidates))))
  return list(unreferenced_candidates)


def garbage_collect_repo(repo, is_purge=False):
  """ Garbage collect the specified repository object. This will remove all
      images, derived images, and other associated metadata, for images which
      are no longer referenced by a tag or another image which is itself
      tagged. Returns True if garbage collection was completed without error
      and False otherwise. Retries are safe and work incrementally, so this
      return value does not need to be checked or handled.
      """
  logger.debug('Garbage collecting repository %s', repo.id)

  # TODO(jschorr): Update GC for the new data model.
  if not is_purge:
    try:
      # Skip any repos with manifest lists in them, for now.
      ManifestChild.get(repository=repo)
      return True
    except ManifestChild.DoesNotExist:
      pass

  if is_purge:
    tag.purge_all_tags(repo)
    images_for_tags_removed = {i.id for i in Image.select().where(Image.repository == repo)}
    return _garbage_collect_from_image(repo, images_for_tags_removed, True)

  images_for_tags_removed = tag.garbage_collect_tags(repo)
  if not len(images_for_tags_removed):
    logger.debug('No images for GC for repo: %s', repo.id)
    return True

  for image in images_for_tags_removed:
    candidate_list = [image.id] + list(reversed(image.ancestor_id_list()))
    for candidate_id in candidate_list:
      if not _garbage_collect_from_image(repo, {candidate_id}):
        return False

  return True


def _garbage_collect_from_image(repo, candidate_orphan_image_set, is_purge=False):
  storage_id_whitelist = set()

  all_images_removed = set()
  all_storage_id_whitelist = set()
  all_unreferenced_candidates = set()

  # Iteratively try to remove images from the database. The only images we can remove are those
  # that are not referenced by tags AND not the parents of other images. We continue removing images
  # until no changes are found.
  iteration = 0
  making_progress = True
  while candidate_orphan_image_set and making_progress:
    iteration = iteration + 1
    logger.debug('Starting iteration #%s for GC of repository %s with candidates: %s', iteration,
                 repo.id, candidate_orphan_image_set)
    candidates_orphans = list(candidate_orphan_image_set)

    with db_transaction():
      # Find the images to delete.
      images_to_gc = (_all_images_for_gc(repo) if is_purge
                      else _filter_to_unreferenced(repo, candidates_orphans))

      # Make sure we are making progress.
      image_ids_to_remove = [candidate.id for candidate in images_to_gc]
      making_progress = bool(len(image_ids_to_remove))
      if len(image_ids_to_remove) == 0:
        # No more images to remove.
        break

      logger.info('Cleaning up unreferenced images: %s', image_ids_to_remove)
      storage_id_whitelist = set([candidate.storage_id for candidate in images_to_gc])

      # Lookup any derived images for the images to remove.
      derived = DerivedStorageForImage.select().where(DerivedStorageForImage.source_image <<
                                                      image_ids_to_remove)

      has_derived = False
      for derived_image in derived:
        has_derived = True
        storage_id_whitelist.add(derived_image.derivative_id)

      # Delete any derived images and the images themselves.
      if has_derived:
        try:
          (DerivedStorageForImage.delete()
           .where(DerivedStorageForImage.source_image << image_ids_to_remove).execute())
        except IntegrityError:
          logger.info('Could not GC derived images %s; will try again soon', image_ids_to_remove)
          return False

      # Delete any legacy references to the images.
      (ManifestLegacyImage
       .delete()
       .where(ManifestLegacyImage.image << image_ids_to_remove)
       .execute())

      # Delete the images themselves.
      try:
        Image.delete().where(Image.id << image_ids_to_remove).execute()
      except IntegrityError:
        logger.info('Could not GC images %s; will try again soon', image_ids_to_remove)
        return False

    # Add the images to the removed set and remove them from the candidate set.
    all_images_removed.update(image_ids_to_remove)
    all_storage_id_whitelist.update(storage_id_whitelist)
    all_unreferenced_candidates.update(images_to_gc)

    candidate_orphan_image_set.difference_update(image_ids_to_remove)

  # If any images were removed, GC any orphaned storages.
  if len(all_images_removed) > 0:
    logger.info('Garbage collecting storage for images: %s', all_images_removed)
    storage_ids_removed = set(storage.garbage_collect_storage(all_storage_id_whitelist))

    # If any storages were removed and cleanup callbacks are registered, call them with
    # the images+storages removed.
    if storage_ids_removed and config.image_cleanup_callbacks:
      image_storages_removed = [
        candidate for candidate in all_unreferenced_candidates
        if candidate.storage_id in storage_ids_removed
      ]
      for callback in config.image_cleanup_callbacks:
        callback(image_storages_removed)

  return True


def star_repository(user, repository):
  """ Stars a repository. """
  star = Star.create(user=user.id, repository=repository.id)
  star.save()


def unstar_repository(user, repository):
  """ Unstars a repository. """
  try:
    (Star.delete().where(Star.repository == repository.id, Star.user == user.id).execute())
  except Star.DoesNotExist:
    raise DataModelException('Star not found.')


def set_trust(repo, trust_enabled):
  repo.trust_enabled = trust_enabled
  repo.save()


def set_description(repo, description):
  repo.description = description
  repo.save()


def get_user_starred_repositories(user, kind_filter='image'):
  """ Retrieves all of the repositories a user has starred. """
  try:
    repo_kind = Repository.kind.get_id(kind_filter)
  except RepositoryKind.DoesNotExist:
    raise DataModelException('Unknown kind of repository')

  query = (Repository.select(Repository, User, Visibility, Repository.id.alias('rid')).join(Star)
           .switch(Repository).join(User).switch(Repository).join(Visibility)
           .where(Star.user == user, Repository.kind == repo_kind))

  return query


def repository_is_starred(user, repository):
  """ Determines whether a user has starred a repository or not. """
  try:
    (Star.select().where(Star.repository == repository.id, Star.user == user.id).get())
    return True
  except Star.DoesNotExist:
    return False


def get_when_last_modified(repository_ids):
  """ Returns a map from repository ID to the last modified time (in s) for each repository in the
      given repository IDs list.
  """
  if not repository_ids:
    return {}

  tuples = (RepositoryTag.select(RepositoryTag.repository, fn.Max(RepositoryTag.lifetime_start_ts))
            .where(RepositoryTag.repository << repository_ids).group_by(RepositoryTag.repository)
            .tuples())

  last_modified_map = {}
  for record in tuples:
    last_modified_map[record[0]] = record[1]

  return last_modified_map


def get_stars(repository_ids):
  """ Returns a map from repository ID to the number of stars for each repository in the
      given repository IDs list.
  """
  if not repository_ids:
    return {}

  tuples = (Star.select(Star.repository, fn.Count(Star.id))
            .where(Star.repository << repository_ids).group_by(Star.repository).tuples())

  star_map = {}
  for record in tuples:
    star_map[record[0]] = record[1]

  return star_map


def get_visible_repositories(username, namespace=None, kind_filter='image', include_public=False,
                             start_id=None, limit=None):
  """ Returns the repositories visible to the given user (if any).
  """
  if not include_public and not username:
    # Short circuit by returning a query that will find no repositories. We need to return a query
    # here, as it will be modified by other queries later on.
    return Repository.select(Repository.id.alias('rid')).where(Repository.id == -1)

  query = (Repository.select(Repository.name,
                             Repository.id.alias('rid'), Repository.description,
                             Namespace.username, Repository.visibility, Repository.kind)
           .switch(Repository).join(Namespace, on=(Repository.namespace_user == Namespace.id)))

  user_id = None
  if username:
    # Note: We only need the permissions table if we will filter based on a user's permissions.
    query = query.switch(Repository).distinct().join(RepositoryPermission, JOIN.LEFT_OUTER)
    found_namespace = _get_namespace_user(username)
    if not found_namespace:
      return Repository.select(Repository.id.alias('rid')).where(Repository.id == -1)

    user_id = found_namespace.id

  query = _basequery.filter_to_repos_for_user(query, user_id, namespace, kind_filter,
                                              include_public, start_id=start_id)

  if limit is not None:
    query = query.limit(limit).order_by(SQL('rid'))

  return query


def get_app_repository(namespace_name, repository_name):
  """ Find an application repository. """
  try:
    return _basequery.get_existing_repository(namespace_name, repository_name,
                                              kind_filter='application')
  except Repository.DoesNotExist:
    return None


def get_app_search(lookup, search_fields=None, username=None, limit=50):
  if search_fields is None:
    search_fields = set([SEARCH_FIELDS.name.name])

  return get_filtered_matching_repositories(lookup, filter_username=username,
                                            search_fields=search_fields, repo_kind='application',
                                            offset=0, limit=limit)


def _get_namespace_user(username):
  try:
    return User.get(username=username)
  except User.DoesNotExist:
    return None


def get_filtered_matching_repositories(lookup_value, filter_username=None, repo_kind='image',
                                       offset=0, limit=25, search_fields=None):
  """ Returns an iterator of all repositories matching the given lookup value, with optional
      filtering to a specific user. If the user is unspecified, only public repositories will
      be returned.
  """
  if search_fields is None:
    search_fields = set([SEARCH_FIELDS.description.name, SEARCH_FIELDS.name.name])

  # Build the unfiltered search query.
  unfiltered_query = _get_sorted_matching_repositories(lookup_value, repo_kind=repo_kind,
                                                       search_fields=search_fields,
                                                       include_private=filter_username is not None,
                                                       ids_only=filter_username is not None)

  # Add a filter to the iterator, if necessary.
  if filter_username is not None:
    filter_user = _get_namespace_user(filter_username)
    if filter_user is None:
      return []

    iterator = _filter_repositories_visible_to_user(unfiltered_query, filter_user.id, limit,
                                                    repo_kind)
    if offset > 0:
      take(offset, iterator)

    # Return the results.
    return list(take(limit, iterator))

  return list(unfiltered_query.offset(offset).limit(limit))


def _filter_repositories_visible_to_user(unfiltered_query, filter_user_id, limit, repo_kind):
  encountered = set()
  chunk_count = limit * 2
  unfiltered_page = 0
  iteration_count = 0

  while iteration_count < 10:  # Just to be safe
    # Find the next chunk's worth of repository IDs, paginated by the chunk size.
    unfiltered_page = unfiltered_page + 1
    found_ids = [r.id for r in unfiltered_query.paginate(unfiltered_page, chunk_count)]

    # Make sure we haven't encountered these results before. This code is used to handle
    # the case where we've previously seen a result, as pagination is not necessary
    # stable in SQL databases.
    unfiltered_repository_ids = set(found_ids)
    new_unfiltered_ids = unfiltered_repository_ids - encountered
    if not new_unfiltered_ids:
      break

    encountered.update(new_unfiltered_ids)

    # Filter the repositories found to only those visible to the current user.
    query = (Repository
             .select(Repository, Namespace)
             .distinct()
             .join(Namespace, on=(Namespace.id == Repository.namespace_user)).switch(Repository)
             .join(RepositoryPermission).where(Repository.id << list(new_unfiltered_ids)))

    filtered = _basequery.filter_to_repos_for_user(query, filter_user_id, repo_kind=repo_kind)

    # Sort the filtered repositories by their initial order.
    all_filtered_repos = list(filtered)
    all_filtered_repos.sort(key=lambda repo: found_ids.index(repo.id))

    # Yield the repositories in sorted order.
    for filtered_repo in all_filtered_repos:
      yield filtered_repo

    # If the number of found IDs is less than the chunk count, then we're done.
    if len(found_ids) < chunk_count:
      break

    iteration_count = iteration_count + 1


def _get_sorted_matching_repositories(lookup_value, repo_kind='image', include_private=False,
                                      search_fields=None, ids_only=False):
  """ Returns a query of repositories matching the given lookup string, with optional inclusion of
      private repositories. Note that this method does *not* filter results based on visibility
      to users.
  """
  select_fields = [Repository.id] if ids_only else [Repository, Namespace]

  if not lookup_value:
    # This is a generic listing of repositories. Simply return the sorted repositories based
    # on RepositorySearchScore.
    query = (Repository
             .select(*select_fields)
             .join(RepositorySearchScore)
             .order_by(RepositorySearchScore.score.desc()))
  else:
    if search_fields is None:
      search_fields = set([SEARCH_FIELDS.description.name, SEARCH_FIELDS.name.name])

    # Always search at least on name (init clause)
    clause = Repository.name.match(lookup_value)
    computed_score = RepositorySearchScore.score.alias('score')

    # If the description field is in the search fields, then we need to compute a synthetic score
    # to discount the weight of the description more than the name.
    if SEARCH_FIELDS.description.name in search_fields:
      clause = Repository.description.match(lookup_value) | clause
      cases = [(Repository.name.match(lookup_value), 100 * RepositorySearchScore.score),]
      computed_score = Case(None, cases, RepositorySearchScore.score).alias('score')

    select_fields.append(computed_score)
    query = (Repository.select(*select_fields)
             .join(RepositorySearchScore)
             .where(clause)
             .order_by(SQL('score').desc()))

  if repo_kind is not None:
    query = query.where(Repository.kind == Repository.kind.get_id(repo_kind))

  if not include_private:
    query = query.where(Repository.visibility == _basequery.get_public_repo_visibility())

  if not ids_only:
    query = (query
             .switch(Repository)
             .join(Namespace, on=(Namespace.id == Repository.namespace_user)))

  return query


def lookup_repository(repo_id):
  try:
    return Repository.get(Repository.id == repo_id)
  except Repository.DoesNotExist:
    return None


def is_repository_public(repository):
  return repository.visibility_id == _basequery.get_public_repo_visibility().id


def repository_is_public(namespace_name, repository_name):
  try:
    (Repository.select().join(Namespace, on=(Repository.namespace_user == Namespace.id))
     .switch(Repository).join(Visibility).where(Namespace.username == namespace_name,
                                                Repository.name == repository_name,
                                                Visibility.name == 'public').get())
    return True
  except Repository.DoesNotExist:
    return False


def set_repository_visibility(repo, visibility):
  visibility_obj = Visibility.get(name=visibility)
  if not visibility_obj:
    return

  repo.visibility = visibility_obj
  repo.save()


def get_email_authorized_for_repo(namespace, repository, email):
  try:
    return (RepositoryAuthorizedEmail.select(RepositoryAuthorizedEmail, Repository, Namespace)
            .join(Repository).join(Namespace, on=(Repository.namespace_user == Namespace.id))
            .where(Namespace.username == namespace, Repository.name == repository,
                   RepositoryAuthorizedEmail.email == email).get())
  except RepositoryAuthorizedEmail.DoesNotExist:
    return None


def create_email_authorization_for_repo(namespace_name, repository_name, email):
  try:
    repo = _basequery.get_existing_repository(namespace_name, repository_name)
  except Repository.DoesNotExist:
    raise DataModelException('Invalid repository %s/%s' % (namespace_name, repository_name))

  return RepositoryAuthorizedEmail.create(repository=repo, email=email, confirmed=False)


def confirm_email_authorization_for_repo(code):
  try:
    found = (RepositoryAuthorizedEmail.select(RepositoryAuthorizedEmail, Repository, Namespace)
             .join(Repository).join(Namespace, on=(Repository.namespace_user == Namespace.id))
             .where(RepositoryAuthorizedEmail.code == code).get())
  except RepositoryAuthorizedEmail.DoesNotExist:
    raise DataModelException('Invalid confirmation code.')

  found.confirmed = True
  found.save()

  return found


def list_popular_public_repos(action_count_threshold, time_span, repo_kind='image'):
  cutoff = datetime.now() - time_span
  return (Repository.select(Namespace.username, Repository.name)
          .join(Namespace, on=(Repository.namespace_user == Namespace.id)).switch(Repository)
          .join(RepositoryActionCount).where(RepositoryActionCount.date >= cutoff,
                                             Repository.visibility == get_public_repo_visibility(),
                                             Repository.kind == Repository.kind.get_id(repo_kind))
          .group_by(RepositoryActionCount.repository, Repository.name, Namespace.username)
          .having(fn.Sum(RepositoryActionCount.count) >= action_count_threshold).tuples())


def is_empty(namespace_name, repository_name):
  """ Returns if the repository referenced by the given namespace and name is empty. If the repo
      doesn't exist, returns True.
  """
  try:
    tag.list_repository_tags(namespace_name, repository_name).limit(1).get()
    return False
  except RepositoryTag.DoesNotExist:
    return True