import hashlib

from contextlib import contextmanager

from app import storage, docker_v2_signing_key
from data import model, database
from endpoints.v2.manifest import _write_manifest
from image.docker.schema1 import DockerSchema1ManifestBuilder

from test.fixtures import *


ADMIN_ACCESS_USER = 'devtable'
REPO = 'simple'
FIRST_TAG = 'first'
SECOND_TAG = 'second'
THIRD_TAG = 'third'


@contextmanager
def set_tag_expiration_policy(namespace, expiration_s=0):
  namespace_user = model.user.get_user(namespace)
  model.user.change_user_tag_expiration(namespace_user, expiration_s)
  yield


def _perform_cleanup():
  database.RepositoryTag.delete().where(database.RepositoryTag.hidden == True).execute()
  repo_object = model.repository.get_repository(ADMIN_ACCESS_USER, REPO)
  model.repository.garbage_collect_repo(repo_object)


def test_missing_link(initialized_db):
  """ Tests for a corner case that could result in missing a link to a blob referenced by a
      manifest. The test exercises the case as follows:

      1) Push a manifest of a single layer with a Docker ID `FIRST_ID`, pointing
          to blob `FIRST_BLOB`. The database should contain the tag referencing the layer, with
          no changed ID and the blob not being GCed.

      2) Push a manifest of two layers:

          Layer 1: `FIRST_ID` with blob `SECOND_BLOB`: Will result in a new synthesized ID
          Layer 2: `SECOND_ID` with blob `THIRD_BLOB`: Will result in `SECOND_ID` pointing to the
                  `THIRD_BLOB`, with a parent pointing to the new synthesized ID's layer.

      3) Push a manifest of two layers:

          Layer 1: `THIRD_ID` with blob `FOURTH_BLOB`: Will result in a new `THIRD_ID` layer
          Layer 2: `FIRST_ID` with blob  `THIRD_BLOB`: Since `FIRST_ID` already points to `SECOND_BLOB`,
                  this will synthesize a new ID. With the current bug, the synthesized ID will match
                  that of `SECOND_ID`, leaving `THIRD_ID` unlinked and therefore, after a GC, missing
                  `FOURTH_BLOB`.
  """
  with set_tag_expiration_policy('devtable', 0):
    location_name = storage.preferred_locations[0]
    location = database.ImageStorageLocation.get(name=location_name)

    # Create first blob.
    first_blob_sha = 'sha256:' + hashlib.sha256("FIRST").hexdigest()
    model.blob.store_blob_record_and_temp_link(ADMIN_ACCESS_USER, REPO, first_blob_sha, location, 0, 0, 0)

    # Push the first manifest.
    first_manifest = (DockerSchema1ManifestBuilder(ADMIN_ACCESS_USER, REPO, FIRST_TAG)
                      .add_layer(first_blob_sha, '{"id": "first"}')
                      .build(docker_v2_signing_key))

    _write_manifest(ADMIN_ACCESS_USER, REPO, first_manifest)

    # Delete all temp tags and perform GC.
    _perform_cleanup()

    # Ensure that the first blob still exists, along with the first tag.
    assert model.blob.get_repo_blob_by_digest(ADMIN_ACCESS_USER, REPO, first_blob_sha) is not None
    assert model.tag.load_tag_manifest(ADMIN_ACCESS_USER, REPO, FIRST_TAG) is not None
    assert model.tag.get_tag_image(ADMIN_ACCESS_USER, REPO, FIRST_TAG).docker_image_id == 'first'

    # Create the second and third blobs.
    second_blob_sha = 'sha256:' + hashlib.sha256("SECOND").hexdigest()
    third_blob_sha = 'sha256:' + hashlib.sha256("THIRD").hexdigest()

    model.blob.store_blob_record_and_temp_link(ADMIN_ACCESS_USER, REPO, second_blob_sha, location, 0, 0, 0)
    model.blob.store_blob_record_and_temp_link(ADMIN_ACCESS_USER, REPO, third_blob_sha, location, 0, 0, 0)

    # Push the second manifest.
    second_manifest = (DockerSchema1ManifestBuilder(ADMIN_ACCESS_USER, REPO, SECOND_TAG)
                        .add_layer(third_blob_sha, '{"id": "second", "parent": "first"}')
                        .add_layer(second_blob_sha, '{"id": "first"}')
                        .build(docker_v2_signing_key))

    _write_manifest(ADMIN_ACCESS_USER, REPO, second_manifest)

    # Delete all temp tags and perform GC.
    _perform_cleanup()

    # Ensure that the first and second blobs still exists, along with the second tag.
    assert model.blob.get_repo_blob_by_digest(ADMIN_ACCESS_USER, REPO, first_blob_sha) is not None
    assert model.blob.get_repo_blob_by_digest(ADMIN_ACCESS_USER, REPO, second_blob_sha) is not None
    assert model.blob.get_repo_blob_by_digest(ADMIN_ACCESS_USER, REPO, third_blob_sha) is not None

    assert model.tag.load_tag_manifest(ADMIN_ACCESS_USER, REPO, FIRST_TAG) is not None
    assert model.tag.load_tag_manifest(ADMIN_ACCESS_USER, REPO, SECOND_TAG) is not None

    assert model.tag.get_tag_image(ADMIN_ACCESS_USER, REPO, FIRST_TAG).docker_image_id == 'first'

    # Ensure the IDs have changed.
    assert model.tag.get_tag_image(ADMIN_ACCESS_USER, REPO, SECOND_TAG).parent.docker_image_id != 'first'
    assert model.tag.get_tag_image(ADMIN_ACCESS_USER, REPO, SECOND_TAG).docker_image_id != 'second'

    # Create the fourth blob.
    fourth_blob_sha = 'sha256:' + hashlib.sha256("FOURTH").hexdigest()
    model.blob.store_blob_record_and_temp_link(ADMIN_ACCESS_USER, REPO, fourth_blob_sha, location, 0, 0, 0)

    # Push the third manifest.
    third_manifest = (DockerSchema1ManifestBuilder(ADMIN_ACCESS_USER, REPO, THIRD_TAG)
                      .add_layer(third_blob_sha, '{"id": "second", "parent": "first"}')
                      .add_layer(fourth_blob_sha, '{"id": "first"}')  # Note the change in BLOB from the second manifest.
                      .build(docker_v2_signing_key))

    _write_manifest(ADMIN_ACCESS_USER, REPO, third_manifest)

    # Delete all temp tags and perform GC.
    _perform_cleanup()

    # Ensure all blobs are present.
    assert model.blob.get_repo_blob_by_digest(ADMIN_ACCESS_USER, REPO, first_blob_sha) is not None
    assert model.blob.get_repo_blob_by_digest(ADMIN_ACCESS_USER, REPO, second_blob_sha) is not None
    assert model.blob.get_repo_blob_by_digest(ADMIN_ACCESS_USER, REPO, third_blob_sha) is not None
    assert model.blob.get_repo_blob_by_digest(ADMIN_ACCESS_USER, REPO, fourth_blob_sha) is not None

    # Ensure new synthesized IDs were created.
    second_tag_id = model.tag.get_tag_image(ADMIN_ACCESS_USER, REPO, SECOND_TAG).docker_image_id
    third_tag_id = model.tag.get_tag_image(ADMIN_ACCESS_USER, REPO, THIRD_TAG).docker_image_id
    assert second_tag_id != third_tag_id