import json
import logging
import hashlib

from collections import namedtuple
from jsonschema import validate as validate_schema, ValidationError

from digest import digest_tools
from image.docker import ManifestException
from image.docker.schema2 import (DOCKER_SCHEMA2_MANIFEST_CONTENT_TYPE,
                                  DOCKER_SCHEMA2_CONFIG_CONTENT_TYPE,
                                  DOCKER_SCHEMA2_LAYER_CONTENT_TYPE,
                                  DOCKER_SCHEMA2_REMOTE_LAYER_CONTENT_TYPE)
from image.docker.schema2.config import DockerSchema2Config

# Keys.
DOCKER_SCHEMA2_MANIFEST_VERSION_KEY = 'schemaVersion'
DOCKER_SCHEMA2_MANIFEST_MEDIATYPE_KEY = 'mediaType'
DOCKER_SCHEMA2_MANIFEST_CONFIG_KEY = 'config'
DOCKER_SCHEMA2_MANIFEST_SIZE_KEY = 'size'
DOCKER_SCHEMA2_MANIFEST_DIGEST_KEY = 'digest'
DOCKER_SCHEMA2_MANIFEST_LAYERS_KEY = 'layers'
DOCKER_SCHEMA2_MANIFEST_URLS_KEY = 'urls'

# Named tuples.
DockerV2ManifestConfig = namedtuple('DockerV2ManifestConfig', ['size', 'digest'])
DockerV2ManifestLayer = namedtuple('DockerV2ManifestLayer', ['index', 'size', 'digest',
                                                             'is_remote', 'urls'])

LayerWithV1ID = namedtuple('LayerWithV1ID', ['layer', 'v1_id', 'v1_parent_id'])

logger = logging.getLogger(__name__)

class MalformedSchema2Manifest(ManifestException):
  """
  Raised when a manifest fails an assertion that should be true according to the Docker Manifest
  v2.2 Specification.
  """
  pass


class DockerSchema2Manifest(object):
  METASCHEMA = {
    'type': 'object',
    'properties': {
      DOCKER_SCHEMA2_MANIFEST_VERSION_KEY: {
        'type': 'number',
        'description': 'The version of the schema. Must always be `2`.',
        'minimum': 2,
        'maximum': 2,
      },
      DOCKER_SCHEMA2_MANIFEST_MEDIATYPE_KEY: {
        'type': 'string',
        'description': 'The media type of the schema.',
        'enum': [DOCKER_SCHEMA2_MANIFEST_CONTENT_TYPE],
      },
      DOCKER_SCHEMA2_MANIFEST_CONFIG_KEY: {
        'type': 'object',
        'description': 'The config field references a configuration object for a container, ' +
                       'by digest. This configuration item is a JSON blob that the runtime ' +
                       'uses to set up the container.',
        'properties': {
          DOCKER_SCHEMA2_MANIFEST_MEDIATYPE_KEY: {
            'type': 'string',
            'description': 'The MIME type of the referenced object. This should generally be ' +
                           'application/vnd.docker.container.image.v1+json',
            'enum': [DOCKER_SCHEMA2_CONFIG_CONTENT_TYPE],
          },
          DOCKER_SCHEMA2_MANIFEST_SIZE_KEY: {
            'type': 'number',
            'description': 'The size in bytes of the object. This field exists so that a ' +
                           'client will have an expected size for the content before ' +
                           'validating. If the length of the retrieved content does not ' +
                           'match the specified length, the content should not be trusted.',
          },
          DOCKER_SCHEMA2_MANIFEST_DIGEST_KEY: {
            'type': 'string',
            'description': 'The content addressable digest of the config in the blob store',
          },
        },
        'required': [DOCKER_SCHEMA2_MANIFEST_MEDIATYPE_KEY, DOCKER_SCHEMA2_MANIFEST_SIZE_KEY,
                     DOCKER_SCHEMA2_MANIFEST_DIGEST_KEY],
      },
      DOCKER_SCHEMA2_MANIFEST_LAYERS_KEY: {
        'type': 'array',
        'description': 'The layer list is ordered starting from the base ' +
                       'image (opposite order of schema1).',
        'items': {
          'type': 'object',
          'properties': {
            DOCKER_SCHEMA2_MANIFEST_MEDIATYPE_KEY: {
              'type': 'string',
              'description': 'The MIME type of the referenced object. This should generally be ' +
                             'application/vnd.docker.image.rootfs.diff.tar.gzip. Layers of type ' +
                             'application/vnd.docker.image.rootfs.foreign.diff.tar.gzip may be ' +
                             'pulled from a remote location but they should never be pushed.',
              'enum': [DOCKER_SCHEMA2_LAYER_CONTENT_TYPE, DOCKER_SCHEMA2_REMOTE_LAYER_CONTENT_TYPE],
            },
            DOCKER_SCHEMA2_MANIFEST_SIZE_KEY: {
              'type': 'number',
              'description': 'The size in bytes of the object. This field exists so that a ' +
                             'client will have an expected size for the content before ' +
                             'validating. If the length of the retrieved content does not ' +
                             'match the specified length, the content should not be trusted.',
            },
            DOCKER_SCHEMA2_MANIFEST_DIGEST_KEY: {
              'type': 'string',
              'description': 'The content addressable digest of the layer in the blob store',
            },
          },
          'required': [
            DOCKER_SCHEMA2_MANIFEST_MEDIATYPE_KEY, DOCKER_SCHEMA2_MANIFEST_SIZE_KEY,
            DOCKER_SCHEMA2_MANIFEST_DIGEST_KEY,
          ],
        },
      },
    },
    'required': [DOCKER_SCHEMA2_MANIFEST_VERSION_KEY, DOCKER_SCHEMA2_MANIFEST_MEDIATYPE_KEY,
                 DOCKER_SCHEMA2_MANIFEST_CONFIG_KEY, DOCKER_SCHEMA2_MANIFEST_LAYERS_KEY],
  }

  def __init__(self, manifest_bytes):
    self._layers = None

    try:
      self._parsed = json.loads(manifest_bytes)
    except ValueError as ve:
      raise MalformedSchema2Manifest('malformed manifest data: %s' % ve)

    try:
      validate_schema(self._parsed, DockerSchema2Manifest.METASCHEMA)
    except ValidationError as ve:
      raise MalformedSchema2Manifest('manifest data does not match schema: %s' % ve)

  @property
  def schema_version(self):
    return 2

  @property
  def config(self):
    config = self._parsed[DOCKER_SCHEMA2_MANIFEST_CONFIG_KEY]
    return DockerV2ManifestConfig(size=config[DOCKER_SCHEMA2_MANIFEST_SIZE_KEY],
                                  digest=config[DOCKER_SCHEMA2_MANIFEST_DIGEST_KEY])

  @property
  def layers(self):
    """ Returns the layers of this manifest, from base to leaf. """
    if self._layers is None:
      self._layers = list(self._generate_layers())
    return self._layers

  @property
  def leaf_layer(self):
    return self.layers[-1]

  def _generate_layers(self):
    for index, layer in enumerate(self._parsed[DOCKER_SCHEMA2_MANIFEST_LAYERS_KEY]):
      content_type = layer[DOCKER_SCHEMA2_MANIFEST_MEDIATYPE_KEY]
      is_remote = content_type == DOCKER_SCHEMA2_REMOTE_LAYER_CONTENT_TYPE

      try:
        digest = digest_tools.Digest.parse_digest(layer[DOCKER_SCHEMA2_MANIFEST_DIGEST_KEY])
      except digest_tools.InvalidDigestException:
        raise MalformedSchema2Manifest('could not parse manifest digest: %s' %
                                       layer[DOCKER_SCHEMA2_MANIFEST_DIGEST_KEY])

      yield DockerV2ManifestLayer(index=index,
                                  size=layer[DOCKER_SCHEMA2_MANIFEST_SIZE_KEY],
                                  digest=digest,
                                  is_remote=is_remote,
                                  urls=layer.get(DOCKER_SCHEMA2_MANIFEST_URLS_KEY))

  @property
  def layers_with_v1_ids(self):
    digest_history = hashlib.sha256()
    v1_layer_parent_id = None
    v1_layer_id = None

    for layer in self.layers:
      v1_layer_parent_id = v1_layer_id

      # Create a new synthesized V1 ID for the layer by adding its digest and index to the
      # existing digest history hash builder. This will ensure unique V1s across *all* schemas in
      # a repository.
      digest_history.update(str(layer.digest))
      digest_history.update("#")
      digest_history.update(str(layer.index))
      digest_history.update("|")
      v1_layer_id = digest_history.hexdigest()
      yield LayerWithV1ID(layer=layer, v1_id=v1_layer_id, v1_parent_id=v1_layer_parent_id)

  def populate_schema1_builder(self, v1_builder, lookup_config_fn):
    """ Populates a DockerSchema1ManifestBuilder with the layers and config from
        this schema. The `lookup_config_fn` is a function that, when given the config
        digest SHA, returns the associated configuration JSON bytes for this schema.
    """
    config_bytes = lookup_config_fn(self.config.digest)
    if len(config_bytes) != self.config.size:
      raise MalformedSchema2Manifest('Size of config does not match that retrieved: %s vs %s',
                                     len(config_bytes), self.config.size)

    schema2_config = DockerSchema2Config(config_bytes)

    # Build the V1 IDs for the layers.
    layers = list(self.layers_with_v1_ids)
    for layer_with_ids in reversed(layers): # Schema1 has layers in reverse order
      v1_compatibility = schema2_config.build_v1_compatibility(layer_with_ids.layer.index,
                                                               layer_with_ids.v1_id,
                                                               layer_with_ids.v1_parent_id)
      v1_builder.add_layer(str(layer_with_ids.layer.digest), json.dumps(v1_compatibility))

    return v1_builder