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.interfaces import ManifestInterface
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.schema1 import DockerSchema1ManifestBuilder
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', 'digest',
                                                             'is_remote', 'urls',
                                                             'compressed_size'])

ManifestImageLayer = namedtuple('ManifestImageLayer', ['history', 'blob_layer', 'v1_id',
                                                       'v1_parent_id', 'compressed_size',
                                                       'blob_digest'])

EMPTY_BLOB_DIGEST = 'sha256:a3ed95caeb02ffe68cdd9fd84406680ae93d633cb16422d00e8a7c22955b46d4'

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(ManifestInterface):
  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
    self._payload = manifest_bytes

    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)

    for layer in self.layers:
      if layer.is_remote and not layer.urls:
        raise MalformedSchema2Manifest('missing `urls` for remote layer')

  @property
  def is_manifest_list(self):
    return False

  @property
  def schema_version(self):
    return 2

  @property
  def manifest_dict(self):
    return self._parsed

  @property
  def media_type(self):
    return self._parsed[DOCKER_SCHEMA2_MANIFEST_MEDIATYPE_KEY]

  @property
  def digest(self):
    return digest_tools.sha256_digest(self._payload)

  @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):
    """ Returns the leaf layer for this manifest. """
    return self.layers[-1]

  @property
  def layers_compressed_size(self):
    return sum(layer.compressed_size for layer in self.layers)

  @property
  def has_remote_layer(self):
    for layer in self.layers:
      if layer.is_remote:
        return True

    return False

  @property
  def blob_digests(self):
    return [str(layer.digest) for layer in self.layers] + [str(self.config.digest)]

  @property
  def local_blob_digests(self):
    return ([str(layer.digest) for layer in self.layers if not layer.urls] +
            [str(self.config.digest)])

  def get_manifest_labels(self, content_retriever):
    return self._get_built_config(content_retriever).labels

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

  def child_manifests(self, content_retriever):
    return None

  def _manifest_image_layers(self, content_retriever, schema2_config=None):
    assert not self.has_remote_layer

    # Retrieve the configuration for the manifest.
    config = schema2_config or self._get_built_config(content_retriever)
    history = list(config.history)
    if len(history) < len(self.layers):
      raise MalformedSchema2Manifest('Found less history than layer blobs')

    digest_history = hashlib.sha256()
    v1_layer_parent_id = None
    v1_layer_id = None
    blob_index = 0

    for history_index, history_entry in enumerate(history):
      if not history_entry.is_empty and blob_index >= len(self.layers):
        raise MalformedSchema2Manifest('Missing history entry #%s' % blob_index)

      v1_layer_parent_id = v1_layer_id
      blob_layer = None if history_entry.is_empty else self.layers[blob_index]
      blob_digest = EMPTY_BLOB_DIGEST if blob_layer is None else str(blob_layer.digest)
      compressed_size = 0 if blob_layer is None else blob_layer.compressed_size

      # Create a new synthesized V1 ID for the history layer by hashing its content and
      # the blob associated withn it.
      digest_history.update(json.dumps(history_entry.raw_entry))
      digest_history.update("|")
      digest_history.update(str(history_index))
      digest_history.update("|")
      digest_history.update(blob_digest)
      digest_history.update("||")

      v1_layer_id = digest_history.hexdigest()
      yield ManifestImageLayer(history=history_entry,
                               blob_layer=blob_layer,
                               blob_digest=blob_digest,
                               v1_id=v1_layer_id,
                               v1_parent_id=v1_layer_parent_id,
                               compressed_size=compressed_size)

      if not history_entry.is_empty:
        blob_index += 1

  @property
  def has_legacy_image(self):
    return not self.has_remote_layer

  def generate_legacy_layers(self, images_map, content_retriever):
    assert not self.has_remote_layer

    # NOTE: We use the DockerSchema1ManifestBuilder here because it already contains
    # the logic for generating the DockerV1Metadata. All of this will go away once we get
    # rid of legacy images in the database, so this is a temporary solution.
    v1_builder = DockerSchema1ManifestBuilder('', '', '')
    self._populate_schema1_builder(v1_builder, content_retriever)
    return v1_builder.build().generate_legacy_layers(images_map, content_retriever)

  def get_leaf_layer_v1_image_id(self, content_retriever):
    # NOTE: If there exists a layer with remote content, then we consider this manifest
    # to not support legacy images.
    if self.has_remote_layer:
      return None

    return list(self._manifest_image_layers(content_retriever))[-1].v1_id

  def get_legacy_image_ids(self, content_retriever):
    if self.has_remote_layer:
      return None

    return [l.v1_id for l in self._manifest_image_layers(content_retriever)]

  def get_schema1_manifest(self, namespace_name, repo_name, tag_name, content_retriever):
    if self.has_remote_layer:
      return None

    v1_builder = DockerSchema1ManifestBuilder(namespace_name, repo_name, tag_name)
    self._populate_schema1_builder(v1_builder, content_retriever)
    return v1_builder.build()

  def unsigned(self):
    return self

  def _populate_schema1_builder(self, v1_builder, content_retriever):
    """ Populates a DockerSchema1ManifestBuilder with the layers and config from
        this schema.
    """
    assert not self.has_remote_layer
    schema2_config = self._get_built_config(content_retriever)
    layers = list(self._manifest_image_layers(content_retriever, schema2_config))
    for index, layer in enumerate(reversed(layers)): # Schema 1 layers are in reverse order
      v1_compatibility = schema2_config.build_v1_compatibility(layer.history,
                                                               layer.v1_id,
                                                               layer.v1_parent_id,
                                                               index == 0,
                                                               layer.compressed_size)
      v1_builder.add_layer(str(layer.blob_digest), json.dumps(v1_compatibility))

    return v1_builder

  def _get_built_config(self, content_retriever):
    config_bytes = content_retriever.get_blob_bytes_with_digest(self.config.digest)
    if config_bytes is None:
      raise MalformedSchema2Manifest('Could not load config blob for manifest')

    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)

    return DockerSchema2Config(config_bytes)

  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,
                                  compressed_size=layer[DOCKER_SCHEMA2_MANIFEST_SIZE_KEY],
                                  digest=digest,
                                  is_remote=is_remote,
                                  urls=layer.get(DOCKER_SCHEMA2_MANIFEST_URLS_KEY))


class DockerSchema2ManifestBuilder(object):
  """
  A convenient abstraction around creating new DockerSchema2Manifests.
  """
  def __init__(self):
    self.config = None
    self.layers = []

  def set_config(self, schema2_config):
    """ Sets the configuration for the manifest being built. """
    self.set_config_digest(schema2_config.digest, schema2_config.size)

  def set_config_digest(self, config_digest, config_size):
    """ Sets the digest and size of the configuration layer. """
    self.config = DockerV2ManifestConfig(size=config_size, digest=config_digest)

  def add_layer(self, digest, size, urls=None):
    """ Adds a layer to the manifest. """
    self.layers.append(DockerV2ManifestLayer(index=len(self.layers),
                                             digest=digest,
                                             compressed_size=size,
                                             urls=urls,
                                             is_remote=bool(urls)))

  def build(self):
    """ Builds and returns the DockerSchema2Manifest. """
    assert self.layers
    assert self.config

    def _build_layer(layer):
      if layer.urls:
        return {
          DOCKER_SCHEMA2_MANIFEST_MEDIATYPE_KEY: DOCKER_SCHEMA2_REMOTE_LAYER_CONTENT_TYPE,
          DOCKER_SCHEMA2_MANIFEST_SIZE_KEY: layer.compressed_size,
          DOCKER_SCHEMA2_MANIFEST_DIGEST_KEY: str(layer.digest),
          DOCKER_SCHEMA2_MANIFEST_URLS_KEY: layer.urls,
        }

      return {
        DOCKER_SCHEMA2_MANIFEST_MEDIATYPE_KEY: DOCKER_SCHEMA2_LAYER_CONTENT_TYPE,
        DOCKER_SCHEMA2_MANIFEST_SIZE_KEY: layer.compressed_size,
        DOCKER_SCHEMA2_MANIFEST_DIGEST_KEY: str(layer.digest),
      }

    manifest_dict = {
      DOCKER_SCHEMA2_MANIFEST_VERSION_KEY: 2,
      DOCKER_SCHEMA2_MANIFEST_MEDIATYPE_KEY: DOCKER_SCHEMA2_MANIFEST_CONTENT_TYPE,

      # Config
      DOCKER_SCHEMA2_MANIFEST_CONFIG_KEY: {
        DOCKER_SCHEMA2_MANIFEST_MEDIATYPE_KEY: DOCKER_SCHEMA2_CONFIG_CONTENT_TYPE,
        DOCKER_SCHEMA2_MANIFEST_SIZE_KEY: self.config.size,
        DOCKER_SCHEMA2_MANIFEST_DIGEST_KEY: str(self.config.digest),
      },

      # Layers
      DOCKER_SCHEMA2_MANIFEST_LAYERS_KEY: [
        _build_layer(layer) for layer in self.layers
      ],
    }
    return DockerSchema2Manifest(json.dumps(manifest_dict, indent=3))