import json

from cachetools import lru_cache
from jsonschema import validate as validate_schema, ValidationError

from image.docker.schema1 import DOCKER_SCHEMA1_MANIFEST_CONTENT_TYPE
from image.docker.schema1 import DockerSchema1Manifest
from image.docker.schema2 import (DOCKER_SCHEMA2_MANIFESTLIST_CONTENT_TYPE,
                                  DOCKER_SCHEMA2_MANIFEST_CONTENT_TYPE)
from image.docker.schema2.manifest import DockerSchema2Manifest

# Keys.
DOCKER_SCHEMA2_MANIFESTLIST_VERSION_KEY = 'schemaVersion'
DOCKER_SCHEMA2_MANIFESTLIST_MEDIATYPE_KEY = 'mediaType'
DOCKER_SCHEMA2_MANIFESTLIST_SIZE_KEY = 'size'
DOCKER_SCHEMA2_MANIFESTLIST_DIGEST_KEY = 'digest'
DOCKER_SCHEMA2_MANIFESTLIST_MANIFESTS_KEY = 'manifests'
DOCKER_SCHEMA2_MANIFESTLIST_PLATFORM_KEY = 'platform'
DOCKER_SCHEMA2_MANIFESTLIST_ARCHITECTURE_KEY = 'architecture'
DOCKER_SCHEMA2_MANIFESTLIST_OS_KEY = 'os'
DOCKER_SCHEMA2_MANIFESTLIST_OS_VERSION_KEY = 'os.version'
DOCKER_SCHEMA2_MANIFESTLIST_OS_FEATURES_KEY = 'os.features'
DOCKER_SCHEMA2_MANIFESTLIST_FEATURES_KEY = 'features'
DOCKER_SCHEMA2_MANIFESTLIST_VARIANT_KEY = 'variant'


class MalformedSchema2ManifestList(Exception):
  """
  Raised when a manifest list fails an assertion that should be true according to the
  Docker Manifest v2.2 Specification.
  """
  pass


class LazyManifestLoader(object):
  def __init__(self, manifest_data, lookup_manifest_fn):
    self._manifest_data = manifest_data
    self._lookup_manifest_fn = lookup_manifest_fn
    self._loaded_manifest = None

  @property
  def manifest_obj(self):
    if self._loaded_manifest is not None:
      return self._loaded_manifest

    self._loaded_manifest = self._load_manifest()
    return self._loaded_manifest

  def _load_manifest(self):
    digest = self._manifest_data[DOCKER_SCHEMA2_MANIFESTLIST_DIGEST_KEY]
    size = self._manifest_data[DOCKER_SCHEMA2_MANIFESTLIST_SIZE_KEY]
    manifest_bytes = self._lookup_manifest_fn(digest)
    if len(manifest_bytes) != size:
      raise MalformedSchema2ManifestList('Size of manifest does not match that retrieved: %s vs %s',
                                         len(manifest_bytes), size)

    content_type = self._manifest_data[DOCKER_SCHEMA2_MANIFESTLIST_MEDIATYPE_KEY]
    if content_type == DOCKER_SCHEMA2_MANIFEST_CONTENT_TYPE:
      return DockerSchema2Manifest(manifest_bytes)

    if content_type == DOCKER_SCHEMA1_MANIFEST_CONTENT_TYPE:
      return DockerSchema1Manifest(manifest_bytes, validate=False)

    raise MalformedSchema2ManifestList('Unknown manifest content type')


class DockerSchema2ManifestList(object):
  METASCHEMA = {
    'type': 'object',
    'properties': {
      DOCKER_SCHEMA2_MANIFESTLIST_VERSION_KEY: {
        'type': 'number',
        'description': 'The version of the manifest list. Must always be `2`.',
        'minimum': 2,
        'maximum': 2,
      },
      DOCKER_SCHEMA2_MANIFESTLIST_MEDIATYPE_KEY: {
        'type': 'string',
        'description': 'The media type of the manifest list.',
        'enum': [DOCKER_SCHEMA2_MANIFESTLIST_CONTENT_TYPE],
      },
      DOCKER_SCHEMA2_MANIFESTLIST_MANIFESTS_KEY: {
        'type': 'array',
        'description': 'The manifests field contains a list of manifests for specific platforms',
        'items': {
          'type': 'object',
          'properties': {
            DOCKER_SCHEMA2_MANIFESTLIST_MEDIATYPE_KEY: {
              'type': 'string',
              'description': 'The MIME type of the referenced object. This will generally be ' +
                             'application/vnd.docker.distribution.manifest.v2+json, but it ' +
                             'could also be application/vnd.docker.distribution.manifest.v1+json ' +
                             'if the manifest list references a legacy schema-1 manifest.',
              'enum': [DOCKER_SCHEMA2_MANIFEST_CONTENT_TYPE, DOCKER_SCHEMA1_MANIFEST_CONTENT_TYPE],
            },
            DOCKER_SCHEMA2_MANIFESTLIST_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_MANIFESTLIST_DIGEST_KEY: {
              'type': 'string',
              'description': 'The content addressable digest of the manifest in the blob store',
            },
            DOCKER_SCHEMA2_MANIFESTLIST_PLATFORM_KEY: {
              'type': 'object',
              'description': 'The platform object describes the platform which the image in ' +
                             'the manifest runs on',
              'properties': {
                DOCKER_SCHEMA2_MANIFESTLIST_ARCHITECTURE_KEY: {
                  'type': 'string',
                  'description': 'Specifies the CPU architecture, for example amd64 or ppc64le.',
                },
                DOCKER_SCHEMA2_MANIFESTLIST_OS_KEY: {
                  'type': 'string',
                  'description': 'Specifies the operating system, for example linux or windows',
                },
                DOCKER_SCHEMA2_MANIFESTLIST_OS_VERSION_KEY: {
                  'type': 'string',
                  'description': 'Specifies the operating system version, for example 10.0.10586',
                },
                DOCKER_SCHEMA2_MANIFESTLIST_OS_FEATURES_KEY: {
                  'type': 'array',
                  'description': 'specifies an array of strings, each listing a required OS ' +
                                 'feature (for example on Windows win32k)',
                  'items': {
                    'type': 'string',
                  },
                },
                DOCKER_SCHEMA2_MANIFESTLIST_VARIANT_KEY: {
                  'type': 'string',
                  'description': 'Specifies a variant of the CPU, for example armv6l to specify ' +
                                 'a particular CPU variant of the ARM CPU',
                },
                DOCKER_SCHEMA2_MANIFESTLIST_FEATURES_KEY: {
                  'type': 'array',
                  'description': 'specifies an array of strings, each listing a required CPU ' +
                                 'feature (for example sse4 or aes).',
                  'items': {
                    'type': 'string',
                  },
                },
              },
              'required': [DOCKER_SCHEMA2_MANIFESTLIST_ARCHITECTURE_KEY,
                           DOCKER_SCHEMA2_MANIFESTLIST_OS_KEY],
            },
          },
          'required': [DOCKER_SCHEMA2_MANIFESTLIST_MEDIATYPE_KEY,
                       DOCKER_SCHEMA2_MANIFESTLIST_SIZE_KEY,
                       DOCKER_SCHEMA2_MANIFESTLIST_DIGEST_KEY,
                       DOCKER_SCHEMA2_MANIFESTLIST_PLATFORM_KEY],
        },
      },
    },
    'required': [DOCKER_SCHEMA2_MANIFESTLIST_VERSION_KEY,
                 DOCKER_SCHEMA2_MANIFESTLIST_MEDIATYPE_KEY,
                 DOCKER_SCHEMA2_MANIFESTLIST_MANIFESTS_KEY],
  }

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

    try:
      self._parsed = json.loads(manifest_bytes)
    except ValueError as ve:
      raise MalformedSchema2ManifestList('malformed manifest data: %s' % ve)

    try:
      validate_schema(self._parsed, DockerSchema2ManifestList.METASCHEMA)
    except ValidationError as ve:
      raise MalformedSchema2ManifestList('manifest data does not match schema: %s' % ve)

  @lru_cache(maxsize=1)
  def manifests(self, lookup_manifest_fn):
    """ Returns the manifests in the list. The `lookup_manifest_fn` is a function
        that returns the manifest bytes for the specified digest.
    """
    manifests = self._parsed[DOCKER_SCHEMA2_MANIFESTLIST_MANIFESTS_KEY]
    return [LazyManifestLoader(m, lookup_manifest_fn) for m in manifests]

  def get_v1_compatible_manifest(self, lookup_manifest_fn):
    """ Returns the manifest that is compatible with V1, by virtue of being `amd64` and `linux`.
        If none, returns None.
    """
    for manifest in self.manifests(lookup_manifest_fn):
      platform = manifest._manifest_data[DOCKER_SCHEMA2_MANIFESTLIST_PLATFORM_KEY]
      architecture = platform[DOCKER_SCHEMA2_MANIFESTLIST_ARCHITECTURE_KEY]
      os = platform[DOCKER_SCHEMA2_MANIFESTLIST_OS_KEY]
      if architecture == 'amd64' and os == 'linux':
        return manifest

    return None