# Source code for asdf.extension._legacy

    import abc
    import warnings
    from functools import lru_cache

    from .. import types
    from .. import resolver
    from ..type_index import AsdfTypeIndex
    from ..exceptions import AsdfDeprecationWarning

    class AsdfExtension(metaclass=abc.ABCMeta):
        """
        Abstract base class defining a (legacy) extension to ASDF.
        New code should use `asdf.extension.Extension` instead.
        """
        @classmethod
        def __subclasshook__(cls, C):
            if cls is AsdfExtension:
                return (hasattr(C, 'types') and
                        hasattr(C, 'tag_mapping'))
            return NotImplemented

        @abc.abstractproperty
        def types(self):
            """
            A list of `asdf.CustomType` subclasses that describe how to store
            custom objects to and from ASDF.
            """
            pass

        @abc.abstractproperty
        def tag_mapping(self):
            """
            A list of 2-tuples or callables mapping YAML tag prefixes to JSON Schema
            URL prefixes.

            For each entry:

            - If a 2-tuple, the first part of the tuple is a YAML tag
              prefix to match.  The second part is a string, where case
              the following are available as Python formatting tokens:

              - ``{tag}``: the complete YAML tag.
              - ``{tag_suffix}``: the part of the YAML tag after the
                matched prefix.
              - ``{tag_prefix}``: the matched YAML tag prefix.

            - If a callable, it is passed the entire YAML tag must return
              the entire JSON schema URL if it matches, otherwise, return `None`.

            Note that while JSON Schema URLs uniquely define a JSON
            Schema, they do not have to actually exist on an HTTP server
            and be fetchable (much like XML namespaces).

            For example, to match all YAML tags with the
            ``tag:nowhere.org:custom` prefix to the
            ``http://nowhere.org/schemas/custom/`` URL prefix::

               return [('tag:nowhere.org:custom/',
                        'http://nowhere.org/schemas/custom/{tag_suffix}')]
            """
            pass

        @abc.abstractproperty
        def url_mapping(self):
            """
            Schema content can be provided using the resource Mapping API.

            A list of 2-tuples or callables mapping JSON Schema URLs to
            other URLs.  This is useful if the JSON Schemas are not
            actually fetchable at their corresponding URLs but are on the
            local filesystem, or, to save bandwidth, we have a copy of
            fetchable schemas on the local filesystem.  If neither is
            desirable, it may simply be the empty list.

            For each entry:

            - If a 2-tuple, the first part is a URL prefix to match.  The
              second part is a string, where the following are available
              as Python formatting tokens:

              - ``{url}``: The entire JSON schema URL
              - ``{url_prefix}``: The matched URL prefix
              - ``{url_suffix}``: The part of the URL after the prefix.

            - If a callable, it is passed the entire JSON Schema URL and
              must return a resolvable URL pointing to the schema content.
              If it doesn't match, should return `None`.

            For example, to map a remote HTTP URL prefix to files installed
            alongside as data alongside Python module::

                return [('http://nowhere.org/schemas/custom/1.0.0/',
                        asdf.util.filepath_to_url(
                            os.path.join(SCHEMA_PATH, 'stsci.edu')) +
                        '/{url_suffix}.yaml'
                       )]
            """
            pass

    class AsdfExtensionList:
        """
        Manage a set of extensions that are in effect.
        """
        def __init__(self, extensions):
            from ._extension import ExtensionProxy
            extensions = [ExtensionProxy.maybe_wrap(e) for e in extensions]

            tag_mapping = []
            url_mapping = []
            validators = {}
            self._type_index = AsdfTypeIndex()
            for extension in extensions:
                tag_mapping.extend(extension.tag_mapping)
                url_mapping.extend(extension.url_mapping)
                for typ in extension.types:
                    self._type_index.add_type(typ, extension)
                    validators.update(typ.validators)
                    for sibling in typ.versioned_siblings:
                        self._type_index.add_type(sibling, extension)
                        validators.update(sibling.validators)
            self._extensions = extensions
            self._tag_mapping = resolver.Resolver(tag_mapping, 'tag')
            self._url_mapping = resolver.Resolver(url_mapping, 'url')
            self._resolver = resolver.ResolverChain(self._tag_mapping, self._url_mapping)
            self._validators = validators

        @property
        def tag_to_schema_resolver(self):
            """Deprecated. Use `tag_mapping` instead"""
            warnings.warn(
                "The 'tag_to_schema_resolver' property is deprecated. Use "
                "'tag_mapping' instead.",
                AsdfDeprecationWarning)
            return self._tag_mapping

        @property
        def extensions(self):
            return self._extensions

        @property
        def tag_mapping(self):
            return self._tag_mapping

        @property
        def url_mapping(self):
            return self._url_mapping

        @property
        def resolver(self):
            return self._resolver

        @property
        def type_index(self):
            return self._type_index

        @property
        def validators(self):
            return self._validators

    def get_cached_asdf_extension_list(extensions):
        """
        Get a previously created AsdfExtensionList for the specified
        extensions, or create and cache one if necessary.  Building
        the type index is expensive, so it helps performance to reuse
        the index when possible.

        Parameters
        ----------
        extensions : list of asdf.extension.AsdfExtension

        Returns
        -------
        asdf.extension.AsdfExtensionList
        """
        from ._extension import ExtensionProxy
        # The tuple makes the extensions hashable so that we
        # can pass them to the lru_cache method.  The ExtensionProxy
        # overrides __hash__ to return the hashed object id of the wrapped
        # extension, so this will method will only return the same
        # AsdfExtensionList if the list contains identical extension
        # instances in identical order.
        extensions = tuple(ExtensionProxy.maybe_wrap(e) for e in extensions)

        return _get_cached_asdf_extension_list(extensions)

    @lru_cache()
    def _get_cached_asdf_extension_list(extensions):
        return AsdfExtensionList(extensions)

    # A kludge in asdf.util.get_class_name allows this class to retain
    # its original name, despite being moved from extension.py to
    # this file.
    class BuiltinExtension:
        """
        This is the "extension" to ASDF that includes all the built-in
        tags.  Even though it's not really an extension and it's always
        available, it's built in the same way as an extension.
        """
        @property
        def types(self):
            return types._all_asdftypes

        @property
        def tag_mapping(self):
            return resolver.DEFAULT_TAG_TO_URL_MAPPING

        @property
        def url_mapping(self):
            return resolver.DEFAULT_URL_MAPPING

    class _DefaultExtensions:
        @property
        def extensions(self):
            from ..config import get_config
            return [e for e in get_config().extensions if e.legacy]

        @property
        def extension_list(self):
            return get_cached_asdf_extension_list(self.extensions)

        @property
        def package_metadata(self):
            return {
                e.class_name: (e.package_name, e.package_version)
                for e in self.extensions
                if e.package_name is not None
            }

        def reset(self):
            """This will be used primarily for testing purposes."""
            from ..config import get_config
            get_config().reset_extensions()

        @property
        def resolver(self):
            return self.extension_list.resolver

    default_extensions = _DefaultExtensions()

    def get_default_resolver():
        """
        Get the resolver that includes mappings from all installed extensions.
        """
        return default_extensions.resolver