# Source code for asdf.util

    import enum
    import inspect
    import math
    import struct
    import types
    import importlib.util
    import re
    from functools import lru_cache

    from urllib.request import pathname2url

    import numpy as np

    from . import constants

    # We're importing our own copy of urllib.parse because
    # we need to patch it to support asdf:// URIs, but it'd
    # be irresponsible to do this for all users of a
    # standard library.
    urllib_parse_spec = importlib.util.find_spec('urllib.parse')
    patched_urllib_parse = importlib.util.module_from_spec(urllib_parse_spec)
    urllib_parse_spec.loader.exec_module(patched_urllib_parse)
    del urllib_parse_spec

    # urllib.parse needs to know that it should treat asdf://
    # URIs like http:// URIs for the purposes of joining
    # a relative path to a base URI.
    patched_urllib_parse.uses_relative.append('asdf')
    patched_urllib_parse.uses_netloc.append('asdf')

    __all__ = ['human_list', 'get_array_base', 'get_base_uri', 'filepath_to_url',
               'iter_subclasses', 'calculate_padding', 'resolve_name', 'NotSet',
               'is_primitive', 'uri_match', 'get_class_name']

    def human_list(l, separator="and"):
        """
        Formats a list for human readability.

        Parameters
        ----------
        l : sequence
            A sequence of strings

        separator : string, optional
            The word to use between the last two entries.  Default:
            ``"and"``.

        Returns
        -------
        formatted_list : string

        Examples
        --------
        >>> human_list(["vanilla", "strawberry", "chocolate"], "or")
        'vanilla, strawberry or chocolate'
        """
        if len(l) == 1:
            return l[0]
        else:
            return ', '.join(l[:-1]) + ' ' + separator + ' ' + l[-1]

    def get_array_base(arr):
        """
        For a given Numpy array, finds the base array that "owns" the
        actual data.
        """
        base = arr
        while isinstance(base.base, np.ndarray):
            base = base.base
        return base

    def get_base_uri(uri):
        """
        For a given URI, return the part without any fragment.
        """
        parts = patched_urllib_parse.urlparse(uri)
        return patched_urllib_parse.urlunparse(list(parts[:5]) + [''])

    def filepath_to_url(path):
        """
        For a given local file path, return a file:// url.
        """
        return patched_urllib_parse.urljoin('file:', pathname2url(path))

    def iter_subclasses(cls):
        """
        Returns all subclasses of a class.
        """
        for x in cls.__subclasses__():
            yield x
            for y in iter_subclasses(x):
                yield y

    def calculate_padding(content_size, pad_blocks, block_size):
        """
        Calculates the amount of extra space to add to a block given the
        user's request for the amount of extra space.  Care is given so
        that the total of size of the block with padding is evenly
        divisible by block size.

        Parameters
        ----------
        content_size : int
            The size of the actual content

        pad_blocks : float or bool
            If `False`, add no padding (always return 0).  If `True`, add
            a default amount of padding of 10% If a float, it is a factor
            to multiple content_size by to get the new total size.

        block_size : int
            The filesystem block size to use.

        Returns
        -------
        nbytes : int
            The number of extra bytes to add for padding.
        """
        if not pad_blocks:
            return 0
        if pad_blocks is True:
            pad_blocks = 1.1
        new_size = content_size * pad_blocks
        new_size = int((math.ceil(
            float(new_size) / block_size) + 1) * block_size)
        return max(new_size - content_size, 0)

    class BinaryStruct:
        """
        A wrapper around the Python stdlib struct module to define a
        binary struct more like a dictionary than a tuple.
        """
        def __init__(self, descr, endian='>'):
            """
            Parameters
            ----------
            descr : list of tuple
                Each entry is a pair ``(name, format)``, where ``format``
                is one of the format types understood by `struct`.

            endian : str, optional
                The endianness of the struct.  Must be ``>`` or ``<``.
            """
            self._fmt = [endian]
            self._offsets = {}
            self._names = []
            i = 0
            for name, fmt in descr:
                self._fmt.append(fmt)
                self._offsets[name] = (i, (endian + fmt).encode('ascii'))
                self._names.append(name)
                i += struct.calcsize(fmt.encode('ascii'))
            self._fmt = ''.join(self._fmt).encode('ascii')
            self._size = struct.calcsize(self._fmt)

        @property
        def size(self):
            """
            Return the size of the struct.
            """
            return self._size

        def pack(self, **kwargs):
            """
            Pack the given arguments, which are given as kwargs, and
            return the binary struct.
            """
            fields = [0] * len(self._names)
            for key, val in kwargs.items():
                if key not in self._offsets:
                    raise KeyError("No header field '{0}'".format(key))
                i = self._names.index(key)
                fields[i] = val
            return struct.pack(self._fmt, *fields)

        def unpack(self, buff):
            """
            Unpack the given binary buffer into the fields.  The result
            is a dictionary mapping field names to values.
            """
            args = struct.unpack_from(self._fmt, buff[:self._size])
            return dict(zip(self._names, args))

        def update(self, fd, **kwargs):
            """
            Update part of the struct in-place.

            Parameters
            ----------
            fd : generic_io.GenericIO instance
                A writable, seekable file descriptor, currently seeked
                to the beginning of the struct.

            **kwargs : values
                The values to update on the struct.
            """
            updates = []
            for key, val in kwargs.items():
                if key not in self._offsets:
                    raise KeyError("No header field '{0}'".format(key))
                updates.append((self._offsets[key], val))
            updates.sort()

            start = fd.tell()
            for ((offset, datatype), val) in updates:
                fd.seek(start + offset)
                fd.write(struct.pack(datatype, val))

    class HashableDict(dict):
        """
        A simple wrapper around dict to make it hashable.

        This is sure to be slow, but for small dictionaries it shouldn't
        matter.
        """
        def __hash__(self):
            return hash(frozenset(self.items()))

    def resolve_name(name):
        """Resolve a name like ``module.object`` to an object and return it.

        This ends up working like ``from module import object`` but is easier
        to deal with than the `__import__` builtin and supports digging into
        submodules.

        Parameters
        ----------

        name : `str`
            A dotted path to a Python object--that is, the name of a function,
            class, or other object in a module with the full path to that module,
            including parent modules, separated by dots.  Also known as the fully
            qualified name of the object.

        Examples
        --------

        >>> resolve_name('asdf.util.resolve_name')
        <function resolve_name at 0x...>

        Raises
        ------
        `ImportError`
            If the module or named object is not found.
        """

        # Note: On python 2 these must be str objects and not unicode
        parts = [str(part) for part in name.split('.')]

        if len(parts) == 1:
            # No dots in the name--just a straight up module import
            cursor = 1
            attr_name = str('')  # Must not be unicode on Python 2
        else:
            cursor = len(parts) - 1
            attr_name = parts[-1]

        module_name = parts[:cursor]

        while cursor > 0:
            try:
                ret = __import__(str('.'.join(module_name)), fromlist=[attr_name])
                break
            except ImportError:
                if cursor == 0:
                    raise
                cursor -= 1
                module_name = parts[:cursor]
                attr_name = parts[cursor]
                ret = ''

        for part in parts[cursor:]:
            try:
                ret = getattr(ret, part)
            except AttributeError:
                raise ImportError(name)

        return ret

    # Kludge to cover up the fact that BuiltinExtension was moved from extension.py
    # to extension/_legacy.py.  Can be removed once BuiltinExtension is dropped
    # in asdf 3.0.
    _CLASS_NAME_OVERRIDES = {
        "asdf.extension._legacy.BuiltinExtension": "asdf.extension.BuiltinExtension",
    }

    def get_class_name(obj, instance=True):
        """
        Given a class or instance of a class, returns a string representing the
        fully specified path of the class.

        Parameters
        ----------

        obj : object
            An instance of any object
        instance: bool
            Indicates whether given object is an instance of the class to be named
        """
        typ = type(obj) if instance else obj
        class_name = "{}.{}".format(typ.__module__, typ.__qualname__)
        return _CLASS_NAME_OVERRIDES.get(class_name, class_name)

    def minversion(module, version, inclusive=True, version_path='__version__'):
        """
        Returns `True` if the specified Python module satisfies a minimum version
        requirement, and `False` if not.

        By default this uses `pkg_resources.parse_version` to do the version
        comparison if available.  Otherwise it falls back on
        `packaging.version.Version`.

        Parameters
        ----------

        module : module or `str`
            An imported module of which to check the version, or the name of
            that module (in which case an import of that module is attempted--
            if this fails `False` is returned).

        version : `str`
            The version as a string that this module must have at a minimum (e.g.
            ``'0.12'``).

        inclusive : `bool`
            The specified version meets the requirement inclusively (i.e. ``>=``)
            as opposed to strictly greater than (default: `True`).

        version_path : `str`
            A dotted attribute path to follow in the module for the version.
            Defaults to just ``'__version__'``, which should work for most Python
            modules.
        """

        if isinstance(module, types.ModuleType):
            module_name = module.__name__
        elif isinstance(module, str):
            module_name = module
            try:
                module = resolve_name(module_name)
            except ImportError:
                return False
        else:
            raise ValueError('module argument must be an actual imported '
                             'module, or the import name of the module; '
                             'got {0!r}'.format(module))

        if '.' not in version_path:
            have_version = getattr(module, version_path)
        else:
            have_version = resolve_name('.'.join([module.__name__, version_path]))

        try:
            from pkg_resources import parse_version
        except ImportError:
            from packaging.version import Version as parse_version

        if inclusive:
            return parse_version(have_version) >= parse_version(version)
        else:
            return parse_version(have_version) > parse_version(version)

    class InheritDocstrings(type):
        """
        This metaclass makes methods of a class automatically have their
        docstrings filled in from the methods they override in the base
        class.

        If the class uses multiple inheritance, the docstring will be
        chosen from the first class in the bases list, in the same way as
        methods are normally resolved in Python.  If this results in
        selecting the wrong docstring, the docstring will need to be
        explicitly included on the method.

        For example::

            >>> from asdf.util import InheritDocstrings
            >>> class A(metaclass=InheritDocstrings):
            ...     def wiggle(self):
            ...         "Wiggle the thingamajig"
            ...         pass
            >>> class B(A):
            ...     def wiggle(self):
            ...         pass
            >>> B.wiggle.__doc__
            u'Wiggle the thingamajig'
        """

        def __init__(cls, name, bases, dct):
            def is_public_member(key):
                return (
                    (key.startswith('__') and key.endswith('__')
                     and len(key) > 4) or
                    not key.startswith('_'))

            for key, val in dct.items():
                if (inspect.isfunction(val) and
                    is_public_member(key) and
                    val.__doc__ is None):
                    for base in cls.__mro__[1:]:
                        super_method = getattr(base, key, None)
                        if super_method is not None:
                            val.__doc__ = super_method.__doc__
                            break

            super(InheritDocstrings, cls).__init__(name, bases, dct)

    class _NotSetType:
        def __repr__(self):
            return "NotSet"

    """
    Special value indicating that a parameter is not set.  Distinct
    from None, which may for example be a value of interest in a search.
    """
    NotSet = _NotSetType()

    def is_primitive(value):
        """
        Determine if a value is an instance of a "primitive" type.

        Parameters
        ----------
        value : object
            the value to test

        Returns
        -------
        bool
            True if the value is primitive, False otherwise
        """
        return (
            value is None
            or isinstance(value, bool)
            or isinstance(value, int)
            or isinstance(value, float)
            or isinstance(value, complex)
            or isinstance(value, str)
        )

    def uri_match(pattern, uri):
        """
        Determine if a URI matches a URI pattern with possible
        wildcards.  The two recognized wildcards:

        "*":  match any character except /

        "**": match any character

        Parameters
        ----------
        pattern : str
            URI pattern.
        uri : str
            URI to check against the pattern.

        Returns
        -------
        bool
            `True` if URI matches the pattern.
        """
        if not isinstance(uri, str):
            return False

        if "*" in pattern:
            return _compile_uri_match_pattern(pattern).fullmatch(uri) is not None
        else:
            return pattern == uri

    @lru_cache(1024)
    def _compile_uri_match_pattern(pattern):
        # Escape the pattern in case it contains regex special characters
        # ('.' in particular is common in URIs) and then replace the
        # escaped asterisks with the appropriate regex matchers.
        pattern = re.escape(pattern)
        pattern = pattern.replace(r"\*\*", r".*")
        pattern = pattern.replace(r"\*", r"[^/]*")
        return re.compile(pattern)

    def get_file_type(fd):
        """
        Determine the file type of an open GenericFile instance.

        Parameters
        ----------
        fd : GenericFile

        Returns
        -------
        FileType
        """
        if fd.peek(5) == constants.ASDF_MAGIC:
            return FileType.ASDF
        elif fd.peek(6) == constants.FITS_MAGIC:
            return FileType.FITS
        else:
            return FileType.UNKNOWN

    class FileType(enum.Enum):
        """
        Enum representing file types recognized by asdf.
        """
        ASDF = 1
        FITS = 2
        UNKNOWN = 3