# Source code for rdflib.util

    """
    Some utility functions.

    Miscellaneous utilities

    * list2set
    * first
    * uniq
    * more_than

    Term characterisation and generation

    * to_term
    * from_n3

    Date/time utilities

    * date_time
    * parse_date_time

    Statement and component type checkers

    * check_context
    * check_subject
    * check_predicate
    * check_object
    * check_statement
    * check_pattern

    """

    from calendar import timegm
    from time import altzone
    # from time import daylight
    from time import gmtime
    from time import localtime
    from time import time
    from time import timezone

    from os.path import splitext
    from io import StringIO

    from rdflib.exceptions import ContextTypeError
    from rdflib.exceptions import ObjectTypeError
    from rdflib.exceptions import PredicateTypeError
    from rdflib.exceptions import SubjectTypeError
    from rdflib.graph import Graph
    from rdflib.graph import QuotedGraph
    from rdflib.namespace import Namespace
    from rdflib.namespace import NamespaceManager
    from rdflib.term import BNode
    from rdflib.term import Literal
    from rdflib.term import URIRef
    from rdflib.py3compat import sign

    __all__ = [
        'list2set', 'first', 'uniq', 'more_than', 'to_term', 'from_n3',
        'date_time', 'parse_date_time', 'check_context', 'check_subject',
        'check_predicate', 'check_object', 'check_statement', 'check_pattern',
        'guess_format', 'find_roots', 'get_tree']

    def list2set(seq):
        """
        Return a new list without duplicates.
        Preserves the order, unlike set(seq)
        """
        seen = set()
        return [x for x in seq if x not in seen and not seen.add(x)]

    def first(seq):
        """
        return the first element in a python sequence
        for graphs, use graph.value instead
        """
        for result in seq:
            return result
        return None

    def uniq(sequence, strip=0):
        """removes duplicate strings from the sequence."""
        if strip:
            return set(s.strip() for s in sequence)
        else:
            return set(sequence)

    def more_than(sequence, number):
        "Returns 1 if sequence has more items than number and 0 if not."
        i = 0
        for item in sequence:
            i += 1
            if i > number:
                return 1
        return 0

    def to_term(s, default=None):
        """
        Creates and returns an Identifier of type corresponding
        to the pattern of the given positional argument string ``s``:

        '' returns the ``default`` keyword argument value or ``None``

        '<s>' returns ``URIRef(s)`` (i.e. without angle brackets)

        '"s"' returns ``Literal(s)`` (i.e. without doublequotes)

        '_s' returns ``BNode(s)`` (i.e. without leading underscore)

        """
        if not s:
            return default
        elif s.startswith("<") and s.endswith(">"):
            return URIRef(s[1:-1])
        elif s.startswith('"') and s.endswith('"'):
            return Literal(s[1:-1])
        elif s.startswith("_"):
            return BNode(s)
        else:
            msg = "Unrecognised term syntax: '%s'" % s
            raise Exception(msg)

    def from_n3(s, default=None, backend=None, nsm=None):
        r'''
        Creates the Identifier corresponding to the given n3 string.

            >>> from_n3('<http://ex.com/foo>') == URIRef('http://ex.com/foo')
            True
            >>> from_n3('"foo"@de') == Literal('foo', lang='de')
            True
            >>> from_n3('"""multi\nline\nstring"""@en') == Literal(
            ...     'multi\nline\nstring', lang='en')
            True
            >>> from_n3('42') == Literal(42)
            True
            >>> from_n3(Literal(42).n3()) == Literal(42)
            True
            >>> from_n3('"42"^^xsd:integer') == Literal(42)
            True
            >>> from rdflib import RDFS
            >>> from_n3('rdfs:label') == RDFS['label']
            True
            >>> nsm = NamespaceManager(Graph())
            >>> nsm.bind('dbpedia', 'http://dbpedia.org/resource/')
            >>> berlin = URIRef('http://dbpedia.org/resource/Berlin')
            >>> from_n3('dbpedia:Berlin', nsm=nsm) == berlin
            True

        '''
        if not s:
            return default
        if s.startswith('<'):
            return URIRef(s[1:-1])
        elif s.startswith('"'):
            if s.startswith('"""'):
                quotes = '"""'
            else:
                quotes = '"'
            value, rest = s.rsplit(quotes, 1)
            value = value[len(quotes):]  # strip leading quotes
            datatype = None
            language = None

            # as a given datatype overrules lang-tag check for it first
            dtoffset = rest.rfind('^^')
            if dtoffset >= 0:
                # found a datatype
                # datatype has to come after lang-tag so ignore everything before
                # see: http://www.w3.org/TR/2011/WD-turtle-20110809/
                # #prod-turtle2-RDFLiteral
                datatype = from_n3(rest[dtoffset + 2:], default, backend, nsm)
            else:
                if rest.startswith("@"):
                    language = rest[1:]  # strip leading at sign

            value = value.replace(r'\"', '"')
            # Hack: this should correctly handle strings with either native unicode
            # characters, or \u1234 unicode escapes.
            value = value.encode("raw-unicode-escape").decode("unicode-escape")
            return Literal(value, language, datatype)
        elif s == 'true' or s == 'false':
            return Literal(s == 'true')
        elif s.isdigit():
            return Literal(int(s))
        elif s.startswith('{'):
            identifier = from_n3(s[1:-1])
            return QuotedGraph(backend, identifier)
        elif s.startswith('['):
            identifier = from_n3(s[1:-1])
            return Graph(backend, identifier)
        elif s.startswith("_:"):
            return BNode(s[2:])
        elif ':' in s:
            if nsm is None:
                # instantiate default NamespaceManager and rely on its defaults
                nsm = NamespaceManager(Graph())
            prefix, last_part = s.split(':', 1)
            ns = dict(nsm.namespaces())[prefix]
            return Namespace(ns)[last_part]
        else:
            return BNode(s)

    def check_context(c):
        if not (isinstance(c, URIRef) or
                isinstance(c, BNode)):
            raise ContextTypeError("%s:%s" % (c, type(c)))

    def check_subject(s):
        """ Test that s is a valid subject identifier."""
        if not (isinstance(s, URIRef) or isinstance(s, BNode)):
            raise SubjectTypeError(s)

    def check_predicate(p):
        """ Test that p is a valid predicate identifier."""
        if not isinstance(p, URIRef):
            raise PredicateTypeError(p)

    def check_object(o):
        """ Test that o is a valid object identifier."""
        if not (isinstance(o, URIRef) or
                isinstance(o, Literal) or
                isinstance(o, BNode)):
            raise ObjectTypeError(o)

    def check_statement(triple):
        (s, p, o) = triple
        if not (isinstance(s, URIRef) or isinstance(s, BNode)):
            raise SubjectTypeError(s)

        if not isinstance(p, URIRef):
            raise PredicateTypeError(p)

        if not (isinstance(o, URIRef) or
                isinstance(o, Literal) or
                isinstance(o, BNode)):
            raise ObjectTypeError(o)

    def check_pattern(triple):
        (s, p, o) = triple
        if s and not (isinstance(s, URIRef) or isinstance(s, BNode)):
            raise SubjectTypeError(s)

        if p and not isinstance(p, URIRef):
            raise PredicateTypeError(p)

        if o and not (isinstance(o, URIRef) or
                      isinstance(o, Literal) or
                      isinstance(o, BNode)):
            raise ObjectTypeError(o)

    def date_time(t=None, local_time_zone=False):
        """http://www.w3.org/TR/NOTE-datetime ex: 1997-07-16T19:20:30Z

        >>> date_time(1126482850)
        '2005-09-11T23:54:10Z'

        @@ this will change depending on where it is run
        #>>> date_time(1126482850, local_time_zone=True)
        #'2005-09-11T19:54:10-04:00'

        >>> date_time(1)
        '1970-01-01T00:00:01Z'

        >>> date_time(0)
        '1970-01-01T00:00:00Z'
        """
        if t is None:
            t = time()

        if local_time_zone:
            time_tuple = localtime(t)
            if time_tuple[8]:
                tz_mins = altzone // 60
            else:
                tz_mins = timezone // 60
            tzd = "-%02d:%02d" % (tz_mins // 60, tz_mins % 60)
        else:
            time_tuple = gmtime(t)
            tzd = "Z"

        year, month, day, hh, mm, ss, wd, y, z = time_tuple
        s = "%0004d-%02d-%02dT%02d:%02d:%02d%s" % (
            year, month, day, hh, mm, ss, tzd)
        return s

    def parse_date_time(val):
        """always returns seconds in UTC

        # tests are written like this to make any errors easier to understand
        >>> parse_date_time('2005-09-11T23:54:10Z') - 1126482850.0
        0.0

        >>> parse_date_time('2005-09-11T16:54:10-07:00') - 1126482850.0
        0.0

        >>> parse_date_time('1970-01-01T00:00:01Z') - 1.0
        0.0

        >>> parse_date_time('1970-01-01T00:00:00Z') - 0.0
        0.0
        >>> parse_date_time("2005-09-05T10:42:00") - 1125916920.0
        0.0
        """

        if "T" not in val:
            val += "T00:00:00Z"

        ymd, time = val.split("T")
        hms, tz_str = time[0:8], time[8:]

        if not tz_str or tz_str == "Z":
            time = time[:-1]
            tz_offset = 0
        else:
            signed_hrs = int(tz_str[:3])
            mins = int(tz_str[4:6])
            secs = (sign(signed_hrs) * mins + signed_hrs * 60) * 60
            tz_offset = -secs

        year, month, day = ymd.split("-")
        hour, minute, second = hms.split(":")

        t = timegm((int(year), int(month), int(day), int(hour),
                    int(minute), int(second), 0, 0, 0))
        t = t + tz_offset
        return t

    SUFFIX_FORMAT_MAP = {
        'rdf': 'xml',
        'rdfs': 'xml',
        'owl': 'xml',
        'n3': 'n3',
        'ttl': 'turtle',
        'nt': 'nt',
        'trix': 'trix',
        'xhtml': 'rdfa',
        'html': 'rdfa',
        'svg': 'rdfa',
        'nq': 'nquads',
        'trig': 'trig'
    }

    def guess_format(fpath, fmap=None):
        """
        Guess RDF serialization based on file suffix. Uses
        ``SUFFIX_FORMAT_MAP`` unless ``fmap`` is provided. Examples:

            >>> guess_format('path/to/file.rdf')
            'xml'
            >>> guess_format('path/to/file.owl')
            'xml'
            >>> guess_format('path/to/file.ttl')
            'turtle'
            >>> guess_format('path/to/file.xhtml')
            'rdfa'
            >>> guess_format('path/to/file.svg')
            'rdfa'
            >>> guess_format('path/to/file.xhtml', {'xhtml': 'grddl'})
            'grddl'

        This also works with just the suffixes, with or without leading dot, and
        regardless of letter case::

            >>> guess_format('.rdf')
            'xml'
            >>> guess_format('rdf')
            'xml'
            >>> guess_format('RDF')
            'xml'
        """
        fmap = fmap or SUFFIX_FORMAT_MAP
        return fmap.get(_get_ext(fpath)) or fmap.get(fpath.lower())

    def _get_ext(fpath, lower=True):
        """
        Gets the file extension from a file(path); stripped of leading '.' and in
        lower case. Examples:

            >>> _get_ext("path/to/file.txt")
            'txt'
            >>> _get_ext("OTHER.PDF")
            'pdf'
            >>> _get_ext("noext")
            ''
            >>> _get_ext(".rdf")
            'rdf'
        """
        ext = splitext(fpath)[-1]
        if ext == '' and fpath.startswith("."):
            ext = fpath
        if lower:
            ext = ext.lower()
        if ext.startswith('.'):
            ext = ext[1:]
        return ext

    def find_roots(graph, prop, roots=None):
        """
        Find the roots in some sort of transitive hierarchy.

        find_roots(graph, rdflib.RDFS.subClassOf)
        will return a set of all roots of the sub-class hierarchy

        Assumes triple of the form (child, prop, parent), i.e. the direction of
        RDFS.subClassOf or SKOS.broader

        """

        non_roots = set()
        if roots is None:
            roots = set()
        for x, y in graph.subject_objects(prop):
            non_roots.add(x)
            if x in roots:
                roots.remove(x)
            if y not in non_roots:
                roots.add(y)
        return roots

    def get_tree(graph,
                 root,
                 prop,
                 mapper=lambda x: x,
                 sortkey=None,
                 done=None,
                 dir='down'):
        """
        Return a nested list/tuple structure representing the tree
        built by the transitive property given, starting from the root given

        i.e.

        get_tree(graph,
           rdflib.URIRef("http://xmlns.com/foaf/0.1/Person"),
           rdflib.RDFS.subClassOf)

        will return the structure for the subClassTree below person.

        dir='down' assumes triple of the form (child, prop, parent),
        i.e. the direction of RDFS.subClassOf or SKOS.broader
        Any other dir traverses in the other direction

        """

        if done is None:
            done = set()
        if root in done:
            return
        done.add(root)
        tree = []

        if dir == 'down':
            branches = graph.subjects(prop, root)
        else:
            branches = graph.objects(root, prop)

        for branch in branches:
            t = get_tree(graph, branch, prop, mapper, sortkey, done, dir)
            if t:
                tree.append(t)

        return (mapper(root), sorted(tree, key=sortkey))

    def test():
        import doctest
        doctest.testmod()

    if __name__ == "__main__":
        # try to make the tests work outside of the time zone they were written in
        # import os, time
        # os.environ['TZ'] = 'US/Pacific'
        # try:
        #    time.tzset()
        # except AttributeError, e:
        #    print e
            # pass
            # tzset missing! see
            # http://mail.python.org/pipermail/python-dev/2003-April/034480.html
        test()  # pragma: no cover