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from collections import defaultdict

from dbworker import DBWorker

class XFeatures(DBWorker):

    """XFeatures are path properties that allow non-nested

       inheritance patterns. Currently used for storing permissions.

    """

    def __init__(self, **params):

        DBWorker.__init__(self, **params)

        execute = self.execute

        execute(""" pragma foreign_keys = on """)

        execute(""" create table if not exists xfeatures

                          ( feature_id integer primary key,

                            path       text ) """)

        execute(""" create unique index if not exists idx_features_path

                    on xfeatures(path) """)

        execute(""" create table if not exists xfeaturevals

                          ( feature_id integer,

                            key        integer,

                            value      text,

                            primary key (feature_id, key, value)

                            foreign key (feature_id) references xfeatures(feature_id)

                            on delete cascade ) """)

    def xfeature_inherit(self, path):

        """Return the (path, feature) inherited by the path, or None."""

        q = ("select path, feature_id from xfeatures "

             "where path <= ? "

             "order by path desc limit 1")

        self.execute(q, (path,))

        r = self.fetchone()

        if r is not None and path.startswith(r[0]):

            return r

        return None

    def xfeature_list(self, path):

        """Return the list of the (prefix, feature) pairs matching path.

           A prefix matches path if either the prefix includes the path,

           or the path includes the prefix.

        """

        inherited = self.xfeature_inherit(path)

        if inherited:

            return [inherited]

        q = ("select path, feature_id from xfeatures "

             "where path like ? escape '\\' and path != ? order by path")

        self.execute(q, (self.escape_like(path) + '%', path,))

        return self.fetchall()

    def xfeature_create(self, path):

        """Create and return a feature for path.

           If the path already inherits a feature or

           bestows to paths already inheriting a feature,

           create no feature and return None.

           If the path has a feature, return it.

        """

        prefixes = self.xfeature_list(path)

        pl = len(prefixes)

        if (pl > 1) or (pl == 1 and prefixes[0][0] != path):

            return None

        if pl == 1 and prefixes[0][0] == path:

            return prefixes[0][1]

        q = "insert into xfeatures (path) values (?)"

        id = self.execute(q, (path,)).lastrowid

        return id

    def xfeature_destroy(self, path):

        """Destroy a feature and all its key, value pairs."""

        q = "delete from xfeatures where path = ?"

        self.execute(q, (path,))

    def feature_dict(self, feature):

        """Return a dict mapping keys to list of values for feature."""

        q = "select key, value from xfeaturevals where feature_id = ?"

        self.execute(q, (feature,))

        d = defaultdict(list)

        for key, value in self.fetchall():

            d[key].append(value)

        return d

    def feature_set(self, feature, key, value):

        """Associate a key, value pair with a feature."""

        q = "insert or ignore into xfeaturevals (feature_id, key, value) values (?, ?, ?)"

        self.execute(q, (feature, key, value))

    def feature_setmany(self, feature, key, values):

        """Associate the given key, and values with a feature."""

        q = "insert or ignore into xfeaturevals (feature_id, key, value) values (?, ?, ?)"

        self.executemany(q, ((feature, key, v) for v in values))

    def feature_unset(self, feature, key, value):

        """Disassociate a key, value pair from a feature."""

        q = ("delete from xfeaturevals where "

             "feature_id = ? and key = ? and value = ?")

        self.execute(q, (feature, key, value))

    def feature_unsetmany(self, feature, key, values):

        """Disassociate the key for the values given, from a feature."""

        q = ("delete from xfeaturevals where "

             "feature_id = ? and key = ? and value = ?")

        self.executemany(q, ((feature, key, v) for v in values))

    def feature_get(self, feature, key):

        """Return the list of values for a key of a feature."""

        q = "select value from xfeaturevals where feature_id = ? and key = ?"

        self.execute(q, (feature, key))

        return [r[0] for r in self.fetchall()]

    def feature_clear(self, feature, key):

        """Delete all key, value pairs for a key of a feature."""

        q = "delete from xfeaturevals where feature_id = ? and key = ?"

        self.execute(q, (feature, key))