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# Copyright 2011 GRNET S.A. All rights reserved.

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from sqlalchemy.sql import select, literal

from sqlalchemy.sql.expression import join, union

from xfeatures import XFeatures

from groups import Groups

from public import Public

READ = 0

WRITE = 1

class Permissions(XFeatures, Groups, Public):

    def __init__(self, **params):

        XFeatures.__init__(self, **params)

        Groups.__init__(self, **params)

        Public.__init__(self, **params)

    def access_grant(self, path, access, members=()):

        """Grant members with access to path.

           Members can also be '*' (all),

           or some group specified as 'owner:group'."""

        if not members:

            return

        feature = self.xfeature_create(path)

        if feature is None:

            return

        self.feature_setmany(feature, access, members)

    def access_set(self, path, permissions):

        """Set permissions for path. The permissions dict

           maps 'read', 'write' keys to member lists."""

        self.xfeature_destroy(path)

        self.access_grant(path, READ, permissions.get('read', []))

        self.access_grant(path, WRITE, permissions.get('write', []))

    def access_clear(self, path):

        """Revoke access to path (both permissions and public)."""

        self.xfeature_destroy(path)

        self.public_unset(path)

    def access_check(self, path, access, member):

        """Return true if the member has this access to the path."""

        if access == READ and self.public_check(path):

            return True

        r = self.xfeature_inherit(path)

        if not r:

            return False

        fpath, feature = r

        members = self.feature_get(feature, access)

        if member in members or '*' in members:

            return True

        for owner, group in self.group_parents(member):

            if owner + ':' + group in members:

                return True

        return False

    def access_inherit(self, path):

        """Return the inherited or assigned (path, permissions) pair for path."""

        r = self.xfeature_inherit(path)

        if not r:

            return (path, {})

        fpath, feature = r

        permissions = self.feature_dict(feature)

        if READ in permissions:

            permissions['read'] = permissions[READ]

            del(permissions[READ])

        if WRITE in permissions:

            permissions['write'] = permissions[WRITE]

            del(permissions[WRITE])

        return (fpath, permissions)

    def access_list(self, path):

        """List all permission paths inherited by or inheriting from path."""

        return [x[0] for x in self.xfeature_list(path) if x[0] != path]

    def access_list_paths(self, member, prefix=None):

        """Return the list of paths granted to member."""

        xfeatures_xfeaturevals =  self.xfeatures.join(self.xfeaturevals)

        selectable = (self.groups.c.owner + ':' + self.groups.c.name)

        member_groups = select([selectable.label('value')],

            self.groups.c.member == member)

        members = select([literal(member).label('value')])

        any = select([literal('*').label('value')])

        u = union(member_groups, members, any).alias()

        inner_join = join(xfeatures_xfeaturevals, u,

                    self.xfeaturevals.c.value == u.c.value)

        s = select([self.xfeatures.c.path], from_obj=[inner_join]).distinct()

        if prefix:

            s = s.where(self.xfeatures.c.path.like(prefix + '%'))

        r = self.conn.execute(s)

        l = [row[0] for row in r.fetchall()]

        r.close()

        return l

    def access_list_shared(self, prefix=''):

        """Return the list of shared paths."""

        s = select([self.xfeatures.c.path],

            self.xfeatures.c.path.like(prefix + '%'))

        r = self.conn.execute(s)

        l = [row[0] for row in r.fetchall()]

        r.close()

        return l