role_id and topic relations fixes

orm/topic.py

@@ -1,10 +1,19 @@
 from typing import List
 from datetime import datetime
-from sqlalchemy import Column, Integer, String, ForeignKey, DateTime
+from sqlalchemy import Table, Column, Integer, String, ForeignKey, DateTime, UniqueConstraint
 from sqlalchemy.orm import relationship, backref
 from orm import Permission
 from orm.base import Base
 
+
+Connection = Table('topic_connections',
+	Base.metadata,
+    Column('child', String, ForeignKey('topic.slug')),
+    Column('parent', String, ForeignKey('topic.slug')),
+    UniqueConstraint('parent', 'child', name='unique_usage')
+)
+
+
 class Topic(Base):
 	__tablename__ = 'topic'
 
@@ -13,6 +22,7 @@ class Topic(Base):
 	createdAt: str = Column(DateTime, nullable=False, default = datetime.now, comment="Created at")
 	createdBy: str = Column(ForeignKey("user.id"), nullable=False, comment="Author")
 	value: str = Column(String, nullable=False, comment="Value")
-	alters = relationship(lambda: Topic, backref=backref("topic", remote_side=[slug]))
-	alter_id: str = Column(ForeignKey("topic.slug"))
-	# TODO: add all the fields
+	# list of Topics where the current node is the "other party" or "child"
+	parents = relationship(lambda: Topic, secondary=Connection, primaryjoin=slug==Connection.c.parent, secondaryjoin=slug==Connection.c.child, viewonly=True)
+	# list of Topics where the current node is the "parent" 
+	children = relationship(lambda: Topic, secondary=Connection, primaryjoin=slug==Connection.c.child, secondaryjoin=slug==Connection.c.parent)