Helper classes to allow recursive automatic joins in peewee

peewee_extensions.py

class Direct:
    def __init__(self, native_key, foreign_key):
        """
        Represents a direct relationship from one 'native'
        model, to one 'foreign' model
        """
        self.native_key = native_key
        self.foreign_key = foreign_key


class Through:
    def __init__(self, native_key, thru_model, thru_key, foreign_key):
        """
        Represents a many-to-many relationship from one 'native' model
        through a 'thru' model, to one 'foreign' mdel
        """
        self.native_key = native_key
        self.thru_model = thru_model
        self.thru_key = thru_key
        self.foreign_key = foreign_key


class Relationship:
    def __init__(self, how, relation):
        """ 
        Representing either a 'Direct' or 'Through'
        relationship for a 'native' model and a 'foreign' model
        """
        self.how = how
        self.relation = relation


class ModelRelationship:
    def __init__(self, data):
        """
        A container for many 'Direct' and 'Through'
        relationships on a given model
        """
        self.data = data

    def has_thru(self, tablename):
        """ Whether a model has a through table or not """
        rel = self.data.get(tablename) == "through"
        return rel.how == "through" if rel else False

    def thru_for(self, tablename):
        """ Return a through model for a given native model """
        return self.data[tablename].relation.thru_model