# routers.py

class ProjectDatabaseRouter:
    """
    A router to control all database operations on models in the
    simpsons and cloudmanager applications.
    """

    def db_for_read(self, model, **hints):
        """Attempts to read simpsons and cloudmanager models go to their specific dbs."""
        {% for database in databases_list %}
        if model._meta.app_label == '{{ database[1] }}':
            return '{{ database[0] }}'
        {% endfor %}
        return 'default'

    def db_for_write(self, model, **hints):
        """Attempts to write simpsons and cloudmanager models go to their specific dbs."""
        {% for database in databases_list %}
        if model._meta.app_label == '{{ database[1] }}':
            return '{{ database[0] }}'
        {% endfor %}
        return 'default'

    def allow_relation(self, obj1, obj2, **hints):
        """Allow relations if both models are in the same database."""
        # Prevents accidental foreign key relationships across different physical DBs
        if ( 
                obj1._meta.app_label in {{ databases_list | map(attribute=1) | list }} or
                obj2._meta.app_label in {{ databases_list | map(attribute=1) | list }}
        ):
            return obj1._meta.app_label == obj2._meta.app_label
        return None

    def allow_migrate(self, db, app_label, model_name=None, **hints):
        """Ensure the app's models only show up in the designated database."""
        {% for database in databases_list %}
        if app_label == '{{ database[1] }}':
            return db == '{{ database[0] }}'
        {% endfor %}
        # Ensure default Django apps (auth, sessions, etc.) don't migrate into simpsons/cloudmanager
        if db in {{ databases_list | map(attribute=0) | list }}:
            return False

        return None