from datetime import date
from neo4j import GraphDatabase

def upsert_fact_with_supersession(
    driver: GraphDatabase,
    entity_id: str,
    property_name: str,
    new_value: str,
    valid_from: date,
    source_doc_id: str,
) -> None:
    """
    Write a new fact, terminating any currently-open assertion for the same property.
    Old assertions are retained for audit; only valid_to is set.
    """
    with driver.session() as session:
        session.run("""
            // Terminate the previous open assertion for this property
            MATCH (e:Entity {id: $entity_id})-[:HAS_FACT]->(f:Fact)
            WHERE f.property_name = $property_name
              AND f.valid_to IS NULL
            SET f.valid_to = date($valid_from) - duration('P1D')
        """, entity_id=entity_id, property_name=property_name,
             valid_from=str(valid_from))

        session.run("""
            // Insert the new assertion with open valid_to
            MATCH (e:Entity {id: $entity_id})
            CREATE (e)-[:HAS_FACT]->(f:Fact {
                property_name: $property_name,
                value:          $new_value,
                valid_from:     date($valid_from),
                valid_to:       null,
                source_doc_id:  $source_doc_id
            })
        """, entity_id=entity_id, property_name=property_name,
             new_value=new_value, valid_from=str(valid_from),
             source_doc_id=source_doc_id)