"""Neo4j connector Client."""
from contextlib import contextmanager

from neo4j import GraphDatabase

import config

neo4j_driver = GraphDatabase.driver(
    config.NEO4J_URL,
    auth=(config.NEO4J_USERNAME, config.NEO4J_PASSWORD),
    max_transaction_retry_time=config.NEO4J_MAX_RETRY_TIME,
)

@contextmanager
def db_session(access_mode=None):
    """Provide a session for series of operations.

    Session will closed once the whole flask request is done. Commit
    and rollbacks has to be managed by caller.

    access_mode: default access mode (read or write) for transactions in
    this session / flask request as we open session once per request.

    Usage:
        # Default usage
        with db_session() as session:
            session.run("MATCH (a:Person {name: $name}) RETURN a", name=name)
        # Auto-commit transaction
            with db_session() as session:
                session.run("CREATE (a:Person {name: $name})", name=name)
        # explicit
        with db_session() as session:
            tx = session.begin_transaction()
            try:
                result = tx.run("CREATE (n:Person{lastname:'test'})")
                tx.commit()
            except CypherError as e:
                tx.rollback()
    """
    neo4j_db = _get_neo4j_session(access_mode)
    yield neo4j_db


def _get_neo4j_session(access_mode):
    """Select appropriate driver based on FFlag."""
    return neo4j_driver.session(default_access_mode=access_mode)