"""Neo4j connector Client."""

from contextlib import contextmanager

from flask import g
from neo4j import GraphDatabase
from participant import config
from participant.api import app
from participant.utils import exception

if config.ENVIRONMENT != config.TEST_ENVIRONMENT:
    try:
        neo4j_driver = GraphDatabase.driver(
            config.NEO4J_URL,
            auth=(config.NEO4J_USERNAME, config.NEO4J_PASSWORD),
        )
    except Exception as err:
        if config.NEO4J_SETUP_READY:
            exception.reraise_exception(err)
        else:
            print('ERROR: Neo4j connection failed due to: {}'.format(err))


@app.teardown_appcontext
def close_db(exc_info):
    """Close session on request teardown.

    So there is no need to do that throughout the code. This gets called
    once per request, so a session lives for a each request instead of
    each query scope.

    Args:
        exc_info(exception): exception instance, if it was not handled.

    """
    if hasattr(g, 'neo4j_db'):
        g.neo4j_db.close()


@contextmanager
def db_session():
    """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.

    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()

    """
    if not hasattr(g, 'neo4j_db'):
        if neo4j_driver:
            g.neo4j_db = neo4j_driver.session(database=config.NEO4J_DATABASE_NAME)
    yield g.neo4j_db