"""pubsalesacc/connectors/neo4j.py — Neo4j graph database connector.

Driver construction is deferred to first use (not at import time) so that a
missing or incorrect .env does not crash the application on startup.

Hostnames and environment names are read from config.NEO4J_HOSTS so they
can be updated without touching connector code.
"""

import logging
import os

from dotenv import load_dotenv
from neo4j import GraphDatabase, Driver

load_dotenv()

logger = logging.getLogger(__name__)

_VALID_ENVS = ("dev", "qa", "prod")


def _get_auth(env: str) -> tuple[str, str]:
    """Return (username, password) for the given Neo4j environment."""
    username = os.getenv("NEO4JUSER")
    if not username:
        raise EnvironmentError("NEO4JUSER is not set in .env")

    env_key_map = {
        "dev": "NEO4JDEVPW",
        "qa": "NEO4JQAPW",
        "prod": "NEO4JPRODPW",
    }
    pw_key = env_key_map.get(env)
    if pw_key is None:
        raise ValueError(
            f"Unknown Neo4j environment '{env}'. Must be one of: {_VALID_ENVS}"
        )

    password = os.getenv(pw_key)
    if not password:
        raise EnvironmentError(f"{pw_key} is not set in .env")

    return username, password


def get_driver(env: str) -> Driver:
    """Return a Neo4j Driver for the specified environment ('dev', 'qa', 'prod').

    The caller is responsible for closing the driver (use as a context manager):

        with get_driver('prod') as driver:
            result = driver.execute_query(...)
    """
    # Import here to avoid circular import; config is safe to import at call time
    from config import NEO4J_HOSTS

    if env not in _VALID_ENVS:
        raise ValueError(
            f"Unknown Neo4j environment '{env}'. Must be one of: {_VALID_ENVS}"
        )

    host = NEO4J_HOSTS[env]
    uri = f"neo4j+s://{host}"
    auth = _get_auth(env)

    logger.debug("Connecting to Neo4j %s at %s", env, host)
    return GraphDatabase.driver(uri, auth=auth)


def connectivity_check(env: str) -> None:
    """Verify connectivity to the given Neo4j environment. Raises on failure."""
    with get_driver(env) as driver:
        driver.verify_connectivity()
    logger.info("Neo4j %s connectivity check passed.", env)